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Who Knew?
The Science of Things
SEPTEMBER 2005

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PALEOANTHROPOLOGY 
Out of Africa

 
Image: Skeleton of hand coming out of sandAre we looking for bones in all the right places?

Scientists are good at finding logical patterns and turning data into a coherent narrative. But the study of human origins is tricky: The bones tell a complicated story. The cast of characters keeps growing. The plot keeps thickening. It's a heck of a tale, still unfolding.
 
More than half a century ago the great biologist Ernst Mayr surveyed the field of paleoanthropology and saw all sorts of diverse characters: Peking man, Java man, and Homo erectus.
 
He figured out that they were all the same thing and helped bring coherence to a rambling tale. By the 1960s the textbook version of human origins looked pretty tidy: Humans evolved in Africa; Homo habilis begat Homo erectus, who begat Homo sapiens. (The Neandertals were sort of a fly in the ointment.)
 
Today the field has again become a rather glorious mess. The central fact of human
evolution is a given—humans descended from a primate that lived in Africa six or seven million years ago—and those who would doubt evolution are arguing against the entire enterprise of science. But even though the basics are established, some key details are still unknown.
 
"Our family tree is no different from that of any other animal. There are a lot of dead ends in it. At certain times you had three, perhaps four species of hominins," says Hans Sues, a paleontologist at the National Museum of Natural History in Washington, D.C.
 
The fossil record is hampered by the fact that bones don't fossilize everywhere. We have essentially no fossils, for example, of chimpanzees, because they live in rain forests, where bones decompose rapidly. "We're missing a whole swath of habitat," says Dan Lieberman, a Harvard paleoanthropologist.
 
Lieberman says that it's time for a new Mayr to come along and figure out what it all means. Lieberman thinks some of his colleagues have tried too hard to tell the story of human origins from a relatively limited set of fossils, particularly those found in the Rift Valley of East Africa.
 
"We're not doing a very good job of being honest about what we don't know," says Lieberman. "Sometimes I think we're trying to squeeze too much blood out of these stones."
 
Lieberman's suggestion raises hackles. Tim White, a paleoanthropologist at the University of California at Berkeley who works in East Africa, says: "People who look for fossils focus on the places with the highest potential. If Lieberman or Sues have good ideas for where others should be looking, why don't they share them?"
 
Earth doesn't yield a perfect database. Still, it's our scientific impulse to impose parsimonious explanations on complex problems in the same way that Newton realized that the fall of the apple and the motion of the planets were governed by the same simple force called gravity. But the process of evolution can't be observed like the fall of an apple. Life—despite all the efforts of modern science—is messy.
 
—Joel Achenbach
Washington Post staff writer






Related Links

More Articles by Joel Achenbach
www.washingtonpost.com/wp-dyn/style/columns/achenbach
Read some of writer Joel Achenbach's columns for the Washington Post.
 
Smithsonian National Museum of Natural History Human Origins Program
www.mnh.si.edu/anthro/humanorigins
This site supports human evolutionary history through the presentation of collected scientific evidence and ongoing research.
 
The Talk.Origins Archive
www.talkorigins.org
Thoughtful Q&As, essays, and a chat room provide a forum to explore the creation versus evolution controversy.





Bibliography

Fischman, Josh. "The Pathfinders." National Geographic (April 2005), 16-27.
 
Morwood, Mike, and others. "
World of the Little People." National Geographic (April 2005), 2-12.
 
Quammen, David. "
Darwin's Big Idea." National Geographic (November 2004), 2-35.




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