Why aren't all animals becoming smarter?

[fo3]

I don't think we're under much selective pressure now, except with regards to infectious disease and general deleterious mutations, however in our evolutionary past we were subject to selection. We exist as we are now because of a precise line of evolutionary changes as a result of natural selection (and I should have put other evolutionary forces as well :shrug

I would assume that humans are under a very large evolutionary pressure to adapt to the changed and changing social environment, and that the selection will result in rather extensive changes in both the brain and human behavior.

 

[thatbiogeek]

Perhaps, I'm really undecided on that one. For adaptation to a changing social environment to occur, a genetic trait must confer a reproductive advantage on its bearer to be selected for. This advantage must be strong enough that it creates an unbalance in subsequent populations where this gene is then favored. I'm not sure we know the extent to which social traits are genetic let alone whether or not they're selected for. If you have any good literature on that, I'd love to read it. I'm really not very well read in the area of human evolution so I'd love to learn more!

 

[fo3]

I am not really familiar with literature myself, I just like to put down a few thoughts where possible to get feedback on it. I just tonight got back to these forums I used to visit back when I planned to study physics, but I remembered that there were other subforums here as well, that might link to my genetic engineering studies.

Anyway, to expand on the previous post - I would think that even though a large part of the social behavior is acquired during the lifetime, the physiology of the brain has a major role in the way they are formed, and, for example, the digital communication lines opened to humans only now will present a lot of things to be adapted to.
I could imagine that stress tolerance will face a lot of improvement, mainly through the fact that people able to face the social stress better will likely live longer and better, will find potential mates more easily, and will provide a more stable environment for offspring.
That, of course, is the first idea popped to my mind, and there will likely be a lot more of examples.

 

[iceaura]

IIRC a 1% advantage in repro in 10% of the population replaces 90% of the genetic pool within a hundred generations. Something like that.

Doubling back is probably under strong genetic control, in squirrels - it's not a lesson best learned by trial and error, and the circumstances don't allow for extensive mental processing.

Squirrels that don't double back as often have a lot more than a 1% advantage in the city, with cars as possibly the major predator. And I would assume that in the wild doubling back varies a lot among squirrels, since such variability is itself a stable strategy - all predictability is bad in the long run, for fleeing prey - so there is variation for car selection to work with.

There have been at least a hundred generations of squirrels subjected to vehicle selection in the big cities of the US - plenty of time for such selection to have fixed new norms of genetically governed behavior.

Car selection is a likely candidate for the beginnings of a human evolutionary change as well - it's the leading cause of death in pre-reproductive humans in the US, and the US seems likely to supply a great deal of the surviving genetics to future human populations.

 

[spuriousmonkey]

A brain is an energy guzzler.

In the average adult human, the brain represents about 2% of the body weight. Remarkably, despite its relatively small size, the brain accounts for about 20% of the oxygen and, hence, calories consumed by the body. This high rate of metabolism is remarkably constant despite widely varying mental and motoric activity.

reference
PNAS | August 6, 2002 | vol. 99 | no. 16 | 10237-10239 Appraising the brain's energy budget

Energy spend on the brain cannot be spend somewhere else. Energy wasted by a large brain needs to be eaten.

You can talk for ages about how smart it would be to be smart, but it is all in your heads. Pun intended. What really matters is that an animal merely has to be adequately adapted to its environment. Anything else is luxury. A waste.

A crocodile doesn't need a larger brain because he is capable to catch smarter prey items with a tiny brain. A larger brain would just mean that he has to eat more. There would be no advantage in that.

Adaptations need to be adequate under most conditions, not best possible under any condition.

 

[Captain Kremmen]

A crocodile doesn't need a larger brain because he is capable to catch smarter prey items with a tiny brain. A larger brain would just mean that he has to eat more. There would be no advantage in that.

Crocodiles are sneaky.
They are an exception to the saying
that if it walks like a duck and talks like a duck
it must be a duck.

Crocodiles look like old rotten logs
They slide along in the water like logs.
Then. Wham!
You're Crocodile food.

 

[Buckaroo Banzai]

Why doesn't evolution generally select for intelligence?
And why have we been the exception?

It does generally select for some degree of available intelligence, but only enough to survival and reproduction. Adding intelligence can also decrease fitness... for bats, apparently there is a corration between larger brains and smaller testes, for example (I don't know if the bigger brained ones are any smarter, however)

There are others exemples I've seen, but I don't quite recall them in detail. I think they were based onthe idea that, in most cases, a slightly better intelligence analizing the situation is outperformed by pure pre-programmed instinct. Once instincts had evolved adapting the species for a certain niche (which will likely happen first), it's reasonably harder to a form of more flexible and complex intelligence to replace it. Usually, the evolutionary steps in that direction would not have enough reproductive advantage, instinct would just do the job, perhaps even better, faster, without wasting time and energy "thinking".

(Some recent mammals, such as the big cats (in a broader sense), had a reasonably increase in brain size... cougars have bigger brains than sabre-tooth cats, if I recall... the same probably happened with other predators... the relative brain size of birds is also reasonably bigger even if compared with dinosaurs with "big" brains, such as troodontids and the like)

Our level of intelligence is somewhat beyond the mininal or optimal required for survival, and some authors, like Darwin himself I think, try to explain that as the result of evolution driven by sexual selection. Sexual selection has the peculiarity of making things evolve beyond what would be "reasonable" for simple survival and reproduction, it can even force the evolution of something that would be otherwise unfit.

That explains why we are an exception, sexual selection does not tends to convergence or paralellism as much as natural selection does, because it's selection targets can be "random", even counter-adaptative, whereas natural selection will tend to repeat itself in similar situations.

Sexual selection wasn't necessarily the sole driver of that evolution, anyway, since this trait turned out to be adaptive, or, phrasing better, we turned out to become adaptively dependant of this trait... even other primates were found to have a correlation between somewhat bigger brains and the number of individuals in their social groups... that's somewhat like an intermediate link between sexual and natural selection, I think.

 

[Buckaroo Banzai]

Why doesn't evolution generally select for intelligence?
And why have we been the exception?

It does generally select for some degree of available intelligence, but only enough to survival and reproduction. Adding intelligence can also decrease fitness... for bats, apparently there is a correlation between larger brains and smaller testes, for example (I don't know if the bigger brained ones are any smarter, however)

I've seen other examples, but I don't quite recall them. I think they were based on the idea that, in most cases, a slightly better intelligence analyzing the situation is outperformed by pure pre-programmed instinct. Once instincts had evolved adapting the species for a certain niche (which will likely happen first), it's reasonably harder to a form of more flexible and complex intelligence to replace it. Usually, the evolutionary steps in that direction would not have enough reproductive advantage, instinct would just do the job, perhaps even better, faster, without wasting time and energy "thinking".

(Some recent mammals, such as the big cats (in a broader sense), had a reasonably increase in brain size... cougars have bigger brains than sabre-tooth cats, if I recall... the same probably happened with other predators... the relative brain size of birds is also reasonably bigger even if compared with dinosaurs with "big" brains, such as troodontids and the like)

Our level of intelligence is somewhat beyond the minimal or optimal required for survival, and some authors, like Darwin himself I think, try to explain that as the result of evolution driven by sexual selection. Sexual selection has the peculiarity of making things evolve beyond what would be "reasonable" for simple survival and reproduction, it can even force the evolution of something that would be otherwise unfit.

That explains why we are an exception, sexual selection does not tends to convergence or parallelism as much as natural selection does, because it's selection targets can be "random", even counter-adaptative, whereas natural selection will tend to repeat itself in similar situations.

Sexual selection wasn't necessarily the sole driver of that evolution, anyway, since this trait turned out to be adaptive, or, phrasing better, we turned out to become adaptively dependant of this trait... even other sorts of primates are found to have a correlation between somewhat bigger brains and the number of individuals in their social groups... that's somewhat like an intermediate link between sexual and natural selection, I think.

 

[granpa]

Nature does not usually select for increase in intelligence greater than that needed for survival.

Ants are collectively quite intelligent
but they are probably not much smarter than they were
60 million years ago.

The difference in our brains from other apes is not great.
We have a greater density of neurons and a bigger, more convoluted brain.
How difficult would that be for nature to select for in other species if intelligence gave a general advantage?
Not difficult at all I think.


Why doesn't evolution generally select for intelligence?
And why have we been the exception?

insect brains have probably reached a limit of some kind.


being intelligent can be an advantage but playing dumb has its advantages too.

 

[Billy T]

Just lucky, I guess. (There is little evidence to suggest that big brains are a long-term stable development of evolution and lots to suggest they are not )

 

[BlueMoose]

New born monkey is smarter than new born human baby, human cant birth babies with brains full developed because their brains would be too big, it isnt easy task to do even now, hence the human baby is helpless and need much more nurturing than monkey.
More protein ~bigger brain ~ harder to give birth ~ born undeveloped
Its many things that had leave us to this point, starting to walk hence more variable food sources, making tools and weapons lead even better quality of food and so on.
Some argues that with vegetation food only we wouldnt be in this stage since in dawn of history mankind they surely couldnt understand meaning of protein, in sense that where in vegetation they could extract enough protein. This couldnt happen of course if we werent primates which came from living in trees.

 

[Captain Kremmen]

It does generally select for some degree of available intelligence, but only enough to survival and reproduction. Adding intelligence can also decrease fitness... for bats, apparently there is a corration between larger brains and smaller testes, for example (I don't know if the bigger brained ones are any smarter, however)

There are others exemples I've seen, but I don't quite recall them in detail. I think they were based onthe idea that, in most cases, a slightly better intelligence analizing the situation is outperformed by pure pre-programmed instinct. Once instincts had evolved adapting the species for a certain niche (which will likely happen first), it's reasonably harder to a form of more flexible and complex intelligence to replace it. Usually, the evolutionary steps in that direction would not have enough reproductive advantage, instinct would just do the job, perhaps even better, faster, without wasting time and energy "thinking".

(Some recent mammals, such as the big cats (in a broader sense), had a reasonably increase in brain size... cougars have bigger brains than sabre-tooth cats, if I recall... the same probably happened with other predators... the relative brain size of birds is also reasonably bigger even if compared with dinosaurs with "big" brains, such as troodontids and the like)

Our level of intelligence is somewhat beyond the mininal or optimal required for survival, and some authors, like Darwin himself I think, try to explain that as the result of evolution driven by sexual selection. Sexual selection has the peculiarity of making things evolve beyond what would be "reasonable" for simple survival and reproduction, it can even force the evolution of something that would be otherwise unfit.

That explains why we are an exception, sexual selection does not tends to convergence or paralellism as much as natural selection does, because it's selection targets can be "random", even counter-adaptative, whereas natural selection will tend to repeat itself in similar situations.

Sexual selection wasn't necessarily the sole driver of that evolution, anyway, since this trait turned out to be adaptive, or, phrasing better, we turned out to become adaptively dependant of this trait... even other primates were found to have a correlation between somewhat bigger brains and the number of individuals in their social groups... that's somewhat like an intermediate link between sexual and natural selection, I think.

The sexual selection idea is interesting, but usually sexual selection picks up on signals which suggest fitness and breeding potential. In humans:
Hair shine, clearness of complexion, straightness of bones etc.

In animals, sometimes an otherwise redundant factor is chosen which requires resources which an unfit animal could not supply. Brilliant colouring, or an extravagant rooster's coxcomb.
Producing a large vulnerable head which requires a huge energy supply would be a step too far.

We have not always been as successful as we are.
So why why it not bred out of us in bad times?

I'm glad you can see the problem anyway.

 

[joepistole]

Let me ask you this, who says they are not getting smarter? Is there any proof? Or is it that we are not really good at gauging. measuring intelligence in other animals? Our ability to communicate with other intelligent animals on this planet is limited at best.

 

[BlueMoose]

Let me ask you this, who says they are not getting smarter? Is there any proof? Or is it that we are not really good at gauging. measuring intelligence in other animals? Our ability to communicate with other intelligent animals on this planet is limited at best.

-My thoughts exactly. Thank you.

 

[Chatha]

Crocodiles are sneaky.
They are an exception to the saying
that if it walks like a duck and talks like a duck
it must be a duck.

Crocodiles look like old rotten logs
They slide along in the water like logs.
Then. Wham!
You're Crocodile food.

I agree, me thinks that crocodiles must be pretty smart to be able to survive on both land and water , at least smart in their own rights. But specie survival is sometimes independent of the specie. Polar bears for example are going to be extinct by 2050 due to global fire(okay, global warming). Some other species are being marginalized due to human encroachment and general negligence. Its hard to put a measure on intelligence when it comes to this topic. From what I understand, some animals are good at emotions and intent, probably better than humans. Some can predict the weather of their ecology, e.t.c.

 

[Buckaroo Banzai]

Producing a large vulnerable head which requires a huge energy supply would be a step too far.

We have not always been as successful as we are.
So why why it not bred out of us in bad times?

I'm glad you can see the problem anyway.

I don't think it would be beyond of the capabilities of the sexual selection, even more if we consider that it does not result in a "pure" sexual adornment, useless for anything else, but coincidentally was the one of the most versatile exaptations ever... even capable of providing adaptive flexibility unseen before for the hard times or new situations of many kinds, allowing humans to inhabit every continent. Additionally, to me the the complex mating rituals of some tiny birds seems to be considerably much more expensive than our brains, proportionally, and even more considering that they don't serve nothing else... aren't there some birds which build even huge pseudo-nests that aren't used for actual nesting of the eggs? And all this sort of things...

There's also the fact that "evolving backwards" is often somewhat hard for many reasons... with purely adaptive traits, there are only pure adaptive reasons - a population can only lose the trait once it's not essential to adaptation anymore; with a sexually selected trait, it would only disappear if the preference for that disappears, going from fixed in a population to nonexistent (or alternatively, the population could split), out-competed by individuals that didn't care about or disliked the trait.

If human intelligence is a target of both natural and sexual selection, its disappearance faces the two obstacles at the same time. I think that would be more likely to the human population decrease than to become "dumber" by selection during bad times - extinction is more common than adaptation.

Not only because of that, but because intelligence is perhaps our main adaptation during bad times, much more than physical strength or whatever else... the individuals in the way to be "Homo retard" would have a harder time and would be less attractive than the smarter ones (but I must admit that pop culture seems to refute that). I also think that primitive cultures probably would have had (or presently still have) some sort of unconscious "eugenics", by not having moral restrictions for taking advantage of someone dumber (or in disadvantage of any kind)... perhaps even the children's bullying could be sometimes lethal or very physically impairing...

Additionally, I think I've read in Geoffrey Miller's "the mating mind", that the brain size is not much needed for intelligence, but structure is far more important, which I think that may save some energy consumption at the same time that retains intelligence. So even in extreme situations perhaps there is room for selecting other thing else than dumbness itself... actual body size perhaps would be one of them, maintaining the brain/body ratio or even increasing it proportionally due to growth's allometry (shorter people have bigger heads, proportionally)...

The neanderthals went extinct anyway... coincidentally (or maybe not, even though I don't think so) their brains were bigger than ours.

 

[MetaKron]

Humans certainly aren't getting smarter, and smart people lose the mating game early.

 

[Grantywanty]

It costs a lot too grow and "feed" a proportionally human sized brain. If the advantages of having such a brain and the intelligence that presumably accompanies it do not outweigh the cost, it would not confer a reproductive advantage to its bearer. It's always tempting to ask questions like this, why aren't animals smarter, why don't humans photosynthesize etc... But it isn't really a great line of thinking in evolutionary biology. Organisms exist in their present state because they have followed a precise line of evolution as a result of natural selection, genetic drift, etc...

You would think however that slightly smarter ___________ would a little better than its peers and that intelligence would tend to get emphasized.

 

[one_raven]

Why doesn't evolution generally select for intelligence?

It selects for fitness - whatever that may be.

And why have we been the exception?

What, other than intelligence and community, do we have?
What advantages do we have for survival?
We are slow, fat, lazy, not terribly good swimmers, not terribly fast runners, relatively hairless (unprotected from the elements), no natural defenses, no natural fighting implements (sharp teeth or claws).

All we have for survival is intelligence and cooperation - without them we would not have survived.

 

[Scull]

It selects for fitness - whatever that may be.

The organism that can best reproduce. Interestingly enough, scientists studying bats have found that bats with bigger testicles have smaller brains and those with bigger brains have smaller testicles. Nature kind-of finds a medium, too small of testicles, you can't reproduce well enough and too small a brain, you can't survive long enough to reproduce.