TITLE: Modern Humans and Neanderthals Had Kids for 7,000 Years and the Legacy Lives in Our Genes
https://www.zmescience.com/science/news-science/modern-humans-and-neanderthals-had-kids-for-7000-years-and-the-legacy-lives-in-our-genes/
EXCERPT: Roughly 50,000 years ago, two species of humans met in the shadow of Eurasian ice sheets. One, Homo sapiens, had just embarked on its conquest of the world after leaving Africa. The other, Homo neanderthalensis, had called Eurasia home for hundreds of thousands of years. They looked into each other’s eyes — and then, they did what humans sometimes do: they had children.
For nearly 7,000 years, these two human species shared more than just the same cold landscapes; they shared their genes. That’s according to new research from two independent studies that narrowed down when Homo sapiens and Neanderthals interbred. The findings suggest that this mixing began about 50,500 years ago and lasted until around 43,500 years ago, just before Neanderthals faded into extinction.
Today, those interludes still ripple through our DNA. For non-Africans, between 1% and 2% of their genome comes from Neanderthal ancestors. But the story of how those genes spread, and why some stuck around while others vanished, is far more intricate than previously thought.
In a recent study published in Science, a team led by researchers from the Max Planck Institute for Evolutionary Anthropology (MPI-EVA) and the University of California, Berkeley, analyzed the genomes of 334 humans. Some were modern, while others belonged to ancient individuals who lived between 2,200 and 45,000 years ago. Their findings pinpoint the Homo sapiens-Neanderthal interbreeding period to a window between 50,500 and 43,500 years ago.
“The timing is really important because it has direct implications on our understanding of the timing of the out-of-Africa migration,” said Priya Moorjani, an assistant professor at UC Berkeley and one of the study’s senior authors. “Most non-Africans today inherit 1-2% ancestry from Neanderthals.”
This timeline is consistent with archaeological evidence. Modern humans and Neanderthals likely shared the plains and forests of Eurasia for 6,000 to 7,000 years. As bands of Homo sapiens spread across the continent, they carried Neanderthal DNA with them.
A separate study, published in Nature, corroborates these findings. This research analyzed seven genomes, each around 45,000 years old, and arrived at the same date for the interbreeding event: about 47,000 years ago.
“We created a catalog of Neanderthal ancestry segments in modern humans,” said Manjusha Chintalapati, a former UC Berkeley postdoctoral fellow. “By jointly analyzing all these samples together, we inferred the period of gene flow was around 7,000 years.”
These genetic findings also complicate the story of Homo sapiens‘ migration out of Africa. The timing of interbreeding suggests that humans had largely spread through Eurasia by about 43,500 years ago. But not every path out of Africa would have led to Neanderthals.
Bands of sapiens leaving Africa via Sinai might have run into Neanderthals, which was the southern limit of that species’ range. But those crossing via the straits between the Red Sea and the Gulf of Aden — believed by some to have been an important route as well — would not have done.
Previously, researchers found that the likeliest region where modern humans and Neanderthals interbred was the Zagros Mountains, a region stretching across present-day Iran, Iraq, and Turkey.
In some parts of the world, like East Asia, people carry about 20% more Neanderthal DNA than Europeans or West Asians. This difference may reflect the different tangled paths that led to encounters between early humans and Neanderthals .
Researchers like Moorjani are also peering into the genes of another mysterious group: the Denisovans. “It’s really cool that we can actually peer into the past and see how variants inherited from our evolutionary cousins, Neanderthals and Denisovans, changed over time,” she said.
TITLE: Humans may not have survived without Neanderthals
https://www.bbc.com/news/articles/cwydgyy8120o
EXCERPTS: The research also gives a new perspective on why Neanderthals died out so soon after modern humans arrived from Africa. No one knows why this happened, but the new evidence steers us away from theories that our species hunted them out of existence, or that we were somehow physically or intellectually superior.
Instead, Prof Krause says that it supports the view that it was due to environmental factors.
"Both humans and Neanderthals go extinct in Europe at this time," he said. "If we as a successful species died out in the region then it is not a big surprise that Neanderthals, who had an even smaller population went extinct."
The climate was incredibly unstable at the time. It could switch from nearly as warm as it is today to being bitterly cold, sometimes within a person's lifetime, according to Prof Chris Stringer of the Natural History Museum in London, who is independent of the new research.
"The study shows that near the end of their time on the planet, Neanderthals were very low in numbers, less genetically diverse than the modern human counterparts they lived alongside, and it may not have taken much to tip them over the edge to extinction," he said.
A separate DNA study, published in the journal Science, shows that modern humans held on to some key genetic traits from Neanderthals that may have given them an evolutionary advantage.
One relates to their immune system. When humans emerged from Africa, they were extremely susceptible to new diseases they had never encountered. Interbreeding with Neanderthals gave their offspring protection.
"Perhaps getting Neanderthal DNA was part of the success because it gave us better adaptive capabilities outside of Africa," said Prof Stringer. "We had evolved in Africa, whereas the Neanderthals had evolved outside of Africa."
"By interbreeding with the Neanderthals we got a quick fix to our immune systems."
TITLE: Without our adventurous, hairy ancestors, we may not be here
https://www.theaustralian.com.au/commentary/without-our-adventurous-hairy-ancestors-we-may-not-be-here/news-story/8d0b1c0b7a347f9b14b0c1c439917344
EXCERPTS: Neanderthals were the first to take the migratory leap about 400,000 years before present. They moved into Europe and evolved there. They could make fire, use basic stone tools and built hearths for cooking and warmth.
It was a tough time to be alive. Climate changed drastically from scorching heat to freezing cold often in the course of an individual’s lifespan.
Approximately 45,000 years ago, Homo Sapiens migrated from Africa to Europe.
The first forays did not end well.
Homo Sapiens had no immunity from diseases swirling around the continent at the time. Interbreeding with our caveman cousins was the way forward, although initially the hybrid progeny of Neanderthal and Homo Sapiens became extinct over just a few centuries, a blink of the eye in evolutionary terms.
Homo Sapiens kept coming from Africa and maintained the habit of horizontal folk dancing with Neanderthals in Europe (whose largest numbers were found in what today is Germany and the Czechia) and over a relatively quick period between 40,000 and 45,000 years ago, their progeny developed immune systems that could overcome diseases found in their new environment.
Independent analysis of the study entitled Neanderthal ancestry through time: Insights from genomes of ancient and present-day humans came from Professor Chris Stringer at the Natural History Museum in London who told the BBC, “Perhaps getting Neanderthal DNA was part of the success because it gave us better adaptive capabilities outside of Africa.”
Rapid natural selection then seems to have retained the Neanderthal good stuff and punted the other Neanderthal genes from our genomes within about 100 generations.
Thick body hair may have offered an evolutionary benefit, especially in cold climes, but where it exists today it is often removed by the non-evolutionary process of back, sack and crack waxing.
As our scientific knowledge of human evolution grows, what strikes the casual observer is the extraordinary success of the human species in such a short space of time.
From approximately 40,000 years BP when Homo Sapiens mingled with Neanderthals, to 9000 years BP present where exists the oldest neolithic archaeological site, Göbekli Tepe in southern Turkey, and two sites in Syria of approximately the same age. These three are the oldest known relics of human civilisation.
Stonehenge and the Egyptian pyramids by contrast are mere toddlers at 5000 years old.
Indeed until the archaeological dig at Göbekli Tepe began in the 1990s, the prevailing archaeological view was that human civilisation was thought to have begun 6000 years BP. Even in the space of ten millennia, the extraordinary pace of human civilisation to where we are now is breathtaking.