What makes us human? We ask this not only in church but also in the science laboratory. One step is to find out what we are not. An interesting answer from the past year is this: We are not Neanderthals.
A Neanderthal is a person not quite like us. The species, Homo neanderthalensis, lived during the past half-million years of prehistory, mostly in Europe, becoming extinct about 30,000 years ago.
In 1856, bones thought to be those of a bear were discovered by quarrymen in the Neander Valley (thal or tal, the modern form for valley) of Germany, now in the state of North Rhine-Westphalia. Since their discovery, we have learned that bones found earlier in Belgium and Gibraltar are now properly classified as Neanderthals.
For some time, paleontologists (scientists who study old bones and fossils) have wondered what happened to the Neanderthals 30,000 years ago.
Did they intermingle and breed with the new human species of people like us, the Cro-Magnons who were moving into Europe during the past 100,000 years? Or, did the Neanderthals find themselves at a disadvantage, with a more primitive culture and life ways, outmaneuvered in the competition for big-game animals and other resources, trapped in a vanishing lifestyle?
The skeletal remains of Neanderthals are distinctive. Their skulls have a large protrusion on the back, an "occipital bun," where our visual cortex is located. They also have bony brow ridges that protrude much farther forward than the smooth foreheads and skulls that you and I possess.
We can easily see the difference in our bones.
That evidence, however, has not stopped some researchers from suggesting that Neanderthals and modern humans might have interbred, so that Neanderthal traits were passed down through modern European peoples. In fact, some scientists have classified the Neanderthal remains as Home sapiens neanderthalensis, implying they are a subspecies of modern humans.
Last August, an international team of researchers led by Richard Green of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, reported that they had successfully analyzed DNA from a Neanderthal bone.
In their research, they analyzed the complete mitochondrial DNA from a Neanderthal bone. Mitochondrial DNA (written mtDNA) is inherited only from one's mother.
The results of their work showed that the mtDNA of Neanderthals is quite different from modern humans. The DNA in our branch of the human family, and theirs, has been separate for about 660,000 years.
During that long time span, according to Green and his colleagues, our genome and that of Neanderthals changed. In the 13 genes they studied, a total genetic length of 16,565 base pairs, modern humans and Neanderthals ultimately became different in 206 base-pair positions.
This difference in 206 base pairs (out of the human complement of 3.2 billion base pairs) is enough to show that the Neanderthals were humans, but not close enough to be considered Homo sapiens, people like us.
So we have a fresh answer: It is highly unlikely that Neanderthals and modern humans interbred in any significant way.
Virginia's science Standards of Learning deal with human evolution in the fossil record in LS.14, after the introduction of related topics in earlier grades.
Walter R.T. Witschey is professor of anthropology and science education at Longwood University.
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