Paleopuzzle: Chomping With No Chompers
April 7, 2005
The toothless skull of an early human ancestor discovered in the Caucasus may attest to evolution's oldest known example of compassion for the elderly and handicapped, scientists report today.
Photo: The toothless skull of an early human ancestor, discovered in the Republic of Georgia, may attest to evolution's oldest known example of some kind of compassion for the elderly and handicapped in society. (Kenneth Garrett/National Geographic Magazine)
Other experts agreed that the discovery was significant, but cautioned that it might be a stretch to interpret the fossil as evidence of compassion.
The well-preserved skull, found in Georgia, belonged to a male Homo erectus about 40 years old. All his teeth, except the left canine, were missing. Regrowth of bone indicated that the man had been toothless for at least two years before he died at what was then an old age. (The discoverers call him the "old man.")
In their report today, in the journal Nature, the discovery team said the 1.77-million-year-old skull "raises questions about alternative subsistence strategies in early Homo." Specifically, how could the man have survived that long, unable to chew the food of a meat-eating society?
In interviews and in the current issue of National Geographic, the paleoanthropologists said caring companions might have helped the toothless man by finding soft plant food and hammering raw meat with stone tools so he could "gum" his dinner. If so, they said, this was evidence of a kind of compassion that had been absent in the ancestral fossil record before the Neanderthals 60,000 years ago.
About the survival of the old man, Dr. David Lordkinidze said in National Geographic, "We're looking at perhaps the first sign of truly human behavior in one of our ancestors."
Dr. Lordkinidze, director of the Georgian State Museum in Tbilisi, led the team that made the discovery, at Dmanisi, a site that has already yielded several skulls and skeletons that are the oldest clear evidence of human ancestors living outside Africa.
Dr. G. Philip Rightmire of Binghamton University in upstate New York, a team member who specializes in Homo erectus, said in an interview that the old man might have been able to take care of himself by cracking bones for the marrow and even softening pieces of meat with stone hammers. But the loss of teeth, signifying either disease or advanced age or both, suggested that he might have needed help.
"The old man is indeed a very interesting specimen," said Dr. Susan C. Anton of New York University, who has conducted research at the Dmanisi site but was not involved in the current report. "It makes the Georgian collection particularly important for looking at variability in populations, and especially for age variability."
But Dr. Anton, an editor of The Journal of Human Evolution, said that "going from the clear biological signals of tooth loss before death to provisioning, compassion and care of the individual by others in the group is something of a leap." She cited examples of toothless chimpanzees surviving without assistance.
"Did this hominid have to do things slightly differently than others in their group?" Dr. Anton said. "Yes. Did that mean that the others were providing care or food or compassion? There's no way to know. But it wouldn't be my first inference."
Paleoanthropologists and archaeologists plan to return to Dmanisi in June to resume excavations, financed in part by the National Geographic Society. Dr. Rightmire said the team planned to widen research to detailed examinations of bones below the skulls, especially those of arms and legs. One objective will be to determine the body size and mass of these early human ancestors, and to judge how close to modern humans they were in their ability to walk and run.