Many of our fellow citizens would be surprised to learn that every human being on the planet is derived from a single common ancestor. This genealogical view has been understood at least since Darwin’s time, and modern science suggests that the common ancestor may be relatively recent, perhaps only a few thousand years ago.
Of course there are also those in our midst who are repelled by the idea that all humans are related. To them, and perhaps to all of us, it is strange solace to know that even those folks who annoy us the most may in fact by our 100th cousin.
But as awesome as it may be to contemplate that the robust diversity of people who share the planet are all relatives, it would be even more astounding to find that all living creatures of every shape and variety share a common ancestor. As astonishing as it might seem at first blush, the anonymous critter who precedes us all does indeed seem to have existed.
In a fascinating paper Douglas Theobald of Brandeis’ Biochemistry Department presents a compelling case for the existence of a universal common ancestor of all life (Nature 465 [13 May 2010] 219–222). The conclusion is based on a complex statistical analysis of a highly conserved protein across the biological taxonomies. Most telling, the result essentially rules out even two independent ancestors, let alone more complex explanations for the origin and evolution of life on earth.
So how will people react to the notion that we humans share a lineage with sloths, rattlesnakes, and E. coli? Even though this has been the mainstream conclusion of evolutionary biologists since Darwin, many will not confront the science but simply dismiss the result because they don’t believe it.
Such is the dilemma of our modern world, where belief trumps evidence, and argument carries the day over analysis.