Why aren't other carnivore species intelligent?
February 23, 2007 8:31 AM   Subscribe

First off, please excuse me for being a Biology ignorant. I seem to remember reading somewhere that men are so intelligent today because of they high protein consumption, in form of meat, which caused the brain to grow during evolution, making our species more intelligent than the others. If this is true, why don't we have superintelligent lions and other carnivore animals walking on twos and building cities and electing the mayor in Lionland, PA? They eat way more meat than we do.
posted by dcrocha to Science & Nature (32 answers total) 1 user marked this as a favorite
Because maybe what you remembered reading was wrong?
posted by chunking express at 8:42 AM on February 23, 2007 [3 favorites]

I don't think protein consumption has much to do with evolution, not directly, anyway. Or what chunking express said.
posted by handee at 8:47 AM on February 23, 2007

Opposable thumbs.
posted by Happy Dave at 8:48 AM on February 23, 2007

It's possible that high protein consumption was a necessary factor which allowed our brains to evolve to a larger size, but "high protein consumption allows the brain to evolve to a larger size" is not the same as "high protein consumption necessitates that the brain will evolve to a larger size."

Also, brain size is not necessarily indicative of intelligence, even when considered relative to the species' body size.
posted by DevilsAdvocate at 8:56 AM on February 23, 2007

I think the protein argument is pretty weak, and I don't think you're going to get a lot of biologists getting behind that one.

Opposable thumbs and the subsequent development of tool use was big, to be sure.

Also, the development of vocal chords, followed by language, was a massive boost to our species development of intelligence. No other species has the capacity to speak like we do, and that's a big reason why you don't see brainy jackals running around giving stock advice. (real jackals, that is)

I'm willing to bet that chimps would be right there with us if they could speak. After all, they've just learned to hunt with spears.
posted by mcstayinskool at 8:58 AM on February 23, 2007

If big brains made a difference the earth would be ruled by elephants and whales.
posted by damn dirty ape at 8:59 AM on February 23, 2007

It looks like either 1) I read it wrong or 2) It was wrong. So if eating meat doesn't make anybody more intelligent, I'll become a vegetarian then. NOT.
posted by dcrocha at 8:59 AM on February 23, 2007

There are several things that you may be getting at...

In the short term, the average first world man (or woman) of 2007 is much more well fed and healthy than his counterpart from 1007. Eating meat is a part of that. Meat has been a luxury item for most of human history, in a way that it is not now. And meat is a very high value food, it gives more nutrients per pound and per calorie than grains. Someone eating a diverse diet, including meat, will be more physically fit, healthier, and smarter than someone restricted to a diet based largely on grains. You can experience clear evidence of this change as you stoop through the doorway of a medieval castle. The doorway was tall enough for its inhabitants, but is too short for you. Medieval people were under nourished, but protein was just one factor. This is not a product of evolution, medieval people were essentially genetically equivalent to modern humans.

On a more evolutionary time scale, there is a theory that intelligence evolved to promote tool use, which allowed access to new food sources. Modern chimps invent tools to harvest ants, for instance, and one chimp can teach another this skill. This adaptability is obviously favored by natural selection, and this adaptability would have allowed humans to become predators of large animals at some point in their evolution. So intelligence allows the consumption of large amounts of protein in human evolution, not the other way around.

(Similarly, incidentally, predators such as lions do tend to be smarter than equally sized herbivores. This is because hunting prey often selects for a brain capable of adaptive behavior, not because protein consumption makes you smart.)
posted by Maastrictian at 9:00 AM on February 23, 2007

IAAP*. First off, the human adaptation writ large is a result of the convergence of our unique set of adaptations. No one is really sure why humans walk upright, but our evolutionary history is vastly different from that of, say, lions. Considering the earliest primates showed up more than 65 millions years ago, our divergence with lions came far longer ago than that (I'm too lazy to look up the exact date). In that tens of millions of years since, primates changed and set up the basis for humans' bipedalism.

Since lions didn't have the same genetic set-up that humans do, and even though they do and did eat a lot of meat, they didn't have the prerequisite features to lead to big brains (or bipedalism). Instead they have other adaptations that allow them to live quite well with little or no predation on themselves: instinctual hunting, stealth, and giant fucking claws and teeth.

Our ginormous (technical term) brains are our primary adaptation, and they do require a ton of energy in development; I believe the brain is the organ with the highest use of energy in development in the entire body. Thus, hominins did need (and still do need) lots of energy to develop those brains**. This explanation is a bit simplistic, as increased energy needs and larger brains must have developed hand in hand gradually over the last four million years, especially the last two million including Homo Erectus, in whom we see the first huge spike in cranial capacity. Still, assuming that humans had increasing caloric needs to allow for said brain development, paleoanthropologists had to come up with an explanatory mechanism. Huge rates of meat consumption (protein and fat being much more calorically packed than carbohydrates) was indeed one of the explanations offered. However, the most likely going theory now is that rather than meat, cooking was the source. A standard omnivorous diet is much less calorically dense than an all-meat diet, but a cooked omnivorous diet blows both of them out of the water in terms of caloric density. Richard Wrangham is the progenitor of the cooking hypothesis: Wrangham 1999, and he has multiple articles published about it if you care to do the research.

On preview:
mcstayinskool, you should read the new book Baboon Metaphysics by Cheney and Seyfarth. They do a convincing job showing that the foundation of language is a complex system of social knowledge that is present in not just humans but most or all monkeys and apes. I just saw Seyfarth speak on Monday; it was an amazingly good lecture.

*I Am A Paleoanthropologist
**Incidentally, these big brains are the reason that our babies are so altricial: they're born earlier in their developmental cycle so our giant baby skulls can fit through our mothers' pelves without killing them.

posted by The Michael The at 9:03 AM on February 23, 2007 [2 favorites]

People didn't evolve because their ancestors ate protein, thereby making the brains of successive generations larger and more intelligent.

Our ancestors happened to occupy a biological niche in which the chances of reproductive success increased with increases in intelligence--to a limit. Too large a brain, and the burden of the larger energy requirement cancels the advantage of intelligence. There is nothing special about intelligence that makes evolution "point" towards increasing it. IF greater intelligence happens to be an advantage, then more intelligent offspring will prosper. After thousands of generations, the laws of probability dominate.

Trying to simplify things down to being all about the brain is a mistake. Your hands, your eyes, your nose and ears, your vocal chords--everything, really--are the way they are because that particular configuration happened to be advantageous for what pre-humans went through. Tackling a gazelle doesn't really require dexterity, intelligence, or speech. It requires some lion-like instincts, huge teeth and claws, and lots of speed and strength, and that's why lions are the way they are. Sounds a little tautological, no?
posted by dsword at 9:04 AM on February 23, 2007

I seem to remember reading somewhere that men are so intelligent today because of they high protein consumption, in form of meat, which caused the brain to grow during evolution,
I just happened to watch "Walking with Cavemen" last night and that particular theory was highlighted. I give no voucher as to the scientific soundness of that television show, but I wonder if that is where you heard/read this theory?

It was only one of many contributing factors (according to this show) along with walking upright (which freed hands for manual dexterity and chest muscles which allowed for development of speech) and coping with a changing environment. Along with speech came an increase in brain complexity and size as we were forced to comprehend others.
posted by Secret Life of Gravy at 9:04 AM on February 23, 2007

Heh. IANAP-- just some one who watches TV.
posted by Secret Life of Gravy at 9:09 AM on February 23, 2007

The theory is a bit more complex than that. Most of the current theories regarding the development of hominid (human or human-like) intelligence propose that climatic changes during the previous space between ice ages dramatically changed the environment over large portions of Africa. In order to survive and exploit these changes, hominids were forced to the ground, and forced to adapt to new food sources, including meat.

The reason why other carnivores didn't develop the same level of intelligence is because evolution tends to take advantage of pre-existing structures and patterns of behavior.

Cats: Flexible grappling paws and very pointy teeth.
Dogs: Extremely efficient running gait and a mix of teeth.
Primates: Gripping fingers, very good close-range vision, and social intelligence.

Cats and dogs didn't have the required anatomy to stand up and go walking on two legs. Early hominids were already likely carrying things short distances on two legs.
posted by KirkJobSluder at 9:10 AM on February 23, 2007

There are many theories about how human intelligence evolved in a short time period. One involves the Ice Age.
posted by Blazecock Pileon at 9:11 AM on February 23, 2007

I was going to post what I learned in a 100-level Anthro course I took (the biological basis for human behavior - I think it was called), but The Michael The said it all and better than I could've.
posted by chndrcks at 9:11 AM on February 23, 2007

Your thought experiment is correct; large carnivores are indeed proof that eating meat does not cause intelligence.
The truth is something more like this: our ancestors lived a lifestyle where intelligence was a helpful trait to have in terms of survival and procreation. A large brain, however, is costly in terms of the protein needed to grow it and the calories needed to keep it running. So there were two opposing selective forces, one (the usefulness of intelligence) tending to cause an increase in brain size, and the other (nutritional cost of a large brain) tending to decrease it.
In this situation, any dietary change that makes more protein and calories available would allow the brain size to be increased. It has been theorized that an increase in meat in the diet, and the discovery of cooking (which makes meat more easily digestible) were two such changes in our history.

This is still a very simplified view of the theory, but less simplified than your version. If you had said "men are so intelligent today because of the[ir] high protein consumption, in form of meat, which allowed the brain to grow during evolution" (ie "allowed" rather than "caused") then your summary would be more accurate. The main point is that there were other factors pushing us towards large brain size, and nutrition was a limiting factor.

On preview, I type too slowly.
posted by nowonmai at 9:20 AM on February 23, 2007

Actually, it's the opposite. A recent study in the British Medical Journal claims that vegetarians tend to have higher IQs than meat eaters.
posted by jk252b at 10:13 AM on February 23, 2007

Actually, that's a classic case of correlation vs causation, which is the problem everyone has addressed in this thread. The OP doesnt need more disinformation suggesting causation of evolution based strictly of diet, thanks.
posted by damn dirty ape at 10:26 AM on February 23, 2007

Actually, it's the opposite. A recent study in the British Medical Journal claims that vegetarians tend to have higher IQs than meat eaters.

So that would explain India taking over the world's software production huh? As I'm a software engineer myself, maybe I'll start eating more vegetables. NOT.
posted by dcrocha at 12:19 PM on February 23, 2007

There is no such thing as Manland, PA; Humanland, PA; or Homoerectusland, PA. I have no idea what you're talking about.
posted by one_bean at 1:21 PM on February 23, 2007

I read your question as being directed at studies of men vs. women. I take it you actually mean humans, given the flow of the thread. Anyway, even today, a drop in protein consumption during pregnancy can lead to a drop in the intelligence of the resulting child. But, as others have pointed out, protein is just one factor in evolution.
posted by acoutu at 1:55 PM on February 23, 2007

There is no such thing as Manland, PA; Humanland, PA; or Homoerectusland, PA. I have no idea what you're talking about.

Maybe he meant Red Lion, PA...
posted by The Michael The at 2:06 PM on February 23, 2007

I heard a talk once claiming that increased availability of omega-3 and omega-6 fatty acids in the diet of early humans might be partly responsible for their burst in intelligence. Specifically, the idea was that the human diet had changed to include more seafood, which were higher in these acids. And we started eating more seafood when we migrated to be near the shore...

Here is a link to a paper which appears to deal with the subject.
posted by wyzewoman at 3:19 PM on February 23, 2007

I was under the impression that eating bone marrow played a significant role in the development of homonid intelligence.

Looked around a bit -- here's some info from the BBC:

But around two million years ago, telltale cut marks on the surface of animal bones reveal that early humans were using crude stone tools to smash open the bones and extract the marrow. Stone tools allowed early Homo to get at a food source that no other creature was able to obtain - bone marrow. Bone marrow contains long chain fatty acids that are vital for brain growth and development. This helped further fuel the increase in brain size, allowing our ancestors to make more complex tools. Link
posted by sentient at 4:02 PM on February 23, 2007

@one_bean: of course there's no Lionland, PA. But if there were superintelligent lions, I assume they would live in Pennsylvania or California, rather than in Kenia.

@acoutu: I meant "humans" rather than men vs women. The question was poorly phrased; I'm not a native English speaker.
posted by dcrocha at 4:29 PM on February 23, 2007

Then of course the reference should have been the Isle of Lion
posted by one_bean at 6:12 PM on February 23, 2007

For what it's worth, back when I was an anthro grad student, we were taught that only a very small percentage of the protein in the diet of the modern hunting-gathering societies came from meat. They're not perfectly analogous to whatever primate ancestors we had, of course, but it's a data point.
posted by mediareport at 7:41 PM on February 23, 2007

Superlions are coming to getcha.
posted by AnyGuelmann at 8:28 PM on February 23, 2007

Are you in Australia? Because I recall, just a month or two ago, snorting in contempt at a series of double-page newspaper spreads put out by some overpaid long-lunch bunch of meat-marketing losers making exactly this claim.

Don't believe everything you read.

Don't believe anything you read in advertising.
posted by flabdablet at 8:32 PM on February 23, 2007

Non-Aussie readers may view the a sample ad from the campaign here:

The Main Meal

Briefly, Sam Neill (of Jurassic Park fame) follows ordinary Australians who eat red meat (often in a caveman-esque manner), pointing out the evolution of our large brains "depended" on red meat, that craving red meat is a 2-million year old instinct, and that we were "meant" to eat red meat (by whom, exactly? The FSM?). He then does The Twist on a beach, for reasons that are not explained. I secretly hope that he will be murdered and eaten by the families he stalks.

It's complete rubbish - but then, what do you expect from our glorious Meat and Livestock Association which has the gall to host its thinly-veiled propaganda on a site called foodfacts.com.au?
posted by obiwanwasabi at 10:00 PM on February 23, 2007

Actually, I didn't read it (or see it) in a TV ad. It was in a "kind of" scientific magazine, one of those targeted at laymen.
posted by dcrocha at 9:30 AM on February 24, 2007

obiwanwasabi, the double-page newspaper ads hurt my brain quite enough; thank you for reminding me yet again why getting rid of my TV was such a good idea :-)

Now I can't decide whether the idea of Sam Neill as meat and/or livestock is appealing or appalling.

I don't think I'd eat 'im.
posted by flabdablet at 5:42 AM on February 25, 2007

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