Timelines for seven species of the Homo genus who lived within 300,000 years ago from the earliest known time to extinction:
Homo erectus: 1,900,000 to 143,000
Homo heidelbergensis: 700,000 to 200,000
Homo naledi: 335,000 to 236,000
Homo floresiensis: 190,000 to 50,000
Homo neanderthalensis: 400,000, to 40,000
Homo denisova: 287,000 to 40,000
Homo sapiens: 200,000 to Present
As far as longevity, no species of our genus, Homo, lived longer than Homo erectus. Their 1.75 million years of survival contrasts with our youthful 200,000 years on this planet. Moreover, after only a few thousand years of co-existing with Denisovans and Neanderthals, both species vanished from the fossil records about 40,000 years ago. Of the seven species of our family listed above, only one species survives the 40,000-year extinction mark from the late Pleistocene and goes into the current epoch of the Holocene: Homo sapiens.
Why did our cousin species go extinct while we were able to survive? The Smithsonian Insider asked paleoanthropologist, Briana Pobiner, for possible explanations:
“Neanderthals were fairly specialized to hunt large, Ice Age animals. But sometimes being specialized isn’t such a good strategy. When climates changed and some of those animals went extinct, the Neanderthals may have been more vulnerable to starvation.
“We also think Homo sapiens had a competitive edge over Neanderthals. There is evidence that early Homo sapiens had long-distance trade networks, possibly buffering them against times of climate change when their preferred foods were not available; Neanderthals did not.
“Neanderthals had physical features that helped them survive cold climates, like large noses to humidify and warm dry, cold air and short, stout bodies to conserve heat, but early Homo sapiens had technology that Neanderthals didn’t, including sewing needles to make clothing, important during the colder periods of the Ice Ages. Homo sapiens also had innovative tools like bows and arrows and seemed to have a more diverse diet than Neanderthals.
“We don’t have evidence of direct combat between the two species, but we know they interacted, because they interbred. Some would say Neanderthals didn’t go extinct, because everyone alive today whose ancestry is from outside of Africa (where Neanderthals never lived) carries a little bit of Neanderthal DNA in their genes.” (Gibbons, 2015)
A recent study by Oren Kolodny, an evolutionary biologist from Stanford, and his colleague, Marc Feldman reached a simple if astonishing result.
“Using what researchers already know about ancient hominin population sizes, migration patterns, and the way ecology works, Kolodny and Feldman built a simple computer model that would simulate Neanderthal and Homo sapiens interactions in Paleolithic Europe. At the start of the simulation, Europe is inhabited by “bands” of Neanderthals that randomly move around and die out. Every so often, a band of modern humans migrates out of Africa and joins the European fray. Bands from each species have equal likelihoods of displacing the other — neither one had an advantage from a natural selection perspective.
“Kolodny knew that one species had to go extinct at the end of each simulation. It’s a basic principle of ecology: Two species cannot occupy the same niche at the same time. Sometimes, species will accommodate competition by developing some kind of specialty — for example, in parts of Israel where two similar species of normally nocturnal mice are found, one species adjusts by becoming active during the day. But hominins are generalists, not specialists, and at the time of Neanderthals’ extinction, archaeological evidence suggests their abilities and behavior were pretty similar to ours.
“Kolodny and Feldman ran their simulation hundreds of thousands of times, changing the values for a number of different variables to reflect the uncertainty that scientists have about this period of human history. But in the vast majority of cases, under a wide range of parameters, the simulation ended with Neanderthals dying out within 12,000 years. They just couldn’t keep up with the slow trickle of human bands that flowed continuously north from Africa.
“This result suggests that the “null hypothesis” — based solely on what we know about basic ecology principles and the gradual human migration into the continent — is sufficient to explain why the Neanderthals disappeared.
“It doesn’t necessarily prove that humans didn’t have a selective advantage, or that climate change didn’t influence the Neanderthals’ fate, Kolodny cautioned. “But even if there were no selection and no climate change, the end result would have been the same. It’s a subtle distinction but it’s important.” (Kaplan 2017)
So we probably didn’t murder our cousins. This study clearly demonstrates that our slow but steady migrations out of Africa and into Eurasia overwhelmed the smaller bands of Neanderthals and Denisovans; they were assimilated into our DNA and the last pure specimens died out about 40,000 years ago.
Once again fiction (Star Trek) foreshadows the evolutionary facts as we play the role of the Borgs. Imagine us saying these lines to the dying Neanderthals and Denisovans: “We are the Humans. Your biological and technological distinctiveness will be added to our own. Resistance is futile.”
And then there was one…