Re: How the environment is able to change your genes?

Leonard Evens wrote:

> John Harshman wrote:
>
>>Artificer wrote:
>>
>>
>>
>>>In theory if our planet starts to slowly become heater and heater
>>>during millions of year our species should evolve to become more
>>>tolerant to high temperature right? Is pretty obvious too me that
>>>people living on more tropical environment tend to have their skin
>>>tanned by the sun but this is not a genetic mutation it is simply a
>>>reaction like painting my car. So I wonder if anybody can explain me
>>>please as "simple" as possible how the environment can direct a
>>>creature to evolve in certain direction or if the environment does not
>>>promote change but instead it simply select the more appropriate
>>>genetics population via natural selection.
>>>
>>
>>Right. The environment doesn't direct evolution. Mutation is random, and
>>some genotypes reproduce better in whatever environment than other
>>genotypes. Natural selection, like you said. Tanning is, by the way, a
>>response that evolved through mutation and natural selection. This
>>general phenomenon is called phenotypic plasticity, and allows a certain
>>amount of adaptation to different environments without genetic change.
>>But phenotypic plasticity itself evolves because it's selectively
>>advantageous.
>>
>
> I'm not sure, but isn't it true that light skin was the adaptation. I
> thought our African ancestors were dark skinned and that skin lightened
> under selective pressure for populations that moved north because of
> Vitamin D metabolism.

That's a whole nother adaptation. We're talking here about the ability
to increase the amount of melanin in your skin in response to exposure
to the sun. Tanning, you know.

.

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