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 Post subject: Re: I Wuz Black n Shiet
PostPosted: Fri Feb 09, 2018 7:55 pm 
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Mac wrote:
Dark brown skin? Blue eyes? Turns out Cheddar Man was a direct ancestor of Tom Jones. Who knew?

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:lol: :lol:

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 Post subject: Re: I Wuz Black n Shiet
PostPosted: Fri Feb 09, 2018 8:50 pm 
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jack t ripper wrote:
Mac wrote:
Dark brown skin? Blue eyes? Turns out Cheddar Man was a direct ancestor of Tom Jones. Who knew?

Image


:lol: :lol:

But then this mystery.

Quote:
The two groups that came to Scandinavia were originally genetically quite different, and displayed distinct physical appearances. The people from the south had blue eyes and relatively dark skin. The people from the northeast, on the other hand, had a variation of eye colours and pale skin.


The first group obviously was the Cheddar Man. How about the second group; way before agriculture was anywhere near. I can understand skin color adaptation, but I don't know why eye color and hair color changes, what is the evolution pressure.

What do you think. I think hanky panky is the explanation.

But then I am probably wrong. Never mind, I like the idea anyway.

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 Post subject: Re: I Wuz Black n Shiet
PostPosted: Fri Feb 09, 2018 9:10 pm 
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Yes, probably sexual selection on eye color although the genes that control for RETINAL pigment may be linked to eye color so one can imagine there might be some protective effect to more retinal pigment in equatorial regions. I think the iris musculature is thick enough to block most light penetrating the iris even in light iris color individuals.

One might also expect retinal pigmentation to be preserved in high albedo environments (snow, ice, blue ocean)

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 Post subject: Re: I Wuz Black n Shiet
PostPosted: Sat Feb 10, 2018 12:55 am 
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The questions I always fail to see unanswered in all paleobiology studies which attempt to go further than the cladistic analyses which fossils in modest numbers can afford to some degree:

1. How many modern humans have you sampled to establish the baselines for estimates of variability at each loci?

2. What proportion of all the loci have been sampled at that intensity?

3. How was the above sampling stratified across the full range of human geographic extent?

4. What were the relative proportional sample sizes for each of the presumably distinctive populations sampled?

Based on (1), through (4) what is the ESTIMATES (with 7.5 billion of us, it is impossible to have anything except an estimate based on a sample) of:

A. The total variability in all loci in the human genome
B. The total variability excluding supposedly "non-coding" loci
C. The total variability at loci which are presumed /expected to have been "hot" with respect to natural selection over the past X period of time?
D. The minimum and maximum number of factors (distinctive breeding populations) estimated?
E. The full range of descriptive variables to account for the non-trivial variability in the factors (populations) observed based on the overall distribution of variability in the whole sample: synthetic tentative conclusions/hypotheses which emerge along the lines of:
(i) the most average population of them all
(ii) the most recently distinguished population of them all
(iii) the oldest minimally intermixed population of them all
or (iv) are these sorts of patterns just "not" visible, suggesting that indeed pan-mixia has prevailed and insufficient time/impermeability to gene flow has existed to actually allow for such distinctions.

Those are just the "getting started questions," that would allow a basic orientation about what we are actually dealing with. In all the years I worked in academia, and often came across genetic analysis papers, but I NEVER encountered any article that specifically laid out these sorts of basic descriptive facts about the variability in the human genome (by which I mean, the ACTUAL genome, all ~7.5 billion sets of genotypes give-or-take). The human genome project only finished actually describing the basic structure of a "typical" human genotype a few years back? Has it been as many as 15 years by now, I don't keep up . . .

I have never looked at the maths, but I have seen plenty of papers that were essentially exploratory small studies (often with convenience samples, not truly random samples) that took a couple hundred samples from this or that population and then compared those individuals with a couple hundred each from two or three other populations and reached [tentative] conclusions.

Now maybe things have changed, and shiploads of cash have been handed forth to allow these human genetic variation research teams to go out and collect the thousands or perhaps even tens of thousands of samples necessary from each of the tens of thousands of ostensibly distinctive human populations out there, but as of the last time I read any of that literature, it sure didn't look like things were moving in that direction.

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 Post subject: Re: I Wuz Black n Shiet
PostPosted: Sat Feb 10, 2018 12:16 pm 
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Well you can certainly say there is insufficient data on Paleolithic DNA. Even so the DNA approach is a lot more convincing than molars. :lol: Look at the Denisovans...just two or three individuals. Sees to me the math is thinner the fewer individuals you have. There could absolutely be other subspecies too. You find a molar in Siberia and then discover the closest living relatives (except for Tom Jones) are Australian aboriginals and headhunters from New Guinea. It's damned fascinating.

There is a new approach where human DNA fragments can be retrieved from cave soil when there are no bones. You might sample the same individuals multiple times but if you just focused on one allele you could at least look at variability.

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 Post subject: Re: I Wuz Black n Shiet
PostPosted: Sat Feb 10, 2018 7:39 pm 
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Horse+donkey=mule. Different species can reproduce.

Why not different species of humans?

No answer forthcoming because any anthropologists who suggests that Africans are not genetically superior in every way would be lynched.

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 Post subject: Re: I Wuz Black n Shiet
PostPosted: Sat Feb 10, 2018 7:53 pm 
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This is a real WRW tread. :lol:

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 Post subject: Re: I Wuz Black n Shiet
PostPosted: Sat Feb 10, 2018 10:03 pm 
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Actually Doggie is exactly right, the ability to form reproductively viable offspring is part of the classical definition of a species.

If 2-4% of European DNA is Neanderthal in origin and 3-4% of Papua New Guinea DNA is Denisovan then it looks like someone has some explaining to do.

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 Post subject: Re: I Wuz Black n Shiet
PostPosted: Sun Feb 11, 2018 12:15 am 
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Quote:
<..>
And, on the pigmentation loci which make modern Europeans very distinctive vis-a-vis other populations, SLC24A5, SLC45A2 and HERC2-OCA2, they were quite different from anything we’ve encountered before. First, these peoples seem to have had a frequency for the genetic variants strongly implicated in blue eyes in modern Europeans close to what you find in the Baltic region. The overwhelming majority carried the derived variant, perhaps even in regions such as Spain, which today are mostly brown-eyed because of the frequency of the ancestral variant. Second, these European hunter-gatherers tended to lack the genetic variants at SLC24A5 and SLC45A2 correlated with lighter skin, which today in European is found at frequencies of ~100% and 95% to 80% respectively.

The reason that one of the scientists being interviewed stated that there was a “76 percent probability that Cheddar Man had blue eyes” is that they used something like IrisPlex. They put in the genetic variants and popped out a probability. The problem is that the training set here is modern groups, which may have a very different genetic architecture than ancient populations. Recent work on Africans and East Asians indicate that the focus on European populations when it comes to pigmentation genetics has left huge lacunae in our understanding of common variants which affect variation in outcome.

East Asians, for example, lack both the derived variants of SLC24A5 and SLC45A2 common in Europeans but are often quite light-skinned. A deeper analysis of the pigmentation architecture of WHG might lead us to conclude that they were an olive or light brown-skinned people. This is my suspicion because modern Arctic peoples are neither pale white nor dark brown, but of various shades of olive.

<..>


https://www.gnxp.com/WordPress/2018/02/ ... published/


There is also mention of the articles claiming "10% DNA" likeness to Cheddar Man, in modern Britons, is likely an invalid claim because they compared using mitochondrial DNA. Likely to be far less.

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 Post subject: Re: I Wuz Black n Shiet
PostPosted: Sun Feb 11, 2018 4:16 pm 
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:lol:

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