Posted on 10/07/2008 11:30:28 AM PDT by Sopater
Human evolution is grinding to a halt because of a shortage of older fathers in the West, according to a leading genetics expert.
Fathers over the age of 35 are more likely to pass on mutations, according to Professor Steve Jones of University College London.
Speaking Tuesday at a UCL lecture entitled "Human Evolution Is Over," Professor Jones will argue that there were three components to evolution — natural selection, mutation and random change.
"Quite unexpectedly, we have dropped the human mutation rate because of a change in reproductive patterns," Professor Jones told The Times.
"Human social change often changes our genetic future," he said, citing marriage patterns and contraception as examples.
Although chemicals and radioactive pollution could alter genetics, one of the most important mutation triggers is advanced age in men.
This is because cell divisions in males increase with age.
(Excerpt) Read more at foxnews.com ...
The fact that anyone supports Obama or the Democrat Party could have told you this...
And if DNA reproduction (and its subsequent mixing in a small population) produces changes, even beneficial ones, might not this be the source of genetic novelty?
The vitamin D question is an interesting one. Are you suggesting vitamin D levels are related to degrees of skin pigmentation?
The environment selects for the change, it doesn't account for the change appearing, the environment ensures that those with the change will have a reproductive advantage.
Yes, DNA replication being error prone, introduces mutations into the human genome, thus being one of the sources of genetic variation/ genetic novelty.
Vitamin D levels are absolutely related to skin pigmentation. An African in Norway needs a vitamin D supplement or they will develop rickets. That is one reason they put Vitamin D in milk. Unfortunately, outside of a few cattle herding populations, most Africans are lactose intolerant and don't drink milk!
If this be the case then are humans changed by selection to make them suitable for the climate they've chosen or do they choose to live in the climate they find most suitable? Perhaps an unanswerable question.
My thought on Vitamin D was whether the level of Vit D would affect the amount of pigmentation in a population as perhaps an abundance of the vitamin (actually part of a hormonal system) might increase pigmentation and a lack reduce it.
Of course northern fish eating people wouldn't figure into this question.
May I test your patience in the future if I find I have other questions? For now my well is dry. Thanks.
I think you are mixing up cause and effect. It doesn't matter if light skinned people moved south instead of north or if dark skinned people moved north not south. Natural selection would sort them out pretty quick. Moreover how would they know? I guess sunburn might make you want to move north, but only if you knew that northern climates had less direct sun; and how would they know that?
If you had a time machine and went back 60,000 years and you isolated a Norwegian population in Africa and isolated an African population in Norway; when you checked back on them in a few thousand years the Africans in Norway would be lighter and the Norwegians in Africa would be darker just due to selection of alleles already present in the population, let alone the selection for or against any new alleles that can and would arise within the populations.
The alleles to make a “black” person are present in a white population, just not prevalent enough to make anybody black without selection acting over numerous generations. Similarly the alleles to make a “white” person are present in a black population.
Also, the mutation would not have to arise more than once in separate individuals. A single disabling mutation of a ‘dark skin’ allele in a single individual could achieve 100% presence in a population where dark skin was making vitamin D synthesis a problem in northern climates.
Vitamin D synthesis takes place in the skin and is dependent upon absorption of energy from sunlight. A dark skinned African in Norway would not get enough sunlight to make enough vitamin D, making the trait of light skin highly selected for.
I have a question for you. With modern medicine in effect in at least the western world, will that have an effect on evolution? It seems like the man who would have died because of a heart problem in childhood 200 years ago, but now can live long enough to reproduce offspring that will also have that heart problem will cause people to be born with more harmful mutations than pre-medicine days? Does this make sense? It seems like modern medicine would change natural selection drastically.
Often times an allele that causes a heart defect when it is present in both copies will confer an advantage when there is only one copy. Medication allowing the person with two copies to reproduce may well increase the prevalence of the allele in the population, but is that a bad thing considering that in one copy it is advantageous and the symptoms from having two copies can be treated such that the opposite sex still finds you a good prospect as a potential mate?
A better example, and one often cited, is eye sight. For the majority of people to be born with good vision, some people are going to be either near sighted or far sighted. It isn't that they have “bad” genes, just an unfortunate combination of good genes. Natural selection before eyeglasses had these people at a disadvantage. But selective pressure eliminating them didn't do anything towards making more humans have perfect eyesight. While allowing them to wear glasses and reproduce (oh those sexy science women in lab coats and glasses. Va va Vooooooom!) hasn't done anything towards making more humans need glasses.
In other words, nearsighted alleles aren't bad unless you get too many, and farsighted alleles aren't bad unless you get too many. Normal people have a good mix and good vision. Eyeglass wearing people have too many alleles of one type or the other, but they don't have “bad” genes, just an unfortunately mix of “good” genes.
For example my dad is nearsighted and my mom is farsighted. Both my brother and I have better than 20/20 vision.
In the distant past it would be doubtful that either of my parents would make it to reproductive age with their bad eye sight, but that isn't necessarily a good thing as it doesn't change the overall ratio of nearsighted vs farsighted alleles; it just eliminates those with an unfortunate mix of those alleles.
I often do confuse cause and effect but I should get a pass on that since they sometimes wear disguises.
Just one more and I’ll be gone for a few days. Is there evidence that lack of Vit. D has been enough of a problem (bone density, etc.) in northern dwellers or early man that selection would (how shall I say it?)... ummm....be useful? Do we know that selection for lighter skin resulted from lower Vit D intake?
I have a bit of trouble framing the question, you see.
Until later and thanks.
There is plenty of evidence of what happens when a dark skinned person moves to where they no longer get enough sunlight or vitamin D. They get rickets.
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