This clip of Harvard-educated geneticist and molecular biologist Dean Hamer is required viewing for anyone who wants a better understanding of the biological origins of sexuality. It happened during the hours-long testimony in the Hawai’i House Of Representatives, as they prepare to vote to legalize marriage equality. Of particular interest is the questioning of anti-gay Rep. Bob McDermott, who seems to be one of those fundamentalists whose view of his own intelligence is highly inflated, with little to back it up. Hamer tears him apart.

Watch the whole thing: