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Humans evolving 100 times faster than historical levels.

latimes.com

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Re: Humans evolving 100 times faster than historical levels.

#11

Post by prat »

slackerIII wrote: post #6
BRadmin wrote: post #3

"Nobody 10,000 years ago had blue eyes," Hawks said. "Why is it that blue-eyed people had a 5% advantage in reproducing compared to non-blue-eyed people? I have no idea." Now that's interesting. Any theories?

The theory I've heard is that a blue iris makes it easier to see pupil dilation, which is an indication of attraction. People are more likely to hook up when they can tell the other person is attracted to them, so...

That is possible, but the gene for blue eyes may also be linked with some other characteristic (biologically more relevant than attraction - like resistance to cancer) that might provide selective advantage. Linkage (close enough genes travel together) among genes plays a huge role in selection but often, and understandably, we regard the the feature that is easily visible to us as essential.

Re: Humans evolving 100 times faster than historical levels.

#12

Post by nopassrecover »

prat wrote: post #11
slackerIII wrote: post #6

Earlier quoted context omitted.

The theory I've heard is that a blue iris makes it easier to see pupil dilation, which is an indication of attraction. People are more likely to hook up when they can tell the other person is attracted to them, so...

That is possible, but the gene for blue eyes may also be linked with some other characteristic (biologically more relevant than attraction - like resistance to cancer) that might provide selective advantage. Linkage (close enough genes travel together) among genes plays a huge role in selection but often, and understandably, we regard the the feature that is easily visible to us as essential.

While it is irrelevant to your point, I'd like to make a note about your example.

Resistance to cancer would likely have little evolutionary value. Most mating and child rearing is done before the average age of cancer, particularly in past societies. I would similarly wager that cancer would not a be a strong enough force (it would usually hit people randomly rather than the entire group simultaneously) to ruin the ability of a tribe to defend itself.

If anything, cancer resistance (which would probably mean less cell mutation ability) would be disadvantageous from an evolution standpoint because you would have less variation and consequently may have trouble adapting.

Re: Humans evolving 100 times faster than historical levels.

#13

Post by nopassrecover »

pmichaud wrote: post #8

I was confused by the part that said white skin allows more sun light to be absorbed. I'm quite sure this is wrong: Dark skin means more light is absorbed, and therefore doesn't bounce back at the viewer's eyes. the only explanation I can think of is that the rules are somehow different for light outside the visible range?

Well the advantage of increased melanin in the skin is protection from UV damage. Perhaps this is what they are referring to.

Re: Humans evolving 100 times faster than historical levels.

#14

Post by anigbrowl »

BRadmin wrote: post #3

"Nobody 10,000 years ago had blue eyes," Hawks said. "Why is it that blue-eyed people had a 5% advantage in reproducing compared to non-blue-eyed people? I have no idea." Now that's interesting. Any theories?

Novelty? I have red hair, which I'm not sure is adaptive (eg it puts me at greater risk for skin cancer) but which partners have rated highly as an attractive feature specifically because it's unusual. Then again I have a compulsive draw towards partners from outside my own ethnic group, so there's some selection bias going on with that interpretation.

Re: Humans evolving 100 times faster than historical levels.

#15

Post by req2 »

nopassrecover wrote: post #12
prat wrote: post #11

Earlier quoted context omitted.

That is possible, but the gene for blue eyes may also be linked with some other characteristic (biologically more relevant than attraction - like resistance to cancer) that might provide selective advantage. Linkage (close enough genes travel together) among genes plays a huge role in selection but often, and understandably, we regard the the feature that is easily visible to us as essential.

While it is irrelevant to your point, I'd like to make a note about your example. Resistance to cancer would likely have little evolutionary value. Most mating and child rearing is done before the average age of cancer, particularly in past societies. I would similarly wager that cancer would not a be a strong enough force (it would usually hit people randomly rather than the entire group simultaneously) to ruin the…

Cancer may simply have been an example of kind, rather than specific to the case at hand; however, I wouldn't disregard it as quickly as you do.

The grandmother hypothesis [http://well.blogs.nytimes.com/2007/10/05/evolutions-secret-w...] supports cancer resistance as an evolutionarily beneficial gene. You also miss the obvious unstated point that cancer resistance itself may just be a side effect of another characteristic, such as more efficient mitochondria.

Your third paragraph fails to support any of its assertions; cancer resistance takes many forms, and most mutations are negative in nature: some math would likely be necessary to support a (carefully worded) argument in either direction.

Re: Humans evolving 100 times faster than historical levels.

#16

Post by breck »

BRadmin wrote: post #3

"Nobody 10,000 years ago had blue eyes," Hawks said. "Why is it that blue-eyed people had a 5% advantage in reproducing compared to non-blue-eyed people? I have no idea." Now that's interesting. Any theories?

"Nobody 10,000 years ago had blue eyes,"

My reaction is that he misspoke here or he overstated his claim to make a point.

I know nothing about the proportion of people with blue eyes back then or right now for that matter. But I think at the very least, you could only make that claim with a tiny, tiny, tiny amount of confidence.

Maybe the proportion of humans with blue eyes was smaller back then, maybe it was larger, or maybe it was the same. I don't know. But to claim nobody 10,000 years ago had blue eyes is an impossible point to prove unless you have DNA samples from every human alive 10,000 years ago. We might be able to say that all the people alive today with blue eyes descended from one ancestor, but we can't claim to know about the population of people with blue eyes back then. For all I know, half the population 10,000 years ago could have had blue eyes but then got wiped out by swine blue.

That's like saying no one 100 years ago was over 7'6" tall. I know a bit more about height and think that this statement may be true. But it would be real hard to prove. Now shift the timespan back by 2 orders of magnitude, and I think it'd be harder to prove.

I'm not saying that the general idea is wrong, but I'm just it would be a good idea to question that claim a lot before thinking about reasons why that might be the case.

Re: Humans evolving 100 times faster than historical levels.

#17

Post by prat »

nopassrecover wrote: post #12
prat wrote: post #11

Earlier quoted context omitted.

That is possible, but the gene for blue eyes may also be linked with some other characteristic (biologically more relevant than attraction - like resistance to cancer) that might provide selective advantage. Linkage (close enough genes travel together) among genes plays a huge role in selection but often, and understandably, we regard the the feature that is easily visible to us as essential.

While it is irrelevant to your point, I'd like to make a note about your example. Resistance to cancer would likely have little evolutionary value. Most mating and child rearing is done before the average age of cancer, particularly in past societies. I would similarly wager that cancer would not a be a strong enough force (it would usually hit people randomly rather than the entire group simultaneously) to ruin the…

I agree about the child bearing age point..resistance to infectious disease may have been a better example.

but re your last point, being prone to cancer could speed up evolution but at the same time could wipe out a sub population? infact- that (probably) holds for anything that speeds up evolution - but again math models would be needed to prove that.

Re: Humans evolving 100 times faster than historical levels.

#18

Post by pedermoeller »

pmichaud wrote: post #8

I was confused by the part that said white skin allows more sun light to be absorbed. I'm quite sure this is wrong: Dark skin means more light is absorbed, and therefore doesn't bounce back at the viewer's eyes. the only explanation I can think of is that the rules are somehow different for light outside the visible range?

As I remember the explanation: Dark skin means more melanin in the skin. Melanin blocks the UV light that the body uses to synthesize D vitamin. So white people in north are better suited for utilizing the scarce sunlight for D vitamin production and black people in the south are better protected against the skin cancer risk caused by the UV radiation.

Re: Humans evolving 100 times faster than historical levels.

#19

Post by igrekel »

pmichaud wrote: post #8

I was confused by the part that said white skin allows more sun light to be absorbed. I'm quite sure this is wrong: Dark skin means more light is absorbed, and therefore doesn't bounce back at the viewer's eyes. the only explanation I can think of is that the rules are somehow different for light outside the visible range?

I wouldn't dismiss this so quickly. It is widely accepted and is also part of what is evaluated when the doctor recommends or not that you give extra vitamin D to your child, having white skin means you need to spend less time in the sun to have sufficient vitamin D and not require supplements.

Perhaps the question is more complex because sunlight is not all in the visible wavelengths and skin is actually translucent and light reaches different level through the skin, melanin prevents parts of the light to reach deeper levels in the skin and also converts parts of light.

Re: Humans evolving 100 times faster than historical levels.

#20

Post by Tichy »

anigbrowl wrote: post #14
BRadmin wrote: post #3

"Nobody 10,000 years ago had blue eyes," Hawks said. "Why is it that blue-eyed people had a 5% advantage in reproducing compared to non-blue-eyed people? I have no idea." Now that's interesting. Any theories?

Novelty? I have red hair, which I'm not sure is adaptive (eg it puts me at greater risk for skin cancer) but which partners have rated highly as an attractive feature specifically because it's unusual. Then again I have a compulsive draw towards partners from outside my own ethnic group, so there's some selection bias going on with that interpretation.

I think being attracted to different ethnic groups might have an advantage, too - keeping diversity in the gene pool up is probably beneficial.
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