5

votes

Why haven't meat-eating monkeys evolved bigger brains?

Answered on September 12, 2014
Created December 23, 2011 at 7:06 PM

I have read of species of monkeys who eat meat, and not only monkeys, why do let's say a lion not evolve bigger brains as we did? They are also meat eaters.

7a6529ea25b655132fe58d793f95547a

(2030)

on March 25, 2013
at 05:18 PM

Very interesting answer, thank you.

Bb3d1772b28c02da2426e40dfcb533f5

(5381)

on June 17, 2012
at 02:06 AM

I beleive its the social complexity that seems to require a more complex brain, and often other intelligence is an offshoot of that. Examples of higher mammals - dolphins/whales, elephants, primates. Dolphins have more evolved frontal lobes than humans. Then again, caledonian(sp) crows can make tools. I guess it relates more to whether there is evolutionary pressure to develop intelligence. Lions do what lions do just fine, carnivore hunting is not that complex. *shrugs*

Medium avatar

(19469)

on June 16, 2012
at 07:18 PM

O_o (peeks behind the curtain)

Medium avatar

(19469)

on June 16, 2012
at 07:17 PM

The difference between monkeys, lions, etc. and humans isn't about meat or vegetables. It is about cooked food vs raw.

A97b68379a576dfa764a4828304d2efb

(4181)

on June 16, 2012
at 06:35 PM

+1 for this answer being spot on and cracking me up.

96440612cf0fcf366bf5ad8f776fca84

(19413)

on December 25, 2011
at 10:48 PM

How else do you expect to "prove" the idea that meat eating causes simians to evolve bigger brains? I've certainly no ideas as to how to induce that. Certainly force feeding monkeys meat and teaching them to hunt is plausible, but how would you measure brain growth in just a few generations and prove a theory like this one?

Ac9425a387b78cb37a01972fe848bddb

(655)

on December 25, 2011
at 06:23 PM

Not at all, however I love exploring my consciousness!

956bcad1d462d433a4e1e22f6e3355d5

(1191)

on December 25, 2011
at 01:24 PM

LOL. "Just wait a few million years". Guess we can only speculate about the future or do you have something to admit? The invention of a time machine perhaps? :)

96bf58d8c6bd492dc5b8ae46203fe247

(37227)

on December 24, 2011
at 03:52 AM

@sage, are you asking me? LOL

4145b36f1488224964edac6258b75aff

(7821)

on December 24, 2011
at 03:48 AM

@Ramsey: Stoned ape is obviously the way we evolved. Can't believe it's not in the textbooks, blatant conspiracy by the man.

518bce04b12cd77741237e1f61075194

(11577)

on December 24, 2011
at 03:36 AM

Yeah, this always bugs me too. It's like the creationist argument "If we came from monkey's, why haven't all the monkey's turned into people yet?". Maybe because monkey's are really good at what they do, and we are good at what we do. Niches are filled, in no particular order and in no particular design. It just happens!

B4e1fa6a8cf43d2b69d97a99dfca262c

(10255)

on December 24, 2011
at 03:20 AM

are you looking for justification for conuming large amounts of hallucinogenic mushrooms?

93ae9f2d376e5426e891a9b58d8302fa

(2936)

on December 24, 2011
at 02:23 AM

We were trackers, needed to track game, but our upright posture raised our noses too high off the ground for natural selection to handle the problem the usual way. So instead of wasting neurons on olfactory tissue, a slight shift was arranged. But that doesn't make us smart. Ask any bloodhound, he'll tell you we're as stupid as they come. But you have to know the secret bloodhound language, communismellication. Good luck trying to wrap your huge flabby brain around that.

Medium avatar

(10663)

on December 24, 2011
at 01:07 AM

A good article about when our brains started getting bigger due to cooking our food to read is Food for Thought in Science June 15, 2007, Vol 316.

D1908552223e8a97b17f02a90cf795bf

(487)

on December 24, 2011
at 12:57 AM

Isn't it more about eating the actual brain, instead of the meat of an animal?

Ac9425a387b78cb37a01972fe848bddb

(655)

on December 24, 2011
at 12:14 AM

What are your thoughts on Terrance Mckenna's "stoned Ape Theory"?

164ed7cd8d84c926bc66f366619bf853

(495)

on December 23, 2011
at 11:07 PM

#3 was my biggest curiosity. Thanks!

96bf58d8c6bd492dc5b8ae46203fe247

(37227)

on December 23, 2011
at 07:26 PM

That doesn't resonate much with me but I do agree that we went back for more of things we tried and a) didn't get sick/die and b) had great flavor or pleasant effects. I'm thinking of fermented things, fruit, etc.

Ac9425a387b78cb37a01972fe848bddb

(655)

on December 23, 2011
at 07:18 PM

Do you think hallucinogenic mushrooms had any part in our evolution? When the rainforest receded into grasslands the primates changed their diet, looking for grubs and things, flipping over cow patties and logs, it's documented. But Mushrooms also grow out of cow manure. We had a sudden spike after 2 million years of evolution, a drastic increase in brain size. Could it be that the eating of the hallucinogenic mushrooms actually increased sensory awareness allowing us to come up with better ideas i.e hunting, mating, survival? This is Terrence Mckenna's "Stoned Ape Theory" not mine...

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14 Answers

21
4145b36f1488224964edac6258b75aff

(7821)

on December 23, 2011
at 09:20 PM

Ok so this is a pet peeve of mine. Actually, maybe it's three.

1) The question, "Why didn't X evolve Y when Z did?" entirely misses the point of evolution. If X had evolved Y, it wouldn't be X anymore. It might even be Z. The ancestry of monkeys and humans split millions of years ago - we're the ones with the big brains.

2) In a million years, maybe lions will have evolved into something intelligent. There's probably a formal fallacy or bias to cover this situation. We are not at the end of evolution right now. It's not over. It's still going on. The selective pressure for tool using symbolic intelligence didn't occur during the past couple million years of lion evolutionary time. Maybe it will over the next million, and then Simba will be wrecking our shit in the Lion Wars.

3) What the hell does meat-eating have to do with intelligence? Sure, eating meat may have been the key to meeting the human brain's caloric needs, but to turn around and wonder why meat doesn't magically make brains larger seems to be an obvious fallacy. If I need nails to build a house, it doesn't follow that any process which requires nails will result in a house. I could just be making a pile of nails. There's a lot of coincidence required to get to human intelligence, and eating meat is only one possibly necessary condition.

4145b36f1488224964edac6258b75aff

(7821)

on December 24, 2011
at 03:48 AM

@Ramsey: Stoned ape is obviously the way we evolved. Can't believe it's not in the textbooks, blatant conspiracy by the man.

164ed7cd8d84c926bc66f366619bf853

(495)

on December 23, 2011
at 11:07 PM

#3 was my biggest curiosity. Thanks!

518bce04b12cd77741237e1f61075194

(11577)

on December 24, 2011
at 03:36 AM

Yeah, this always bugs me too. It's like the creationist argument "If we came from monkey's, why haven't all the monkey's turned into people yet?". Maybe because monkey's are really good at what they do, and we are good at what we do. Niches are filled, in no particular order and in no particular design. It just happens!

Ac9425a387b78cb37a01972fe848bddb

(655)

on December 24, 2011
at 12:14 AM

What are your thoughts on Terrance Mckenna's "stoned Ape Theory"?

A97b68379a576dfa764a4828304d2efb

(4181)

on June 16, 2012
at 06:35 PM

+1 for this answer being spot on and cracking me up.

11
A968087cc1dd66d480749c02e4619ef4

(20436)

on December 23, 2011
at 07:12 PM

Because they aren't smart enough.

Edit:

Really, monkeys don't eat a lot of meat. Chimps, who eat the most, only eat 2-4% of calories as meat. They can go months without it. A lion is already optimized for meat eating. Humans need bigger brains for hunting (tracking, mental maps, tool making, planning and communicating). Fire and cooking may also have had something to do with it. If you are really interested, you should read Richard Wrangham's Catching Fire.

8
D12142c8cafb16d9af10b3362cb8fb62

(1590)

on December 23, 2011
at 07:31 PM

Why do they need to? They're well adapted to their current climate with no significant evolutionary pressure for them to change (perhaps deforestation will change this).

Eating meat doesn't make a species more intelligent. Eating meat (high calorie food more generally) ''allows'' greater brain expansion; it's not a causational factor.

5
E639bc85fd42430285596434a6515ad5

(2226)

on December 24, 2011
at 12:52 AM

As Dave S. hinted at, the answer is in Richard Wrangham's book.

Every species would benefit from being smarter. The answer to why some species or another isn't smarter does not lie in the limited benefits of being smart. It lies in the extravagant costs.

A big brain requires a lot of calories to support.The gut competes with the brain for calories. For any given caloric intake, the bigger the gut is, the smaller the brain can be. So in order to evolve a large brain, a species needs to be able to evolve a small gut. The way to evolve a small gut is to eat cooked foods, which require less digestive effort.

Humans developed a large brain when they started getting most of their calories from cooked foods. Monkeys and other species have yet to tame fire. They live on raw foods, which require a larger digestive effort, and therefore larger guts ??? and proportionally smaller brains.

93ae9f2d376e5426e891a9b58d8302fa

(2936)

on December 24, 2011
at 02:23 AM

We were trackers, needed to track game, but our upright posture raised our noses too high off the ground for natural selection to handle the problem the usual way. So instead of wasting neurons on olfactory tissue, a slight shift was arranged. But that doesn't make us smart. Ask any bloodhound, he'll tell you we're as stupid as they come. But you have to know the secret bloodhound language, communismellication. Good luck trying to wrap your huge flabby brain around that.

Medium avatar

(10663)

on December 24, 2011
at 01:07 AM

A good article about when our brains started getting bigger due to cooking our food to read is Food for Thought in Science June 15, 2007, Vol 316.

5
96bf58d8c6bd492dc5b8ae46203fe247

(37227)

on December 23, 2011
at 07:12 PM

We can start with maybe they haven't needed to. Most species change out of need or improved reproduction.

If monkeys or lions are thriving there's no incentive to grow bigger brains that will force trade-offs in other characteristics (such as less able to sprint through the tree-tops or smaller teeth and jaws). If they are really thriving, they may change because there are things they no longer need (body fur, claws, etc.) as the brain grows larger.

Again, I am not a scientist. Your hypothesis may vary.

96bf58d8c6bd492dc5b8ae46203fe247

(37227)

on December 24, 2011
at 03:52 AM

@sage, are you asking me? LOL

96bf58d8c6bd492dc5b8ae46203fe247

(37227)

on December 23, 2011
at 07:26 PM

That doesn't resonate much with me but I do agree that we went back for more of things we tried and a) didn't get sick/die and b) had great flavor or pleasant effects. I'm thinking of fermented things, fruit, etc.

B4e1fa6a8cf43d2b69d97a99dfca262c

(10255)

on December 24, 2011
at 03:20 AM

are you looking for justification for conuming large amounts of hallucinogenic mushrooms?

Ac9425a387b78cb37a01972fe848bddb

(655)

on December 25, 2011
at 06:23 PM

Not at all, however I love exploring my consciousness!

Ac9425a387b78cb37a01972fe848bddb

(655)

on December 23, 2011
at 07:18 PM

Do you think hallucinogenic mushrooms had any part in our evolution? When the rainforest receded into grasslands the primates changed their diet, looking for grubs and things, flipping over cow patties and logs, it's documented. But Mushrooms also grow out of cow manure. We had a sudden spike after 2 million years of evolution, a drastic increase in brain size. Could it be that the eating of the hallucinogenic mushrooms actually increased sensory awareness allowing us to come up with better ideas i.e hunting, mating, survival? This is Terrence Mckenna's "Stoned Ape Theory" not mine...

Medium avatar

(19469)

on June 16, 2012
at 07:18 PM

O_o (peeks behind the curtain)

4
66974b2cb291799dcd661b7dec99a9e2

(11121)

on December 24, 2011
at 05:42 AM

Evolution is not a 1:1 correlation. Eating meat simply does not equate to developing a bigger brain. Other factors like developing & using tools, the development of speech, complex social systems have to be factored in. Nature is very complex. I don't need to understand every nuance of human evolution to know how to eat what is good for me. It seems to me the more I let go and become more animal-like the easier it is to be human.

3
9d43f6873107e17ca4d1a5055aa7a2ad

on December 24, 2011
at 07:31 AM

Maybe you should read the actual Expensive Tissue Hypothesis. It's about calorie limits constraining selection of expensive tissue (like brain), not about meat = smart.

3
93ae9f2d376e5426e891a9b58d8302fa

(2936)

on December 23, 2011
at 07:19 PM

Our upright posture, and the small profile it presents to the midday sun, allowed us to become the lords of the savanna during the hottest time of day. So, in effect, our legs led to the big brain. The bipedalism came first, don't yet know how or why we adopted it, but all our other weird idiosyncrasies followed after that.

http://tinyurl.com/3jqbmuo

2
B8592e62f9804ddabae73c1103d6bcb9

(1956)

on June 16, 2012
at 11:35 PM

Because their MYH16 gene is still functional, in all humans the gene is faulty. This gene regulates the growth of the temporalis muscle which is used for chewing and anchors on the top of the brain case. The muscle anchor stops the brain case from physically growing. Chimp's brain cases stop growing at equivalent age of 3 compared with 20 in humans. As this muscle is needed for chewing, until chimps reduce the tough leaves from their diet to the point that they no longer need such huge temporalis; ie the meat content of their diet increases.

Dogs have a working MYH16 gene as they need to gnaw bones, it is highly likely lions are the same.

http://en.wikipedia.org/wiki/MYH16_gene

Chimps and other primates are very intelligent, capable of many amazing things including culture and using sign language. Brain size has very little to do with intelligence. For example Einstein's brain was quite small and women's brains are smaller than men's although they're most intelligent on average. What increases instead if the DENSITY of the neurons.

2
34b560c8b9ce660d7839fb7e29d7be89

on December 25, 2011
at 11:26 AM

I was watching Nova on PBS tonight and the show What Darwin Never Knew was on. There is this hypothesis based on an observation of the human genome made by Hansell Stedman of the Univeristy of Pennsylvania School of Medicine. Specifically that an observed defect in our genome that codes for a particular type of muscle making gene limits the development of our jaw muscles--the same gene in apes is not defective. Our bite-force is just a fraction of an apes. The hypothesis is that the power of the jaw muscle limits brain growth. The muscles for chewing pull against the plates that make up the skull, the greater force causes the skull plates to fuse together after only 3-4 years of age in apes, in humans those plates may not stop growing completely until age 30. That means that in humans, brain capacity may grow into adulthood whereas for apes it stops very early.

The obvious conclusion would be that the meat-eating monkeys might be consuming a necessary element for greater brain growth but that there are other physiologic limits on the size of their skulls. So while a higher protein intake may be necessary for building larger brains, there are also physical limits involved which means that simply supplying a monkey with more protein has little or nothing to do with other selective forces that dictate whether or not an organism develops an attribute which requires more resources to maintain.

7a6529ea25b655132fe58d793f95547a

(2030)

on March 25, 2013
at 05:18 PM

Very interesting answer, thank you.

2
96440612cf0fcf366bf5ad8f776fca84

(19413)

on December 24, 2011
at 04:12 AM

Just wait a few million years and see what happens. If mutations similar to what allowed humans to evolve repeat, you'll see the same results. If not, wait a few more million years.

It is after all random chance that drives the mutations, and not all are beneficial.

96440612cf0fcf366bf5ad8f776fca84

(19413)

on December 25, 2011
at 10:48 PM

How else do you expect to "prove" the idea that meat eating causes simians to evolve bigger brains? I've certainly no ideas as to how to induce that. Certainly force feeding monkeys meat and teaching them to hunt is plausible, but how would you measure brain growth in just a few generations and prove a theory like this one?

956bcad1d462d433a4e1e22f6e3355d5

(1191)

on December 25, 2011
at 01:24 PM

LOL. "Just wait a few million years". Guess we can only speculate about the future or do you have something to admit? The invention of a time machine perhaps? :)

1
C4f1a0c70c4e0dea507c2e346c036bbd

on December 25, 2011
at 03:34 PM

We don't need Dr. Zayas like chimps walking around flinging explosive turds at people. Be thankful that their brains haven't evolved.

0
77877f762c40637911396daa19b53094

(78467)

on June 16, 2012
at 04:40 PM

THIS IS THE TRUTH:

BECAUSE THEY DON'T COOK THEIR FOOD. AS SIMPLE AS THAT.

0
Cf4576cbcc44fc7f2294135609bce9e5

on December 24, 2011
at 06:39 AM

i bet if you did a study. eating meat has a zero predictability with regards to brain size. its just more hog wash that sounded good at the time and so it gets repeated often. if any thing it was the larger brain that got the naked ape the meat in the first place. yes i think i will go with my statement. it sounds more plausible. well, at least with my brain ratio i can buy all the meat i can eat if i want it.

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