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Author: VanSickle, C

Source: AMERICAN SCIENTIST, 104 (6):354-361; NOV-DEC 2016 

Abstract: 

At the end of the 19th century, when Charles Darwin was writing about human evolution, many scholars thought the evolutionary path to humans was a straight line. This conception seemed reasonable at a time when we hadn’t yet found many types of hominin fossils: It was easy to imagine older-looking species coming first, followed by less old-looking species, and culminating in Homo sapiens sapiens.

Today, however, we have a lot more fossils to fit into the hominin lineage, and what we’ve found is that evolution rarely proceeds in a straight line. As with other animal species, our evolutionary history is complex, with certain traits evolving multiple times, more species diversity than was initially imagined, and few indicators of which path led to humans. This situation means that whenever fossil evidence of a new species is discovered, it has the potential to change the entire “map” of human evolution. Lately the map has begun to look less like a direct route than the roadways of a complex city, complete with dead ends, detours, roundabouts, and side roads representing both the fossils we know and the hominin species we haven’t discovered yet.