As I recall from college anthropology, human childbirth is painful (and sometimes even fatal) precisely because our craniums are so large, relative to other mammals and relative to the size of our frames. (Humans have the highest ratio of brain mass to body mass; whales come in second.) If so much of our brain mass were hypothetically unnecessary, then humans with smaller brains would be more likely to pass on their genes, as those childbirths would less frequently be fatal. Over time, humans would come to have much smaller craniums (90% smaller, if the urban myth were true), not the large craniums that we currently possess. The fact that evolution is willing to pay such a high penalty (increased childbirth fatalities) for large brains indicates that there must be an offsetting evolutionary advantage to having large brains. The notion that much of our brain is therefore "unused" doesn't really make sense from an evolutionary standpoint.
Do you have a reference regarding your claim about brain mass to body mass ratio? This [highnorth.no] seems to indicate otherwise. (Mice are highest, humans are second, various dolphins are third and fourth.. whales are pretty far down.)
I think the parent poster meant Encephalization Quotient. Basically, its the brain/body mass ratio for a particular animal compared to the brain/body mass ratio for the "average" mammal.
The fact that evolution is willing to pay such a high penalty (increased childbirth fatalities) for large brains indicates that there must be an offsetting evolutionary advantage to having large brains. The notion that much of our brain is therefore "unused" doesn't really make sense from an evolutionary standpoint.
Then why do I have an appendix? (Or slim body hairs?)
Evolution does not look at any one characteristic. It looks at the whole of the being. And, between equally fit species, there's still a measure of chance.
Let's ignore the obvious rebuttal to your point (use of the brain's savant abilities is proportional; if we have a brain half the design, we might have half of the all-around intelligence) and focus on the evolutionary advantages of having unused brain tissue.
First off, we're able to survive brain damage much easier. Being able to be thwacked in the head and still bring food home--and maybe go out and hunt some more the next day--is an obvious evolutionary advantage.
Secondly, it increases mating. Having a bigger brain means our heads are shaped different--in a more asthetically pleasing fashion. The face is a human's primary means of identification and emotional communication--a clearer face is an obvious evolutionary advantage, within the species.
Thirdly, it's entirely possible that over the uncounted generations of prehistory, human-ancestor-groups who had savants among them simply outperformed other human-ancestor-groups who did not, thus neccistating a retention of the savant abilities. Not a clear evolutionary advantage, but a distinct possibility.
While your childbirth arugment is a good one, for it to work we'd need to have some mechanism to actually shrink brain mass at the start. Bugger me if I can think of one that'd work--larger hips would be a much easier evolutionary adaptation.
I don't think I agree with anything you wrote:-) Just reading through, and this is longer than I intended, but what the hell...
Then why do I have an appendix? (Or slim body hairs?)
Because there is very little selective pressure to remove these low-cost (in evolutionary terms) additions to the body. This is assuming that you can get rid of X without affecting Y, which is a heck of an assumption - most of our body parts are created/regulated by the interaction over time of *lots* of different genetic codes, your overall genetic code is not a blueprint you can just erase part of... Besides, they're not useful *now*. They presumably were *once*, and they may yet be again. Not in our lifetime, I suspect:-) but possibly in the future...
Let's ignore the obvious rebuttal to your point (use of the brain's savant abilities is proportional; if we have a brain half the design, we might have half of the all-around intelligence) and focus on the evolutionary advantages of having unused brain tissue.
How do you *know* it's proportional ? It may be highly non-linear in nature. Intelligence could be an emergent property, as opposed to intrinsic. There could be a minimum (or maximum) neuron-quantity threshold for intelligence to occur, the decision-surface for relative intelligence could be as complex as a fractal plane. We don't know.
First off, we're able to survive brain damage much easier. Being able to be thwacked in the head and still bring food home--and maybe go out and hunt some more the next day--is an obvious evolutionary advantage.
I think you're overlooking the incredibly difficult process humans go through in childbirth. The non-assisted mortality rate (for both mother and child) is far higher than any other mammalian species on the planet. Primate females almost always give birth without excessive labour. Human females labour can last over several hours, although today the child is more likely to be induced or surgically delivered. Only 200 years ago, death in childbirth was commonplace for those who could not afford assistance.
In contrast, being hit on the head hard enough to significantly break the skull will pretty much cause damage whatever size brain you have. Since all the higher-order functionality is on the outside of the brain (grey matter), that's the area that would be damaged anyway. If you don't break the skull, you're likely to just get a bruise either way, so long as you don't make a habit of it...
Don't forget that (unless our ancestors were particularly keen on headbutting cliffs) this would be an effect on 1 person. The do-or-die childbirth thing is an issue for every human born. I suspect nature might come down on the side of the majority...
Secondly, it increases mating. Having a bigger brain means our heads are shaped different--in a more asthetically pleasing fashion. The face is a human's primary means of identification and emotional communication--a clearer face is an obvious evolutionary advantage, within the species.
Um. No. If we all had faces the size of pygmy monkeys, we'd probably have designs on our chests or backs, or some other method of recognition. Sexual preference is closely tied to genetic fitness, not the other way around.
Consider that healthy-but-pug-ugly A has a 85% chance of surviving to breeding-age (and hanging around afterwards for protection etc.) because he's got strong arms. Handsome bigheaded B has only a 50% chance of making it, but he looks really cool. Unfortunately for B, the numbers are against him. No matter how many doting females are queueing up (hah!), if he only has a 50% chance of making it, his genes (and those of the doting females, since they choose B) are far more likely to be swept down evolution's sewer. The corollary is that the female
I don't think he wanted to debate individual points with you. I think his overall point was that there are probably several explanations for why evolution has chosen large brains for us and not selected against it (yet). There's probably a fifth explanation that makes even more sense. So don't jump to the conclusion that we "think" with all of our brain simply because natural selection should otherwise have selected for smaller brains; there may be oth
Then why do I have an appendix? (Or slim body hairs?)
We don't know; overly reductionist thinking has led us to believe that vestigial body parts have no function, but some evidence suggests that the appendix is integral (though obviously not essential) to the immune system. Debates are out there on this topic, google it.
Likewise with the lack of abundant human body hair. The only other mammals with hair like ours (forget the head for a moment) are either acquatic (from hippos to cetaceans) or subterrane
Then why do I have to scrape my face every morning? Some evolutionary joke means that if I don't, I'll soon be sucking on last week's eggs and tripping over neverending beard, something chicks don't dig. Maybe beards (and head hair) are ways of ensuring that we use sharp implements -- blame it on the black monolith...
It's actualy possible to groom and keep clean a beard, and a good portion of human women consider a beard attractive.
Likewise, there are human breeds that have little to no facial hair; bein
Then why do I have an appendix? (Or slim body hairs?)
If having an appendix is more harmful than not having one, then there'd be selective pressure that would tend to eliminate it. If having an appendix is beneficial, then selective pressure will tend to retain it.
However, if having an appendix is neither more harmful nor more beneficial than not having one, then there'd be no selective pressure either way. Thus the status quo will tend to be conserved in that respect.
If having an appendix is more harmful than not having one, then there'd be selective pressure that would tend to eliminate it. If having an appendix is beneficial, then selective pressure will tend to retain it.
Your statement only holds true if the benefit/harm hapens within the earlier parts of life. If you live long enough to pass on your genes, then have some type of major genetic problem that kicks in later in life, your children will likely have the same thing happen. Waiting until later in life t
Then why do I have an appendix? (Or slim body hairs?)
Yes, I too will focus on just this one quote.:)
Let's all remember, people, that evolution isn't "over" yet. We're still evolving, and presumably always will be. Just because something unnecessary or even harmful hasn't been removed from the human genome yet doesn't mean that it won't be removed eventually.
For that matter, let's not forget that even more complicated scenarios are possible. Perhaps in 20,000 years the human appendix will have turned
in fact, larger hips would increase the energy required for females to walk and would decrese their abilities to climb trees and so-on.
plus, your assertion that bigger brains = bigger faces = increased mating potential is bunk - look at all those animals, quite happy to get on and fuck, without massive faces = squirrels? rabbits? lobsters? how about animals with large faces and small brains - horses? llamas?
larger brains equalling more aesthetically pleasing faces? so are better looking people automatical
plus, your assertion that bigger brains = bigger faces = increased mating potential is bunk
Why? Because you have other animals with smaller brains? Are _you_ attracted to a bright colorful bird? I didn't think so.
larger brains equalling more aesthetically pleasing faces? so are better looking people automatically smarter? Ask most of us/. crowd - big brains doesnt automatically equal good looks.
Aside from the conceit that/.ers think that we're smarter than everyone else (we're not), having a bigg
"Then why do I have an appendix?" This is a good question.
I have read that if the appendix were to become smaller it would often become infected and lead to death. While the appendix has shrunk because it is useless it can't shrink further because the risk of fatal infection.
The notion that much of our brain is therefore "unused" doesn't really make sense from an evolutionary standpoint.
It isn't that there are sections of the brain that are never used. It is that each individual has sections of their brain that they do not use. It sort of stands to reason that there are parts of the brain that mathematicians use more fully than musicians and vice versa, just as there are muscles that sprinters use that wrestlers don't and vice versa. Evolution doesn't know exactly what envi
10% of a larger brain is still more than 10% of a smaller brain. I would venture to guess that the randomness of evolution causes the mutation that is statistically more likely (increase in brain size) to be selected over the mutation that is "better" (more efficient use of brain). And perhaps having a large, inefficient, difficult-to-birth brain improved the overall chances of survival and reproduction; even though it made the birthing process more difficult.
There's also another important information relevant to this: Humans babies take longer to develop than most mammal infants. Most mammals are walking and poking around quite sooner than human babies.
This is because the human brain continues to develop after birth. It actually gains a lot of volume during childhood, outside the womb. That's why it takes longer for human babies to develop and it's what allows us to have large brains without causing huge birth death rates.
Could it be that if our brains were 90% smaller, we'd just use 10% of that smaller brain? Maybe our heads are this because because we can only use 10% of our brain mass effectively, so to get a useful brain, it has to be very large.
Maybe the male brain kicks in at a higher capacity during the courting process. They're nicer, more vocal, more considerate, spend all kinds of time with one thought going through their minds: "How am I going to get into her pants?" Of course, during normal tests (math, grammar, IQ, MRI), they're not thinking of much at all, more like: "Why do the tiles over here have all those little holes and the ones over there don't?" Therefore, the larger brain does improve the odds of that male getting a mate (or
"Be there. Aloha."
-- Steve McGarret, _Hawaii Five-Oh_
Large cranium... (Score:5, Insightful)
Re:Large cranium... (Score:1, Interesting)
Re:Large cranium... (Score:1)
In this case, humans have the highest EQ.
http://serendip.brynmawr.edu/bb/kinser/Int3.html [slashdot.org]
Re:Large cranium... (Score:1)
Re:Large cranium... (Score:1)
try this [brynmawr.edu]
Re:Large cranium... (Score:5, Insightful)
Then why do I have an appendix? (Or slim body hairs?)
Evolution does not look at any one characteristic. It looks at the whole of the being. And, between equally fit species, there's still a measure of chance.
Let's ignore the obvious rebuttal to your point (use of the brain's savant abilities is proportional; if we have a brain half the design, we might have half of the all-around intelligence) and focus on the evolutionary advantages of having unused brain tissue.
First off, we're able to survive brain damage much easier. Being able to be thwacked in the head and still bring food home--and maybe go out and hunt some more the next day--is an obvious evolutionary advantage.
Secondly, it increases mating. Having a bigger brain means our heads are shaped different--in a more asthetically pleasing fashion. The face is a human's primary means of identification and emotional communication--a clearer face is an obvious evolutionary advantage, within the species.
Thirdly, it's entirely possible that over the uncounted generations of prehistory, human-ancestor-groups who had savants among them simply outperformed other human-ancestor-groups who did not, thus neccistating a retention of the savant abilities. Not a clear evolutionary advantage, but a distinct possibility.
While your childbirth arugment is a good one, for it to work we'd need to have some mechanism to actually shrink brain mass at the start. Bugger me if I can think of one that'd work--larger hips would be a much easier evolutionary adaptation.
Re:Large cranium... (Score:5, Insightful)
Because there is very little selective pressure to remove these low-cost (in evolutionary terms) additions to the body. This is assuming that you can get rid of X without affecting Y, which is a heck of an assumption - most of our body parts are created/regulated by the interaction over time of *lots* of different genetic codes, your overall genetic code is not a blueprint you can just erase part of... Besides, they're not useful *now*. They presumably were *once*, and they may yet be again. Not in our lifetime, I suspect :-) but possibly in the future...
How do you *know* it's proportional ? It may be highly non-linear in nature. Intelligence could be an emergent property, as opposed to intrinsic. There could be a minimum (or maximum) neuron-quantity threshold for intelligence to occur, the decision-surface for relative intelligence could be as complex as a fractal plane. We don't know.
I think you're overlooking the incredibly difficult process humans go through in childbirth. The non-assisted mortality rate (for both mother and child) is far higher than any other mammalian species on the planet. Primate females almost always give birth without excessive labour. Human females labour can last over several hours, although today the child is more likely to be induced or surgically delivered. Only 200 years ago, death in childbirth was commonplace for those who could not afford assistance.
In contrast, being hit on the head hard enough to significantly break the skull will pretty much cause damage whatever size brain you have. Since all the higher-order functionality is on the outside of the brain (grey matter), that's the area that would be damaged anyway. If you don't break the skull, you're likely to just get a bruise either way, so long as you don't make a habit of it...
Don't forget that (unless our ancestors were particularly keen on headbutting cliffs) this would be an effect on 1 person. The do-or-die childbirth thing is an issue for every human born. I suspect nature might come down on the side of the majority...
Um. No. If we all had faces the size of pygmy monkeys, we'd probably have designs on our chests or backs, or some other method of recognition. Sexual preference is closely tied to genetic fitness, not the other way around.
Consider that healthy-but-pug-ugly A has a 85% chance of surviving to breeding-age (and hanging around afterwards for protection etc.) because he's got strong arms. Handsome bigheaded B has only a 50% chance of making it, but he looks really cool. Unfortunately for B, the numbers are against him. No matter how many doting females are queueing up (hah!), if he only has a 50% chance of making it, his genes (and those of the doting females, since they choose B) are far more likely to be swept down evolution's sewer. The corollary is that the female
Re:Large cranium... (Score:3, Insightful)
I don't think he wanted to debate individual points with you. I think his overall point was that there are probably several explanations for why evolution has chosen large brains for us and not selected against it (yet). There's probably a fifth explanation that makes even more sense. So don't jump to the conclusion that we "think" with all of our brain simply because natural selection should otherwise have selected for smaller brains; there may be oth
Re:Large cranium... (Score:2)
We don't know; overly reductionist thinking has led us to believe that vestigial body parts have no function, but some evidence suggests that the appendix is integral (though obviously not essential) to the immune system. Debates are out there on this topic, google it.
Likewise with the lack of abundant human body hair. The only other mammals with hair like ours (forget the head for a moment) are either acquatic (from hippos to cetaceans) or subterrane
Re:Large cranium... (Score:1)
It's actualy possible to groom and keep clean a beard, and a good portion of human women consider a beard attractive.
Likewise, there are human breeds that have little to no facial hair; bein
Re:Large cranium... (Score:1)
If having an appendix is more harmful than not having one, then there'd be selective pressure that would tend to eliminate it. If having an appendix is beneficial, then selective pressure will tend to retain it.
However, if having an appendix is neither more harmful nor more beneficial than not having one, then there'd be no selective pressure either way. Thus the status quo will tend to be conserved in that respect.
Re:Large cranium... (Score:1)
Your statement only holds true if the benefit/harm hapens within the earlier parts of life. If you live long enough to pass on your genes, then have some type of major genetic problem that kicks in later in life, your children will likely have the same thing happen. Waiting until later in life t
Re:Large cranium... (Score:0)
Yes, I too will focus on just this one quote.
Let's all remember, people, that evolution isn't "over" yet. We're still evolving, and presumably always will be. Just because something unnecessary or even harmful hasn't been removed from the human genome yet doesn't mean that it won't be removed eventually.
For that matter, let's not forget that even more complicated scenarios are possible. Perhaps in 20,000 years the human appendix will have turned
Re:Large cranium... (Score:2)
plus, your assertion that bigger brains = bigger faces = increased mating potential is bunk - look at all those animals, quite happy to get on and fuck, without massive faces = squirrels? rabbits? lobsters? how about animals with large faces and small brains - horses? llamas?
larger brains equalling more aesthetically pleasing faces? so are better looking people automatical
Re:Large cranium... (Score:1)
Why? Because you have other animals with smaller brains? Are _you_ attracted to a bright colorful bird? I didn't think so.
larger brains equalling more aesthetically pleasing faces? so are better looking people automatically smarter? Ask most of us
Aside from the conceit that
Re:Large cranium... (Score:0)
My head is now spinning with horrible jokes about peacocks. Thanks, buddy.
Re:Large cranium... (Score:0)
I have read that if the appendix were to become smaller it would often become infected and lead to death. While the appendix has shrunk because it is useless it can't shrink further because the risk of fatal infection.
Re:Large cranium... (Score:3, Insightful)
The notion that much of our brain is therefore "unused" doesn't really make sense from an evolutionary standpoint.
It isn't that there are sections of the brain that are never used. It is that each individual has sections of their brain that they do not use. It sort of stands to reason that there are parts of the brain that mathematicians use more fully than musicians and vice versa, just as there are muscles that sprinters use that wrestlers don't and vice versa. Evolution doesn't know exactly what envi
Re:Large cranium... (Score:1)
Re:Large cranium... (Score:1)
This is because the human brain continues to develop after birth. It actually gains a lot of volume during childhood, outside the womb. That's why it takes longer for human babies to develop and it's what allows us to have large brains without causing huge birth death rates.
Re:Large cranium... (Score:2)
Another theory (Score:2)