WASHINGTON — JUST as asteroid impacts and chains of volcanic eruptions may have caused five mass extinctions on Earth through the eons, mankind may cause the Earth's "Sixth Extinction," Richard Leakey says.
"Unless we change, we are likely over the next three decades to lose 50 percent of the species we know on this planet" through environmental destruction, he says.
"And yet it could be stopped" in the short term, the famed paleoanthropologist told reporters at a National Geographic luncheon last week.
"One of the sadnesses that I feel, is that the Rio de Janeiro conference [the June Earth Summit] came up with such a big agenda with such a huge budget, and that much of it won't happen because people are afraid of something [that big and expensive]," he said.
"If we could simply take a few small steps at a time, I think we could stop the worst scenario - that loss [of species] over three decades."
Mr. Leakey, whose family's fossil finds in Africa have made an important and well-publicized contribution to what the world knows of mankind's biological origin, is in the United States promoting his new book, "Origins Reconsidered: In Search of What Makes Us Human" (Doubleday: 375 pp., $25).
In his philosophical evolution, Leakey left his scientific career in 1989 to head the Kenya Wildlife Service.
He has been charged with ending rampant elephant and rhinoceros poaching and building a wildlife-management structure that will preserve and expand the tourist industry's important role in Kenya. Leakey claims that poaching has ended in Kenya - an example of one of the smaller environmental steps he urges worldwide.
The move from studying man's history to preserving his environment is a clear manifestation of Leakey's guiding principle: "The past is the key to our future."
Leakey told reporters that his new book is a "sort of epilogue" to his thoughts on human origins. It focuses on his ideas about the origin of human consciousness and concludes with where he thinks man is going.
Leakey suggested in his talk that, much as Kenya has done in wildlife conservation, Homo sapiens can at least make short-term progress in preserving the environment. But in the end, Leakey's book projects that the pressures of human populations are likely to inflict the "Sixth Extinction" that could take mankind with it. That event, he suggests, will be a mere "blip" in Earth's continued evolution.