Climate, diet, and natural selection changed the African settlers in Europe.

White people’s ancestors weren’t white. As our species – Homo Sapiens – was rooted in Africa and started spreading all over the globe some 100,000 years ago, we know for sure that the first modern men and women were black. But how did they develop pale skin?

Studies published by anthropologists in the journals Science and LiveScience (and here) show that the pale skin, as well as other traits such as tallness and the ability to digest milk as adults, appeared in most of the continent relatively recently. They clearly suggest that most modern Europeans don't look much like those of 8,000 years ago.

The findings about the origins of Europeans – and white people in general – first shocked scientists but researchers who have sequenced the genomes of ancient populations have no doubt. By comparing key parts of the DNA across the genomes of 83 ancient individuals from archaeological sites throughout Europe, international teams of anthropologists, archeologists, and geneticists learned that Europeans today are a mix of the blending of at least three ancient populations of hunter-gatherers and farmers who moved into Europe in separate migrations over the past 8,000 years.

One study revealed that a massive migration of Yamnaya herders from the steppes north of the Black Sea may have brought Indo-European languages to Europe about 4,500 years ago.

Another study drilled down further into that data to search for genes that were under strong natural selection - including traits so favorable that they spread rapidly throughout Europe in the past eight millennia. By comparing the ancient European genomes with those of recent ones from the 1000 Genomes Project, the researchers found five genes associated with changes in diet and skin pigmentation that underwent strong natural selection.

More to read:
Why did our ancestors eat each other 1.45 million years ago?

First, they confirmed an earlier report that the hunter-gatherers in Europe could not digest the sugars in milk 8,000 years ago.

They also noted an interesting twist: The first farmers also couldn't digest milk. The farmers who came from the Near East about 7,800 years ago and the Yamnaya pastoralists who came from the steppes 4,800 years ago lacked the version of the LCT gene that allows adults to digest sugars in milk. It wasn't until about 4,300 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 millennia. 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.

The obtained data confirmed that about 8,500 years ago, early hunter-gatherers in Spain, Luxembourg, and Hungary also had darker skin: They lacked versions of two genes - SLC24A5 and SLC45A2 – which lead to depigmentation and, therefore, pale skin in Europeans today.

More to read:
New clues why Neanderthals lost to modern humans

But in the far north - where low light levels would favor pale skin - the scientists found a different picture in hunter-gatherers: Seven people from the 7,700-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 5,800 years ago when it swept up to high frequency.

The researchers 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 8,000 years ago, with a boost coming from the Yamnaya migration, starting 4,800 years ago.

More to read:
Human ancestors were almost extinct 900,000 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 8,000 years ago, according to a paper now posted on the bioRxiv server. Spaniards, in particular, shrank in stature 6,000 years ago, perhaps as a result of adapting to colder temperatures and a poor diet.

One interesting theory is that sexual selection may have played a role, as males in northern latitudes preferred paler skin and stronger female partners – which normally were “taller”.

The paper did not specify why these genes might have been under such strong selection. But the likely explanation for the pigmentation genes is the need to maximize vitamin D synthesis.

Vitamin D is essential for bone development and the body's defense against certain diseases. In regions with weaker sunlight, insufficient vitamin D absorption would have reduced the life expectancy of our African ancestors. As they migrated further north, natural selection favored individuals with lighter skin, enabling better vitamin D production, which led to progressively lighter skin over generations.

People living in northern latitudes often don't get enough ultraviolet (UV) light to synthesize vitamin D in their skin so natural selection has favored two genetic solutions to that problem - evolving pale skin that absorbs UV more efficiently or favoring lactose tolerance to be able to digest the sugars and vitamin D naturally found in milk.

The findings suggest that the genetic development of the arriving settlers in Europe was shaped by their diet, sexual preferences, and adaptation to the new habitat.

***
NewsCafe relies in its reporting on research papers that need to be cracked down to average understanding. Some even need to be paid for. Help us pay for science reports to get more interesting stories. Use PayPal: office[at]rudeana.com or paypal.me/newscafeeu.