Some 600 or 700 million years ago, before animal life made a sudden evolutionary shift and diverged into nearly all the major animal divisions we know from fossils, primitive animals were inventing the genes that would make it all possible.
No one knows what it looked like. There is virtually no clear fossil evidence. But now scientists believe they have found a way - using genes preserved in and common to modern animals - to look past the fossil record to our most distant common ancestors.
Writing this week (Aug. 14) in the journal Nature, and following up on a series of recent papers, molecular biologist Sean Carroll of the Howard Hughes Medical Institute at the University of Wisconsin-Madison, Neil Shubin from the University of Pennsylvania, and Cliff Tabin of Harvard Medical School, sketch out a radical new way of looking back in time.
"The fossil record prior to the Cambrian is so scant nobody knows the origin of animal life," said Carroll. But now "we're drawing a picture of something no one has ever seen."
Carroll is one of a growing number of scientists now using the techniques of modern molecular biology to look into the murky waters of distant evolutionary biology. They are looking so far back that there are virtually no fossils or other physical clues to what the Earth's earliest animals were like.
But Carroll and others are now finding powerful evidence that an ancient common ancestor - a worm-like animal from which most of world's animals subsequently derived - invented a set of body-building genetic machinery so successful and malleable that it has survived to this day.
"This is stunning," said Carroll. "Nobody thought that this animal was so sophisticated. We're talking about the common ancestor of all the most successful animals on Earth."