Richard Leakey and Donald Johanson at the AMNH

Seeing Richard Leakey and Donald Johanson give a joint presentation about human evolution would be like seeing Willie Mays and Mickey Mantle talk about about baseball. Their most famous finds --- Turkana Boy by Leakey's team and Lucy by Johanson's --- rank among the most significant scientific discoveries of the twentieth century, and their work has profoundly reshaped the story of humanity's past. Forced into a media-inflamed rivalry, the two men had not shared a stage for 30 years. Little wonder, then, that last night's sold-out event, hosted by Sanjay Gupta, was billed as "historic" (or "pre-historic," as the joke went) and attracted desperate ticket-seekers offering triple-digit sums for a chance to attend.

Yesterday was the 86th anniversary of the arrest of John Scopes for teaching evolution in a public school in Tennessee, so fittingly both Leakey and Johanson took the opportunity to emphasize the mountain of evidence for the development of homo sapiens from earlier hominids. But they also talked --- Leakey wittily, Johanson passionately --- about the importance of paleoanthropology to our understanding of ourselves both in historic terms and beyond, arguing that the recognition of our place in evolution's sweeping story binds us more firmly to the natural world. The subject is so fascinating, and their ideas so rich and engrossing, that only spending an hour and a half in their company felt like seeing the glint of a Pleistocene tooth poking out of a swath of unexplored earth.