"My spouse, my cousin" math quiz

An unanswered question on sexual selection in humans.

The general belief among scientists is that modern humans were originally dark skinned. After their migration into Europe roughly 50K years ago, the lack of sunlight favored what is commonly called "white" skin, but is in reality "thin" skin. All human beings have mostly white material under the epedermis, the thin skin simply makes it more visible. This thin skin meant you were more likely to die of skin cancer, but it allowed for the more efficient production of vitamin D and you were healthier for your child bearing ages. Natural selection does not really care about what happens to you after you reproduce.

One issue with this theory is that there are people at high latitudes in siberia with dark skin. It is generally explained that those people ate much more fish, and got plenty of vitamin D in that manner.

But, remember that while there were probably less than a million humans alive in the whole world during the paleolithic, that individually they were just as intelligent (or as stupid) as modern humans. There could have been an Albert Einstein who grew up in a small village. The question is whether white skin was favored by sexual selection. It's not clear if all the dark skin people got rickets and died out on their own, or if they were bred out of existence.

Quote: pacomartin

Natural selection does not really care about what happens to you after you reproduce.

Oh, yes it does.

Do children with two parents to look after them ahve a better chance to grow up to reproduce? Of course they do. Ergo natural selection favors parents who live long after their offspring are born.

There's a similar argument about grandparents and the accumulation of knowledge.

Quote: Nareed

Oh, yes it does.

I agree. Some say, and I agree, that the evolutionary reason women live longer than men is they are useful raising grandchildren or other young children, while old men are pretty useless.

Quote: Wizard

I agree. Some say, and I agree, that the evolutionary reason women live longer than men is they are useful raising grandchildren or other young children, while old men are pretty useless.

Could be.

Another thing I didn't mention is that the times an individual manages to reproduce also affect natural selection, or are affected by it. Male bees reproduce once and then die. Human males can reproduce any number of times. of course, a bee will ahve hundreds or thousands of descendants and the hive will take care of them. A human will have one child at a time (we can discount twins and higher as anomalies without significant statistical impact, but you'd know more about that) and he needs to help to care for them.

To be sure there are exceptions, but throughout human history fathers have helped in raising the children, even if only to the extent of providing food and protection to the mother and the children. That counts, too.

Quote: Nareed

To be sure there are exceptions, but throughout human history fathers have helped in raising the children, even if only to the extent of providing food and protection to the mother and the children. That counts, too.

I don't dispute that. I never said that men are only good as sperm donors. However, after a certain age the kids are grown, the father is old, and becomes more of a burden than a benefit to the family and society, at least in caveman times. I argue that is the reason that men tend to die younger than women.

Quote: Wizard

I don't dispute that. I never said that men are only good as sperm donors. However, after a certain age the kids are grown, the father is old, and becomes more of a burden than a benefit to the family and society, at least in caveman times. I argue that is the reason that men tend to die younger than women.

I wasn't disputing that, and some men are no good even as sperm donors (I name no names, but some of them have been banned repeatedly from this forum).

Anyway, I wasn't disputing your theory, merely adding to reasons why natural selection isn't done with an orgnaism once it reproduces. Offhand I can't think of any other than insects which die as soon as they mate or give birth, but even in species where the male, or female, have nothing to do with the offspring, few die soon after mating, laying eggs or giving birth. Most stick around to reproduce again and again.

That's because an organism that can mate only once has less chances of passing on its genes than one that mates several times. Consider sea turtles. The adults don't ever see the offspring, yet they are among the longest lived vertebrates around.