Human or hybrid? The big debate over what a species really is
BIOLOGY is a messy business. Witness these sage words: “It is really laughable to see what different ideas are prominent in various naturalists minds, when they speak of ‘species’… It all comes, I believe, from trying to define the undefinable.”
Strong stuff. And from a surprising source. Charles Darwin wrote those lines in a letter to fellow naturalist Joseph Hooker, just three years before the publication of On the Origin of Species. Darwin clearly had a problem with the word to which his name is now so intimately linked. It turns out he is not alone. Today, almost 160 years after he revolutionised biology, how to define a species is more problematic than ever.
You probably learned that a species is a group of individuals that can breed to produce fertile offspring, but this is just one of dozens of competing definitions. The lack of consensus on what a species is has big implications for how we think about the natural world and for our efforts to conserve it. But the problems go even deeper. Recent revelations about interbreeding between what some regard as separate species of ancient humans have left many of us wondering: who are “we”, who are “they” and are we actually all one and the same? In other words, how we define a species has become a question at the very heart of human identity. Perhaps it is time to rethink the whole concept.
The idea that the living world is divided into distinct species has deep roots. Frank Zachos at the Natural History Museum Vienna, Austria, suspects it predates …