For years, scientists opposed to Darwin's theory have proposed their own theory that evolution could have taken place by pure providence—randomly inherited traits only some of which endure by surviving. For instance, the lengthening of the giraffe's neck, if random, would have occurred as a result of both long-neck and short-neck giraffes evolving, but the short-neck ones didn't survive because they couldn't reach the food. Darwin, on the other hand, believed in the selection of successive traits where a common neck-lengthening trend resulted in the long-neck giraffes we know today.

Now the collaborative study, performed by researchers at the Technion Institute of Technology in Israel, the United States, France and Germany, claims to prove that Darwin was right—successive traits are deterministic, not random.

"Random development would not have created such unifying trends," said professor Benjamin Podbilewicz from the Technion department of biology. "We conclude that the observed development was deterministic, not random."

To prove the point, the researchers tracked the development in 51 species of nematode—a worm species that reproduces so quickly that its evolution can be easily tracked in the lab. By following the changes in 40 characteristics of the nematode, they found that the statistically valid means of evolution was natural selection of successive traits.

Previous studies attempting to confirm Darwin's theory of evolution did not focus on the mechanism propelling trait inheritance. Now that the mechanism of evolution has been confirmed to be deterministic in worms, Podbilewicz hopes to reconfirm its applicability to all living things—including humans.