In the early 20th century modern genetics was integrated into evolutionary theory and the resulting neo Darwinism, or New Synthesis, was hailed as a great advance. Darwin didn’t know the details of how biological variation arose but now that gap was filled in—from changing allele frequencies to genetic mutations, modern genetics provided the answer. Biological variation arose from gene sequence variations. But this version 2.0 of Darwin’s theory would go long without its own difficulties, as exemplified yet again by recent research on the origin of the domesticated chicken. Read more