Aeon has a fantastic article about the fact of horizontal gene transfer. I certainly never learned about this in school, and it has interesting implications for the idea that GMO agriculture methods are 'unnatural'.
Highly recommended is a previous article on epigenetics and the utility of the 'selfish gene' analogy. The idea that genes are not the fundamental unit of change in evolution, but merely the institutionalization of changes that have already occurred, is really fascinating and shows how much biology has advanced in the last 20 years.