by Roger Kaza
Today, Neanderthal genes. The University of Houston presents this program about the machines that make our civilization run, and the people whose ingenuity created them.
The Max Planck Institute, in Leipzig, Germany, recently announced its discovery that much of the human race has inherited a small part of its DNA from the Neanderthals. This confirmed what had been theorized for decades: that these two related yet distinct species of hominid had interbred in the distant past. Question: What would Charles think?
Neanderthals, our distant mirror.
Charles Darwin, that is. We celebrated the naturalist's 200th birthday last year, and the 150th anniversary of The Origin of Species. The usual understanding of Darwin's revolutionary theory is that variations or mutations in the gene pool are what cause the giraffe to get taller, the cheetah to get faster. The best adaptors pass on the best genes. Darwin's famous example was the finches of Galapagos, each evolving differently shaped beaks, depending on the type of food they forage.
But random mutation isn't the only vehicle Darwin proposed for the evolution of species. In a later work, The Descent of Man, he suggested that species change over time because of the choices individual creatures make in picking a mate. He called this process sexual selection, and it's a theory now supported by a century of research.
Darwin was twenty years old when the first Neanderthal remains were discovered.
Think of the peacock. The explanation for his audacious beauty is that generations of peahens chose those males with the most extravagant plumage, and passed on their flamboyant genes. Sexual selection can also work in other ways: bull elks, for example, fight each other for dominance, and the winner takes all the females. Their offspring benefit from inheriting the bull's hardy genes; but maybe more important, these choices lead to the betterment of the species as a whole. Sexual selection explains why some species develop dimorphism, or radical differences in the size and appearance between males and females. Instead of merely random mutation, individuals of a species make mating choices that eventually change their gender's appearance over time.
But if all this talk of "selection" and "choices" make it sound like we're ascribing human-like attributes of free agency to the denizens of the animal kingdom — well, let's look in the mirror. We humans use language such as "falling" in love, or "chemistry" to describe our human bonding. Those don't exactly sound voluntary. And let's not forget that for much of history, and indeed in much of the world still today, mates are chosen not by the individual, but by the family, or tribe, or clan—for the betterment of the species.
Which brings back the question of those liaisons between Neanderthals and Homo sapiens, so many tens of thousands of years ago. Was Darwin's theory at work? Were these encounters voluntary or coerced, sanctioned or deviant? Those terms reflect a kind of human concern to which no amount of genetic sleuthing will ever reveal an answer. The last Neanderthal disappeared some 25,000 years ago. They're gone — except for the telltale strands of DNA, coiled in every cell of you or me.
I'm Roger Kaza, at the University of Houston, where we're interested in the way inventive minds work.
The Max Planck Institute for Evolutionary Anthropology, which has now decoded much of the Neanderthal genome, is the primary resource for studying the Neanderthal/Homo sapiens connection. Thanks to them for permission to use the leading photo above.
Wikipedia entry on the Neanderthal admixture hypothesis, which has a long history of speculation.
Wikipedia entry on Sexual Selection.
The Third Chimpanzee, a 1992 book by Jared Diamond, discusses human origins, anatomy and sexual selection.
Thanks to Matthew Wilson at the Cohen studio, Chautauqua Institution, for assistance in recording this episode.
Musical transitions by Andrew Lienhard
Photo credits: Mirror photo: Michael Hofreiter and Knut Finstermeier/MPI EVA.
Young Darwin photo courtesy Wikipedia.