Paleoanthropology is a discipline known as much for its feuds as for its findings. Among the best known of these clashes is a longstanding one between two of the field's most famous scientists, Donald Johanson and Richard Leakey. Both have led expeditions that made such extraordinary fossil discoveries as the 3.2-million-year old "Lucy" skeleton from Hadar, Ethiopia (Johanson), and the 1.6-million-year-old "Turkana Boy" skeleton from Turkana, Kenya (Leakey)—and both have done much to popularize human origins. Theirs started off as a friendly rivalry. In a book I wrote with Johanson called Lucy's Legacy (Harmony, 2009), Johanson described it thusly:

"Friendly rivalry is at times a good thing because it motivates us all to work a little harder, a little longer, and take chances we otherwise might not take. Chief among my rivals was Richard Leakey, son of Louis and Mary, who had made some spectacular finds at Lake Turkana in Kenya, including a specimen known as 1470, then considered the earliest evidence of Homo. Tall and lanky with sun-bleached hair and boyish good looks, Richard exuded authority and confidence. We'd met several times, and the previous year I'd brought [a fossil knee from Hadar] to Nairobi so that his team at the National Museums of Kenya could make a cast of it. He graciously allowed me to see their hominid fossil collection, including specimens that hadn't been published yet or even announced. Honored to be a member of the "inner circle" of scholars who were granted such access, I felt it was now my turn to return the favor, so I invited Richard; his wife Meave; and his mother Mary, to Hadar. A licensed pilot, he flew to Ethiopia in his own plane and landed at our hastily cleared airstrip, dubbed Hadar International Airport….As they walked Hadar's astonishingly fossil-rich hillsides, I enjoyed watching their dumbstruck expressions, thinking that was how I must have looked to Maurice [Taeib] when I first came here.

Over dinner we debated the fossil identification of the new hominid jaws that Alemayehu [Asfaw] had found. Richard favored classifying the larger one as part of a member of our own genus, Homo, whereas I thought it belonged to a male australopithecine. We weren't just arguing about the jaws, though. Richard believed that the 1470 skull was 3 million years old. But like many other experts in the field I suspected the geological dating was wrong because the animal remains found along with it, particularly the pigs, were identical to those from the Omo that were dated at about 2 million years. Although we disagreed, I was thrilled to be exchanging ideas with some of the giants in the field….

On Saturday we drove Richard and his group out to the airstrip, helped them load up, and waved good-bye as they took off for the flight back to Kenya. The following day I found Lucy."

That was 1974. Lucy—and the question of her place in the family tree—intensified this rivalry, because Johanson proposed that Lucy's species, Australopithecus afarensis, was older than and ancestral to our genus, Homo, whereas Leakey argued that Homo had very ancient roots, which would have excluded the then-known australopithecines as ancestors. Their disagreement on this matter culminated in a very public falling-out in 1981 during a recorded debate between the two men at the American Museum of Natural History in New York City that was later broadcast on Cronkite's Universe. Roger Lewin and Virginia Morell have written at length about this drama-filled moment, as have others.

So it's a big deal that Johanson and Leakey met once again at the American Museum of Natural History and shared the stage for the first time in 30 years to discuss human origins and why it matters. CNN chief medical correspondent Sanjay Gupta moderated the discussion on May 5, which started at 6:30 p.m. EDT and was streamed live at:


Top: Johanson via Wikimedia Commons/Marlith (left) and Leakey Flickr/Ed Schipul (right)

Bottom: Johanson (left) and Leakey via Wikimedia Commons/William Campbell/Sygma/Corbis (right)