Paleoanthropology is the branch of anthropology associated with fossil hominids. Is it related to gene-environment interactions…?? CERTAINLY…!! Evolution of all life on Earth involves the constant formation of new species — in response to environmental adversity; whichever species is better (or best) at improving survival (finding food, avoiding predators, producing the strongest offspring for the next generation) — ultimately will become the winner in the game of “survival of the fittest.” New genes, new alleles arise in response to environmental signals (diet, climate, and random events)…
It was “the shot heard ’round the world,” or more accurately, “the finger that started a whole new revolution in paleontology ’round the world.” In 2008, archaeologists working in Denisova Cave in southern Siberia, Russia, uncovered a tiny bone — the tip of the little finger of an ancient human that lived there — tens of thousands of years ago. The fragment didn’t seem THAT remarkable, but it was well preserved, giving researchers hope that it harbored intact DNA [see attached pdf].
A team of geneticists at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, removed 30 milligrams of bone and managed to extract enough intact DNA to analyze it. They first were able to sequence the entire mitochondrial genome. The DNA did not match that of modern humans, nor of Neanderthals (the other likely candidate). It was a new population, which they dubbed “Denisovans”” after the cave; the team announced this result in March 2010. Up to that point, researchers had used preserved bones to identify every species or population of hominin (the group that includes all modern and ancient humans and their immediate ancestors).
Nine months later, researchers completed the entire nuclear genome from that finger bone, which yielded much more fascinating information; it showed that the Denisovans were a sister group to the Neanderthals, which lived in Europe and western Asia for hundreds of thousands of years. The team also described the discovery of a molar tooth, which — on the basis of its mitochondrial DNA — was Denisovan; it was unusually large, unlike teeth from modern human or Neanderthal. Even more surprisingly, the team reported that present-day people living on the islands of New Guinea and Bougainville (in southwestern Pacific Ocean) have inherited 4–6% of their DNA from Denisovans, even though these islands are ~8,500 km from Denisova Cave. This finding implied that modern humans had interbred with Denisovans, and that Denisovans were once widespread all across Asia.
If Denisovans had ranged as far as it seemed, where were the fossils? Had paleoanthropologists not yet found them, or were they sitting, unrecognized, in museum collections? Now, 15 years after the first report on this
hominin, numerous fossils in museums and elsewhere have also been identified (in retrospect) as Denisovan. Some were located from the Tibetan plateau; one was hidden in a well in China for decades; another was dredged from the bottom of the sea. They reveal a diverse, adaptable Denisovan population that lived in frigid Siberia, at the high altitudes of Tibet, and in the tropics. What they have found so far could force a complete reconsideration of the origin of our species.
The story of hominins starts in Africa, where the oldest known species all lived. The earliest one found outside of Africa was Homo erectus, which inhabited what is now Georgia 1.8 million years ago and soon spread as far east as the island of Java in Indonesia (Georgia — located within the Caucasus Mountains, on the southeastern shore of the Black Sea). Later came the Neanderthals (Homo neanderthalensis), which dispersed throughout Europe and western Asia, sometimes venturing as far east as Denisova Cave. At the same time, the Denisovans were living in eastern Asia.
Our own species, Homo sapiens, was the last to evolve — appearing at least 200,000 years ago in Africa. One fossil find in Morocco suggests that modern humans might date back more than 300,000 years. H. sapiens left Africa in several waves, eventually replacing all other hominins; but, before they did, some of them mated with
Neanderthals and Denisovans. Today, the highest levels of Denisovan DNA are found in The Philippines, but Denisovan DNA is widespread in people from southeast Asia, including Papua New Guinea.
When researchers set out to find Denisovan fossils, they discovered that one had been collected decades before — and had gone unrecognized. It was a lower jawbone in the Baishiya Karst Cave on the Tibetan plateau (China). In a 2019 study, researchers at the Chinese Academy of Sciences in Beijing identified the bone as Denisovan, and dated it to at least 160,000 years ago (by measuring radioactive decay in the sediment stuck to the bone’s surface). The following year, the same team reported finding Denisovan DNA preserved in the sediments of that same cave; this discovery indicated that Denisovans were present there around 100,000 and 60,000 years ago, and that they might remained there until ~45,000 years ago. These two studies established that Denisovans lived successfully on the high-altitude Tibetan plateau — which aligns with a 2014 genetic study, reporting that modern Tibetans inherited a Denisovan genetic variant that helps them to cope with low oxygen levels (presumably from ancient interbreeding between modern humans and Denisovans in that region).
Denisovans are unique in that they are known mainly from genetic data, not from fossils. Thus, Denisovans might turn out to belong to a species that has already been defined morphologically, rather than being something wholly new. Genetic results have pointed to a shared common ancestor of modern humans, Neanderthals, and Denisovans that lived several hundred thousand years ago. That common ancestor may well have lived somewhere in Europe or Asia, and then it split three ways. In this view, the population ancestral to H. sapiens migrated back to Africa, and the Neanderthal and Denisovan lineages spread across Eurasia. Some are even suggesting that H. sapiens might have originated in multiple source populations, spanning both Africa and western Eurasia(!!)
The figure at top of p. 842 [see attached pdf] is an excellent visual summary of paleoanthropology up to this moment. Homo erectus arose in Africa ~2 million years ago and then spread to western Asia and eastern Asia. Probably Homo neanderthalensis split off as a successful branch of H. erectus ~500,000 years ago, originating in Africa, then migrating to western and central Eurasia. Likewise, Homo sapiens diverged ~300,000 years ago from H. erectus while still in Africa. Denisovans became distinct from the H. erectus branch ~200,000 years ago, arising not in Africa but in eastern Asia.
This research field is a great example of what “science” is all about. Textbooks had been written, generations of students had been taught “the facts up to that moment,” and then — along comes a fossil of a little finger fragment — which turns everything upside down. In retrospect, DNA from fossils collected over several decades were then ultimately sequenced, and a major breakthrough (sitting right under our noses) completely changes the basic concepts of almost all previously established “facts.” ☹
DwN
Nature, 22 May 2025; 641: 841-842