The human type

Every species named by science has a “type” attached to it: an individual specimen that serves as the definitive example of that species. And yes, that includes humans: the type human was born in 1707.

Alexander Roslin [Public domain]
Defining a species is a difficult business. The boundaries between different species are not always easy and clear: different species can sometimes interbreed (like lions and tigers) and even within a single species there is always genetic variation and historical variation. Dogs are descended from wolves, so at what point did they become a distinct species? Or are they all just wolves at heart?

When biologists define a species, they must attach the name to a specific physical specimen of that species. The Tyrannosaurus Rex, for example, is represented by a pile of bones kept in the American Museum of Natural History in New York. Biologists wanting to (for example) compare their own fossils to the T-Rex to see whether they’ve discovered a new species or not would use the bones in that museum as their reference point.

This works fine for newly discovered species – you find a specimen, you preserve it and file it away in a natural history museum, and the type is clear and unambiguous. But we’ve only been following this process for a hundred years or so. What about species that we knew about before type specimens were a thing?

Taxonomists, fortunately, have a whole set of protocols for how to handle such situations, and an international organisation – the International Commission on Zoological Nomenclature – to help resolve them. In the case of species without a specific type, a specimen is chosen retrospectively to represent that species. It’s known as a lectotype.

So, who is the lectotype human? Who is the universal standard for… us? The commission’s protocols state that

For a nominal species or subspecies established before 2000, any evidence, published or unpublished, may be taken into account to determine what specimens constitute the type series.

In other words, they pull in any evidence from the original namer of the species to identify the type.

Carl Linnaeus, the inventor of biological naming conventions, came up with the name Homo Sapiens. But we have no evidence that he examined any specimens to define it… except, presumably, himself. So Carl Linnaeus, the Swedish biologist born in 1707 and died in 1778, has become the type for humanity. Said specimen is buried in Uppsala Cathedral. I don’t think other biologists are allowed to do comparisons with it, though.

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