Gosh-wow! Science - Evolution P*rn Division.

Urchin predation "causes" Sea Lillies to "walk."

Nature teems with examples of evolutionary arms races between predators and prey, with the predator species gradually evolving a new mode of attack for each defensive adaptation that arises in the prey species.

These adaptations are often portrayed as reciprocal, with prey and predator acting as two sides in an endless evolutionary tug of war known as co-evolution.

Now a University of Michigan paleontologist and his colleagues report an example of a much more one-sided, asymmetrical predator-prey relationship. The predators in this case are sea urchins, and over a nearly 200-million-year span they appear to have been in the driver's seat, forcing evolutionary adaptations upon marine animals called crinoids, which include the sea lily.

Hungry sea urchins even drove the formerly stationary, or sessile, sea lilies to develop the ability to escape by creeping along the ocean floor.

Of course, can we really say that there is a "cause and effect" relationship. Sea Lillies would have been throwing off the mutations that permitted creeping in any event. Can we say that random chance wouldn't have led to creeping even without Urchin predation?

The other problem with the idea of "cause" is that Urchin predation doesn't "cause" the mutation. In fact, how there can be any development of new structures at all is a mystery.

But it is, nevertheless, really cool!