After the plant material is consumed, it is mixed with saliva in the rumen and reticulum and separates into solid and liquid material. Howler Monkeys are the largest monkey species, growing up to 1m and weighing around 5 kilograms. Location The place in the world where something is found. Archived from the original on October 25, Animals may also have unusual gaits that are used occasionally, such as for moving sideways or backwards. Canine teeth are generally found at the front of the jaw and are used for piercing and biting prey.
I say unfortunately, because the bacteria in the colon produce vitamin B12, but not much of it is absorbed; not enough to maintain good health, so humans are dependant on dietary B12, whch can only be found in animal foods. Chimpanxees, like gorillas, are hind-gut digesters and cannot be compared to humans.
There cecum is very long, the human cecum is abouut an inch long. The apes have a very long apenndix and will die without it; we all know humans can live well without an appendix.
Apes have a much large colon and far less small bowels than a human. It is a false claim that the human small intestines, which are there mainly for absorption, contains a host of enzymes which can break down cellulose. In fact, no animal on this earth can digest cellulose. Ruminants first do heavy mechanical damage by having a better set of flat molars for grinding, but then to top that, they have the abikity to regurgitate the vegetation between the movement to each stomach and chew it some more — this is called chewing their cud.
Humans cannot regurgitate our food to chew several times because of the acidic nature of the contents of the stomach. Rumiants have no acid in ther stomach. Humans have no protozoa in their entire body, not even in the colon, but ruminants are dependent on protozoa.
If you were to remove the colon from an chimpanzee, it will die. Many humans live without colons. I was left with only 2 feet of colon and I do fine. Humans are not hind gut digesters, so I still stand on my original point.
Yes, I may have been out of line calling her a troll, but the way she worded it came accross as a troll. When anyone begins their comment with insults to my intelligence, it would always seem they were looking to pick a fight, and to me that is a troll. I appologize if I offended, but it is important to me that i defend what I write, because I have done massive research into the human digestive system, because my life depends on it.
Tzakis, who performed my intestinal transplant, feels I understand the human GI tract better than he does. I get tons and tons of nasty letters from vegans and that probably makes me a bit gun shy. I do not approve many of them because they contain nothing but insults and profanity and no science whatsoever.
She did however accuse me of being completely wrong in my science and even misquoted things said in the article which were not there. Yes, I felt insulted and attcked by the nature of her reply, like she was going to school me, yet every thing she claim I had already addressed correctly in the article or she was spouting flat out pseudoscience.
Much of her science was seriously flawed. I appologize if it seemed to harsh, must have been the mood I was in that day. I thank you for writing and appologize if I offended, but I will always defend my position with science. Meat isnt bad as long as it is organic.
Can we survive just off of it alone? Sure if you want to be ketogenic forever… Maybe not the kind meat sold nowadays. Can you live just being a vegan? If you had not much intestine, how well does the intestine work with meat.
Stomachs are bad arse, dont get me wrong. But, you might be an exceptional personal or a freak. Hi Zane, thanks for commenting. I am certainly a biological freak, but not because of my digestive system, All of the times I surprised and astonished the doctors had more to do with some weird ability I have to survive low blood pressures which usually kill people, but I assure you, your stomach works much like my own.
Yes, I was only left with about 8 inches of small intestines. Basically the food which emptied from my stomach came directly out of the duodenum and out the stoma. In all reality, what came out of the stoma was really what you would expect to come from the duodenum in any healthy person, there was nothing abnormal about me. The digestive system is very complex and very difficult to understand. Many people have misconceptions of the role that the intestines play and attribute a lot of digestion to them, when in reality their job is mostly one of nutrient absorption.
Though some digestion takes place along the way, the greater part of reducing the food to liquid is handled first by the mouth and teeth. The teeth do a majority of mechanical damage grinding and pulverizing solids into a softer material, increasing surface area and exposing more of the cells to the acids and enzymes in the stomach and duodenum.
Also, do not overlook the fact that the human saliva contains many enzymes, mostly amylase, an enzyme which breaks down carbohydrate bonds, so even complex carbohydrates are reduced to simple sugars before reaching the stomach and absorb quickly into the blood stream. This is one of the problems with the modern american diet rich in carbohydrates which spike blood sugar far too fast for the pancreas to deal with.
Having a stoma which came directly off the duodenum gave no time for the stomach acid to be neutralized , so I felt the full force of the stomach acid when I experienced the all too often ostomy leaks which allowed the stomach acid to cover the sensitive skin of my stomach area. Believe me when I tell you, that acid had plenty of corrosive ability to reduce any animal protein to liquid in short order. It burned very much like car battery acid and left my skin red and inflamed for days.
Since most food will sit in this bath of acid and enzymes for two hours or more as the stomach agitates it by churning, the animal cells, which are only made of cholesterol, break down quickly to solution.
The duodenum is a very over-looked organ. It may be only 4 to 6 inches long and follows immediately after the stomach, but it contains many ducts where biliary secretions of specific enzymes, designed to break down chemical bonds of the 3 major macronutrients we eat. Lipase, for breaking down fats, protease for breaking down proteins and amylase to break carbohydrate bonds, reducing starches to simple sugars or monosaccharides.
Many of these enzymes are secreted by the pancreas, except bile, which is secreted by the liver, stored in the gall bladder and released when fat is present. Bile is not an enzyme, but rather an emulsifier. Think of it like the way water will not mix with oil, but if you add an egg yolk, which acts as an emulsifier, the two become one as mayonnaise,.
In a similar way, bile, which is made of cholesterol and salts, makes the fat join with the watery chime, so all will be ready to be absorbed as it enters the jejunum. The stomach, with its high acid content, array of enzymes do most of the work which the teeth and saliva did not finish. Cellulose plant cell walls is a very hard carbohydrate equivalent to wood and is indigestible by any animal in the world. Even termites are dependent on bacteria which lives in their stomachs to ferment the wood cellulose and then feed them with the by-product.
Most modern pesticides are designed to target the bacteria rather than the termite, because once the bacteria dies, the termite dies of starvation. This is true in all ruminant animals and hind-gut digesters. They have many microbes within their multiple stomachs or hind-gut to ferment the cellulose for them and feed them the butyrate a short chain triglyceride — saturated fat.
The human stomach is virtually sterile, as is all the small bowels, making us an omnivore who must get our fat from dietary sources. A human is not a hind-gut digester as our closest relative, the chimpanzee is and cannot convert cellulose to a fatty acid; actually our colon can, but we do not absorb much from the colon, certainly not enough to sustain us. The proof is that the chimp has a much larger ratio of colon, cecum and appendix and much less small bowels for absorption.
There is evidence that our most ancient ancestor; Australopithecus, best example; Lucy , shows evidence of being a hind-gut digester, eating mostly fruits and vegetation, but this is a pre-hominid relative of man, being nothing we would consider a hominid. She had an extremely small brain, not much bigger than a modern chimpanzee. Proof of this was found in the bones of paleolithic hominids who showed signs of carrying the same parasite as the ancestors to the modern hyenas, which heavily suggested they were eating on the same meat as the hyenas, also suggesting that early hominids were scavengers.
I personally believe they were scavenging until their brains grew large enough that they began creating weapons which allowed them to chase predators away from fresh kills, then eventually becoming good enough with weapons to become the apex predator. It is interesting that only the human developed the ability to throw objects in an overhand motion with deadly accuracy. This skill requires a very large portion of the brain to accomplish this very technical task, yet it is so ingrained in humans, that even two year old children can toss objects overhand and usually hit their target and certainly most of our sports are based on this ability.
If you would like to red more about this amazing human adaptation Which helped us grow our brains and conquer the world , the following is an article detailing the evolution from a Harvard Publication: I know that PETA likes to spread some pseudoscience they pulled directly from their asses, because not one respectable anthropologist would agree with their claim that humans evolved as an herbivore.
The Harvard article reports what the top anthropologists believe based on the evidence they have found, not what there wishful thinking wants them to believe. It is for this reason that I believe that we are better adapted to digesting meat with higher efficiency and what I saw in the ostomy bag would support that thesis. Then there came fire! As the hominids began cooking their food, the nutrients became even easier to extract and absorb, even from the vegetables, and the brain grew more, allowing the invention of greater technology for both hunting, food preparation and cooking.
This also lessened the need for the large powerful jaw for chewing which Lucy had. Our jaws shrunk and certain teeth became unnecessary, which is why wisdom teeth become more of a problem than anything else.
Everything which came out of my stomach is exactly what should have been expected in anyone with a healthy stomach and duodenum. We cannot digest cellulose, except what we happen to chew well enough, but humans are no longer designed for that type of chewing. This is why ruminant animals have flat molars without ridges. Our molars have peaks and valleys, not as extreme as a pure carnivore, but far more than a ruminant.
Theses ridges are for tearing meat, but since we usually cut our meat, these are not really necessary. Even worse, we lack the jaw power. Apes have very large jaw muscles which attach to a crest atop their skull, the human jaw muscles anchor to the cheek bone and temporal side of the skull and are far too weak to efficiently crush raw vegetation.
We also lack the extreme side to side chewing motion necessary for grinding vegetation. So we can always expect to find un-chewed vegetables and seeds passing through the human digestive system whole think of corn.
This is why we get more from vegetables which are cook or fermented. This how the human lost much of that heavy plant digestion tools, from cooking and fermenting vegetation for eons. Without any help from outside sources, the human being has everything necessary to digest meat and the animal products and get most the available nutrients from it. I still believe we are an omnivore, because there are many nutrients we have become dependent on getting from plants, nuts or fruits, we just are not as efficient at digesting them and therefor cannot live on them exclusively.
Of the two food sources, we are far better equipped to digest meat and animal foods fully, getting far more nutrition from animal products that we do from vegetation. Meat is poison to the human because it does rot in the gut and remnants of this crap is found even years later in the human gut..
He is totally full of BS. STOP telling lies, Melvin. Do some research before spouting nonsense! ON Reading all this I now know it rambles and I am not up to editing it all. So much for posting when tired and in pain. Wow the last resort of those with no real facts to debate with… just personal attacks and meaningless profane labels. I have killed and eaten a lot of trout, catfish, sea bass, salmon, cut-throat etc in my time.
Mind you I hate this trend in factory farming where they force animals to grow rapidly and they kill them way too soon in intensive farms where many of the animals have active infections.
All slaughtered way too soon for quick cash. I dislike it when foul, pigs and steers are filled with chemical crap to force them to grow fast, given antibiotics so you can back them together without quite killing them, and then are slaughtered way too young this has given us antibiotic resistant infections too.
That kid of ranching gives people meat without real flavor that is not good for them. It is expensive, but not as expensive as chemo or a funeral. Alternative medicine that HEALS problems — instead of putting you on a conveyer belt of medication that just covers up the symptoms with docs who never ever ask WHY you got sick in the first place.
Far more alternative medicine is now based on hard science research than there is in modern western medicine. Last year I saw a rheumatologists who was using methods based on a study that had been shown as crap by the World Health Organization a study of 5 people with no double blind or control group, all participants were hand picked by one doctor to prove HIS POINT, and not one of the subjects had the disease according to the WHO.
I hate it when people base their life choices or their way of treating patients on bad information…. Then again the real world can be scary. In fact, real fat the butter, suet and lard that used to be quite common is not the danger we have been told it is.
The Framingham heart study showed this as fact and then the data was twisted to try and say the opposite …. In order to survive my own health issues more on that later I read a lot of research papers and medical abstracts. I have too do this in order to get better which I have been doing — to the amazement of the docs. I also have a sister in law who has a PDH in biochemistry, was a university professor at Georgetown Clair Booth Luce Chair , worked a Lawrence Livermore Labs and is now working in epigenetics in her own non-profit.
She agrees with what We do in OUR house. She knows my research and choices are correct, and that the docs have their heads buried someplace … perhaps in the sand… or maybe in a place that is dark and stinky.
Any doc who does not have a microscope in their practice, is NOT a scientist. All they know is: A good modern E. However western docs are utter crap at dealing with any chronic problem or preventative medicine. Not one of them though to check me for gallbladder disease because my liver bloods were always fine and they ARE fine … until the months right before you are likely to DIE. My gallbladder got to be football sized instead of marble sized with irregular thickening well over 1cm in places and with polyps.
He told her to go see her gastroenterologist. Had they not assumed and had then run tests done real science they would have caught it years earlier. Meanwhile I had a very bad attack. I had a branch of my hypatic artery blow. Thankfully my blood is so screwed up or was back then before my research that I barely bled at all at the time…thanks to red cells that are totally the wrong shape, far too many red cells polycythemnia and enough fibrin for 10 people. For instance, in I screwed up in the kitchen and buried a steak knife down to the bone on my index finger near the big knuckle…and it did not BLEED at all.
It only left a dark mark on the skin like a hair fine bruise. I did not mange get even one drop of blood out of it from squeezing to try and get the blood to clean it out. So…had I not STILL been very sick from the joys of irresponsible corporate petro-chemistry, and stayed that way from docs who never bothered to do acy testing — i.
As a result although I did lose 5 units of blood out my backside and into my belly.. There is a point to take into account here. If meat or gluten was the big evil, they would have had armies of the disabled — filled with people with IBS, crones, Fibomyalgia and Chronic Fatigue Syndrome which would have made it very hard to oppress millions of people through bloody warfare.
Then again it was also an era where we had constant farm, city and home use of DDT, 24D, Diazanone etc …. Hell, we had a can of DDT on top of the fridge for killing the flies. So now I have serious health issues. The worst of the lot give me rapidly forming burning blisters — some of which are huge and go very deep — all the way down into the fat layer where you can see my capillaries.
So it just builds up. Given enough time the villi take serious damage. And because the small intestine and villi sit right next to a large portion of the lymphatic system in order for us to absorb nutrients …the lymphatic system also takes damage from absorbing all that rubbish. The lymphatic system has no pump or filter. It can get bogged down, clogged and filled with chemical crap easily.
The gut can no longer do its job right with all this going on. And people still go on eating poisoned groceries, fast food, etc. They are too tired by then to do anything complicated in the kitchen.. There is no room for a real pantry for food storage either. But then people have had a long tradition of embracing the irrational, ignoring reality and rewriting history to fit what they want to believe in or to avoid what scares them.
The popes envoy to Galileo refused to look in the telescope lest his faith be lessened and he did not dispute what could be sen throuth it.
I am what you might call a rational greenie. I like science and there is certainly nothing wrong with making a good living so long as you are not an ass about it. Incidentally speaking of poisoning people back before King James got a hold of the Bible for his English translation note that he was an unstable nut-case who though witches were out to get him — under the bed, in his shoes, everywhere there was this old testament bible verse which therefor only applied to JEWISH people and it said:.
It said nothing about witches. HE King James personally believed that witches wanted to poison him. Then again King James and other people before him changed other piece of the bible. The KJ version was going to be read by average people so it could NOT be a contradiction to accepted theology.
Now in that era, women had no rights and were property. St Augustine paved the way for some of this. I would assume that you have a much broader selection of fresh food there. Here in the U. Thanks for stopping by and for the words of encouragement, Bob. I definitely subscribed to the email announcement and have already posted your article on the dangers of colonoscopies to my facebook page. Thanks, Bob, for helping to spread the information.
Stanton has some great information at his site Gnolls. He has a very direct approach to delivering comprehensive facts. Odd, considering my great-grandmother ate meat,and my 96 year old grandmother and my 93 year old grandfather and my 93 year old great grandfather, weird I think she is secretly doing it just to lose weight and also that besides that fact it might give you cancer she has no other moral reason to do so. I lost my bowels due to the incompetence of a group of doctors.
A gastroeterologist attempted a colonoscopy and perforated the colon. He and another group of doctors ignored my complaints of pain for nearly 4 days. In that time of massive hemorrhaging, a partial occlusion formed in the superior mesenteric artery — and again, the doctors failed to diagnose it for more than a week. The bood flow was severely decreased to the intestines and all of my bowels became ischemic.
Vegans use lots of scare tactics to get people to change to their lifestyle. Most of the time they know nothing that they claim to. There are no links to meat causing cancer.
Some processed meats can contain carcinogenic chemicals, but in very low doses. This is why I stray away from processed meats Spam, cold cuts, hot dogs, etc. Fresh meat will never give anyone cancer. They can claim all the health benefits they wish, but in the real world, the healthiest people I know are not vegan.
But, some of the sickest people I know are. They go to the doctors more often and take way more medications and supplements. It is a horrible disease. Try avoiding wheat and products made from wheat. Gluten is very rough on the intestinal walls. I still have 20 inches of native colon which I was able to spare by giving up wheat. And those things are quite healthy for us and there are great nutrients extracted from them farther in the digestive process.
The stomach is only one part of a long system. Now if we all had all types of whole veggies in our poop not just the corn kernels — that might be something to consider. Hi Sara, thanks for commenting. You seem to have missed the point of the article completely. The point of the post was not to denigrate vegetables as a food source, but rather to counter the ignorant and deceitful claim by vegans that humans cannot digest meat.
According to vegan pseudoscience, meat is indigestible by humans and putrefies in the colon. Although vegetables are an important source of many nutrients and a healthy part of a good diet, humans actually digest meat more efficiently than vegetables.
Your claim that the intestines contain enzymes to digest every part of vegetation, like broccoli, is not accurate. The parts of the intestines that I was missing are mostly used for absorption, not digestion. I now have a complete digestive system due to the transplant. Yet, I still found whole pieces of vegetables in the ostomy. The level of nutrition that we receive from most vegetables are contingent on how well they are cooked and chewed. Other than colonic bacteria, humans have absolutely no enzymes that can break-down plant cellulose they must be mechanically broken by chewing.
This is why ruminant animals have multiple chambered stomachs and chew their cud several times. If the human digestive tract could so efficiently break down vegetation as you suggested, then why would ruminants have evolved such a large and energy gobbling digestive tract? Explain to me why they evolved four stomachs if the tiny human intestine could do the trick — and why do they have such a large cecum, whereas the human cecum is almost non-existent?
I eat plenty of vegetables. Because vegetables are so difficult to digest, I ferment a lot of my vegetables to get more out of them. Humans get more nutrition from well cooked or fermented vegetables than raw.
Most vegetables are indigestible to humans in their raw state and most grains are down-right toxic to humans in their raw state, because of the high level of lectins and phytates.
I have started eating only meat due to the fact that I personally cannot digest veggies….. Your argument presents a straw man logical fallacy. Of course the human body can digest meat. Our bodies do not have the physiological trademarks of traditional carnivores.
There is no straw many fallacy here, but your argument is certainly an argument from ignorance fallacy. Just because you are ignorant of the claim does not mean it has never been made. One the flip side of your argument, humans do not digest vegetation as well as ruminant animals either, because we are not herbivores, but are omnivores.
Humans do synthesize all of the enzymes necessary to digest meat, unlike total herbivores, who do not. My observation in undeniable. All of the meat that I consumed was completely reduced to liquid by the time it exited the duodenum, yet many pieces of whole vegetables were undigested. You act as though all carnivores digest meat with the same efficiency — nothing could be further from the truth.
Cats are better suited for softer organs and muscles, whereas canines have the ability to digest much tougher cartilage and bone. Crocodilians have such powerful stomach acid that they can digest bone, horns, antlers and hooves. My post is hardly a straw man fallacy when you, yourself are claiming that we do not digest meat very well and my claim is that we digest it very well. How is completely reducing it to liquid before it reaches the small bowels not very efficient?
You are the one with the straw man fallacy by trying to make the argument that I claimed that humans were carnivores. Where in this article did I make such a claim? Human beings are omnivores and can adapt to eating many different foods. Inuit people have proven that humans can thrive on animal products alone, if necessary. I see much of the laziness, cynicism and various BS you have commented on in the medical field.
This article is garbage. And of course there were whole pieces of lettuce and plant matter coming out the stomach. Most of our digestion is done in our stomach. The acids in out stomach do a great job breaking down proteins. When that animal protein liquid goes into the rest of the GI tract after the stomach it turns into a thick sludge. Which can hinder overall digestion.
Bit saying we can eat meat. But our diet should be based on plant spruces more so than animal sources. So let me get this straight — the stomach does a great job breaking down animal proteins but upon leaving the stomach it becomes a thick sludge that I presume is indigestible. And the grammatical and spelling errors make it nearly unreadable. Thanks for blowing some fresh air into the stench that wafted this way.
Trolls can be irritating. Thanks for attempting to leave a comment. I believe that Bob was being very polite saying your comment was nearly unreadable. As much as a wanted to understand your comment it was completely incoherent. Can you site any studies that prove that the chyme containing animal proteins and fats are indigestible, or more accurately, inabsorbable?
Because it makes absolutely no sense. Once exiting the duodenum, which is where all the pancreatic enzymes and bile are secreted, the protein chains have been reduced to simple amino acids. Amino acids from plants are no different from those of animals. So why would animal amino acids be less absorbable?
An amino acid is an amino acid — plant or animal. You admit that animal proteins are properly digested in the stomach and duodenum If you know what that is , but then say they cannot be digested further down the bowels. This is absurd, because little to no digestion takes place beyond the duodenum — only absorption. The jejunum and ileum are filled with villi, which are predominantly for absorption of nutrients from the cyme.
Your science is quite flawed and it is obvious that you WANT to believe something, but have no biological knowledge or evidence to back it up. Read a biology book on digestion and take a course in English and then come back and we can debate this intelligently. The issue with the plant proteins was that a percentage of them were not efficiently broken down in the stomach and duodenum. What vegetable protein had been thoroughly chewed and digested would be absorbed. Problem is, humans cannot thoroughly chew our food as well as a ruminant, therefore much of the nutrients contained within the cellulose are never digested — this is why people find whole kernels of corn in there crap.
You never find whole pieces of meat in your stool, do you? Both animal and plant nutrients are good for us, the fact of the matter is that we are better designed, by nature, to extract nutrients more efficiently from animal cells because the cell walls are more permeable than cellulose.
Your argument did nothing to prove that our diet should be predominantly plant based, other than you saying so at the end of your ridiculous rant about sludge. Please show us some scientific evidence, outside of some claim on PETAs website who are not scientists by any stretch , that may substantiate your thesis. I know what I saw coming out of my stoma. I have a very highly intelligent readership and they demand scientific evidence, not vegan propaganda, to support dietary claims. Fresh vegetables are fine apparently, but if you steam them or cook them in any way they loose nutritional value and the digestive system starts to reject them.
Thanks Taylor for writing. I saw that movie also and did not see much in the line of scientific evidence or studies to support those claims, other than some people looking into the camera and making those claims basically like, believe me because I said so and I am in a movie with some impressive letters after my name.
People can claim anything they want after all, PETA boldly claims humans cannot digest meat , but showing the studies to support those claims is another story. I am referring to the claim that the body attacks cooked vegetables as a foreign invader. As a matter of fact, there is better evidence that overcooking meat can cause Advanced glycation end-product AGE by burning proteins and lipids.
This is a good reason not to overlook or fry meat at high temperatures. It creates inflammation, but nothing like a full blown immune response like that movie suggested. Some food allergies can cause an immune response, otherwise, only pathogens or toxins trigger any dangerous immune response.
Creating inflammation is something different than what the movie producers were suggesting. There is truth that vegetables and fruits do lose nutritional value when cooked so do animal products , but that is also a very deceptive statement when only offered without the other variables. Fruits are a different story, because they are the ovary of a plant and designed and offered up by the plant for ingestion in order to spread their seeds.
Many vegetables are not digestible to human beings — some are downright toxic to us if not cooked. Lectins are destroyed by heat — and lectins will kill a human being. The problem is, that we are not designed to chew our food with the same efficiency as a ruminant — nor are we hind gut digesters, like other primates. This is most likely why humans began to supplement their diet with meat a long time ago — more likely, we lost the ability to properly chew and ferment vegetation at the same time we began to introduce more animal products into our diets which were more nutrient dense than vegetation anyway.
For those that suggest that we can chew food well enough to rupture every cell wall of the impermeable cellulose of plants would be completely ignoring the fact that ruminants evolved multi-chamber stomachs, far stronger jaw muscles, the ability of extreme side-to-side jaw movement and large flat molars humans have rigged molars. Why would ruminants have evolved all that equipment if the tiny, weak, human jaw and teeth are sufficient enough, to not only rupture cellulose walls, but we also had no need to regurgitate our food and re-chew it several times?
Anthropological evidence suggests that we lost the larger teeth, stronger jaw and larger hind gut after adopting meat and animal products intimidatedour diets.
There are some who like to argue that raw vegetables are healthier, because many enzymes which are heat sensitive are destroyed when cooked. The other option would be to juice them, but then the vegetables are also heated by the high-speed blades of the juicer, thereby destroying as many nutrients as if cooked.
But, we do not get more from most of the vegetables we eat when in their raw state, we actually get more from those that are cooked, because it helps break down the cellulose for us. This can be confusing, because many call corn a vegetable, when it is in reality a grain and beans are seeds, not vegetables. The leafy green part of the plant and the stalks are vegetables. I ferment vegetables, which probably maintains the highest amount of nutrients. The rumen stomach is a large fermentation vat, which is why cattle smell like fermented vegetation even to the extent of alcohol when you are near them.
The cultures in the fermentation field are able to digest the cellulose plant walls that we are incapable of digesting. Animal cells have a membrane of cholesterol — something we make enzymes lipase to digest. Plants have a cell membrane made of indigestible carbohydrates, which humans have no mechanism with which to efficiently rupture them.
Even ruminants must repeatedly chew and ferment them to break down those cell membranes, which house the nutrients inside. In recent years, there have been far more humans killed in the western world by consuming raw vegetables, than meat, raw dairy or eggs combined. I guess far more people consume raw vegetables, because they are convinced they are healthier or they are attempting to lose weight.
The whole idea of eating salad to lose weight was based on the idea that we cannot digest the vegetation to release the carbohydrates within — right? It was thought to be just stomach filler. So, whoever invented the idea of a salad knew that we could not digest raw vegetation well, nor get much from it. Just think, if we could digest vegetables like a ruminant, salads would be the most fattening of foods, with all those carbohydrates.
Problem is, we cannot get to those carbohydrates, ruminants can. Back to my original point…. Everyone knows the dangers of raw meat, so they avoid it. But, some of the recent outbreaks of food borne pathogens salmonella, e. Recent culprits have been bean sprouts. I thank you for writing, but I have yet to see any evidence to support the idea that the human body attacks cooked vegetables.
Have you seen any scientific information basically, by what biological mechanism does this happen? What cells of the immune systems are involved and why? If someone is eating burnt vegetables, it might make some sense, but I see no reason why steamed or sauté vegetables would have that effect. I mean, everything that we eat is a foreign invader, unless we were only eating our own flesh. Otherwise, I think it may be just more vegan propaganda in an attempt to frighten people from animal products.
I was still eating some salads then, because that was before the transplant, do my immune system was not yet compromised. Thanks again for writing and for the questions. There are NO clear links to meat and disease. The studies performed are based on outdated information started by Ancel Keys in with his 6 country study which he ignored reliable data from 16 other countries, which ruin his time-line when added in.
Once Professor Keys was appointed to the board of the AHA American Heat Association in the the myth began to grow and no one dared question it any further. All other test since as the Framingham study have been acheived via questionares sent to people to fill out — How scientific is that? It is well known to scientist that the government accepted this myth most likely due to the pushing of more grain in our diet — which is killing us Since most funding for these studies come from government monies, every scientist knows thet their experiments will go unfunded and could lose tenure as many prfessor have who disagreed with the myth if their results show anything different than what the hand-that-feeds wants — therefor, they make sure that the data ia skewed to fit the desired answer.
Scientist have to eat and support their families also, so they comply. But, there are many independent test that have been done that have easily proved the opposite. Try doing some more research on the subject before calling someone a liar.
The test which show meat consumpption for superior health than grains were all clinical studies, far more reliable than the observational studies done by those which show the oppossite and the only studies which show that meat is bad are all observasional in nature — leaaving out many variables, like excessive drinking, drug use and smoking.
You have been lied to — we all have. Absolutely spot on from my observations and readings. The last ice age ended roughly 10, years ago and lasted about , years.
Fruit in the diet would have been almost nil. After the development of agriculture there is clear evidence of a significant decline in health — this occurred roughly 6, BC I believe.
Human populations that took up farming became shorter — as much as half a foot, extreme dental issues and chronic diseases. The hunter gatherers before not all became farmers and their health did not deteriorate which suggests the health issues directly tied to the farming life had been supremely fit and healthy until death, without any of the issues their farming neighbours were experiencing.
The rest of the diet should be vegetables, preferably hardier vegetables that do better in a colder climate. You especially want to stay away from dairy, most grains, processed foods and most simple carbohydrates. I know this is a article in of itself but people have to learn about these things and the more noise we make the better. It helps that I also moved into the bush, got some pets and started drinking water that hadnt been treated.
I read most of your website a couple of years ago and noticed at that time there was a large gap of time with no new postings. Just checked back this evening and was glad to see you are still alive and kicking and writing. Tried Paleo and then tried Soylent. Take care and keep writing! Sorry for the delay in responding to your comment Holiday madness and family in town and all. I also apologize for my absence of any new material in a long while. I really do wish to get back to publishing new stuff, but I have had so many other things to take care of.
After nearly dying several times, I now realize how short life can be and just how fast everything can go wrong. I have also been conducting a lot of investigation, because I did not want to continue to write the same things over and over. I have met several business insiders one a retired nurse who helped in thousands of colonoscopies and the other a medical equipment distributer who have helped me with a lot of proof of what I suspected.
I think people will be shocked at just how bad this endoscope business is run. I thank you for checking on me. I hope you a lot of luck in finding a diet which works best for you. I know what you mean about the paleo and the amount of cooking involved. I really enjoyed reading your fascinating blog, there is so much content I will return to again and again..
If you have any questions, please feel free to write me. Thank you Cindy for stopping by and reading. I apologize to all my readers for not publishing anything new in a while. I have had a lot of deaths of people close to me including my father who is still alive, but has had several strokes and left mentally crippled. There will be some shocking stuff when I do publish these articles. In that time, I have been contacted by some industry insiders who have provided me with the proof of everything I suspected about colonoscopies and the news was even worse than I anticipated, so be prepared for some serious shit!
On top of many other things, I was diagnosed with Multiple Myeloma about a year ago and needed to undergo treatments. It is in full remission at this time, but this was quite distracting and another reason I was not publishing.
I thank every one for their patience and concern for my well being. I have received so many encouraging emails from readers who were concerned that I was very ill or possibly died I can understand why they thought that.
These emails meant a lot to me. Thank you for the links and information Pam. I will look into this much further. I am doing quite well and I hope you too are doing well.
It is really difficult to watch a father go through something like this, because I know he would never want to be treated this way if he still had a perfectly functioning brain. I know that he never wanted to live that way. I beleieve that a lot of needless suffering had been brought about by the doctors as they drove his cholesterol lower and lower each years since his heart attack in I am sure he would have prefered to drop dead of one massive heart attack than whither away like this.
Doctors act as if cholesterol is some pesky chemical by-product which is toxic to us. Sometimes I believe that many of the doctors have convinced themselves of this — almost as if cholesterol is like C02, ammonia, uric acid, or something the body produces through respiration and must be gotten rid of or it will kill us.
In truth, cholesterol is a very important antioxident and is the base for most of our hormones, the production of vitamin D, every cell membrane in our body and makes up the bulk of the brain and nervous system. When my father had his first heart attack six years ago and the doctors started all of that cholesterol pseudoscience, I tried my hardest to have him dump those drugs and also dump all of the wheat and other grains from his diet, but that was not going to happen. Unfortunately, it worked out about the way I feared it would.
He would have been much better off to even drop dead of a massive heart attack than slowly decay the way he is doing. He has now had a stroke in ever major part of the brain and is totally confused. He requires 24 hour a day assistance and will spend his remaining days in a hospital or assisted living facility.
I thank you for your concerns. Have you ever tried an all meat diet or zero carb diet? Thanks for your article. I really enjoyed your replies to the ones who wanted to disagree with you.
Brought even more clarity to the original article. Really appreciate you taking the time to write all you did. Makes it so clear about the human digestive system. Thank you for the kind words of encouragement. Otherwise, I have no problem with different opinions. I guess I can get a little too rough at times, which was pointed out to me once. I still feel that I handled it properly because I felt she was a troll. I get so many vegan trolls write here that I can spot them a mile away.
The human digestive system can be confusing, because it is unlike any other species on earth because of the fact that our ancestors cooked their food and our digestive tract adapted to this. Since cooking and later fermenting foods is basically a form of predigestion, powerful chewing was no longer necessary and the acid could reduce in our stomachs.
We gave up the hind-gut digestion of our most ancient ancestors in order to evolve a larger set of small bowels for more absortion from the nutrient dense diet they ate.
It required less energy for our digestive system, which was more energy which could be allotted to a larger brain. I find it all real fascinating. All of the great apes genetically closets to humans are hind-gut digesters and have a much smaller set of small intestines compared to a human, but they have a much, much large colon, cecum and appendix.
Most of their absorption comes from the hind-gut. In fact, if you remove the colon for a chimpanzee, it will die, unlike humans, who can live fine without a colon, cecum or appendix.
We relay so little on the intake from these organs they have become basically vestigial. This change came about strictly from cooking foods, both meat and vegetables. Losing my bowels made me learn so much more about the digestive system than I ever knew before and I was studying for a Masters in biochemistry back when I went to college in the s.
I have yet to scratch the surface of all I have learned and wish to write even more detailed articles on this subject I have had some major distraction recently, but hope to soon be publishing again.
Like you, I will limit my comments to what I know from my own experience and not from what I have read or heard. I have been eating complete zero carb for a little over six years without interruption.
I only eat beef, pork, chicken, shrimp, scallops, and eggs. My mainstay is beef. That is it for me. I eat nothing of plants. I do not take any supplements. Literally, it has been just meat and eggs for six years.
I am in excellent health. I go to the doctor perhaps once a year for an annual check up. My blood tests come back within the normal range. My lipid profile is extraordinary i. HDL ; triglycerides I have stable energy throughout the day. I never feel hunger, but I have a strong appetite when I eat. I eat absolutely no fiber, but my bowel movements are regular and effortless. I have not ingested any Vitamin C over the past six years, but I do not have scurvy. According to modern-day myths, I should have died long ago because of the way I eat.
Wolverine, you have done a great thing by posting about your personal experience. Most people simply believe all the garbage feed them by the establishment, which includes most of the medical profession and government bureaucrats. Thank you for your honesty. You just keep eating everything they say will kill you and probably live to be It has really surprised me how many people I have talked to believe that humans have to eat grains. Most people seem to believe that there are some nutrients that we can only get from grains.
I keep telling them that if anyone was going to fail by dropping grains from their diet, it would be me. I have transplant bowels which certainly do not absorb as efficiently as native bowels do, yet I have not eaten any grains for more than 5 years.
They said that every transplant recipient they have on file have to take some supplements, yet every time they have run a blood profile for nutrition on me, I am never defiant in any nutrient.
I sure think this goes to prove that humans do not need grains, and why would we? No human ever ate grains until about 10, years ago, 20, tops. How could any species become dependent on a food they only began eating 10, years ago? I appreciate the kind words and apologize for taking so long to reply. Things have been a bit crazy recently. Interesting note re ostomy bags. We are also trained in helping with the psychological problems some people have in coming to terms with having a bag,.
Nursing assistants will also be trained in changing the bags and helping the patient manage their new situation. Thanks Helena for the information.
I am always interested in the different ways the medical trade do things around the globe. Here in the states, or at least here in Florida or the six different hospitals I spent time in as a short bowel patient , the initial training for the stoma and ostomy care is typically given by the wound care specialist, but then all ostomy care, or at least the dirty work of emptying the bag, measuring the stool and documenting the data is delegated to the Tech as though these people do not have enough to do in a 12 hour shift.
The nurses also have an incredible amount of work to do in their shift as well, but the work of ostomy stuff typically falls to the Tech.
I do remember one time a very young and inexperienced nurse was instructed to empty my ostomy and I knew I was in trouble right away because I could clearly see she was holding the end of the bag at a lower elevation than my stoma was at, but before I could even let a squeak from my mouth, she quickly pulled the plug on the bag.
Though she had place a container under the bag opening, it was ineffective as the pressure from the gravity shot the contents clear over the container and all over the bed. Luckily, I was quite experienced at that time and leaped out of the bed before the hydrochloric acid bath could run down and beneath my back as a nurse, you know that those gowns lend no protection in the back. I felt bad for the young nurse, because the acid was all over her hands, but of course, the skin on the hands is far more robust and rugged than the softer tissue on our backs and buttocks and I had already experienced just how badly that stomach acid can burn.
I believe at that time I was NPO and had been NPO for several weeks because I had a fistula which had formed between an abdominal phlegmon from an abscess and the stretch of intestine which led to my stoma, therefor allowing stool to pass into the abscess region.
The doctors had suspended all drinking and eating for an indefinite period, until imaging showed that the fistula had closed. Of course, having both nutrition and hydration being infused, it was not necessary for me to eat or drink anything to stay alive, but that still does not mean that it is not hard to go without food and drink, even from a psychological state.
Even with TPN and hydration infusion, we still get thirsty and our stomach still growls with hunger. After that incident, my wife decided to take over all ostomy duties. In fact, I was able to empty and change my own ostomy without such mishaps. I have not finished reading your piece yet but will do so soon. Interesting comments as well. Glad I found your page. We did indeed, as a species, eat meat early on.
Some think that this might have been one mechanism in our developing larger brains and becoming human. The human brain is a hungry beast. When I was a child we had very little meat and it is my belief that, like carnivores in general, we do not need to eat it every day but do need it. It gives us a lot more energy per kilo as the work of turning vegetation into good quality protein has already been done for us by the cow, sheep etc.
We did not evolve to eat vegetables, just fruit, nuts and meat I think. Except that evolution is a continuous thing and maybe we did once we learned how to cook. Most vegetables have to be cooked ie the cellulose is damaged by the heat — remember those early biology classes when you had to dunk a piece of cabbage in hot water before you could do the iodine test on it for us to be able to digest them at all and some are actually poisonous if eaten raw; kidney beans and casava spring to mind.
The learning how to make fire and cook was also a great leap forward as it enabled mankind to make use of vegetables. I am summarising a lot of reading here.
The best and possibly only valid reason to become vegetarian or vegan to my mind is the desire not to kill and eat the flesh of another animal. As a gardener though I always apologised to the cabbage when I killed it just the same as to the chicken.
Silly but there you go. As an omnivore, we do not required a steady feed of meat, but as I tried to point out in this piece, we are very well adapted to digesting meat protein and unlike vegetation cellulose all meat protein is reduced to solution by the time it empties from the stomach. I had learned this in school, but getting to actually see it with my own eyes certainly confirmed everything I was taught by responsible teachers rather than some of the myths and wishful thinking which can be found on the web where lies abound.
Cellulose is impossible for any animal, including insects, to digest in any manner other than the mechanical act of chewing and grinding. Unfortunately, the human molars have ridges that are too tall for proper grinding, besides the fact that our jaw does not have the extreme side to side movement of ruminant animals who also have perfectly flat molars. Even termites cannot digest cellulose, but are dependent on bacteria in their gut to ferment the cellulose and then feed them.
In fact, most modern chemicals used to kill termites are designed to attack and destroy the bacteria within the termite, rather than the insect itself.
Once the bacteria in their gut is destroyed, the termite will starve to death. Cows do not survive on a low fat diet because the cultures in their stomach convert fiber to fat, which is where all that saturated fat in their milk and meat is derived from.
We have had ruminant animals have their cultures killed after treatments with antibiotics to clear infections. At that point, we have to inject a large bolus pill down their throat with a special device to replant probiotics into all four chambers of their stomach or the ruminant will die.
Humans are not dependent on any bacteria to feeds us, we are perfectly capable of getting all of our nutrition from the food we eat, as long as it is cooked and contains some meat. In fact, much of our gut, especially the hind gut colon, cecum, appendix have shrunk throughout our existence as a species because we basically predigest our food through cooking or fermentation as you have pointed out. We cannot extract much nutrients from raw vegetables.
Unfortunately, there are a lot of misconceptions these days because anyone with a laptop computer can publish a website full of nonsense and pseudoscience and many of these are more religiously or politically motivated and written by people clueless in even basic science. As an animal, we are far better equipped to digest meat than we are at digesting and extracting nutrients from vegetation, especially uncooked.
Veganism is only possible today because of technology and would have been impossible for humans even a few hundred years ago. Vegetarianism would have been possible since agriculture began because protein needs could have been met with seeds and beans, but some animal products eggs, milk, cheese, etc.
Unfortunately, seeds and beans can become quite problematic in the long run and as you have mentioned, are very toxic in their raw state because of lectins which are destroyed by heat. The only protection early humans had from these toxins was the fact that these foods are also indigestible to all mammals, so there would have been no way to be exposed to the poison as any seeds or beans eaten would simply pass straight through us. This is what the plant depends on for us or some animal to eat their young and deposit it somewhere else far from the parent with a little fertilizer to go along with the effort.
Even children know that corn will not digest, but joke and giggle about finding whole corn kernals on their stool, but somehow this fact has escaped some wishful adults who now believe our ancestors somehow thrived on grains and beans. Until humans learned to cook and process food, grains and beans were off the menu and I believe should still be off the human menu for optimum health.
These are the genetic offspring of the parent plant and unlike fruits, are not offered up as a free lunch. They are defended by plenty of chemical warfare, which is the only weapon most plant have at their disposal. Fruits are meat offered up as a temptation to consume the offspring, which are indigestible to most animals and for good reason.
Most fruit seeds are quite deadly carrying enough toxins to kill or render someone quite sick if one was to grind up the fruit seeds and ingest them. Eaten with the fruit, they will simply pass through us, which is what the plant needs an animal to do to spread them out over distances as not to compete for the same sunlight and soil. Animal parents typically sport fangs, stingers, claws or just tremendous size or brute strength which with to defend there offspring form predators.
This is actually convenient for the predator, because once the parent is gone, the offspring are truly helpless — not so with plants. Those lectins can be destroyed by heat, but there are other defenses, like that of the soybean. Soy defends its young by offering them up for free only to have the babies laced with birth control pills rendering the predator sterile, unable to produce a new generations to attack the next crop of offspring.
Mammal classification has been through several iterations since Carl Linnaeus initially defined the class. Since Simpson's classification, the paleontological record has been recalibrated, and the intervening years have seen much debate and progress concerning the theoretical underpinnings of systematization itself, partly through the new concept of cladistics.
Though field work gradually made Simpson's classification outdated, it remains the closest thing to an official classification of mammals. The three largest orders in numbers of species are Rodentia: The next three biggest orders, depending on the biological classification scheme used, are the Primates including the apes , monkeys and lemurs ; the Cetartiodactyla including whales and even-toed ungulates ; and the Carnivora which includes cats , dogs , weasels , bears , seals and allies.
These were grouped into 1, genera , families and 29 orders. The word " mammal " is modern, from the scientific name Mammalia coined by Carl Linnaeus in , derived from the Latin mamma "teat, pap". In an influential paper, Timothy Rowe defined Mammalia phylogenetically as the crown group of mammals, the clade consisting of the most recent common ancestor of living monotremes echidnas and platypuses and therian mammals marsupials and placentals and all descendants of that ancestor.
Ambondro is more closely related to monotremes than to therian mammals while Amphilestes and Amphitherium are more closely related to the therians; as fossils of all three genera are dated about million years ago in the Middle Jurassic , this is a reasonable estimate for the appearance of the crown group.
Kemp has provided a more traditional definition: In , the mammals were comprehensively revised by Malcolm C. McKenna and Susan K. Their book, Classification of Mammals above the Species Level ,  is a comprehensive work on the systematics, relationships and occurrences of all mammal taxa, living and extinct, down through the rank of genus, though molecular genetic data challenge several of the higher level groupings. McKenna inherited the project from Simpson and, with Bell, constructed a completely updated hierarchical system, covering living and extinct taxa that reflects the historical genealogy of Mammalia.
Molecular studies based on DNA analysis have suggested new relationships among mammal families over the last few years. The relationships between these three lineages is contentious, and all three possible different hypotheses have been proposed with respect to which group is basal. These hypotheses are Atlantogenata basal Boreoeutheria , Epitheria basal Xenarthra and Exafroplacentalia basal Afrotheria. Estimates for the divergence times between these three placental groups range from to million years ago, depending on the type of DNA used such as nuclear or mitochondrial  and varying interpretations of paleogeographic data.
The cladogram above is based on Tarver et al. Crown group mammals evolved from earlier mammaliaforms during the Early Jurassic. The cladogram takes Mammalia to be the crown group. The first fully terrestrial vertebrates were amniotes. Like their amphibious tetrapod predecessors, they had lungs and limbs.
Amniotic eggs, however, have internal membranes that allow the developing embryo to breathe but keep water in. Hence, amniotes can lay eggs on dry land, while amphibians generally need to lay their eggs in water. The first amniotes apparently arose in the Pennsylvanian subperiod of the Carboniferous. They descended from earlier reptiliomorph amphibious tetrapods,  which lived on land that was already inhabited by insects and other invertebrates as well as ferns , mosses and other plants.
Within a few million years, two important amniote lineages became distinct: One synapsid group, the pelycosaurs , included the largest and fiercest animals of the early Permian. Therapsids , a group of synapsids, descended from pelycosaurs in the Middle Permian, about million years ago, and became the dominant land vertebrates.
Those stages were characterized by: The Permian—Triassic extinction event about million years ago, which was a prolonged event due to the accumulation of several extinction pulses, ended the dominance of carnivorous therapsids.
By the Jurassic, the dinosaurs had come to dominate the large terrestrial herbivore niches as well. The first mammals in Kemp's sense appeared in the Late Triassic epoch about million years ago , 40 million years after the first therapsids.
They expanded out of their nocturnal insectivore niche from the mid-Jurassic onwards;  The Jurassic Castorocauda , for example, was a close relative of true mammals that had adaptations for swimming, digging and catching fish. The fossil is nearly complete and includes tufts of fur and imprints of soft tissues. The oldest known fossil among the Eutheria "true beasts" is the small shrewlike Juramaia sinensis , or "Jurassic mother from China", dated to million years ago in the late Jurassic.
These are not found in any modern placental, but they are found in marsupials, monotremes, other nontherian mammals and Ukhaatherium , an early Cretaceous animal in the eutherian order Asioryctitheria. This also applies to the multituberculates. These epipubic bones seem to function by stiffening the muscles during locomotion, reducing the amount of space being presented, which placentals require to contain their fetus during gestation periods.
A narrow pelvic outlet indicates that the young were very small at birth and therefore pregnancy was short, as in modern marsupials. This suggests that the placenta was a later development.
One of the earliest known monotremes was Teinolophos , which lived about million years ago in Australia. Hadrocodium , whose fossils date from approximately million years ago, in the early Jurassic, provides the first clear evidence of a jaw joint formed solely by the squamosal and dentary bones; there is no space in the jaw for the articular, a bone involved in the jaws of all early synapsids.
The earliest clear evidence of hair or fur is in fossils of Castorocauda and Megaconus , from million years ago in the mid-Jurassic. In the s, it was suggested that the foramina passages in the maxillae and premaxillae bones in the front of the upper jaw of cynodonts were channels which supplied blood vessels and nerves to vibrissae whiskers and so were evidence of hair or fur;   it was soon pointed out, however, that foramina do not necessarily show that an animal had vibrissae, as the modern lizard Tupinambis has foramina that are almost identical to those found in the nonmammalian cynodont Thrinaxodon.
When endothermy first appeared in the evolution of mammals is uncertain, though it is generally agreed to have first evolved in non-mammalian therapsids. The evolution of erect limbs in mammals is incomplete — living and fossil monotremes have sprawling limbs.
The parasagittal nonsprawling limb posture appeared sometime in the late Jurassic or early Cretaceous; it is found in the eutherian Eomaia and the metatherian Sinodelphys , both dated to million years ago. They are omnipresent in non-placental mammaliformes, though Megazostrodon and Erythrotherium appear to have lacked them.
It has been suggested that the original function of lactation milk production was to keep eggs moist. Much of the argument is based on monotremes, the egg-laying mammals. Therian mammals took over the medium- to large-sized ecological niches in the Cenozoic , after the Cretaceous—Paleogene extinction event approximately 66 million years ago emptied ecological space once filled by non-avian dinosaurs and other groups of reptiles, as well as various other mammal groups,  and underwent an exponential increase in body size megafauna.
Molecular phylogenetic studies initially suggested that most placental orders diverged about to 85 million years ago and that modern families appeared in the period from the late Eocene through the Miocene. The earliest known ancestor of primates is Archicebus achilles  from around 55 million years ago.
Living mammal species can be identified by the presence of sweat glands , including those that are specialized to produce milk to nourish their young. For the most part, these characteristics were not present in the Triassic ancestors of the mammals. The majority of mammals have seven cervical vertebrae bones in the neck , including bats , giraffes , whales and humans. The exceptions are the manatee and the two-toed sloth , which have just six, and the three-toed sloth which has nine cervical vertebrae.
The lungs of mammals are spongy and honeycombed. Breathing is mainly achieved with the diaphragm , which divides the thorax from the abdominal cavity, forming a dome convex to the thorax. Contraction of the diaphragm flattens the dome, increasing the volume of the lung cavity. Air enters through the oral and nasal cavities, and travels through the larynx, trachea and bronchi , and expands the alveoli.
Relaxing the diaphragm has the opposite effect, decreasing the volume of the lung cavity, causing air to be pushed out of the lungs. During exercise, the abdominal wall contracts , increasing pressure on the diaphragm, which forces air out quicker and more forcefully.
The rib cage is able to expand and contract the chest cavity through the action of other respiratory muscles. Consequently, air is sucked into or expelled out of the lungs, always moving down its pressure gradient. The mammalian heart has four chambers, two upper atria , the receiving chambers, and two lower ventricles , the discharging chambers. After gas exchange in the pulmonary capillaries blood vessels in the lungs , oxygen-rich blood returns to the left atrium via one of the four pulmonary veins.
Blood flows nearly continuously back into the atrium, which acts as the receiving chamber, and from here through an opening into the left ventricle.
Most blood flows passively into the heart while both the atria and ventricles are relaxed, but toward the end of the ventricular relaxation period , the left atrium will contract, pumping blood into the ventricle. The heart also requires nutrients and oxygen found in blood like other muscles, and is supplied via coronary arteries. The integumentary system is made up of three layers: The epidermis is typically 10 to 30 cells thick; its main function is to provide a waterproof layer.
Its outermost cells are constantly lost; its bottommost cells are constantly dividing and pushing upward. The middle layer, the dermis, is 15 to 40 times thicker than the epidermis.
The dermis is made up of many components, such as bony structures and blood vessels. The hypodermis is made up of adipose tissue , which stores lipids and provides cushioning and insulation. The thickness of this layer varies widely from species to species; : It is a definitive characteristic of the class. Though some mammals have very little, careful examination reveals the characteristic, often in obscure parts of their bodies.
Herbivores have developed a diverse range of physical structures to facilitate the consumption of plant material. To break up intact plant tissues, mammals have developed teeth structures that reflect their feeding preferences. For instance, frugivores animals that feed primarily on fruit and herbivores that feed on soft foliage have low-crowned teeth specialized for grinding foliage and seeds.
Grazing animals that tend to eat hard, silica -rich grasses, have high-crowned teeth, which are capable of grinding tough plant tissues and do not wear down as quickly as low-crowned teeth. The stomach of Artiodactyls is divided into four sections: After the plant material is consumed, it is mixed with saliva in the rumen and reticulum and separates into solid and liquid material. The solids lump together to form a bolus or cud , and is regurgitated. When the bolus enters the mouth, the fluid is squeezed out with the tongue and swallowed again.
Ingested food passes to the rumen and reticulum where cellulytic microbes bacteria , protozoa and fungi produce cellulase , which is needed to break down the cellulose in plants. The caecum is either absent or short and simple, and the large intestine is not sacculated or much wider than the small intestine. The mammalian excretory system involves many components. Like most other land animals, mammals are ureotelic , and convert ammonia into urea , which is done by the liver as part of the urea cycle.
Only the mammalian kidney has a bean shape, although there are some exceptions, such as the multilobed reniculate kidneys of pinnipeds, cetaceans and bears.
In the embryo, the embryonic cloaca divides into a posterior region that becomes part of the anus, and an anterior region that has different fates depending on the sex of the individual: As in all other tetrapods, mammals have a larynx that can quickly open and close to produce sounds, and a supralaryngeal vocal tract which filters this sound.
The lungs and surrounding musculature provide the air stream and pressure required to phonate. The larynx controls the pitch and volume of sound, but the strength the lungs exert to exhale also contributes to volume. More primitive mammals, such as the echidna, can only hiss, as sound is achieved solely through exhaling through a partially closed larynx. Other mammals phonate using vocal folds , as opposed to the vocal cords seen in birds and reptiles. The movement or tenseness of the vocal folds can result in many sounds such as purring and screaming.
Mammals can change the position of the larynx, allowing them to breathe through the nose while swallowing through the mouth, and to form both oral and nasal sounds; nasal sounds, such as a dog whine, are generally soft sounds, and oral sounds, such as a dog bark, are generally loud.
Some mammals have a large larynx and thus a low-pitched voice, namely the hammer-headed bat Hypsignathus monstrosus where the larynx can take up the entirety of the thoracic cavity while pushing the lungs, heart, and trachea into the abdomen.
Ultrasound is inaudible to birds and reptiles, which might have been important during the Mesozoic, when birds and reptiles were the dominant predators. This private channel is used by some rodents in, for example, mother-to-pup communication, and by bats when echolocating. Toothed whales also use echolocation, but, as opposed to the vocal membrane that extends upward from the vocal folds, they have a melon to manipulate sounds.
Some mammals, namely the primates, have air sacs attached to the larynx, which may function to lower the resonances or increase the volume of sound. The vocal production system is controlled by the cranial nerve nuclei in the brain, and supplied by the recurrent laryngeal nerve and the superior laryngeal nerve , branches of the vagus nerve.
The vocal tract is supplied by the hypoglossal nerve and facial nerves. Electrical stimulation of the periaqueductal gray PEG region of the mammalian midbrain elicit vocalizations. The ability to learn new vocalizations is only exemplified in humans, seals, cetaceans, elephants and possibly bats; in humans, this is the result of a direct connection between the motor cortex , which controls movement, and the motor neurons in the spinal cord.
The fur of mammals has many uses protection, sensory purposes, waterproofing, and camouflage, with the primary usage being thermoregulation. Mammalian coats are colored for a variety of reasons, the major selective pressures including camouflage , sexual selection , communication and physiological processes such as temperature regulation. Camouflage is a powerful influence in a large number of mammals, as it helps to conceal individuals from predators or prey.
Mammals with a darker colored coat can absorb more heat from solar radiation, and stay warmer, and some smaller mammals, such as voles , have darker fur in the winter. The white, pigmentless fur of arctic mammals, such as the polar bear, may reflect more solar radiation directly onto the skin. The ancestral condition for mammal reproduction is the birthing of relatively undeveloped, either through direct vivipary or a short period as soft-shelled eggs.
This is likely due to the fact that the torso could not expand due to the presence of epipubic bones. The oldest demonstration of this reproductive style is with Kayentatherium , which produced undeveloped perinates , but at much higher litter sizes than any modern mammal, 38 specimens. In male placentals, the penis is used both for urination and copulation.
Depending on the species, an erection may be fueled by blood flow into vascular, spongy tissue or by muscular action. A penis may be contained in a sheath when not erect, and some placentals also have a penis bone baculum. Marsupials typically have forked penises while the monotreme penis generally has four heads with only two functioning. The testes of most mammals descend into the scrotum which is typically posterior to the penis but is often anterior in marsupials.
Female mammals generally have a clitoris , labia majora and labia minora on the outside, while the internal system contains paired oviducts , uteri , cervices and a vagina. Marsupials have two lateral vaginas and a medial vagina. The "vagina" of monotremes is better understood as a "urogenital sinus". The uterine systems of placental mammals can vary between a duplex, were there are two uteri and cervices which open into the vagina, a bipartite, were two uterine horns have a single cervix that connects to the vagina, a bicornuate, which consists where two uterine horns that are connected distally but separate medially creating a Y-shape, and a simplex, which has a single uterus.
Most mammals are viviparous , giving birth to live young. However, the five species of monotreme, the platypus and the four species of echidna, lay eggs. The monotremes have a sex determination system different from that of most other mammals. Viviparous mammals are in the subclass Theria; those living today are in the marsupial and placental infraclasses. Marsupials have a short gestation period, typically shorter than its estrous cycle and gives birth to an undeveloped newborn that then undergoes further development; in many species, this takes place within a pouch-like sac, the marsupium , located in the front of the mother's abdomen.
This is the plesiomorphic condition among viviparous mammals; the presence of epipubic bones in all non-placental mammals prevents the expansion of the torso needed for full pregnancy. The mammary glands of mammals are specialized to produce milk, the primary source of nutrition for newborns.
The monotremes branched early from other mammals and do not have the nipples seen in most mammals, but they do have mammary glands. The young lick the milk from a mammary patch on the mother's belly. Nearly all mammals are endothermic "warm-blooded".
Most mammals also have hair to help keep them warm. Like birds, mammals can forage or hunt in weather and climates too cold for ectothermic "cold-blooded" reptiles and insects. Endothermy requires plenty of food energy, so mammals eat more food per unit of body weight than most reptiles. A rare exception, the naked mole-rat produces little metabolic heat, so it is considered an operational poikilotherm.
Among mammals, species maximum lifespan varies significantly for example the shrew has a lifespan of two years, whereas the oldest bowhead whale is recorded to be years. In a study by Hart and Setlow,  it was found that DNA excision repair capability increased systematically with species lifespan among seven mammalian species.
Species lifespan was observed to be robustly correlated with the capacity to recognize DNA double-strand breaks as well as the level of the DNA repair protein Ku Most vertebrates—the amphibians, the reptiles and some mammals such as humans and bears—are plantigrade , walking on the whole of the underside of the foot. Many mammals, such as cats and dogs, are digitigrade , walking on their toes, the greater stride length allowing more speed.
Digitigrade mammals are also often adept at quiet movement. This even further increases their stride length and thus their speed. Giant anteaters  and platypuses  are also knuckle-walkers. Some mammals are bipeds , using only two limbs for locomotion, which can be seen in, for example, humans and the great apes. Bipedal species have a larger field of vision than quadrupeds, conserve more energy and have the ability to manipulate objects with their hands, which aids in foraging.
Instead of walking, some bipeds hop, such as kangaroos and kangaroo rats. Animals will use different gaits for different speeds, terrain and situations. For example, horses show four natural gaits, the slowest horse gait is the walk , then there are three faster gaits which, from slowest to fastest, are the trot , the canter and the gallop. Animals may also have unusual gaits that are used occasionally, such as for moving sideways or backwards. For example, the main human gaits are bipedal walking and running , but they employ many other gaits occasionally, including a four-legged crawl in tight spaces.
Gaits can be grouped into categories according to their patterns of support sequence. For quadrupeds, there are three main categories: Running is considered to occur when at some points in the stride all feet are off the ground in a moment of suspension.
Arboreal animals frequently have elongated limbs that help them cross gaps, reach fruit or other resources, test the firmness of support ahead and, in some cases, to brachiate swing between trees. In the spider monkey, the tip of the tail has either a bare patch or adhesive pad, which provides increased friction.
Claws can be used to interact with rough substrates and reorient the direction of forces the animal applies. This is what allows squirrels to climb tree trunks that are so large to be essentially flat from the perspective of such a small animal. However, claws can interfere with an animal's ability to grasp very small branches, as they may wrap too far around and prick the animal's own paw.
Frictional gripping is used by primates, relying upon hairless fingertips. Squeezing the branch between the fingertips generates frictional force that holds the animal's hand to the branch. However, this type of grip depends upon the angle of the frictional force, thus upon the diameter of the branch, with larger branches resulting in reduced gripping ability. To control descent, especially down large diameter branches, some arboreal animals such as squirrels have evolved highly mobile ankle joints that permit rotating the foot into a 'reversed' posture.
This allows the claws to hook into the rough surface of the bark, opposing the force of gravity. Small size provides many advantages to arboreal species: Both pitching and tipping become irrelevant, as the only method of failure would be losing their grip. Bats are the only mammals that can truly fly. They fly through the air at a constant speed by moving their wings up and down usually with some fore-aft movement as well.
Because the animal is in motion, there is some airflow relative to its body which, combined with the velocity of the wings, generates a faster airflow moving over the wing. This generates a lift force vector pointing forwards and upwards, and a drag force vector pointing rearwards and upwards. The upwards components of these counteract gravity, keeping the body in the air, while the forward component provides thrust to counteract both the drag from the wing and from the body as a whole.
The wings of bats are much thinner and consist of more bones than that of birds, allowing bats to maneuver more accurately and fly with more lift and less drag. These sensitive areas are different in bats, as each bump has a tiny hair in the center, making it even more sensitive and allowing the bat to detect and collect information about the air flowing over its wings, and to fly more efficiently by changing the shape of its wings in response.
Fossorial creatures live in subterranean environments. Many fossorial mammals were classified under the, now obsolete, order Insectivora , such as shrews, hedgehogs and moles.
Fossorial mammals have a fusiform body, thickest at the shoulders and tapering off at the tail and nose. Unable to see in the dark burrows, most have degenerated eyes, but degeneration varies between species; pocket gophers , for example, are only semi-fossorial and have very small yet functional eyes, in the fully fossorial marsupial mole the eyes are degenerated and useless, talpa moles have vestigial eyes and the cape golden mole has a layer of skin covering the eyes.
External ears flaps are also very small or absent. Truly fossorial mammals have short, stout legs as strength is more important than speed to a burrowing mammal, but semi-fossorial mammals have cursorial legs. The front paws are broad and have strong claws to help in loosening dirt while excavating burrows, and the back paws have webbing, as well as claws, which aids in throwing loosened dirt backwards. Most have large incisors to prevent dirt from flying into their mouth.
Fully aquatic mammals, the cetaceans and sirenians , have lost their legs and have a tail fin to propel themselves through the water.
Flipper movement is continuous. Whales swim by moving their tail fin and lower body up and down, propelling themselves through vertical movement, while their flippers are mainly used for steering. Their skeletal anatomy allows them to be fast swimmers.
Most species have a dorsal fin to prevent themselves from turning upside-down in the water. The forelimbs are paddle-like flippers which aid in turning and slowing. Semi-aquatic mammals, like pinnipeds, have two pairs of flippers on the front and back, the fore-flippers and hind-flippers.
The elbows and ankles are enclosed within the body. In addition to their streamlined bodies, they have smooth networks of muscle bundles in their skin that may increase laminar flow and make it easier for them to slip through water.
They also lack arrector pili , so their fur can be streamlined as they swim. Many mammals communicate by vocalizing. Vocal communication serves many purposes, including in mating rituals, as warning calls ,  to indicate food sources, and for social purposes. Males often call during mating rituals to ward off other males and to attract females, as in the roaring of lions and red deer.
For example, if an alarm call signals a python, the monkeys climb into the trees, whereas the eagle alarm causes monkeys to seek a hiding place on the ground. Some of the rumbling calls are infrasonic , below the hearing range of humans, and can be heard by other elephants up to 6 miles 9. Mammals signal by a variety of means. Many give visual anti-predator signals , as when deer and gazelle stot , honestly indicating their fit condition and their ability to escape,   or when white-tailed deer and other prey mammals flag with conspicuous tail markings when alarmed, informing the predator that it has been detected.
To maintain a high constant body temperature is energy expensive — mammals therefore need a nutritious and plentiful diet. While the earliest mammals were probably predators, different species have since adapted to meet their dietary requirements in a variety of ways. Some eat other animals — this is a carnivorous diet and includes insectivorous diets. Other mammals, called herbivores , eat plants, which contain complex carbohydrates such as cellulose.
An herbivorous diet includes subtypes such as granivory seed eating , folivory leaf eating , frugivory fruit eating , nectarivory nectar eating , gummivory gum eating and mycophagy fungus eating.
The digestive tract of an herbivore is host to bacteria that ferment these complex substances, and make them available for digestion, which are either housed in the multichambered stomach or in a large cecum. Carnivorous mammals have a simple digestive tract because the proteins , lipids and minerals found in meat require little in the way of specialized digestion.
Exceptions to this include baleen whales who also house gut flora in a multi-chambered stomach, like terrestrial herbivores. The size of an animal is also a factor in determining diet type Allen's rule. Since small mammals have a high ratio of heat-losing surface area to heat-generating volume, they tend to have high energy requirements and a high metabolic rate. Larger animals, on the other hand, generate more heat and less of this heat is lost. They can therefore tolerate either a slower collection process carnivores that feed on larger vertebrates or a slower digestive process herbivores.
The only large insectivorous mammals are those that feed on huge colonies of insects ants or termites. Some mammals are omnivores and display varying degrees of carnivory and herbivory, generally leaning in favor of one more than the other. Since plants and meat are digested differently, there is a preference for one over the other, as in bears where some species may be mostly carnivorous and others mostly herbivorous.
The dentition of hypocarnivores consists of dull, triangular carnassial teeth meant for grinding food. Hypercarnivores, however, have conical teeth and sharp carnassials meant for slashing, and in some cases strong jaws for bone-crushing, as in the case of hyenas , allowing them to consume bones; some extinct groups, notably the Machairodontinae , had saber-shaped canines. Some physiological carnivores consume plant matter and some physiological herbivores consume meat.
From a behavioral aspect, this would make them omnivores, but from the physiological standpoint, this may be due to zoopharmacognosy. Physiologically, animals must be able to obtain both energy and nutrients from plant and animal materials to be considered omnivorous. Thus, such animals are still able to be classified as carnivores and herbivores when they are just obtaining nutrients from materials originating from sources that do not seemingly complement their classification.
Many mammals, in the absence of sufficient food requirements in an environment, suppress their metabolism and conserve energy in a process known as hibernation. In intelligent mammals, such as primates, the cerebrum is larger relative to the rest of the brain.
Intelligence itself is not easy to define, but indications of intelligence include the ability to learn, matched with behavioral flexibility.
Rats , for example, are considered to be highly intelligent, as they can learn and perform new tasks, an ability that may be important when they first colonize a fresh habitat. In some mammals, food gathering appears to be related to intelligence: Tool use by animals may indicate different levels of learning and cognition.
Brain size was previously considered a major indicator of the intelligence of an animal. Since most of the brain is used for maintaining bodily functions, greater ratios of brain to body mass may increase the amount of brain mass available for more complex cognitive tasks.
Comparison of a particular animal's brain size with the expected brain size based on such allometric analysis provides an encephalisation quotient that can be used as another indication of animal intelligence. Self-awareness appears to be a sign of abstract thinking. Self-awareness, although not well-defined, is believed to be a precursor to more advanced processes such as metacognitive reasoning.
The traditional method for measuring this is the mirror test , which determines if an animal possesses the ability of self-recognition. Eusociality is the highest level of social organization. These societies have an overlap of adult generations, the division of reproductive labor and cooperative caring of young.
Usually insects, such as bees , ants and termites, have eusocial behavior, but it is demonstrated in two rodent species: Presociality is when animals exhibit more than just sexual interactions with members of the same species, but fall short of qualifying as eusocial. That is, presocial animals can display communal living, cooperative care of young, or primitive division of reproductive labor, but they do not display all of the three essential traits of eusocial animals.
Humans and some species of Callitrichidae marmosets and tamarins are unique among primates in their degree of cooperative care of young. A fission-fusion society is a society that changes frequently in its size and composition, making up a permanent social group called the "parent group".
Permanent social networks consist of all individual members of a community and often varies to track changes in their environment. In a fission—fusion society, the main parent group can fracture fission into smaller stable subgroups or individuals to adapt to environmental or social circumstances.
For example, a number of males may break off from the main group in order to hunt or forage for food during the day, but at night they may return to join fusion the primary group to share food and partake in other activities.
Many mammals exhibit this, such as primates for example orangutans and spider monkeys ,  elephants,  spotted hyenas ,  lions,  and dolphins. Solitary animals defend a territory and avoid social interactions with the members of its species, except during breeding season. This is to avoid resource competition, as two individuals of the same species would occupy the same niche, and to prevent depletion of food. In a hierarchy , individuals are either dominant or submissive.
A despotic hierarchy is where one individual is dominant while the others are submissive, as in wolves and lemurs,  and a pecking order is a linear ranking of individuals where there is a top individual and a bottom individual.
Pecking orders may also be ranked by sex, where the lowest individual of a sex has a higher ranking than the top individual of the other sex, as in hyenas. All higher mammals excluding monotremes share two major adaptations for care of the young: These imply a group-wide choice of a degree of parental care. They may build nests and dig burrows to raise their young in, or feed and guard them often for a prolonged period of time. Many mammals are K-selected , and invest more time and energy into their young than do r-selected animals.
When two animals mate, they both share an interest in the success of the offspring, though often to different extremes. Mammalian females exhibit some degree of maternal aggression, another example of parental care, which may be targeted against other females of the species or the young of other females; however, some mammals may "aunt" the infants of other females, and care for them.
Mammalian males may play a role in child rearing, as with tenrecs, however this varies species to species, even within the same genus. For example, the males of the southern pig-tailed macaque Macaca nemestrina do not participate in child care, whereas the males of the Japanese macaque M.
Non-human mammals play a wide variety of roles in human culture. They are the most popular of pets , with tens of millions of dogs, cats and other animals including rabbits and mice kept by families around the world.