Sex.The mid-20th century's most influential academic was probably Alfred Kinsey, whose high-school classmates half-jokingly called him the "Second Darwin." Kinsey's 1948 and 1953 books on sexuality contended that adultery is normal and homosexual experiences not uncommon, for "the mammalian backgrounds of human behavior [made it] difficult to explain why each and every individual is not involved in every type of sexual history."
(Later, researchers found that Kinsey's stats were cooked, but in the meantime the American Law Institute's Model Penal Code, published in 1955, had a major effect in eliminating or reducing penalties for sex crimes: "Virtually a Kinsey document," one biographer called the Code. More recently, John West's Darwin Day in America cites textbook claims that casual sex is an evolutionary adaptation that gives "obvious reproductive advantages"—and we should not raise our standards because "we cannot escape our animal origins.")
Abortion.Evolution proponents contributed mightily to its legalization, and in a way more direct than the general teaching that human life has no intrinsic value. Robert Williams, president of the Association of American Physicians, said in 1969 that "the fetus has not been shown to be nearer to the human being than is the unborn ape." He talked of "the recapitulation of phylogeny by ontogeny"—the mistaken theory that an unborn child's development mimics purported evolutionary progress. The most influential pro-abortion legal expert during the 1960s, Cyril Means, argued that babies are sub-human—and the Supreme Court's 1973 Roe v. Wade decision played off his mean-hearted briefs.
Infanticide.I debated Princeton's Peter Singer in 2004 and had several conversations with him about his defense of infanticide. That year he said, "All we are doing is catching up with Darwin. He showed in the 19th century that we are simply animals. Humans had imagined we were a separate part of Creation, that there was some magical line between Us and Them. Darwin's theory undermined the foundations of that entire Western way of thinking about the place of our species in the universe."
We could run through many more areas. Daniel Dennett in Darwin's Dangerous Idea hit it right: Darwin created a "universal acid" that eats through any "meaning coming from on high."