Strictly speaking, Trying Leviathan is not about evolution. It is about a remarkable legal clash between "common sense" and "expert opinion" — a theme all too familiar in the ongoing creationism/evolution wars. As such it has valuable lessons for us. It is also a terrific read.
The case, Maurice v Judd, played out in the Mayor's Court in New York City in 1818. Because of alleged adulteration of fish liver oil, then an important commodity, the New York state legislature had mandated government inspection thereof — with an inspection fee, and a hefty fine for those failing to comply. At issue was whether whale oil was "fish oil" for the purpose of the statute. The argument boiled down to whether or not whales were fishes. Distinguished zoologist and all-around savant Samuel L Mitchill was the star witness, presenting all the latest arguments from comparative anatomy to demonstrate that whales were mammals, not fishes.
One might expect such erudition to carry the day, but it did not. The lead attorney for the other side, William Sampson, played cleverly on anti-intellectualism to discredit Mitchill as a dilettante and out of touch with reality. Nor did the rhetorical manipulation stop at mere anti-intellectualism. Sampson exploited resentment of what was perceived as New England snobbery, portraying the notion that cetaceans were mammals as a Yankee insult to good old New York common sense: "a mere provincial usage" his co-counsel, John Anthon, called it. And Mitchill had testified that "a whale is no more a fish than a man." Anthon exploited this to tie scientific taxonomy to the slavery question and racial anxiety. He posited a scenario in which Mitchill, using all the same arguments he had adduced in claiming a whale was a mammal, now claimed that an orangutan was a man, and indeed "entitled to vote in our public elections." Sampson cautioned the jury that the distinctness of man from the lower orders would be cast into doubt if this newfangled comparative anatomy were to be recognized in a court of law: "Yes, gentlemen of the jury, in the same order with man, they place the monkey, ape and baboon; all equally related, and differing from the lord of the creation only as they differ from each other" (p 84-5). It is hard to tell which of these ploys was most effective, but something worked, since the jury took only fifteen minutes to rule that a whale was a fish.
The court recommended that the legislature revisit the statute and decide for itself whether it wanted whale oil included. It did not, and amended the statute forthwith.
As we all know, evolutionary biologists are prone to lose debates to creationists if they assume that scientific "knowledge" by its very nature must vanquish creationist "ignorance". Maurice v Judd shows that the same sociological forces and the same rhetorical ploys can maintain their vigor for nearly two centuries, and warns us that when elite culture gets too far ahead of popular culture, it loses its relevance. I think about this every time I explain to students why cladistic reasoning tells us that the "Class Reptilia" does not exist, and that birds are a subset of dinosaurs. It sounds just as "airy-fairy" as the whale-as-mammal theory did in New York in 1818 and is received with appropriate incredulity.