Lamarck proposed a scientific theory called “inheritance of acquired character-istics.” To understand it, let’s consider giraffes, a descendant of ancient creatures that supposedly were similar to modern antelopes. How did the giraffe evolve its long neck?

According to Lamarckian logic, thousands and thousands of years ago, some an-telopes felt the need to feed on tree leaves beyond the reach of their mandibles. They began stretching their necks to get them. As a consequence, they were born with slightly longer necks than the previous generation. But this is like saying that if I start doing heavy bodybuilding today and become a clone of Sylvester Stallone, my kids will be born with steel muscles. To the followers of Lamarckism, form literally follows function. The former pushes the latter.

Thanks to Charles Darwin, though, we now know that evolution doesn’t work that way. Darwin’s On the Origin of Species was published in 1859 and offered an alternative to Lamarck’s hypothesis. The force that moves evolution forward is not the acquisition of characteristics and skills inherited by kin, but the natural selection of traits that help an organism survive in its environment. What Dar-win did was to invert Lamarck’s logic: Function doesn’t determine form. In fact, in many cases, the opposite is true. [..] This is called variation. [...] In other words, the need to reach higher every day (the function) didn’t force the development of longer necks (the form). Longer necks were the result of random genetic mutations that were nonrandomly filtered (that is, selected) by the envi-ronment. In nature, then, relationships between forms and functions are much more complex than what Sullivan thought.