Imagine for a moment that tomorrow we find humans on another planet. It’s an unlikely scenario to be sure, but you can imagine the theories that people might venture to explain their existence. They might propose that humans on this other planet descended from ancient earthlings who in prehistoric times had the technology to travel there. Or that humans on both planets were planted there by aliens. Or that conditions on the other planet are so similar to those found on Earth that humans evolved on both planets simultaneously. Then again, perhaps God created humans on both planets.
A very similar problem confronted the European mind in the modern period (though the analogy is not perfect). As Europeans embarked on great voyages of discovery from the 15th through to the 19th centuries, they were at a loss to explain how the native peoples they encountered in distant lands actually got there. Europeans generally assumed that all people descended from Adam and Eve – a view called monogenism – and so it was unclear how native humans came to exist in ‘New Worlds’ oceans apart from the original Garden of Eden. What is more, non-Europeans looked and acted differently. Before Charles Darwin, and for some time after him, there was no generally accepted explanation of these physical and cultural differences.
The challenge for early moderns, then, was to find a plausible explanation for how physical differences between humans arose if all humans on Earth descended from Adam and Eve. Some thinkers, such as the German naturalist Johann Friedrich Blumenbach (1752-1840), thought that human diversity arose through ‘degeneration’ from the original humans, where degeneration is caused by environmental features such as what your ancestors ate or the climate they inhabited.
A more radical way to explain human diversity involved accepting polygenism – the view that God originally created multiple first human mating pairs besides Adam and Eve. In the hypothetical scenario above, polygenism is akin to thinking that God created humans on both planets. As it happens, many influential 19th-century scientists in the United States were polygenists, turning to the theory as a means of explaining human racial differences – differences that were front and centre in American life. Proponents of polygenism argued that racial differences were fixed, some of them recruiting the theory to justify enslaving peoples whom God had made ‘lesser’.