What's in a Species Name?

The most famous Latin name for a species must surely be “Tyrannosaurus rex”. Or just T.rex, as all dino fans know it so fondly. Recently I learnt that the naming convention for species (called “binomial nomenclature”) has 2 parts:

-         The first part is the genus; (I have no clue what a genus means!)

-         The second identifies the species within the genus.

Now keep in mind that we came up with this convention a couple of centuries back. And therefore, the genus was being decided based on appearance and visible (or inferable) attributes of the specimen.

Today, writes Svante Pääbo in his excellent book, Neanderthal Man: In Search of Lost Genomes, we can study the DNA of a specimen to know which species shared ancestors, and which ones are ancestors of which others. And so often we find that seemingly unrelated species shared common ancestors, or one was an ancestor of the other, even though they may have no visible similarities! As you can imagine, this new way of analyzing specimen often flat out contradicts the older non-DNA techniques used for centuries when it comes to species.

In any case, continues Pääbo, there is no clear definition of how you demarcate a species. The common idea that two species are demarcated if they can’t breed together or if they can’t produce a fertile offspring isn’t valid. He points out that polar bears and grizzly bears occasionally breed and produce fertile offspring. Yet, it sounds crazy to say they are the same species given how different they are!

When Pääbo and his team analyzed the DNA of Neanderthals, they found that they were a separate species from good old Homo Sapiens, and the two shared a common ancestor at some point. But, and this is key, there had also been interbreeding between the two! It fell upon Pääbo to give a come up with a name for the new species. He hated the prospect. Why?

“It has a tendency to elicit scientific debates that have no resolution. For example, if researchers refer to Neanderthals as “Homo neanderthalenis”, they indicate that they regard them as a separate species… If researchers say “Homo sapiens neanderthalenis”, they indicate that they see them as a subspecies.”

Controversy aside, how do you classify species that interbred?! The nomenclature wasn’t designed for this! Even worse, the binomial nomenclature system has another flaw, writes Pääbo:

“Once a name is in taxonomic literature, it cannot be withdrawn later.”

This whole binomial nomenclature seems very stupid to me: once a name has been (mis)assigned to a (non)species, we’re stuck. How do we then know which names correspond to “real” species as opposed to the “mistaken” species? And in any case, we don’t even know how to demarcate a species! And yet this system lives on… As Obelix would say, “These species namers are crazy!”