Via Boingboing, I found this wonderful entry at BiblioOdyssey featuring illustrations from "a 1753 work called 'Collection des Animaux Quadrupèdes' which forms part of an enormous 36-volume series ('Histoire Naturelle') issued over a forty year period by Georges-Louis Leclerc, Comte de Buffon."
The name "Buffon" was familiar, and sure enough upon checking I confirmed that it was Buffon who had claimed that something about North America produced small, weak and degenerate plants and animals - including human animals. At American Scientist Keith Thomson describes Buffon's assertions:
Buffon was not the first to assert American degeneracy, and this idea was not based on natural history alone: Politics also played a part. Buffon's immediate source was a book by a Spanish naval officer, Don Antonio d'Ulloa (Relación histórica del viaje hecho de orden de su Majestad a la América Meridional, 1748). d'Ulloa's thesis was that the human condition in the Americas was degenerate as a result of a long history of colonialism, slavery, exploitation of natural resources and subjugation of the native peoples. To d'Ulloa, it was natural that America lacked the large mammals of the Old World and was rife with noxious insects and poisonous reptiles.
Buffon, focusing on North America, developed d'Ulloa's observations into a complex theory in which climate played a central role. In his ninth volume, published in 1761, Buffon compared mammalian species and noted examples in which the same species lived on both sides of the Atlantic Ocean. He claimed the New-World versions were always smaller and weaker. European livestock exported to America were always stunted. Species indigenous to the New World were always smaller than comparable species in the Old World (the largest American mammal was the tapir, nowhere near the size of an elephant). Of American Indians, he wrote, "the organs of generation (of the savage) are small and feeble. He has no hair, no beard, no ardour for the female. Though nimbler than the European, his strength is not so great. His sensations are less acute; and yet he is more timid and cowardly." And so on.
All of which roused a perturbed Thomas Jefferson to refute Buffon's claims by, among other thing, arranging to have the carcass of a moose shipped to Paris:
When he arrived [in Paris], Jefferson sent Buffon a copy of [his] Notes [on the State of Virginia] and the skin of a large panther, and was subsequently invited to dine with Buffon at the Jardin du Roi, Paris's magnificent botanical garden. Of that meeting Jefferson later wrote, "in my conversations with the Count de Buffon . . . I find him absolutely unacquainted with our Elk and our deer. He has hitherto believed that our deer never had horns more than a foot long." So Jefferson decided to show him a full-grown American moose. He wrote to General John Sullivan, president (governor) of New Hampshire, for help in getting a large specimen, instructing him that the bones of the head and legs should be left in the skin so that it could be mounted in a life-like manner. Eventually a "seven-foot tall" moose was collected in Vermont and shipped to Paris.
Many years later, Daniel Webster told the story that Jefferson had had the moose set up in the hall of his apartment and invited Buffon to see it. Confronted with that stark refutation of his earlier thesis, Buffon was said to have exclaimed, "I should have consulted you, Monsieur, before I published my book on natural history, and then I should have been sure of my facts." It would be nice if this story were true. In fact, Buffon, by this time old and sick, was away from Paris when the moose arrived in October 1787. Jefferson sent it to Buffon's long time associate, zoologist Louis-Jean-Marie D'Aubenton, for the great man to see when he returned. Although most of the hair had fallen off the hide, the antlers sent by Sullivan were from a smaller animal and the whole carcass was probably rancid, Jefferson was "in hopes that Monsieur de Buffon will be able to have it stuffed, and placed on his legs in the King's Cabinet."
The illustration at the top is courtesy of peacay's Flickr photostream.
Addendum: If you're looking for more detail, try Keith S. Thompson's longer paper, Jefferson, Buffon, and the European View of America.