Why are some discoveries welcomed, whereas others are received with skepticism? I am prompted to ask this by recent developments in paleoanthropology. On the face of things, the story is an old one: International team finds startling new fossil human, oldest of its type in the region; experts agog. The catch is that the new find now being hailed merely echoes an earlier one in the same place, by many of the same researchers—but the early find was received with a "wait and see" attitude, if not outright disbelief. What makes the difference?

The original find, in 1991, was a primitive human mandible or jaw found at the then newly discovered fossil site of Dmanisi in the Republic of Georgia. A joint German-Georgian team of scientists and students excavated there for some months, recovering beautiful fossils of extinct species like saber-toothed cats, elephants and rhinos, along with some crude stone tools. On the last day—similar episodes are so common that the Last Day Find is practically a cliché—Antje Justus, a German graduate student, freed a partial skeleton of a saber-toothed cat from the sediments in her area of the dig. Lying directly underneath the extinct cat was the fossilized jaw of a primitive human, with a complete set of teeth. This was the find everyone had been hoping for all summer long.

click for full image and caption

click for full image and caption

In that moment, Dmanisi was transformed from being an interesting site to being one of major significance for human origins. Although the jaw itself could not be dated directly (as is often the case), its inferred age was impressive. The most recent record of the extinct animals found at Dmanisi turned out to be about 1.2 million years ago, while the fresh-looking lava that lay underneath the fossil-bearing sediments was estimated to be about 1.8 million years old, according to preliminary radiometric dating. That meant that the owner of the Dmanisi mandible lived in the interval between 1.2 and 1.8 million years ago, making it the earliest evidence of Homo erectus from the Eurasian continent by a significant margin.

The first I heard of the find was in December of 1991, when Justus, paleontologist Leo Gabunia of the Republic of Georgia National Academy of Sciences, and dig director David Lordkipanidze of the Georgia State Museum traveled to a conference on Homo erectus at the Senckenberg Museum in Frankfurt, Germany. Gabunia and Justus gave a joint presentation briefly describing the site, the fauna, the tools, the jaw and the preliminary dates. They generously brought the original fossil with them, so that colleagues could examine it firsthand during the workshop portion of the conference.

I knew most of the conference participants, but Gabunia, Justus and Lordkipanidze seemed to have come out of nowhere, speaking of a site I couldn't find without an atlas. Gabunia is a quiet, silver-haired man who spoke in French so clear that even I understood the jaw's anatomy. Justus put the find in context, speaking in articulate English and looking even younger than she was. Lordkipanidze fell somewhere in the middle in terms of age and personality; his English was excellent, his enthusiasm palpable, and he was obviously knowledgeable. If they were even half right in what they were saying, this was a very important new find indeed.