In just over a decade, our understanding of the recent period of human evolution has been revolutionized. New excavations and the application of exciting scientific methods provide extraordinary insights into our ancient past and overturn past truths.
We now know that just 40,000 years ago, there were perhaps six different lineages of humans on Earth, including Neanderthals, Denisovans, the “Hobbits” of Flores (Homo floresiensis), Homo luzonensis on the island of Luzon in the Philippines, in addition to us (Homo sapiens).
We also know that we carry a genetic inheritance from the period in which we rode these lost cousins. And that genetic inheritance could have been one of the keys to how we ultimately succeeded and spread so widely across the planet.
Our species, Homo sapiens, evolved in Africa about 300,000 years ago. Prior to 2010, the dominant thought among scientists was that these people had very little, if any, contact with other now-extinct human relatives (the best known being the Neanderthals) as they left Africa for themselves. go to Eurasia. It is not known exactly when this happened.
I believe there were several movements outside of Africa, roughly 160,000 to 60,000 years ago, but the most important in our history were the most recent. In some archaeological sites in Europe, there is a gap between the later archaeological layers of Neanderthals and the beginning of later layers containing evidence of Homo sapiens. This suggested that perhaps in these regions the two groups might not even have met.
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In 2010, however, scientists in Leipzig, Germany announced that they had sequenced the majority of the Neanderthal genome. Analysis showed that humans inherit a small amount of Neanderthal DNA and that there was, in fact, crossbreeding between our two groups.
It was a big surprise to many at the time. It has been suggested that the two groups met briefly, possibly somewhere in the Near East, with humans subsequently carrying low but similar levels of Neanderthal genetic ancestry to all parts of the world.
A few years later, in 2014, my research group at the University of Oxford discovered that in Europe, Neanderthals and Homo sapiens had in fact overlapped for a considerable time: up to 5,000 years, before the disappearance of the Neanderthals about 40,000 years ago. The disappearance of the Neanderthals was therefore a longer and longer process than previously thought.
About 45,000 to 40,000 years ago, it seems we were contemporary and had ample time to meet and interact. New evidence that I describe in my book The world before us suggests an even wider overlap, both in Europe and in other parts of Eurasia.
Given this coexistence and the genetic exchange that occurred, could there also have been a cultural exchange between the two groups? Many paleoanthropologists have thought for decades that if there is a cultural exchange, there would probably be a way: from the so-called superior Homo sapiens to less able Neanderthals.
Recent work on Neanderthals and their world has shown that, far from the backward caves widely popularized in the 19-20e Century, they formed a group of capable and often sophisticated hunter-gatherers, present for more than 250,000 years, surviving periods of often significant climatic variability. Evidence is emerging that before modern humans arrived, they did certain things that were previously considered our exclusive domain – Homo sapiens.
Fascinating new evidence, for example, now suggests that the Neanderthals may have been the first rock painters in Europe. Small calcium carbonate concretions that slowly developed on painted surfaces can be dated using traces of radioactive uranium isotopes. Extremely old ages have been obtained, showing that some of the painted caves in Spain are over 65,000 years old.
It was a time when the Neanderthals were the sole occupants of Europe. Archaeologists have assumed for decades that all the ancient art drawn on cave walls was produced by modern humans. These new results challenge this view.
Likewise, we are also beginning to recognize evidence that Neanderthals behave in other ways that we often refer to as “behaviorally modern”; possibly wearing ornaments made from eagle talons, decorating with feathers, using mineral dyes, and preparing skins probably for clothing using deliberately chosen bone implements.
I wonder if we should view the period of overlap evident in the archaeological record as a period where there could have been an exchange of ideas, creativity and technology between the two groups as they met. and interacted, rather than in a way as previously thought. .
Increasingly, we are seeing evidence of periodic contact between these different groups and interbreeding between humans and others. Recent work we published in April 2021 showed that the genomes of early modern humans in Eurasia often contain long pieces of Neanderthal DNA. This indicates that interbreeding between the two groups sometimes occurred only a few generations before that person’s life, as the DNA was not subsequently split into smaller blocks with the modern-only human generations (this process is called “ recombination ”). It is an extraordinary thought that 20 percent or more of the entire Neanderthal nuclear genome can be mapped from all the genomes of living people.
Evidence is building that shows that the genetic variants we inherited from these ancient linkages – from Neanderthals but also from another group of eastern Eurasia called the Denisovans – have important implications for us today. These range from positive (without Denisovan DNA, Tibetans could not live at altitude and New Guineans would not have the same levels of resistance to certain tropical diseases) to less positive (genetic variants coding for diabetes of type II, lupus and smoking addiction come from Neanderthals).
It is becoming increasingly evident that “hybridization” between different human groups may have been crucial as our ancestors settled in new and harsh environments. Through hybridization, we were able to obtain rapid genetic benefits from human lines that had occupied these regions for millennia. These benefits, along with other behavioral and technological adaptations we see in archaeological records, have helped Homo sapiens become a very successful “invasive species”, moving to all parts of the planet and adapting to life there.
Why, then, did the Neanderthals and other groups finally disappear from the archaeological record? There are intriguing demographic clues pulled from high-coverage genetic analysis of human bones. DNA analysis of some late Neanderthals shows that they have long stretches of “homozygosity,” when two alleles at a gene locus that are identical in both parents are inherited, suggesting that these parents must to have been closely related.
This, and other evidence from population genetics and archeology, supports the idea that Neanderthals likely lived in small groups and in general low numbers. It is highly likely that no more than 5,000 Neanderthals lived in Eurasia at a time. Could have been a major difference from Homo sapiens.
A slow trickle of newly arrived modern humans, without any substantial cognitive or behavioral benefits, might have been all that was needed on the part of humans to doom the Neanderthals to oblivion. Little by little, we will also learn the fate of the other members of the great human family who once lived on Earth and what role we played in their demise.
We have always considered ourselves unique. It turns out that at the time of evolution, this uniqueness did not exist until yesterday.
The world before us: how science reveals a new story of our human origins by Tom Higham is now available (£ 20, Viking).
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