Before Charles Darwin, the leading evolutionary theorist was Jean-Baptise Lamarck, who believed organisms acquired traits over their lifetimes that they then passed onto their children. This theory has been roundly disproved...but in the case of roundworms, Lamarck was actually right.
The classic example of Lamarckian evolution is giraffes. According to Lamarck, giraffes developed their long necks by stretching them upwards to feed on tall leaves. In his view, some giraffes managed to stretch their necks out over the course of their lifetime, giving them an advantage over the other giraffes which they then passed onto their children. While some of his basic mechanics weren't far off from what Darwin ultimately developed, Lamarck was led astray by his emphasis on acquired traits instead of the random mutations that underpin Darwinian evolution.
But now, two centuries later, Lamarck is getting a small measure of vindication. In at least one species, evolution by acquired traits really does exist, according to researchers at Columbia University.
Via Gary Schmidt