"What Ardi tells us is there was this vast intermediate stage in our evolution that nobody knew about," said Owen Lovejoy, an anatomist at Kent State University in Ohio, who analyzed Ardi's bones below the neck. "It changes everything."
Then he said love made humans evolve! Well, he always said it, but is still:
"Divergent big toes are associated with grasping, and this has one of the most divergent big toes you can imagine," Jungers said. "Why would an animal fully adapted to support its weight on its forelimbs in the trees elect to walk bipedally on the ground?"
One provocative answer to that question—originally proposed by Lovejoy in the early 1980s and refined now in light of the Ardipithecus discoveries—attributes the origin of bipedality to another trademark of humankind: monogamous sex.
Virtually all apes and monkeys, especially males, have long upper canine teeth—formidable weapons in fights for mating opportunities.
But Ardipithecus appears to have already embarked on a uniquely human evolutionary path, with canines reduced in size and dramatically "feminized" to a stubby, diamond shape, according to the researchers. Males and female specimens are also close to each other in body size.
Lovejoy sees these changes as part of an epochal shift in social behavior: Instead of fighting for access to females, a male Ardipithecus would supply a "targeted female" and her offspring with gathered foods and gain her sexual loyalty in return.
To keep up his end of the deal, a male needed to have his hands free to carry home the food. Bipedalism may have been a poor way for Ardipithecus to get around, but through its contribution to the "sex for food" contract, it would have been an excellent way to bear more offspring. And in evolution, of course, more offspring is the name of the game (more: "Did Early Humans Start Walking for Sex?").
Just funny to me-- if I had stayed at Kent for the graduate program, would I have been working on this? Would Ardipithicus have been the last ten years of my life? I think I prefer what happened to the alternative, even given how much I dig on extinct hominids. Still; good to see the old alma mater kicking ape ass & taking hominid names! Or whatever. Just remember kids: there is no such thing as a "missing link!"