What makes us human? It’s a big question. Is it our language, our intelligence, or even
something a simple as our thumbs? Something has to separate us from our slightly dimmer
ape cousins and ever since Darwin popularised the idea of natural selection and evolution
academics have been arguing about what made humans so unique and dominant. Proposed theories
include Man the Hunter, Man the Runner, and even Man the Aquatic ape. But today we’re
going to look at a theory put forward by primatologist Richard Wrangham, Man the Chef. Could something
like cooking have given us that evolutionary advantage, transforming us from ape into human?
Let’s find out.
Roll Intro
We are the only species that cooks our food. Language, intelligence, and thumbs can be
found in other species across our planet, but only humans get pizza.
It’s a common belief that cooking is a recent innovation. Something Homo Sapiens invented
after already assuming our modern evolutionary form. We imagine our natural diet as one of
raw meat, fruit, and vegetables not unlike that of Chimps. The core belief of the Raw
Foodist movement is that we’d be a lot healthier if we only ate raw food. Can we actually survive
on raw food though?
There are Medieval reports of Mongol soldier riding for weeks without starting a single
fire. Draining blood from their horses for sustenance or throwing a chunk of meat under
their saddles in the morning, which friction would tenderise for their evening meal. Thus
inventing steak Tartare. This raw diet obviously didn’t have any negative effects on Mongols
soldiers, judging from their ability to conquer all the things. Many people tout this as an
example of the strength of the raw food diet. Forgetting that as soon as they stopped riding
the Mongols were just as eager as anyone to partake in a nice Mongolian BBQ. The Mongols
may prove that we can survive on raw food for some time, but Wrangham believes that
we evolved to eat cooked food.
Let’s look at an experiment conducted by the BBC in 2006. They took 9 dangerously unhealthy
people, stuck em in an enclosure in Paignton Zoo and only feed them raw fruit, veg, nuts,
and a small amount of cooked fish. They all ate their recommended caloric intakes, between
2000-2300 calories. For the participants the results were great. Their blood pressure fell
to normal levels and they lost an average of 4.4kg each. Great for modern overweight
people but if our ancestors ate such a high quality diet, took in all their needed calories
and still lost weight it would be devastating from an evolutionary standpoint. Chimps would
have grown fat on this diet, why didn’t humans?
Well for one, raw food diets always result in weight lose. Among people that eat raw
food diets ⅓ show signs of chronic energy deficiency. In women raw foodists 50% stop
menstruating, which while protecting them from bears, it does have serious consequences
for fertility. This isn’t an attack on the Raw Food diet as it’s a diet many people
enjoy. However, its effects would be horrible for the population of our hunter-gather ancestors.
Just from an evolutionary standpoint reduced fertility in those eating raw food diets would
have given those eating cooked food a huge baby-making advantage.
We lose weight on raw food diets because cooked foods provide more energy, calorie-wise. Energy
gain is our primary reason for eating. You may be wondering why cooked food provides
more energy. It does so because reducing the size of food particles through crushing and
grinding or by softening them through cooking makes them easier to digest. Hard foods are
predictably tougher to digest, meaning that you need to use more energy to break them
down. We even have research proving this.
Japanese scientists gave ten rats ordinary food pellets which required a fair amount
of chewing. They gave another 10 rats the exact same pellets except that they had been
soften by increasing their air content. Everything else in the rats lives stayed the same. After
32 weeks the soft-pellets rats were an average of 37 grams heavier and had 30% more abdominal
fat. Enough to be classified as obese. The soft food was easier to digest so the rats
didn’t have to expend as much energy digesting their food. Resulting in a net energy gain.
Ok, so cooking foods gave our ancestors more energy. What does that mean? Well first we’ll
have to look at something called an evolutionary trade-off. In order to increase one trait
you need to decrease another. Ostriches are excellent runners at the expense of flying,
turtles have protective shells but sacrifice mobility, and giraffes have long necks but
it makes shopping for scarves awkward.
During our evolution there was a digestive evolutionary trade-off. Compared to other
apes we have tiny mouths, stomachs, guts, and colons along with weak jaws. Wrangham
speculates that as our ancestors started eating cooked foods everyday natural selection began
to favour those with smaller and less demanding guts. Digestion can require as much energy
as movement does, so those with smaller guts wasted less energy digesting their food. Smaller
guts provided an energy surplus. Our guts are 40% smaller than would be expected in
a primate our size. So what did we trade our digestive system for? Bigger brains! Primates
with smaller guts have bigger brains on average. Our big brains were paid for by our small
guts. This is known as the expensive tissue hypothesis.
Wrangham suggests that by using the expensive tissue hypothesis we can assume that Home
Erectus came about because of cooking. His reasoning is that before 2 million years ago
there is no evidence of the controlled use of fire. And after that there are 3 major
changes that result in new species of Homo. Homo Erectus 1.8 million years ago, Homo Heidelbergensis
800,000 years ago, and Homo Sapien 200,000 years ago. He rules out the changes from Erectus
to Heidelbergensis and from Heidelbergensis to Sapien because the changes are too small
to indicate a massive change in diet, they were mostly physical changes in the face and
brain enlargements. So the only remaining option is the shift from our apelike ancestors
the Homo Habilis into Homo Erectus 1.8 million years ago. To understand why Wrangham pinpoints
this shift as the origin of cooking we need to take a closer look at both of these species.
Homo Habilis were much better climbers than Erectus, they were much smaller standing at
around 1.2 metres, and had much bigger teeth than any other species of Homo. Indicating
that they chewed a lot. Habilines are so apelike that there is disagreement on whether they
should even be classified as Homo.
Now let’s look at Homo Erectus. With their evolution we see the largest reduction in
tooth size, the largest increase in body size and a loss of shoulder and arm adaptations
that helped us climb. Erectus had a smaller gut and a much larger brain, 42% larger to
be exact. They were also the first species of Homo to spread out of Africa. These reductions
in tooth and gut size along with the ability to move into unknown habitats show us that
Erectus had clearly developed some new way of extracting energy from their environments.
Wrangham suggests the it was cooking.
Now that Wrangham has shown that cooking may have transformed our ape bodies into modern
human ones he goes on to explain how it also created our minds and societies. Let’s look
at some of the examples he gives.
Chewing: Raw food takes forever to chew. Chimps in Tanzania spend more than 6 hours a day
chewing. Chewing is their full time job. Humans by comparison spend very little time chewing.
If we had to eat like Chimps it’s estimated that we would spend 42% of our day chewing.
Currently we spend less than 5% of our day chewing. This left us with a lot of time to
hunt, invent, and eh...make more people. Weaning: Babies are weak and constantly trying
to die. Their teeth are useless meaning they can’t chew anything solid for years. But
softening food allowed us to switch from milk to solid food much earlier. Giving us access
to more energy and ensuring healthier development. Nakedness: Fur keeps animals warm and negates
the need for pants. Human however are naked and require pants. This is fire’s fault
because fire gave us the ability to stay warm. So those with less fur didn’t freeze to
death and luckily enough they got the benefit of being able to run farther without overheating.
Resulting in them being better hunters and therefore they passed on their genes successfully.
Because everyone knows the best way to land a lady is to kill a large African mammal and
present it to her. That’s how cooking made us human. The biological
benefits of cooking our food forged the bodies and minds we needed to become highly intelligent
and social creatures. The rest is history…
If you found this video entertaining then i would high recommend you check out this
video by Smart by Design. It's about why humans evolved bipedalism and it's fascinating. Click
the I in the corner of the screen or see the link in the description.
Now this is only one hypothesis out of many on how humans evolved. I included what I think
are Richard Wrangham’s strongest points from his book Catching Fire: How Cooking Made
Us Human. Others I left out either because I found them unconvincing, such as his theory
on the evolution of marriage due to cooking, and because including them all would result
in an extremely long video. I recommend you check out his book and all of my sources in
the description. Down there you’ll also find links to my social media and merchandise.
Thanks for watching.