National Geographic : 2015 Oct
Homo sapiens Two m.y.a . H. naledi H. naledi H. naledi Earlier divergence? Australopithecus anamensis A. afarensis A. garhi A. robustus A. boisei H. habilis H. rudolfensis H. sp. (species unknown) A. sediba Kenyanthropus platyops H. erectus H. heidelbergensis H. neanderthalensis A. africanus A. aethiopicus Three m.y.a . Four m.y.a. Today One Million Years Ago (m.y.a.) EARLY HOMO H. naledi’s anatomy—transitional between australopithecines and Homo—is most compatible with an age of some two to two and a half million years. Australopithecines Early species were adapted to climbing as well as bipedalism; later species had more specialized diets of tough, fibrous foods. Homo Long lower legs were adapted to walking and running; smaller teeth and larger brains in later H. erectus could indicate hunting and eating more meat. A RECENT COUSIN If H. naledi is less than a million years old, then our ancestors shared the African landscape with a small-brained form of Homo much more recently than thought. NUDGING OUT LUCY Though it’s highly unlikely, if H. naledi is extremely old, it could call into question the idea that Lucy’s species, A. afarensis, was on our direct evolutionary lineage. JASON TREAT, NGM STAFF SOURCES: LEE BERGER, WITS; JOHN HAWKS, UNIVERSITY OF WISCONSIN-MADISON A Place in Time Mixed soil sediments in the cave where H. naledi was found make it difficult to date the bones. High-tech dating methods could provide an age. Three possibili- ties are considered here—any of which would throw a curve into current thinking on human evolution.