Ardi and the human family tree

Move over, “Lucy,” said Larry Dignan in ZDNet. The “fabled” 3.2 million-year-old fossil was “bumped” out of “science’s limelight” Thursday by Ardi—or Ardipithecus ramidus—an earlier human ancestor from Ethiopia’s Afar desert, dating back 4.4 million years. Ardi and her peers represent a middle stage in human evolution, which, surprisingly, was “more modern” than today’s apes and chimpanzees.

That’s important, because for a long time evolutionary biologists thought of chimps as “time machines,” said Joel Achenbach in The Washington Post, or a view into what our common ancestor with apes looked like. But Ardi would be a step back for both humans and chimps, a “sort of hybrid” hominid who mostly lived in trees but also walked upright—“if the scientists are correct,” that is. “Human origins is a field with high stakes and small bones.”

And the bones to this “new alleged missing link” were so fragmented and delicate, said Casey Luskin in the Discovery Institute’s Evolution News & Views, that it took the team of scientists and “reconstructionists” 15 years to put Ardi together. So pardon my “initial reaction of skepticism” to their “Rosetta stone”–level claims.

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There’s room for skepticism about whether Ardi was a biped, said Jamie Shreeve in National Geographic, but not about her importance to the field of human evolution. Assuming Ardi did walk on two legs, though, there’s a “provocative theory” as to why: sex. In that scenario, males shifted from fighting each other for mates to a “‘food for sex’ contract” model in which they earned sex by bringing home food—and you need free hands to carry food.