Gene SLC24A5 and selection...., page 1

Originally posted by Lillo
this gene decide about the pigmentation of the skin. The humans who presented this defect produced more vitamin D in the region of the world where there is less light

Okay, let's see if there aren't some issues we can't clear up.

You are in fact correct, the evidence suggests that the gene in question is in fact involved with skin pigmentation. This is the fact of the research. The hypothesis about skin pigmentation, vitamin D, and European migration are not facts in the same sense. They are speculation based on facts.

but.... some says that, base on the evolutionism, only the population who presented this defect, could survive in region where there less sun. And so, this is why there were no black people, anymore in region like europe, ural, ... What? This is to say that only a few of the travelers survived far from Africa??? Or that the women didn't make baby with the men who where not "affected"?

As the other poster mentioned, evolutionary theory doesn't speak to absolutes, only to probabilities. A certain mutation may increase the probability that an organism will survive long enough to reproduce under a particular set of selective conditions. There are in fact very few absolutes in Biology.

In my opinion, it is more probable that the human gene "adapt" to the local condition... through unveiled "decisional" behavior or system. What do you think about it?

I think what you are saying is that is the genes somehow respond to environmental influence and adapt (mutate) as a function of particular selective conditions.

Sort of opens up a big can of worms for me, but I'll try to be brief.

This isn't generally how Darwinian Theory is thought to operate, it's generally thought to operate via selective pressure on random variations that result from processes such as genetic recombination, and random mutation.

However, this is not to say there isn't a precedent for what appears to be adaptive behavior in populations of microorganisms. Some bacteria - under certain selective (stressful) conditions engage in hypermutation of specific regions of chromosal or extrachromosomal DNA. Though, bacteria can afford to do this due their rapid rate of reproduction and single-celled lifestyle.

Thus far, it doesn't appear that multicellular organisms that contain a wide variety of differentiated tissues and interacting parts, are capable of such a feat. For all the cells of your body to engage in hypermutation would likely not be good.

Though there is a precedent for this. The human immune system can produce likely an infinite number of antibodies; and this accomplished via hypermutation of very specific regions of the genome by very specific cell types. The process - thus far anyway appears to be very limited in multi-cellular eukaryotes, but is becoming more widely recognized as occuring in prokaryotes.

BTW, I think what you are referring to with respect to the Mayans is Niacin deficiency. There's lots of niacin present in corn, but is not bio-available unless you prepare the corn via cooking in 'lime water.' I am not sure exactly how you were trying to correlate this with the other stuff, but I am actually intrigued by such things myself. How did they know how to do that? It's sort of interesting, but nothing I've ever really studied in depth.

[edit on 20-12-2005 by mattison0922]