26
   

Does everyone agree that we evolved from Africa?

 
 
Olivier5
 
  2  
Reply Wed 21 Jun, 2017 03:05 pm
Fair skin in modern humans is recent (neolithic), therefore not linked with Neanderthal.


How Europeans evolved white skin
By Ann GibbonsApr. 2, 2015 , 5:00 PM
http://www.sciencemag.org/news/2015/04/how-europeans-evolved-white-skin

ST. LOUIS, MISSOURI—Most of us think of Europe as the ancestral home of white people. But a new study shows that pale skin, as well as other traits such as tallness and the ability to digest milk as adults, arrived in most of the continent relatively recently. [...] most modern Europeans don’t look much like those of 8000 years ago.

The origins of Europeans have come into sharp focus in the past year as [a recent] study revealed that amassive migration of Yamnaya herders from the steppes north of the Black Sea may have brought Indo-European languages to Europe about 4500 years ago.

Now, a new study from the same team drills down further into that remarkable data to search for genes that were under strong natural selection—including traits so favorable that they spread rapidly throughout Europe in the past 8000 years. [...]

First, the scientists confirmed an earlier report that the hunter-gatherers in Europe could not digest the sugars in milk 8000 years ago, according to a poster. They also noted an interesting twist: The first farmers also couldn’t digest milk. The farmers who came from the Near East about 7800 years ago and the Yamnaya pastoralists who came from the steppes 4800 years ago lacked the version of the LCT gene that allows adults to digest sugars in milk. It wasn’t until about 4300 years ago that lactose tolerance swept through Europe.

When it comes to skin color, the team found a patchwork of evolution in different places, and three separate genes that produce light skin, telling a complex story for how European’s skin evolved to be much lighter during the past 8000 years. The modern humans who came out of Africa to originally settle Europe about 40,000 years are presumed to have had dark skin, which is advantageous in sunny latitudes. And the new data confirm that about 8500 years ago, early hunter-gatherers in Spain, Luxembourg, and Hungary also had darker skin: They lacked versions of two genes—SLC24A5 and SLC45A2—that lead to depigmentation and, therefore, pale skin in Europeans today.

But in the far north—where low light levels would favor pale skin—the team found a different picture in hunter-gatherers: Seven people from the 7700-year-old Motala archaeological site in southern Sweden had both light skin gene variants, SLC24A5 and SLC45A2. They also had a third gene, HERC2/OCA2, which causes blue eyes and may also contribute to light skin and blond hair. Thus ancient hunter-gatherers of the far north were already pale and blue-eyed, but those of central and southern Europe had darker skin.

Then, the first farmers from the Near East arrived in Europe; they carried both genes for light skin. As they interbred with the indigenous hunter-gatherers, one of their light-skin genes swept through Europe, so that central and southern Europeans also began to have lighter skin. The other gene variant, SLC45A2, was at low levels until about 5800 years ago when it swept up to high frequency.

The team also tracked complex traits, such as height, which are the result of the interaction of many genes. They found that selection strongly favored several gene variants for tallness in northern and central Europeans, starting 8000 years ago, with a boost coming from the Yamnaya migration, starting 4800 years ago. The Yamnaya have the greatest genetic potential for being tall of any of the populations, which is consistent with measurements of their ancient skeletons. In contrast, selection favored shorter people in Italy and Spain starting 8000 years ago, according to the paper now posted on the bioRxiv preprint server. Spaniards, in particular, shrank in stature 6000 years ago, perhaps as a result of adapting to colder temperatures and a poor diet.

Surprisingly, the team found no immune genes under intense selection, which is counter to hypotheses that diseases would have increased after the development of agriculture.
0 Replies
 
Blickers
 
  1  
Reply Wed 21 Jun, 2017 03:05 pm
@Foofie,
Quote Foofie:
Quote:
Random mutations do not come frequently enough to think that a random mutation for lighter skin came often enough so that a group could then populate the "out of Africa" group to the present day population in a comparatively short evolutionary time.

It's not so much random mutation as the fact that after the Homo Sapiens moved into colder, darker places in Europe and Africa, those born with slightly lighter skin, (there's always a small variation in skin color among any group), resisted disease better and had more kids. Repeat that process for 50 generations or so and bingo!-the whole population has much lighter skin.

The last part of the process in Europe only happened about 8,000 years ago. Europeans were dusky-hued, then along came the farmers. You can get vitamin D from sunlight, from fish, and from game. When the Europeans' diet switched to grain for protein, which has no vitamin D at all, the lighter skinned Europeans again got more vitamin D out of the sun than their darker hued companions, resisted disease better and had more kids, and the skin lightening process repeated itself.

Neanderthals were not necessary for this process, in fact when the final lightening process occurred 8,000 years ago, Neanderthals were long gone. As it turned out, mixing with Neanderthals might have been part of the process of the initial skin lightening starting 45,000 years ago.
Setanta
 
  3  
Reply Wed 21 Jun, 2017 04:00 pm
Darker skin comes not just from the melanin bodies in the skin, but from exposure to sunlight as well, and the higher the sun in the sky, the greater the protection needed--and the melanin bodies respond by pumping out the melanin. The reverse of that process applies, too. Melanin bodies give off heat in the tropic and subtropic climate where we are thought to have arisen. The reverse of that process holds, too. When there is less heat, and the sun is less nearly overhead, then less melanin is produced. People could easily have had lighter skin colors in just a few generations.

(If there is anyone here who actually believes that Foofie/Miller knows anything about this topic, or any other for that matter, I have a bridge you might be interested in purchasing.)
rosborne979
 
  1  
Reply Wed 21 Jun, 2017 04:52 pm
@Blickers,
It bears repeating that it is not specific random mutations which drive evolution, but selective pressures applied to populations which are already full of variations. Eventually the variant alleles within the gene pool come to dominate the population and the population appears to change.
Foofie
 
  0  
Reply Fri 23 Jun, 2017 01:15 pm
@Setanta,
Setanta wrote:

... The reverse of that process holds, too. When there is less heat, and the sun is less nearly overhead, then less melanin is produced. People could easily have had lighter skin colors in just a few generations.

(If there is anyone here who actually believes that Foofie/Miller knows anything about this topic, or any other for that matter, I have a bridge you might be interested in purchasing.)


I guess you've explained why African-Americans are going to be white any time now. Especially, Blacks that are Canadian citizens.

0 Replies
 
Foofie
 
  -1  
Reply Fri 23 Jun, 2017 01:18 pm
@rosborne979,
rosborne979 wrote:

It bears repeating that it is not specific random mutations which drive evolution, but selective pressures applied to populations which are already full of variations. Eventually the variant alleles within the gene pool come to dominate the population and the population appears to change.


In the case of dark skin, and little vitamin D, the surviving population becomes very small, and the eventual new and larger population is very homogeneous genetically. Supposedly, Europeans have much less genetic diversity compared to Africans. That might explain why the plagues in the middle ages wiped out a third of Europe so easily.
0 Replies
 
Leadfoot
 
  1  
Reply Tue 27 Jun, 2017 02:32 pm
@farmerman,
Quote:

We can pretty accurately claim that the phylogenetic type section (the location of a species origin) is always within the geographic area where the most of the varied fossils of the supersedious genera are found.

Just days after our exchange, a new homo species was found far north of the accepted 'birthplace of man' and reliably dated 100k yrs earlier than any in Mesopotamia. I don't have access to the article but you have probably seen it yourself since you follow this stuff.

What do yo make of it?e

Edit: Here is a link to an article on it.

https://www.nytimes.com/2017/06/07/science/human-fossils-morocco.html
0 Replies
 
Leadfoot
 
  1  
Reply Tue 27 Jun, 2017 02:51 pm
Sorry, Mesopotamia should have been Ethiopia in last post.
Blickers
 
  1  
Reply Tue 27 Jun, 2017 11:04 pm
@Leadfoot,
So, since the two oldest Homo Sapiens prior to this find, (which might or might not be Homo Sapien), are in Omo Ethiopia, (195,000 years old), and Herto, Ethiopia, (155,000 years old). So Farmerman's statement seems to check.
Leadfoot
 
  1  
Reply Wed 28 Jun, 2017 06:35 am
@Blickers,
I'm not following your logic. If those two examples from Ethiopia are < 200k yrs old, how could they be the origin of a group that is 295k yrs old from Morocco?

One possible conclusion is that Homo evolved multiple times in different places. 'Evolution' must then be given even more 'magical' powers!

In any case, the find obviously means that the origin story of Homo must be re-written as the NYTimes article said.
Blickers
 
  2  
Reply Wed 28 Jun, 2017 09:24 pm
@Leadfoot,

We don't know that the Morocco find IS a Homo Sapien. It possibly was a Homo Heidelbergensis, which most researchers think was the species both Homo Sapiens and Neanderthal/Denisovan came from.
Leadfoot
 
  1  
Reply Thu 29 Jun, 2017 08:34 am
@Blickers,
Small snippet from the NYTimes article:
[quote]Fossils discovered in Morocco are the oldest known remains of Homo sapiens, scientists reported on Wednesday, a finding that rewrites the story of mankind’s origins and suggests that our species evolved in multiple locations across the African continent.

“We did not evolve from a single ‘cradle of mankind’ somewhere in East Africa,” said Philipp Gunz, a paleoanthropologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and a co-author of tweet on new studies on the fossils, published in the journal Nature. “We evolved on the African continent.”

Until now, the oldest known fossils of our species dated back just 195,000 years. The Moroccan fossils, by contrast, are roughly 300,000 years old. Remarkably, they indicate that early Homo sapiens had faces much like our own, although their brains differed in fundamental ways.[/quote]
This is what the article I cited said. The article quotes the highly respected journal 'Nature'. If you want to say the fossils were not Homo Sapiens or there is serious doubt, you will have to provide some evidence of that beyond your assertion.

Where did you get your information from?
Olivier5
 
  1  
Reply Thu 29 Jun, 2017 10:53 am
@Leadfoot,
That's an astounding and fascinating study. I'd love to see it corroborated but more, eg a carbon dating of these bones. The dating technique they use, thermoluminescence, is considered sound but still in its early days. I wonder why stratigraphy wasn't used. It's another dating technique, the oldest one, based on geologic strata. Guess I should read the Nature article...
0 Replies
 
ehBeth
 
  1  
Reply Thu 29 Jun, 2017 11:06 am
http://www.sciencemag.org/news/2017/06/world-s-oldest-homo-sapiens-fossils-found-morocco



http://www.sciencemag.org/sites/default/files/styles/inline__699w__no_aspect/public/70609N_Drupal_Africa.png?itok=AItyuq-1

ehBeth
 
  2  
Reply Thu 29 Jun, 2017 11:09 am
from above link

Quote:
This scenario hinges on the revised date for the skull, which was obtained from burnt flint tools. (The tools also confirm that the Jebel Irhoud people controlled fire.) Archaeologist Daniel Richter of the Max Planck in Leipzig used a thermoluminescence technique to measure how much time had elapsed since crystalline minerals in the flint were heated by fire. He got 14 dates that yielded an average age of 314,000 years, with a margin of error from 280,000 to 350,000 years. This fits with another new date of 286,000 years (with a range of 254,000 to 318,000 years), from improved radiometric dating of a tooth. These findings suggest that the previous date was wrong, and fit with the known age of certain species of zebra, leopard, and antelope in the same layer of sediment. “From a dating standpoint, I think they’ve done a really good job,” says geochronologist Bert Roberts of the University of Wollongong in Australia.

Once Hublin saw the date, “we realized we had grabbed the very root of the whole species lineage,” he says. The skulls are so transitional that naming them becomes a problem: The team calls them early H. sapiens rather than the “early anatomically modern humans” described at Omo and Herto.

Some people might still consider these robust humans “highly evolved H. heidelbergensis,” says paleoanthropologist Alison Brooks of The George Washington University in Washington, D.C. She and others, though, think they do look like our kind. “The main skull looks like something that could be near the root of the H. sapiens lineage,” says Klein, who says he would call them “protomodern, not modern.”

The team doesn’t propose that the Jebel Irhoud people were directly ancestral to all the rest of us. Rather, they suggest that these ancient humans were part of a large, interbreeding population that spread across Africa when the Sahara was green about 300,000 to 330,000 years ago; they later evolved as a group toward modern humans. “H. sapiens evolution happened on a continental scale,” Gunz says.

Support for that picture comes from the tools that Hublin’s team discovered. They include hundreds of stone flakes that had been hammered repeatedly to sharpen them and two cores—the lumps of stone from which the blades were flaked off—characteristic of the Middle Stone Age (MSA). Some researchers thought that archaic humans such as H. heidelbergensis invented these tools. But the new dates suggest that this kind of toolkit, found at sites across Africa, may be a hallmark of H. sapiens.

The finds will help scientists make sense of a handful of tantalizing and poorly dated skulls from across Africa, each with its own combination of modern and primitive traits. For example, the new date may strengthen a claim that a somewhat archaic partial skull at Florisbad in South Africa, roughly dated to 260,000 years ago, may be early H. sapiens. But the date may also widen the distance between H. sapiens and another species, H. naledi, that lived at this time in South Africa.

Olivier5
 
  1  
Reply Thu 29 Jun, 2017 11:28 am
@ehBeth,
Thanks for the info re. dating being well done in the study.

I find the link proposed between protosapiens and the Middle Stone Age technology powerful.

Guys, we're now 300,000 years old. Twice as old as earlier thought... and counting.
0 Replies
 
rosborne979
 
  2  
Reply Thu 29 Jun, 2017 02:03 pm
@ehBeth,

It looks to me like the whole continent was probably just crawling with hominids in various forms. The fact that fossils were discovered in those particular locations probably has more to do with local geology and fossilization probability than it does with where they lived or originated. And we've probably only found 1/100th (or less) of the variants which existed over that swath of time.
Blickers
 
  1  
Reply Thu 29 Jun, 2017 06:54 pm
@Leadfoot,
Quote Leadfoot:
Quote:
This is what the article I cited said. The article quotes the highly respected journal 'Nature'. If you want to say the fossils were not Homo Sapiens or there is serious doubt, you will have to provide some evidence of that beyond your assertion.


From ehBeth's article, for one thing.
Quote:
Some people might still consider these robust humans “highly evolved H. heidelbergensis,” says paleoanthropologist Alison Brooks of The George Washington University in Washington, D.C.


Plus the fact that for a Homo Sapien, this person has really, really large brow ridges.
http://i68.tinypic.com/2eukiu8.jpg
Leadfoot
 
  1  
Reply Fri 30 Jun, 2017 07:29 am
@Blickers,
Nevertheless, the consensus of the experts in that field is that it was Homo sapiens found in Morocco. We'll stand by for more info.

But it cannot be ignored that the finding totally shakes up the previous consensus that Homo S. evolved out of one particular place in E. Africa.

Ros may be right that the whole continent was crawling with different versions of 'humans'. Which presents yet another amazing feat that evolution is supposedly able to accomplish in a relative eye blink of geologic time (about 100 Thousand years). That evolution must be powerful stuff, and yet it hasn't done anything for the cockroach. It has stayed the same old bug for 450 Million years.

ehBeth
 
  1  
Reply Fri 30 Jun, 2017 08:44 am
@rosborne979,
rosborne979 wrote:
And we've probably only found 1/100th (or less) of the variants which existed over that swath of time.



that's my sense of it

definitely one of the wonders of science - always new things to discover/learn
 

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