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Thursday, Dec. 30, 2004
2004: A VINTAGE YEAR
Controversies cloud a breakthrough find on 'once-luxuriant bush'
By ROWAN HOOPER
This year has been a vintage one for biologists interested in human evolution. In a cave on an Indonesian island, the remains of a new species of human were found, a species that lived only 18,000 years ago and hence overlapped with modern Homo sapiens.
This, the most important discovery of 2004, was also one of the most controversial. The discovery of the skeleton -- dubbed Florence after its scientific name, Homo floresiensis -- was first reported in the British-based journal Nature. Earlier this month it was named runner-up in the "breakthroughs of the year" awarded by rival journal Science, based in the United States.
Florence made the front pages of newspapers worldwide. Later in the year Science published a paper by an Indonesian paleoanthropologist, Teuku Jacob, of Gadjah Mada University. Jacob, who was not one of the scientists who wrote the Nature paper, claimed that Florence was not a new species, but his motives are suspect. It appears he was angry not to have been involved in one of the most important scientific discoveries ever made in his country. The team that uncovered the skeleton reject his claims that Florence is simply a modern human with a small head, but remarkably, Jacob has made off with the original bones, so no independent checks can be made. He says he'll return the bones in January. However, we can be quite sure that Florence and the six other skeletons found on the island do belong to the new species.
This remarkable find brings to mind a comment by the paleontologist Stephen Jay Gould, who died in 2002. "Homo sapiens," Gould said, "is the only surviving branch of a once-luxuriant bush."
Gould might adjust his words if only he were alive to see the bones of Florence, thought to have evolved from Homo erectus. For the discovery suggests that we might not be the only surviving branch of the bush.
A species of ox unknown to science was discovered as recently as 1992. If an ox species can go undiscovered, might there be other species of primates, even of our own Homo genus, eking out an existence in a remote jungle somewhere?
If a living individual was found, the shockwaves would be unprecedented. You can be sure that Science would make it breakthrough of the year, even if it was first published by its rival.
As it was, with only bones found, the No. 1 spot this year went to the evidence collected by the Mars rovers, Opportunity and Spirit. That data (published in Science, naturally), conclusively showed that water once flowed on the surface of our nearest planetary neighbor. Whether life once flourished there, however, is another matter. But the discovery of another hominid species that lived so recently on Earth, almost into the historical past, resonates as powerfully as even the possibility of alien life on the planet next door.
"It's extremely rare to find a hitherto unknown species of human living in the recent geological past," said Richard Roberts, of the School of Earth and Environmental Sciences, University of Wollongong, Australia, and one of the authors of the Nature paper. "Generally it's the oldest occurrence of a hominid that makes waves, not the most recent!"
Why did it make such waves? The reason is that it challenges our sense of uniqueness. We are without doubt the dominant organism on the planet and, often unconsciously, we feel that that is the way it should be. We feel it is our right to be at the top of the ladder. The discovery that another species of human lived alongside us fairly recently shakes that assumption to its core.
Homo floresiensis took part in communal, organized hunts; it used fire and made stone tools. In other words, it was a fellow human. There is no ladder. As Gould said, there is a luxuriant bush.
Anything that rattles our assumptions is a good thing. This year we heard that one of our closest relatives, the bonobo (formerly known as pygmy chimpanzees), is closer to extinction than was already feared. A World Wide Fund for Nature survey carried out in the only country where bonobos live -- the war-torn Democratic Republic of Congo -- suggested that the population has fallen from 50,000 to a potentially unsustainable 10,000.
Relatives in trouble
Gorillas, chimps and bonobos: Our closest relatives are in serious trouble. But we are almost inured to news of species extinction. More excitement was generated by Florence (an extinct human species) than the news that a closely related great ape is in danger of extinction.
After Florence, news of the discovery of another important set of ape bones, this time found near Barcelona in Spain, was received without fuss. The bones were fossils of an ape species that was new to science, called Pierolapithecus catalaunicus. The Spanish paleontology team who found them showed that the species lived about 13 million years ago, and had a stiff lower spine and other adaptations for climbing.
What this means, they said (in the November edition of Science), is that this species was probably close to the last great ape ancestor, the last common ancestor to all living great apes, including humans.
Ironically, just as we are learning more about the luxuriant bush of human relatives, that bush is being rapidly pruned back. Perhaps the discovery of Florence will remind us of our position in the world before it is too late.
A book of Natural Selections columns translated into Japanese, "Nou to sekkusu no seibutsugaku (Evolution, Sex and the Brain)," is published by Shinchosha. Rowan Hooper is a biologist at Trinity College, Dublin. He welcomes readers' comments and questions at email@example.com