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Author Topic:   A question about evolution
CRR
Member (Idle past 2243 days)
Posts: 579
From: Australia
Joined: 10-19-2016


Message 19 of 70 (798357)
02-01-2017 11:27 PM
Reply to: Message 1 by Micah8294
02-01-2017 4:19 PM


The worldwide uniformity of humans indicates a relatively recent radiation which hasn't allowed time for some features to develop. Also humans have the ability to wear clothes and find or make shelter which helps alleviate the pressure of natural selection.
It's not necessarily the case that Africans developed black skin, it could be that Europeans developed white skin. It could have a lot to do with the founder effect if the original groups to move into different countries already had a propensity to lighter or darker skin. Technically we are all different shades of brown so it's not really that big a difference.
Black skin might absorb more heat but it also radiates more heat and the higher levels of melanin help to reduce effects of higher ultraviolet radiation so black is not necessarily a disadvantage compared to white skin.

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CRR
Member (Idle past 2243 days)
Posts: 579
From: Australia
Joined: 10-19-2016


Message 32 of 70 (798526)
02-03-2017 4:44 AM
Reply to: Message 20 by Coyote
02-01-2017 11:38 PM


I think Eskimos have relatively dark skin because they are derived from the same stock as American Indians. Sunlight and diet are probably minor factors. I.e founder effect.

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CRR
Member (Idle past 2243 days)
Posts: 579
From: Australia
Joined: 10-19-2016


Message 38 of 70 (798717)
02-05-2017 1:45 AM
Reply to: Message 37 by NoNukes
02-04-2017 2:30 PM


@NoNukes.
The same stock as Amer-indians means the ancestors of both probably migrated from Asia across the Bering Strait land bridge.
The American Indian skin colour was traditionally called red, but that was relative to other skin colours and not fire engine red. We are all part of a continuum of skin colour and it's not a black and white issue in most cases.
White Europeans still have a variation in skin colour but they are typically a much lighter shade than "red' Amer-indians or "black" Africans. Truly, colour is only skin deep.

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CRR
Member (Idle past 2243 days)
Posts: 579
From: Australia
Joined: 10-19-2016


Message 46 of 70 (799218)
02-08-2017 6:31 AM
Reply to: Message 45 by NoNukes
02-08-2017 5:02 AM


the origin of skin colors which are inheritable.
There really is only one skin colour; brown. This is caused by melanin and depending on how much we have we can vary from white (little melanin) to black (lots of melanin). This is controlled by several genes giving about 64 shades of brown.
The theory that best fits the facts is that Adam and Eve were created with 2 alleles for each of these genes so they had the genetic potential for all skin colours. Their children would have had a variety of skin colours. Some black, some white, some in between. Assuming random pairing in this generation some couples would have had both black, both white, or some mixture. This would then have created families where some had skin colour predominately at both ends of the range.
So how did we get races with different skin colours? Perhaps an event that divided the population into family groups, some white, some black, most in between. The Tower of Babel meets that requirement. The new languages groups would have kept families together and locked skin colours into language groups. As these groups spread out they took their new languages and skin colours with them.
Selection and drift could then have acted to reduce variation within each group.

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CRR
Member (Idle past 2243 days)
Posts: 579
From: Australia
Joined: 10-19-2016


Message 56 of 70 (801069)
03-03-2017 4:56 AM
Reply to: Message 53 by Pressie
02-09-2017 4:20 AM


Do people with darker skin colour have more or less genetic information than people with lighter skin colour?
Generally the same. They have the same number of functional genes. However I have read that red hair is due to a defect in the MC1R gene so there would be a loss of genetic information in that case.

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CRR
Member (Idle past 2243 days)
Posts: 579
From: Australia
Joined: 10-19-2016


Message 57 of 70 (801070)
03-03-2017 4:57 AM
Reply to: Message 55 by AZPaul3
02-09-2017 6:53 PM


Step 2
Evolution did it.

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CRR
Member (Idle past 2243 days)
Posts: 579
From: Australia
Joined: 10-19-2016


Message 60 of 70 (801083)
03-03-2017 7:01 AM
Reply to: Message 59 by AZPaul3
03-03-2017 6:54 AM


Re: Step 2
"An MC1R that is hitting on all cylinders keeps red hair away. So it makes sense that people with red hair usually have an MC1R gene that has a small difference in it that keeps it from working quite right." Is it possible to end up with red hair by getting the red hair gene from just one parent? | The Tech Interactive

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CRR
Member (Idle past 2243 days)
Posts: 579
From: Australia
Joined: 10-19-2016


Message 67 of 70 (801279)
03-04-2017 6:31 PM
Reply to: Message 66 by AZPaul3
03-04-2017 10:12 AM


Re: Step 2
"A study on unrelated British and Irish individuals demonstrated that over 80% of people with red hair and/or fair skin that tan poorly have a dysfunctional variant of the MC1R gene."
"As humans migrated north, the absence of high levels of solar radiation in northern Europe and Asia relaxed the selective pressure on active MC1R, allowing the gene to mutate into dysfunctional variants without reproductive penalty, then propagate by genetic drift."
Melanocortin 1 receptor - Wikipedia
@caffeine also raises some interesting issues.
At this stage I'm probably getting out of my depth in genetics and particularly MC1R, so I'll make this my last comment.

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