What are the implications for later hominids (Australopithecus)?
• There are several alternative hypotheses about evolutionary relationships described and illustrated in the lead (summary) paper in Science. Australopithecus may have evolved directly and rapidly from Ardipithecus ramidus between 4.4 and 4.1 million years ago. Another possibility is that Ardipithecus ramidus was a relict species that may have persisted alongside its descendant Australopithecus. • Testing these hypotheses will require additional fossils from other sites. So far, however, Ardipithecus has always been found in older strata than Australopithecus, and the two have not yet been found at the same time horizon. • Ardipithecus shows that hominids became fundamentally terrestrial only at the Australopithecus stage of evolution. Australopithecus had forfeited much of its climbing ability (they were almost as bad at climbing in trees as are humans), and were probably the first hominids to range extensively into more open habitats. Their skulls and teeth indicate that their broade
