Tutu Hockey: New Studies Change Our Understanding of Our Meeting With Neanderthals

THEORY THEORY THEORY - not FACT

New Studies Change Our Understanding of Our Meeting With Neanderthals
It's true that we met and mixed with Neanderthals many times, but only one 'gene flow event' produced all non-Africans alive today, and it was later than we thought, studies find

Illustration of the Zlatý kůň/Ranis group. Around 45,000 years ago, individuals from Ranis in Germany and Zlatý kůň in Czechia likely traveled together across the open steppe landscapes of Europe.Credit: Tom Björklund

Ruth Schuster

Dec 12, 2024
Somewhere on the path out of Africa, our ancestors encountered Neanderthals, and their joint children would beget all non-African humans alive today. Now two new research papers have shed startling new light on how this happened.
The papers, "Earliest modern human genomes constrain timing of Neanderthal admixture" in Nature led by researchers at the Max Planck Institute for Evolutionary Anthropology in Germany and "Neanderthal ancestry through time: Insights from genomes of ancient and present-day humans" in Science were published Thursday.
The Nature paper by Arev Sümer, Johannes Krause and colleagues analyzes seven modern humans who lived in Europe 49,000 to 42,000 years ago – the earliest humans in Europe to be studied to date.
The Science paper by Leonardo Iasi, Priya Moorjani and colleagues analyzed 300 current and ancient individuals to study the timing and the duration of the intermixing.
Previous research showed three major Homo sapiens-Neanderthal admixture events: over 200,000 years ago, 120,000 to 105,000 years ago and then after 60,000 years ago. But the new work implies that all non-Africans today result from a lineage of modern humans that mixed with Neanderthals 49,000 to 45,000 years ago in a single event.
By single event we don't mean one coupling on one starry night, but a process of gene flow that may have lasted centuries or even a few thousand years when the two species overlapped, the researchers say.
The other mixing events did happen. They resulted in hybrid human-Neanderthals. We have found traces of these hybrids. The other lineages went extinct. Ours didn't.

The Zlatý kůň skull: Fossil of an Early Homo sapiens woman discovered in the Koněprusy Caves, Czech Republic. Her line went extinct Credit: Marek Jantač, Anthropology Department, National Museum, Prague
Caught knapping
The genetic material for the new work was recovered from seven people who lived 49,000 to 42,000 years ago in Ranis, Germany and Zlatý kůň in the Czech Republic. Though the two towns are 230 kilometers distant, the seven were related, Sumer said in a press conference.
The Zlatý kůň people were cousins of the Ranis people, fifth or sixth degree. The team also identified the earliest modern family at Ranis: a mother and daughter, found with a second- (or third-) degree cousin.
The people at Zlatý kůň and Ranis were not our ancestors: their line died out. But they had the same Neanderthal background that we do.
Which means? About 50,000 years ago a band of modern humans left Africa. Possibly while crossing through the Middle East, they mated with Neanderthals about 49,000 to 45,000 years ago. Reaching Europe, the descendants of the band split up, with one branch forming the Zlatý kůň and Ranis family, which died out. Another branch became our ancestors.
The humans and Neanderthals may have lived in proximity for thousands of years, the researchers say. That doesn't necessarily mean they were having relations for 5,000 years.

Prosek (main) Dóme of the Koněprusy caves where early modern humans lived about 46,000 years agoCredit: Martin Frouz
We have no idea how "it" went down, the archaeologists clarified in the press conference. There is no archaeological or cultural evidence whatsoever to temper our fancies in this context. We can't even point at clear cultural transfer.
Note the heartbreak of the Lincombian-Ranisian-Jerzmanowician cultural complex from about 45,000 years ago, Krause says.
LRJ artifacts characterized by sophisticated leaf-shaped stone blades have been found stretching from Britain to Poland in Europe. Note that even in that space, the LRJ sites are very rare, yet they badly muddied the waters because, based on the timing and geography, it was assumed to be a very late and highly skilled Neanderthal culture.
It turned out that modern humans had reached northern Europe by 45,000 years ago. The suggestion arose that the blades were so advanced, the Neanderthals encountered modern humans who graciously taught them extreme knapping.

The known distribution of the Lincombian-Ranisian-Jerzmanowician culture or technocomplex, about 45,000 years ago.Credit: Albin L
Recently analysis in an LRJ site in Thuringia deduced that after all, the LRJ makers were modern humans who had penetrated northern Europe that long ago. Ditto regarding the gorgeous Châtelperronian technology; we don't know who made it – Neanderthals, modern humans, hybrids.
So we have no evidence of transfers between Neanderthals and modern humans but do have solid evidence for sex, leading Priya Moorjani to observe that we were all one species.
"The differences we imagine between these groups weren't very big," she says. "They could mix and did so for a long period of time and lived side by side over time, so I think that shows we were far more similar than different. I would expect exchange of ideas and cultures."
X marks the missing spot
Maybe. The new analyses suggest our Neanderthal ancestry component took shape very fast after that single putative gene flow event, within 100 generations, Krause says, thanks to strong selection of Neanderthal genes. In other words, some Neanderthal heredity strongly supported our occupation of Europe and other genes could have been deadly for us.
Think of it this way. You are an early modern human venturing into prehistoric Europe, which was colder, and the pathogens were different. Neanderthals had been there for hundreds of thousands of years and had adapted to it, developing immunities to the pathogens. Your hybrid children could gain immunity from the Neanderthal parent, conferring a great advantage.
But some genes would not work well for us. Some parts of our genome have heavy Neanderthal signals and others have none (and such was the case already in the earliest hybrids, Krause explains).
Such as, we ladies have almost no Neanderthal or Denisovan signals in our X chromosome.

Illustration of the woman in Zlatý kůň, who belonged to the same population as the Ranis individuals and was closely related to two of them.Credit: Tom Björklund
Does that imply the sex was confined to human women with Neanderthal men? It does not.
"There are regions in our genome that don't tolerate Neanderthal DNA," Krause explains. Perhaps human fetuses with a Neanderthal X chromosome weren't viable. Neanderthal women with human men may not have been a match made in heaven.
A 'success story'
So what have we? Seven people at two spots in Central Europe who lived about 49,000 to 42,000 years ago and had the same Neanderthal sequences we do, but who are not our ancestors. Their line died out. But they stemmed from the same group that was ancestral to us, which had met Neanderthals 80 to 50 generations earlier – likely in the Near East and possibly in Israel.

Upper jaw found in Misliya Cave, Israel from ~200,000 years ago and identified as Homo sapiensCredit: Israel Hershkovitz / Tel Aviv University
We know Homo sapiens and Neanderthals co-occupied our region. In fact Israeli researchers suspect that the Levant was a land where Homo sapiens and Neanderthals struggled over eons. So possibly a small group of humans venturing out of Africa ran into Neanderthals in the Middle East, and their children continued onto Europe, where the lineage of Ranis and Zlatý kůň would die out. But ours would stride on.
It bears adding: If they mixed over centuries or a few thousand years – geologically that's an eyeblink but in terms of human history, consider how much has happened in the last 7,000 years, such as the rise of civilization, Benjamin Peter points out.
"I think it reasonable to assume lots of different things were happening in that time period – not one event or one culture or one group that interacted with Neanderthals but a lot of population structures, people different from each other that all interacted with Neanderthals," he speculates. The teams note that other early human lines who died out in Europe, for instance in Bulgaria and Romania, evinced signs of additional admixture.
But in the group that survived, maybe all in all there were a couple of hundred Neanderthals interacting with a group of humans numbering maybe 5,000 and the result is We.

Bacho Kiro Cave in Bulgaria, where Homo sapiens lived 46,000 years agoCredit: Nenko Lazarov
Can all this genetic analysis tell us what the early Europeans and Neanderthals looked like? No. Krause points out that dozens of genes at a minimum affect skin color and at this point in the science, we can't even tell based on genetics what our own species looks like at a distance.
"If we apply methods developed in Europe [to deduce skin color based on genetic analysis], they don't work in South Africa. These methods are population-specific. So if the European methods don't work there, how would they work for Neanderthals?" he says. He suspects that being fairly freshly out of Africa, the early modern humans in Europe all had dark skin and eyes.
As for Neanderthal appearance, most of the skin color variants we can identify in Neanderthal genomes aren't present in Homo sapiens, so we don't know what they do. And we have gene variants that Neanderthals don't have, and all this means exactly nothing. So we can't say our ancestors saw blond Neanderthals and swooned. Or vice versa.
Anyway, about 39,500 years ago all human lineages in Europe died out – Neanderthals and early modern humans alike, including the small modern human bands at Ranis and Zlatý kůň. Except for our ancestors, who had reached Europe about 43,500 years ago, according to the latest analysis, and somehow weathered whatever happened, and were fruitful and multiplied and peopled the continents, eventually walking over the Bering Bridge to the Americas and sometimes, with dogs in tow.
Separate work implies that Denisovans, a sister species to Neanderthals (or are we all one?), survived in Southeast Asia, mixing with humans, until perhaps 15,000 years ago. Maybe they did, but we won.
We won? A little humility might be in order. The human story isn't just a story of success. "We also went extinct several times," points out Science coauthor Benjamin Peter. In fact we always went extinct in Europe, and all other modern humans in Europe joined the Neanderthals in that final void, except for one little band that didn't. The end.
Click the alert icon to follow topics:
Israel archaeology

Evolution

COMMENT:
James Louder

14.12.2024

While this study casts new and very interesting light on the timing of Neanderthal and Sapiens hybridization among the ancestors of today's Eurasians 49-42 KYA, it doesn't address the introgression of Neanderthal genes among aboriginal Australian/Oceanian peoples. According to an earlier study, also from the Max Planck Institute [Malaspinas, Westaway, et al. Nature 538], this occurred in the range of ~60 KYA. It appears to follow an Out-of-Africa event around ~72 KYA involving the common ancestors of all modern non-Africans.