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Recently, there was a comment left by Carl on my Veganism post from October of 2007. In his comment, he made the following claim:

Just before man began to take it’s first steps towards being the humans we are today, it is actually a fact that humans began to eat legumes. Legumes have a high protein content, and also many essential vitamins and nutrients necessary for the brains development, thus making your argument completely invalid, and void of any factual basis.

My first thought was that it sounds like vegan propaganda intended to really drive home the point that humans evolved as vegetarians. As far as I know, legumes (beans) don’t contain the long-chain fatty acids EPA and DHA that are necessary for the brain’s development. But I decided to look a bit further into it. Here’s what I’ve come up with. I would love for someone to prove otherwise, as when it comes down to it, I have no dog in the fight. I simply want to understand what works best for my body. Carl, if you’re out there, please provide some references to back your claim up.

I’ll start with just some evidence that has been found of when certain foods entered the human diet. Evidence has been found regarding the use of seafood in the diet of H. sapiens in Africa:(1)

“Our findings show that at 164,000 years ago in coastal South Africa humans expanded their diet to include shellfish and other marine resources, perhaps as a response to harsh environmental conditions,”

But that’s only looking at seafood. What about terrestrial flesh?(2)

Carnivorous humans go back a long way. Stone tools for butchering meat, and animal bones with corresponding cut marks on them, first appear in the fossil record about 2.5 million years ago.

Two-and-a-half million years is a long time. Since humans have been eating meat for a couple million years, it follows that we have to find evidence of legumes being consumed more than 2.5 million years ago. Since the Agricultural Revolution, which brought along the domestication of grains, legumes, and animals, only occurred about 10,000 years ago, the “beans as primary protein” crowd is off to a bad start. The only mention of plant seed (legumes fitting this category) consumption before this time that I’ve been able to find is 160,000 years ago.(3) That there seems to be enough to close the door, but let’s explore further.

Let’s look at one other thing that it seems preclude legumes from having been a significant contributor to the early protohuman diet: fire. The earliest evidence of human control of fire is 1.4-1.5 million years ago, though this is disputed. The earliest undisputed evidence is only 230,000 years ago, only 1/10th the time that evidence shows the human lineage to have consumed meat.(4) Let’s compromise and say 750,000 years, some three times as long as is unequivocally accepted.

Why is fire important to this discussion? Because legumes are full of antinutrients that must be neutralized in some way lest they wreak havoc on the body. There are a few ways to neutralize these antinutrients: fermentation, sprouting, and soaking before long cooking.(5) We know that soybeans are harmful if not properly fermented.(6) Other legumes also share some antinutrient features:(7)

As with grain consumption, there are hunter-gatherers who have been documented eating legumes. However, under most cases, the legumes are cooked or the tender, early sprouts eaten raw rather than the mature pod. Some legumes in their raw state are less toxic than others. However, most legumes in their mature state are non-digestible and/or toxic to most mammals when eaten in even moderate quantities.

There’s also the fact that certain vitamins essential to human health are only available in animal products, such as vitamin B12. Any diet that requires supplementation to be complete is obviously not one that humans could have evolved with nor one that is optimal.

Let’s take a look at the construction of the human digestive tract and compare it to purely herbivorous and carnivorous animals. Many pro-vegetarian sites come up with lots of “proof” that the human digestive tract is identical to that of herbivores.(8)(9) You’ll find claims like “humans don’t have claws, which all carnivores have,” “humans don’t have sharp teeth” (except those ones called canines!), and “humans have digestive tracts 10-12 times their body length just like herbivores.” But if we look at Dr. Loren Cordain’s analysis, he points out that humans do have small sharp teeth in front (those aforementioned “canines”) and actually have a digestive tract shorter than that of the dog.(10) The key point is that humans are omnivores not carnivores, so any comparison to carnivores or herbivores is going to turn up some similarities.

There are also quite a few other attempts to discredit meat-eating as a whole that vegetarians like to use. One site makes the following point:(8)

However, eating raw or bloody meat disgust us as humans. Therefore, we must cook it and season it to buffer the taste of flesh.

That, my friends, is societal conditioning. There are plenty of people that eat raw meat (steak tartare anyone?), raw eggs, and raw seafood (oysters-on-the-half-shell?). Many Hispanic countries have a dish known as ceviche (or seviche or cebiche) which is raw seafood marinated in citrus juices to “cook” the flesh. But rest assured that heat never touches the meat. I know plenty of people that eat extremely rare meat, me being one of them. Cooking meat is an aversion to parasites, not that we can’t or won’t eat raw meat. And disgust at the sight, smell, or taste of raw meat is pure societal conditioning.

And then there’s this claim:(9)

No matter how much fat carnivores eat, they do not develop atheroschlerosis. It’s virtually impossible, for example, to produce atheroschlerosis in the dog even when 100 grams of cholesterol are added to its meat ration. (This amount of cholesterol is approximately 200 times the average amount that human beings in the USA eat each day!) In contrast, herbivores rapidly develop atheroschlerosis if they are fed foods, namely fat and cholesterol, intended for carnivores…

But that’s based on faulty logic regarding the role of cholesterol and fat in the atherogenic process.

Here’s a fun one: brain size and intelligence. If you look at this site, we see the claim that carnivores have small brains and are less capable of adaptive reasoning, while vegetarians and humans have large brains and are able to rationalize. First, has anyone seen even the dumbest dog learn how to sit, lay, and roll over in exchange for a treat? That sure seems like adaptive behavior to me, but we’ll move on to something more concrete. Brain-to-body-mass ratio, or the Encephalization Quotient (EQ), “is a rough estimate of the possible intelligence of an organism.”(11) Dolphins have the largest EQ of all cetaceans. The diet of dolphins is mainly fish and squid and they are commonly considered one of the most intelligent animals around. Sharks, definitely a carnivore, have the highest EQ of all fish species. Sharks are at least intelligent enough to figure out how to work together.(12) But what about mammals?

Looking at a chart of mammalian EQs shows that humans (which we have to exclude for this discussion), dolphins, chimpanzees, and rhesus monkeys top the list.(13) We’ve already discussed the seafood-heavy diet of dolphins. Chimpanzees and rhesus monkeys eat lots of fruit, but rhesus monkeys are also known to tap into invertebrates and Jane Goodall, an excellent source for information on chimpanzees, has mentioned that chimps hunt prey like red colobus monkeys and eat some 35 species of vertebrates.(14) So it looks like the rhesus monkey is the closest thing to a vegetarian at the top of the list. But the herbivores sure do bring up the bottom: rabbit, sheep, horse. I think we can all agree that little of value one way or the other can be gleaned from this and it’s merely a “fact” the author assumed wouldn’t be checked. That’s ignoring the circular logic of “humans are vegetarians because vegetarians have larger brains and humans have the largest brains.”

Finally, there have been points in the history of the Earth that it was covered in ice. In the industry, we call these “ice ages” (no, not the movies). All sarcasm aside (for at least a sentence or two), there have been at least four of these events. During these extreme cold periods, vegetable sustenance would be difficult, if not impossible to find, pretty much making it mandatory that humans subsisted on meat during these times.

What it boils down to is that I can’t find any facts to support the notion that legumes were consumed heavily in the human diet prior to the Agricultural Revolution some 10 millennia ago. Given all of the evidence for meat consumption in the evolutionary human diet and the lack of evidence for legume consumption, it defies logic to make a claim that legumes made a major contribution to human evolution. Have I missed something? Does someone have a source that can back up the legumes claim?

Sources:
(1) Earliest Evidence Of Modern Humans Detected
(2) “Evolving to Eat Mush”: How Meat Changed Our Bodies
(3) Natural food-Grains Beans and Seeds
(4) When was fire first controlled by human beings?
(5) Legumes (beans): Poor source of hard-to digest nutrition
(6) Newest Research On Why You Should Avoid Soy
(7) The Late Role of Grains and Legumes in the Human Diet, and Biochemical Evidence of their Evolutionary Discordance
(8) How humans are not physically created to eat meat
(9) Are humans designed to eat meat?
(10) Functional and Structural Comparison of Man’s Digestive Tract with that of a Dog and Sheep
(11) Encephalization Quotient - Wikipedia
(12) Smart Sharks
(13) A New Hypothesis for Sleep: Tuning for Criticality, Table 1 on Page 4
(14) The Predatory Behavior and Ecology of Wild Chimpanzees


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