The American Museum of Natural History in New York has an absorbing diorama that records the moment of their passing. It depicts life-sized re-creations of a male and a female walking side by side across the ancient African plain. They are hairy and chimplike in dimensions, but have a bearing and gait that suggest humanness. The most striking feature of the display is that the male holds his left arm protectively around the female's shoulder. It is a tender and affecting gesture, suggestive of close bonding.

The tableau is done with such conviction that it is easy to overlook the consideration that virtually everything above the footprints is imaginary. Almost every external aspect of the two figures—degree of hairiness, facial appendages (whether they had human noses or chimp noses), expressions, skin color, size and shape of the female's breasts—is necessarily suppositional. We can't even say that they were a couple. The female figure may in fact have been a child. Nor can we be certain that they were australopithecines. They are assumed to be australopithecines because there are no other known candidates.

I had been told that they were posed like that because during the building of the diorama the female figure kept toppling over, but Ian Tattersall insists with a laugh that the story is untrue. "Obviously we don't know whether the male had his arm around the female or not, but we do know from the stride measurements that they were walking side by side and close together—close enough to be touching. It was quite an exposed area, so they were probably feeling vulnerable. That's why we tried to give them slightly worried expressions."