The Shape of Life . The Conquerors

Making the Leap: How Arthropods Left the Sea

Life's transition from the sea to the land was perhaps as much of an evolutionary challenge as Genesis. What forms of life were able to make such a drastic change in lifestyle? -- Jane Gray and William Shear

Video: Shear assembles microfossils to find the first land-based arthropods

Bill Shear, a biologist at Hampden-Sydney College in Virginia, has always held a keen interest in the evolution of insects and spiders. He and his colleagues helped to reveal some of the earliest tiny land arthropods among primitive land plant fossils. To get a clearer look at these fossils, Shear used hydrofluoric acid to dissolve away the surrounding rock and expose the organic fragments of both the fossilized plants and minute animals.

After extracting the microfossils from the rock, Shear painstakingly pieced together the exposed fragments and in so doing, revealed a whole suite of arthropods, including one similar to a modern spider.

"I can remember seeing some of the really striking fossils for the first time," he recalls. "I got a feeling of excitement that's probably very similar to scoring the big touchdown at the homecoming game. You just feel on top of the world, and it makes it worth all of the tedious searching and work that leads up to that."

Shear's work is consistent with what other scientists have found -- arthropods did not move from sea to land in one invasion. Instead, many different groups invaded the land independently.

Hampden-Sydney, VA
	Dr. William Shear Biography and Career Q & A