Why modern Homo sapiens replaced all other humans [View all]

The other Homo sapiens

We are just one branch of a diverse human family tree. Aside from Neanderthals, who were they – and why did we replace them?

https://aeon.co/essays/why-one-branch-on-the-human-family-tree-replaced-all-the-others


The cave of Es-Skhul, Mount Carmel, Israel. Photo supplied by the author



On the western slope of Mount Carmel, in Israel, lies the cave of Es-Skhul. About 140,000 years ago, during the Ice Age, nomadic hunter-gatherers made camp here. The sea to the west had receded, exposing a broad plain covered with groves of live oak, almond and olive, meadows filled with asphodel and anemone. Herds of fallow deer, rhinoceros and aurochs roamed the plains. People hunted animals with stone-tipped spears, and foraged wild mustard and olives. And when they died, they buried their dead by the mouth of the cave. The skeletons found here represent some of the earliest known members of our species, Homo sapiens. But these Homo sapiens were very different from us.


3D scan of Skhul V, recovered from Skhul cave. Courtesy the Smithsonian Institution

Their skulls retained anatomical features seen in primitive humans like Neanderthals – huge brow ridges, massive jaws, thick skulls. But, despite their primitive appearance, they weren’t our ancestors; they appear too late in time. They’re a side branch of our evolutionary tree, one that went extinct, leaving no descendants. Why did we survive, while they didn’t?

The answer may lie in their skulls. They lacked the peculiar anatomical traits that modern humans share – small brow ridges, bubble-shaped skulls, reduced jaws, thin cranial bones – which are typical of juveniles of other hominins and apes. Compared with other hominins, we’re literally baby-faced. Selection for juvenile traits – low aggression, openness to novelty and new people – likely made us more social, and produced our immature-looking skulls as a side-effect. Ironically, it may have been this sociability and low aggression that made modern humans so incredibly dangerous to these primitive Homo sapiens.

Skhul Cave was first excavated in 1929, and parts of 10 skeletons were eventually found. Soon after, the remains of at least 28 people, dating to 90,000 years ago, were discovered near Nazareth at nearby Qafzeh Cave. When they were first found, the Skhul and Qafzeh remains were among the oldest known Homo sapiens. Today, a century later, they still are, and their meaning is still debated.


Qafzeh skull. Courtesy Wikipedia

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