Okay, it’s a dumb question. But I’ve heard from a number of places that eating meat gave human brains a boost in size. Usually this comes up in threads defending our sacred right to eat meat without guilt.
I eat meat, but like most humans, I am an omnivore. Cats are true carnivores. So why are their brains still so teeny tiny that they have no foreheads? Was there just not enough room for expansion?
I’ve had ten cats over the years, not counting kittens, and all of them were rock stupid. Well, except for one. He was scary smart. He was the only one of my cats to die relatively young. Coincidence?
Cats have teeny tiny brains because cats are teeny tiny. I expect, though, that if you compared their brain:body mass ratio to other carnivores, it’d be about comparable, and probably larger than most herbivores.
Also keep in mind that domesticated animals are often stupider than their wild ancestors.
Of the 2 cats I have right now, one is the smartest cat I’ve ever had, and the other is dumb as a post. But it looks like they have about the same size brain.
Eating meat makes larger brains possible, but evolution doesn’t develop complex adaptions just because it can. Cats don’t need large brains to be successful hunters, and probably wouldn’t be much better as hunters even if you did give them larger brains. Humans developed large brains in part because we weren’t good at much else, and larger brains were a very useful survival trait for us.
This post might sound a bit like a joke, but it sums up the point very accurately: each species has a brain as big as it needs to be. Humans could have humungous brains but we couldn’t move, and we’d kill our mothers on the way out, and we would need to eat a whole lot more just to get the energy to power the brain.
Absolute brain size isn’t a great measure. Ratios are better, brain to mass like gazpacho’s link shows, or a ratio of the “thinking” parts of the brain to the rest/whole brain (our cortex is much larger comparatively than other species). I don’t know which thing the OP is talking about, but are we sure it’s causation and not correlation? As above, maybe bigger brains co-developed with carnivorism, because the latter is necessary for the former, and the former makes one more skilled at the latter.
Cecil has an article on why measuring cat intelligence is hard. On my lap is a cat who would a genius as a human. He would also probably be serving a long prison term due to his idiocy (!=lack of smarts) and poor impulse control.
You have it backwards. Humans evolved larger brains for whatever reason. (Personally I think it was due to social competition with other other humans.) Adding more meat to the diet just gave us the ability to grow larger brains. It wasn’t like we started eating meat, and that caused our brains to grow. Crocodiles eat almost entirely meat and fish, and have teensy brains.
For their size, cats have big brains. They’re a lot smarter than rabbits or other herbivores of the same size - which is generally true of carnivores.
Well, as my cat’s vet says whenever I complain about Tiger doing something particularly dumb, “They can’t all be rocket scientists”.
My parents always had cats (including one that was very offended when I came along). One of those cats was smart enough that you had to spell things out if you didn’t want her to understand them. That cat lived for 15+ years, just as a point of information.
Cats use their brains for cat purposes, which may be baffling to humans. This makes assessment of “IQ” difficult. Tiger is probably pretty smart (I’ve caught her rearranging my Windows desktop icons into the same pattern multiple times), it just doesn’t usually show.
Moreover, felids and canids today have more brainpower than the more primitive carnivores from which they evolved many millions of years ago. Those earlier species were somewhat more like weasels, badgers, civets, racoons, and so forth.
One of my pet peeves in questions on evolutionary biology is that inevitably someone will be compelled to offer an “answer” like this one, that is supposed to offer some great insight but really is entirely pointless.
In fact, at least in principle every evolutionary development* is* explicable. That’s the whole point of science in general and evolutionary biology in particular. What you probably mean is that the trait may not be adaptive; or it may not have developed through selection; or that we simply don’t have enough information to explain it. But there is always going to be some basic reason why the trait exists, whether it’s developmental inertia, genetic drift in small populations that caused that trait to go to fixation, or selection for some other linked factor, or any number of other explanations.
In this particular case, there are correlations, both ecologically and physiologically, between carnivory and brain development. Asking why a particular kind of animal may be an exception to such a rule is basic to evolutionary biology. Dismissing it as “gosh, maybe we just can’t know” contributes nothing to the discussion.
I don’t think my comment was pointless, and for all the accepted understanding about the evolution of biological features, much of it comes down more heavily on the “accepted” than on “understanding” - and you’ve conceded this with the phrase “in principle.”
I don’t in any way mean it’s pure guesswork and golly, but the number of absolutes is far less than the number of still malleable theories.
The problem is with the original question, which is wrong (cats have brains entirely in proportion to their size and ecological niche), and assumes that there is some hard and fast link between meat-eating and brain size. Those are what I was addressing, not the truthiness of evolutionary biology.
If this is what you had said, I wouldn’t have taken issue with your post. You implied that cat brain size might be inexplicable, rather than exactly what might be expected. While there is no hard and fast link between brain size and carnivory, examining deviations from the correlation can give insight into other evolutionary factors involved (such as sociality).
It is actual thought that social hunters do generally have the biggest brain size. But as it so happens lions and tigers are an exception to that rule as they are two closely-related, similarly-sized species, where the the solitary hunters (tigers) have bigger brains than the social hunters (lions).