Monday, March 28, 2011

Wonderful life


It has been called a "walking cactus."

It is the cover creature of the February 24 issue of Nature, reconstructed here from fossils found in Cambrian deposits in China, a 500-million-year-old wormlike animal about as long as my finger, with armored and possibly articulated legs. Its name is Diania cactiformis, and its discoverers suggest it may be connected to the origins of the arthropods, a hugely diverse phylum of animals with external skeletons, segmented bodies and jointed appendages.

The arthropods make up more than 80 percent of living animal species, including scorpions, crabs, earwigs and butterflies.

Stephen Jay Gould wrote brilliantly (and controversially) about the weird creatures of the Cambrian in a book called Wonderful Life. Certainly, it was a time of wonderful diversification, sometimes called "The Cambrian Explosion." Gould proposed that many of these fossil creatures were dead ends. Which ones impressed their body plans on the future was something of a crap shoot, he said. Given a different roll of the dice, the animals on earth today might have been very different.

It is the dearest conceit of our species that we are inevitable, necessary, central to creation, that in this universe of more than 100 billion galaxies we -- Homo sapiens, bipedal, internal-skeletons, bilaterally symmetric -- are the apple of the Creator's eye, that the whole shebang was arranged for us alone. Sometimes we define our specialness even more narrowly, as when some of us imagine (for example) that the point of creation was to make white, English-speaking, American Christians.

Just how contingent was the evolution of life I will leave to the biologists to figure out, but the fossil record shows unambiguously that the Creator was more whimsical than we are generally wont to admit. The "walking cactus" looks weird to us, but that is only because it is unfamiliar. Is it really weirder, say, than a woolly bear caterpillar, to which it might be ancestrally related? And if the Cambrian rocks of Earth hold such gems of whimsy, imagine what specialness-deflating surprises reside in those 100 billion other galaxies.