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Old October 20th, 2017, 10:59 AM   #1
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What Does 'Race' Tell Us About Ourselves And Others

First, this article by Carl Zimmer focuses on the most common signifier of racial identity: skin color. But what causes differences in skin pigmentation and does it a scientific categorizing of different populations by race?
Quote:

For centuries, skin color has held powerful social meaning — a defining characteristic of race, and a starting point for racism.

“If you ask somebody on the street, ‘What are the main differences between races?,’ they’re going to say skin color,” said Sarah A. Tishkoff, a geneticist at the University of Pennsylvania.

On Thursday, Dr. Tishkoff and her colleagues showed this to be a profound error. In the journal Science, the researchers published the first large-scale study of the genetics of skin color in Africans.

The researchers pinpointed eight genetic variants in four narrow regions of the human genome that strongly influence pigmentation — some making skin darker, and others making it lighter.

These genes are shared across the globe, it turns out; one of them, for example, lightens skin in both Europeans and hunter-gatherers in Botswana. The gene variants were present in humanity’s distant ancestors, even before our species evolved in Africa 300,000 years ago.

The widespread distribution of these genes and their persistence over millenniums show that the old color lines are essentially meaningless, the scientists said. The research “dispels a biological concept of race,” Dr. Tishkoff said.

Humans develop color much as other mammals do. Special cells in the skin contain pouches, called melanosomes, packed with pigment molecules. The more pigment, the darker the skin.

Skin color also varies with the kind of pigments: Melanosomes may contain mixtures of a brown-black called eumelanin and a yellow-red called pheomelanin.

To find the genes that help produce pigments, scientists began by studying people of European ancestry and found that mutations to a gene called SLC24A5 caused cells to make less pigment, leading to paler skin. Unsurprisingly, almost all Europeans have this variant.“We knew quite a lot about why people have pale skin if they had European ancestry,” said Nicholas G. Crawford, a postdoctoral researcher at the University of Pennsylvania and a co-author of the new study. “But there was very little known about why people have dark skin.”African populations vary tremendously in skin color, and Dr. Tishkoff reasoned that powerful genetic variants must be responsible.

Studying 1,570 people in Ethiopia, Tanzania and Botswana, she and her colleagues discovered a set of genetic variants that account for 29 percent of the variation in skin color. (The remaining variation seems tied to genes yet to be discovered.)

One variant, MFSD12, was particularly mysterious: No one knew what it did anywhere in the body. To investigate its function, the researchers altered the gene in reddish lab mice. Giving them the variant found in darker-skinned Africans turned the mice gray.

As it turned out, MFSD12 can affect the production of brown-black eumelanin, producing a darker skin color.

The eight gene variants that Dr. Tishkoff and her colleagues discovered in Africans turned out to be present in many populations outside the continent. By comparing the DNA of these people, the researchers were able to estimate how long ago the genes appeared.

They turned out to be immensely old. A variant for light skin — found in both Europeans and the San hunter-gatherers of Botswana — arose roughly 900,000 years ago, for example.

Even before there were Homo sapiens, then, our distant forebears had a mix of genes for light and dark skin. Some populations may have been dark-skinned and others light-skinned; or maybe they were all the same color, produced by a blend of variants.

Neanderthals split off from our own ancestors an estimated 600,000 years ago, spreading across Europe and eastern Asia. While they became extinct about 40,000 years ago, some of their DNA has survived.

These hominins inherited the same combination of variants determining skin color, Dr. Tishkoff and her colleagues also discovered. It’s possible that some populations of Neanderthals, too, were light-skinned, and others dark-skinned.

Living humans come packaged in a wide range of hues — from pale and freckly in Ireland to dark brown in southern India, Australia and New Guinea. Researchers have argued that these varying colors evolved partly in response to sunlight.

The idea is that people who live with intense ultraviolet light benefited from dark color, pigments that shielded important molecules in their skin. In places with less sunlight, people needed lighter skin, because they were able to absorb more sunlight to make vitamin D.

The new genetic evidence supports this explanation, but adds unexpected complexity. The dark-skinned people of southern India, Australia and New Guinea, for example, did not independently evolve their color simply because evolution favored it.

They inherited the ancestral dark variants Dr. Tishkoff’s team found in Africans. “They had to be introduced from an African population,” said Dr. Tishkoff.

Yet the same is true for some genes that produce light skin in Asia and Europe. They also originated in Africa and were carried from the continent by migrants.

As Africans moved into Europe and Asia, they interbred with Neanderthals on several occasions. Last week, Michael Dannemann and Janet Kelso of the Max Planck Institute for Evolutionary Anthropology in Germany reported that people in Britain still carry a number of Neanderthal variants that color skin.

Some of the newly discovered genes appeared relatively recently in our evolution.

The pale-skin variant of SLC24A5 that’s overwhelmingly common in Europe, for example, is a recent addition to the genome, arising just 29,000 years ago, according to the new study. It became widespread only in the past few thousand years.

Dr. Tishkoff and her colleagues found it frequently not just in Europe, but also in some populations of lighter-skinned Africans in East Africa and Tanzania. Studies of ancient DNA recently discovered in Africa point to an explanation.

Several thousand years ago, it seems, a migration of early Near Eastern farmers swept into East Africa. Over many generations of interbreeding, the pale variant of SLC24A5 became common in some African populations.

In all, the new study provides “a deeper appreciation of the genetic palette that has been mixed and matched through evolution,” said Nina Jablonski, an expert on skin color at Pennsylvania State University.
Genes for Skin Color Rebut Dated Notions of Race, Researchers Say | Portside

It needs to be noted that other morphological characteristics besides skin color such as skull and facial spapes and sizes can and do vary over time. Many white supremacists learned this the hard way when they got all excited and started a circle jerk over "Kennewick Man," a very early North American skeleton found in Washington State a number of years ago. And even though Kennewick Man was on the Pacific Coast, they got all excited and proclaimed him as proof of their bullshit "Solutrean Theory" of ancient European arrivals in North America...which until Kennewick were relegated to claims about design and shape of spearheads and other weapons that most archaeologists didn't consider as proof of anything! Long story short, when a full DNA examination of Kennewick Man was finally approved, his origins turned out to be pretty much as expected...similar to other west coast arrivals over 10,000 years ago.

What made him distinct and started the flurry, was that his skull was elongated...sort of European looking to some observers and a cottage industry was off and running. A second look should have told people that the same groups of people can look much different over long expanses of time just through genetic drift and how the local environment and sexual selection etc. alters which characteristics are advanced and which ones decline.

It was pointed out at the time that a similar development had taken place in Clovis skeletons, and it was more likely that long ago...when groups in Central Asia moved west and east in different directions, they would look more similar back then, and less similar as time went by. But all that aside, there will no doubt be another Kennewick man for the Solutreans to get excited about in the future!

About those Neanderthals.......
Quote:
Assessing the genetic contribution of Neanderthals to non-disease phenotypes in modern humans has been difficult because of the absence of large cohorts for which common phenotype information is available. Using baseline phenotypes collected for 112,000 individuals by the UK Biobank, we can now elaborate on previous findings that identified associations between signatures of positive selection on Neanderthal DNA and various modern human traits but not any specific phenotypic consequences. Here, we show that Neanderthal DNA affects skin tone and hair color, height, sleeping patterns, mood, and smoking status in present-day Europeans. Interestingly, multiple Neanderthal alleles at different loci contribute to skin and hair color in present-day Europeans, and these Neanderthal alleles contribute to both lighter and darker skin tones and hair color, suggesting that Neanderthals themselves were most likely variable in these traits.

Introduction

Interbreeding between Neanderthals and early modern humans has been shown to have contributed about 2% Neanderthal DNA to the genomes of present-day non-Africans. This Neanderthal DNA has apparently had both positive and negative effects. Together with the rapid decrease in Neanderthal ancestry after introgression, the depletion of Neanderthal DNA around functional genomic elements in present-day human genomes suggests that a large fraction of Neanderthal alleles are deleterious in modern humans.1, 2, 3, 4
http://www.cell.com/ajhg/fulltext/S0002-9297(17)30379-8

So, if you're still demanding something..anything that's uniquely European, it's the higher percentage of various Neanderthal alleles still in modern European-origin genomes. Our "cave man" genes are for good and mostly for bad if you want it..but I guess that makes you the white man if it really matters so much!
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Old November 15th, 2017, 04:36 AM   #2
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Isn't Racism evil hating Group against black Citizen in America and Sweden ?? And Germany last one last 97 years when hockey become A Sports for Christians then in Asia with Turkey, South Korea and Japan is fine werening White citizen in Europe with hockey Cultures in North Europe even Germany are hockey cultures !!!
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Old November 15th, 2017, 04:38 AM   #3
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I couldn't miss hockey and soccer are two big Sports for Christians.
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