Evolution develops fantastic solutions, but slowly
Very slowly. Richard Dawkins, in Climbing Mount Improbable, points out how people looking at, say, the human eye and wondering how on earth that could have evolved, are looking at the sheer cliffs of the north face of Mount Improbable, with the eye way up near the peak and us at the foot of the cliff, thinking, “There is no way to get up there.” But if we travel around to the foot of the mountain on the south side—which is a great distance away—we see a flat plain starting a gradual slope, so gradual that going up it is a stroll, not a climb or even a hike. But the slope stretches a very great distance indeed, and when we reach the end, we find ourselves standing atop those cliffs that seemed unclimbable.
He develops this analogy in several directions, quite usefully, but take a look at the length of that slope, as Susan Milius reports in Science News:
A new effort to date the early history of modern animals finds a lot of evolutionary dawdling.
The last common ancestor of all living animals probably arose nearly 800 million years ago, a multidisciplinary research team reports in the Nov. 25Science. From that common ancestry, various animal lineages diverged and evolved on their own paths. Yet the major animal groups living today didn’t arise until roughly 200 million years later, in an exuberant burst of forms preserved in fossils during what’s called the Cambrian explosion.
“There’s a deeper history that’s been missing from the fossil record,” says study coauthor Kevin Peterson of Dartmouth College. He and his colleagues have been pushing back that date for a last common ancestor, and now, he reports, the analysis has the broadest reach yet. “We show that animals evolved quite a bit before they show up in the fossil record.”
This work updates the notion of a long evolutionary lag, when much of the basic biological toolkit was already in place for a later surge of new body forms, says paleontologist and study coauthor Douglas Erwin of the National Museum of Natural History in Washington, D.C., and the Santa Fe Institute.
“The Cambrian explosion is like the industrial revolution,” Erwin says. Inventions that would later be important for a major shift in technology — or, in this case, genetic novelties important for evolution — appeared long before they played a role in widespread changes that had a major impact on life.
For understanding animal origins, the new paper “is really worthwhile as it stands back and tries to make sense of the whole picture,” says James Valentine of the University of California, Berkeley, who studies animal evolution.
Just what happened with animals during that Cambrian explosion remains one of the more celebrated puzzles in the history of life. Charles Darwin mused over how diverse animal forms appear suddenly (geologically speaking) without much in the way of precursors. Darwin’s answer, as Erwin puts it, was that paleontologists just needed to look harder.
More than a century of hard looking has turned up some signs, fossils as well as traces of biological chemistry, of enigmatic animal life before the Cambrian period began about 541 million years ago. Yet the relationship to modern animals often is not clear. Theories themselves have exuberantly exploded in number and form.
For the new study, Erwin and the rock side of the team . . .
