WASHINGTON -- This week, a 47 million-year-old fossil was put on display at New York's American Museum of Natural History. Scientists accorded the event enormous attention, as did the press. The creature may be related to us, though it looks like a cat, not a chimpanzee, and certainly nothing like your mother or father or even one of your more eccentric aunts or uncles. Evolutionists tell us that of all the creatures known to science, we humans are most closely related to chimpanzees.
That is not the whole story, of course. According to a very fine book that I have been reading, "Why Evolution Is True," by Jerry A. Coyne, an evolutionary biologist at the University of Chicago, mankind can be traced back over 3 billion years, to our most distant relatives: self-replicating molecules. The fossil unveiled at the American Museum of Natural History is a relative newcomer, but she (the creature was a young female) has cleared up a debate among scientists. Anthropologists had been pretty certain that we evolved from apelike ancestors, but they had been divided on precisely which one. There were two, the family Tarsiidae -- whose descendants, the tarsiers, are jungle creatures now living in Asia -- and the family Adapidae, who were precursors of the lemur of Madagascar.
Scientists base their speculations on fossils that are rarely complete. Some scientists have extrapolated our ancestors from as little evidence as a tooth. The lucky ones have had a jawbone or a rib or some other skeletal fragment. This week's fossil displayed in New York is a complete skeleton, except for a missing lower leg. From it, evidence mounts that our ancestors were the Adapidae, the precursors of the lemur. "Lemur advocates will be delighted," Tim White, a California paleontologist, is quoted as saying in The Wall Street Journal, "but tarsier advocates will be underwhelmed." Scientists are given to such disputes, and then there are the creationists, who doubt we have any animal ancestors whatsoever. Let the debate continue.
What I have found fascinating in Coyne's book is how very old Earth is. Some of his evidence comes from fossils and measurements of the radioactivity in the layers of stone that harbors the fossils. The radioactivity gives us a good idea of the stone's age, and the progression of the fossils gives us an idea of their steady development.