By the 17th century, the Americas had been discovered and were being explored. This led to new problems. All the species had to be spread again from one point, after the flood. The obvious answer was that man had spread over the continents after the destruction of the Tower of Babel. The different groups took animals with them. Some of the results seemed peculiar, though: "why had the natives of North America taken rattlesnakes, but not horses", wondered Sir Thomas Browne in 1646? "How America abounded with Beasts of prey and noxious Animals, yet contained not in that necessary Creature, a Horse, is very strange."