Like us, early humans ran the gamut

STONY BROOK (US) — Although they did not act “modern,” new evidence suggests humans living in East Africa 200,000 years ago were as complex in their behavior as humans living today.

In a paper recently published in Current Anthropology, John Shea asserts that some of the behaviors associated with modern humans—specifically our capacity for wide behavioral variability—did occur among early humans.

“Archaeologists have been focusing on the wrong measurement of early human behavior,” says Shea, professor of anthropology at Stony Brook University and a research associate with the Turkana Basin Institute in Kenya. “The search has been for evidence of ‘behavioral modernity,’ a quality supposedly unique to Homo sapiens, when archaeologists ought to have been investigating ‘behavioral variability,’ a quantitative dimension to the behavior of all living things.”

The idea that human evolution follows a progressive trajectory is one of the most deeply-entrenched assumptions about Homo sapiens evolution. In fact, archaeologists have long believed that modern human behaviors emerged tens of thousands of years after our species first evolved.

While scientists disagreed over whether the process was gradual or quick, they have agreed that Homo sapiens once lived who were very different from us.

The European Upper Paleolithic archaeological record has long been the standard against which the behavior of earlier and non-European humans is compared. During the Upper Paleolithic (45,000-12,000 years ago), Homo sapiens fossils first appeared, together with complex tool technology, carved bone tools, complex projectile weapons, advanced techniques for using fire, cave art, beads, and other personal adornments.

Similar behaviors are either universal or very nearly so among recent humans, and, thus, archaeologists cite evidence for these behaviors as evidence of human behavioral modernity.

Yet, the oldest Homo sapiens fossils occur between 100,000-200,000 years ago in Africa and southern Asia and in contexts lacking clear and consistent evidence for such behavioral modernity. For decades anthropologists contrasted these earlier “archaic” African and Asian humans with their “behaviorally modern” Upper Paleolithic counterparts, explaining the differences between them in terms of a single “human revolution” that fundamentally changed human biology and behavior.

Archaeologists disagree about the causes, timing, pace, and characteristics of this revolution, but there is a consensus that the behavior of the earliest Homo sapiens was significantly different than that of more-recent “modern” humans.

“Comparing the behavior of our most ancient ancestors to Upper Paleolithic Europeans holistically and ranking them in terms of their ‘behavioral modernity’ is a waste of time,” argues Shea. “There are no such things as modern humans, just Homo sapiens populations with the capacity for a wide range of behavioral variability. Whether this range is significantly different from that of earlier and other hominin species remains to be discovered, but the best way to advance our understanding of human behavior is by researching the sources of behavioral variability.”

Shea tested the hypothesis that there were differences in behavioral variability between earlier and later Homo sapiens using stone tool evidence dating to between 250,000-6,000 years ago in eastern Africa, which features the longest continuous archaeological record of Homo sapiens behavior.

“A systematic comparison of variability in stone tool making strategies over the last quarter-million years shows no single behavioral revolution in our species’ evolutionary history,” says Shea. “Instead, the evidence shows wide variability in stone tool making strategies over the last quarter-million years and no single behavioral revolution. Particular changes in stone tool technology are explicable in terms of principles of behavioral ecology and the costs and benefits of different tool-making strategies.”

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