Today, we look for an historical Eve in her garden. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.
Stephen Jay Gould has become a fine public voice in matters of biology, geology, and evolution. He writes complex ideas down in words that you and I can fathom. Now he talks about a new notion of a common ancestor.
Humanoids have been around over two million years. This new ancestor is only a tenth that age -- only 200,000 years. Older humanoids might've been our cousins. But they weren't ancestors.
Advocates of that idea call the new ancestor Eve. Why Eve and not Adam? The answer has to do with the basis of the theory.
Certain of our cells carry building blocks called mitochondria. Both our mother and father contributed to our genetic makeup. But only our mother gave us our mitochondria.
Mitochondria are useful in tracking kinship. Some years ago, Argentine grandmothers fought to get back children who'd been kidnapped by the dictatorship. They used a mitochondrial DNA test to identify the children.
Now ethno-biologists put mitochondrial data into computers. They can do their calculations many ways. But every path leads to one specific ancestor or another. One path leads to the bones of certain 200,000-year-old African women. Since we can't yet trace male genes, we give those women the collective name of Eve.
Some people wonder if there's a Biblical angle on all this. But looking for a single mother of our species misses the point. This Eve opens much deeper questions about our place in the scheme of things. Gould says we're really just an afterthought in evolution. In his words,
We are a thing, a singular event, an item of history -- not the predictable result of necessary improvement. Homo sapiens is one of the twigs [on the tree of life], not [a] grand, overarching predictability.
We'd rather've been shaped by millions of years of competitive selection into a large-brained super-animal. We want to be the focus of history, not one of its byroads.
But then, this Eve doesn't offer a scientific answer to the question of our place in the cosmos. Besides, another theme entirely is rising in scientific circles.
It is that our Earth might be a single system. Maybe we're elements that participate in sustaining the Earth that sustains us. Maybe Earth is far more than a backdrop against which we played the drama of evolution. Maybe we have to see our own progression as part of the changing equilibrium of Earth as a whole.
If that's the case, this new Eve takes on a very different meaning. For then our presence on Earth represents the solution of some problem -- not the result of a competitive skirmish for survival.
I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.
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Gould, S.J., Eve and Her Tree. Discover, July 1992, pp. 32-33.
Lovelock, J.E., Gaia: A New Look at Life on Earth. Oxford: Oxford University Press, 1987 (an updated reprinting of a 1979 book.)
Joseph, L.E., Gaia: The Growth of an Idea. New York: St. Martin's Press, 1990.
Gibbons, A., An About-Face for Modern Human Origins. Science, Vol. 256, 12 June, 1992, pg. 1521. (The tracing of our origins to an Eve in Africa is under severe attack. However, the notion of a very specific, and fairly recent, ancestor is quite alive.)
For more on the idea of Earth as a coherent system, see Episodes 699 and 700. I'm grateful to Professor Blaine Cole, UH Biology Department, for his counsel on this episode.