Neanderthals didn't give us red hair but they certainly changed the way we sleep

October 6, 2017 by Darren Curnoe, The Conversation
Artist’s reconstruction of a Neanderthal male, at the Neanderthal Museum, Germany. Credit: Stephan Sheer/Wikimedia Commons, CC BY-SA

Geneticists have now firmly established that roughly two percent of the DNA of all living non-African people comes from our Neanderthal cousins.

It's difficult to imagine why our early ancestors would have mated with them. Neanderthals were a different species to us after all, and the thought of it seems distasteful to us today.

Hindsight is a wonderful thing of course, and armed with so few facts about the circumstances surrounding this interspecies dalliance, we mustn't be too quick to judge.

Still, scientists are learning a great deal now about how active this Neanderthal DNA is in our bodies and the role that it might be playing in determining how we look and behave as well as our susceptibility to certain diseases.

One of the very first features suggested as having a Neanderthal origin was . A set of Neanderthal genes responsible for both light hair and skin colour was identified by geneticists more than a decade ago and linked to human survival at high latitude, light poor, regions like Europe.

Because the Neanderthals had lived in Europe for several hundred thousand years, it was reasoned that gave them light skin and hair colour helping to prevent diseases like rickets from occurring.

But as is so often the case in science, the situation is far more complicated than most of us would have imagined. Red hair wasn't inherited from Neanderthals at all. It now turns out they didn't even carry the gene for it!

Red hair is a uniquely human feature, according to a new study by Michael Danneman and Janet Kelso of the Max Planck Institute for Evolutionary Anthropology and published in the The American Journal of Human Genetics.

It's striking and paradoxical that half of all the Neanderthal genes in our genome play a role in determining skin and hair colour. Yet this new research shows us that Neanderthal genes have no more influence over these features than the unique human genes we carry for them.

What does all of this mean? Well, over time, tens of thousands years in fact, natural selection has produced a fine balance between Neanderthal and human genes for these features. We might think of lightly skinned and haired people today as having the best bits of both genomes for these traits.

Some of the other skin colour genes inherited from Neanderthals include one associated with both the ease with which people tan and the incidence of childhood sunburn.

Another surprise for me in this new study was the role that Neanderthal genes play in human sleep patterns, as determined by the body's circadian rhythms. The natural cycles of night and day, and their length, which vary enormously with latitude and season, are strong influences over our circadian rhythms.

Danneman and Kelso searched for a link between latitude and the prevalence of a Neanderthal form of a gene (ASB1) which plays a role in determining whether you are an 'evening person', and is associated with the need for daytime napping as well as being tied to narcolepsy.

It turns out that indeed non-African populations living far away from the equator today show a higher prevalence of ASB1 than people living close to it.

Human are medically important because of the well known 24-hour variation in blood levels of glucose, insulin and leptin, which controls our appetite. Clock variability underpins short sleep episodes, sleep deprivation and poor quality sleep, which have all been associated with diabetes, metabolic syndrome, increased appetite, and even obesity.

Some of the other newly discovered Neanderthal genes in the human genome are linked to body height in adults as well as the stature reached by children at 10 years of age, pulse rate, and the distribution of fat in the legs.

Other Neanderthal genes apparently help determine our mood, as influenced by our exposure to sunlight, or even whether we like to eat pork or not.

It's no longer such a novelty that our ancestors interbred with archaic humans like the Neanderthals. No more lame jokes from me about 'shagging the ancestors'!

Their decision to mate with the Neanderthals, what ever the reason, continues to reverberate after tens of thousands of years. Neanderthal are playing a very real role today in influencing how we look, feel and behave, including even some commonly suffered diseases often linked to a Western lifestyle and diet.

All of this reinforces once again how remarkable and surprising our evolutionary history as a species truly is. And it brings into sharp relief the very real importance of our evolution for a proper understanding of many of the challenges humankind faces globally today.

Explore further: No signs of incest in new Neanderthal woman genome

More information: The Contribution of Neanderthals to Phenotypic Variation in Modern Humans, American Journal of Human Genetics (2017). 10.1016/j.ajhg.2017.09.010 , www.cell.com/ajhg/fulltext/S0002-9297(17)30379-8

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etherair
3.3 / 5 (7) Oct 06, 2017
The author has a problem with the sexual nature of animals. This really distracted from the article's factual references.
Perhaps if he rewrote this without his repressed childhood hangups it would be both informative AND readable.
dnatwork
4 / 5 (4) Oct 06, 2017
based entirely on judgment and prudery, rendering any information useless
michael_frishberg
5 / 5 (6) Oct 06, 2017
"Neanderthals were a different species to us after all"
Since we could mate with them, and have offspring capable of having children, they weren't THAT different...
StevenGMP
4 / 5 (6) Oct 06, 2017
Darren Curnoe writes, "It's difficult to imagine why our early ancestors would have mated with them. Neanderthals were a different species to us after all, and the thought of it seems distasteful to us today."

This is so fraught with racism, I don't even know where to begin. Replace the word "Neanderthal" in the above with "native", "black", "aboriginal" etc. and it sounds like all the other colonialist apologies for racist thinking. And remember, these hateful remarks are being applied to my great-great(x1000) grandparents, and to yours.
sascoflame
5 / 5 (2) Oct 07, 2017
1. The author of the article is so squeamish about sex that it gets in the way of understanding his field. Humans are the most oversexed animal on the planet and have had more interspecies sexual relations than any other mammal.

2. It's striking and paradoxical that half of all the Neanderthal genes in our genome play a role in determining skin and hair colour. Yet this new research shows us that Neanderthal genes have no more influence over these features than the unique human genes we carry for them.

So our genes for skin color have no influence over skin color? It sounds like a contradiction in terms to me.
IanPerkins
5 / 5 (4) Oct 07, 2017
I was basicallly taught that species cannot interbreed by definition. So what's all this about Neanderthals being a different species yet successfully breeding with humans?
I'd love an explanation!
ArtKns
4 / 5 (4) Oct 07, 2017
"It's difficult to imagine why our early ancestors would have mated with them. Neanderthals were a different species to us after all, and the thought of it seems distasteful to us today.

Hindsight is a wonderful thing of course, and armed with so few facts about the circumstances surrounding this interspecies dalliance, we mustn't be too quick to judge"
=======================
Hindsight??? More like blinders! It's hard to imagine our ancestors *NOT* mating! Just ask Catherine the Great or the sheep in Idaho (I am not being facetious), how unlikely that is. I have often wondered why that mental block has lasted so long. Do our scientists have no concept at all about human behavior?

As has been noted by almost all the previous posters, the author's racist bias is very evident as well as his holier-than-thou hypocritical judgmental attitude. To allow this to be published does not speak well of phys.org.
ddaye
5 / 5 (3) Oct 08, 2017
There are 7 billion of us today because humans find a considerable range of appearances appealing or acceptable for mates. Also there is a long history of humans taking pains to find mates from outside their tribes to minimize inbreeding, and that's another factor that could be involved in mating outside our close species.
savvys84
not rated yet Oct 09, 2017
Lol, then im a neanderthal
torbjorn_b_g_larsson
5 / 5 (1) Oct 09, 2017
"It's difficult to imagine why our early ancestors would have mated with them".

It has been claimed that we would not see a Neanderthal as remarkable if he or she walked clothed trough a large city.

"Neanderthals were a different species to us after all."

This study may change that, but it remains an open question. Early data was seeing some incipient breeding barriers in sperm alleles, but later data has fleshed that out and is completely consistent also with free breeding. The scarcity of alleles would be partly explained by Out-Of-Africans having 10 times the population at the breeding events. And partly by the recent Neanderthal bottleneck that had their alleles as drift products which selection in larger populations tended to weed out.
torbjorn_b_g_larsson
5 / 5 (1) Oct 09, 2017
I was basicallly taught that species cannot interbreed by definition. So what's all this about Neanderthals being a different species yet successfully breeding with humans?
I'd love an explanation!


Actually speciation specialist Jerry Coyne has referred to results that 2-5 % of species are without completely impermeable species barriers, as we would expect by the nature of the speciation process.

Basically the same thing you expect when you see tree branches. They branch away as the tree grows, and you cannot easily tell when and where. (If you cut open a tree, branches starts a bit in when the tree was younger.)
Cusco
5 / 5 (1) Oct 09, 2017
I was basicallly taught that species cannot interbreed by definition. So what's all this about Neanderthals being a different species yet successfully breeding with humans?
I'd love an explanation!


There are multiple definitions about what constitutes a "species", that is just one of them.
leetennant
5 / 5 (1) Oct 09, 2017
"Neanderthals were a different species to us after all"
Since we could mate with them, and have offspring capable of having children, they weren't THAT different...


I know high school science is all about the "lies we tell to children" thing and they have to simplify it for us but I've never been able to get over my high school definition of speciation as "not being able to mate with". If different species can't produce viable offspring then that suggests Neanderthals weren't a different species. Except of course they were. As you say, they can't have been that different.

As to the author - if humans have been known to mate with apes then I hardly think Neanderthals are that much of a stretch. Monkeys and apes will regularly mate with other primates of different species as well.

But he is right in a way. Our modern sensibilities regarding consent have bred a distaste for the darker side of human sexuality. And frankly that's not a bad thing.
ArtKns
not rated yet Oct 11, 2017
"Our modern sensibilities regarding consent have bred a distaste for the darker side of human sexuality. And frankly that's not a bad thing."

That's a generalization that is full of holes. Not the least it implies a behavior adhered to by 100% of the population which is simply not true. As I stated above, some humans even today have no compunction against "mating" with non-humans. To postulate that Neanderthal or other homos on warpaths would not pillage and rape females that were near indistinguishable from their own tribe's females is pure fantasy!

The sexual drive for all species is very powerful and should not be underestimated.
TheGhostofOtto1923
not rated yet Oct 12, 2017
Tropical interlopers naturally seek to gain environmental adaptations of temperate and subarctic dwellers for their offspring, and vice-versa, as it helps them to survive to reproduce.

Conversely, indigenes would resist this incursion as interloper genes would reduce the chances for survival of their offspring.

This resistance is the heart of speciation. Adaptations are acquired through much time and effort and sacrifice so to speak, over the course of many generations, and it makes sense that indigenes would resist losing them.

This explains to an extent the disproportionate prejudice of temperate-adapted whites against darker-skinned tropical peoples, which apparently extends beyond the normal animosity found among tribes.

And it may also explain why indigenes in tropical climes seem to hate white colonists so much.
https://youtu.be/KpaWtrEqga0
TheGhostofOtto1923
not rated yet Oct 12, 2017
The sexual drive for all species is very powerful and should not be underestimated
The 'sex drive' of a species is determined by its environment. Generally, the farther north a species resides the more seasonal it's reproduction becomes. Offspring produced in early spring have the best chance of surviving the coming winter.

It is possible that Neanderthal had become seasonal breeders and when the cromags arrived and tribal conflict ensued, Neanderthal couldnt replace battle losses as fast as the interlopers, whose repro rate had been determined by the high attrition rates found in tropical environments.

They were as a result outgrown and overwhelmed, and ceased to exist as a separate species.
TheGhostofOtto1923
not rated yet Oct 12, 2017
some humans even today have no compunction against "mating" with non-humans
Non-procreative sex may be a natural response to overpopulation. Similar adaptations can be found in many species, and since the human race has always suffered from overgrowth we should expect to find them in ours.

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