In 2013 the world followed, via tweets, blogs and videos, as scientists negotiated the underground system of caves known as Rising Star just outside Johannesburg, South Africa. Ultimately the researchers, working under the direction of paleoanthropologist Lee Berger of the University of the Witwatersrand, would bring up more than 1,500 bones and bone fragments belonging to an archaic human species. The team has concluded that the fossils represent a previously unknown relative of ours, now named Homo naledi.
The Rising Star find is only one in a rash of recent discoveries that has extended—and revised—the complex story of human evolution. New fossils are adding branches to our family tree; climate data are revealing the conditions under which the predecessors of our own species evolved their hallmark traits; cognitive studies are homing in on what distinguishes us from our great ape cousins; and DNA analyses are illuminating the extent to which human species interbred—and how we ourselves continue to evolve.
Arguably, no chapter of the human odyssey has been so dramatically rewritten as the one detailing the ascent of Homo sapiens. Far from being an evolutionary slam dunk destined for world domination from the outset, H. sapiens no sooner debuted than it nearly went extinct as a result of climate change. Neither is the cognitive divide between H. sapiens and archaic species nearly so pronounced as some scholars had envisioned. Discoveries of sophisticated tools and symbolic items reveal that Neandertals were far more technologically advanced and cultured than previously supposed.
In this special edition of Scientific American, we explore the evolution of those characteristics that make us human—from our upright stance to our peerless ability to collaborate. Our tale has three chapters. The first examines our tangled family tree and the factors that favored the survival of our branch to the exclusion of others. The second takes stock of how humans differ from other primates—from hairless skin to unmatched creativity to widespread monogamy—and considers how these features may have set us up to thrive. The third ponders the future of human evolution in a world brimming with technological fixes for everything from loneliness to disease.
We hope you enjoy this story, seven million years in the making. It is not the final word, of course. Just as human evolution seems to be accelerating, so, too, is the pace of paleoanthropological discovery. But we wouldn't have it any other way.