Dead Pig Walking: Aardvarks, “Living Fossils” in the Bush
“Porc formiguer” by MontageMan is the author of the original image, I did the crop – Cropped from File:Porcs formiguers (Orycteropus afer).jpg. Licensed under CC BY 2.5 via Wikimedia Commons – http://commons.wikimedia.org/wiki/File:Porc_formiguer.JPG#mediaviewer/File:Porc_formiguer.JPG
Most species have a lot of cousins.
Over millions upon millions of years, evolution splits off different variations on a theme, often several of them, all of which continue to evolve towards the versions we know today. But the evidence of a common ancestor remains, as does the evidence of their ongoing evolution; if evolution weren’t continuing to change species, chimps wouldn’t be related to us, they would BE us!
A very few species, though, exist as a sort of evolutionary remnant. They look almost exactly the same as their ancient ancestors, and no other surviving species seem to come from the same branch of the evolutionary tree. These species are commonly referred to as “living fossils,” and one of the strangest of them is the aardvark.
The aardvark’s status as an evolutionary leftover explains some of this odd-looking animal’s most bizarre features.
The scientific name for the group that includes the aardvark and its extinct relatives, Tubulidentata, hints at one of the aardvark’s most distinctive—and anachronistic—features: its strange teeth.
Most mammals have teeth generally like ours; they have one main pulp-cavity covered over by a layer of dentin then a layer of enamel.
An aardvark’s tooth is a much earlier evolutionary model: it looks almost like hundreds of straws standing upright in a cluster. Each of these little tubes is held to one another by the same material that holds our teeth in our jaws, and they’re constantly being worn away and regrown. A single aardvark tooth can have as many as 1,500 of these small channels.
Aardvarks are able to live with just a few of these primitive teeth (adult aardvarks retain just 12-14 teeth towards the back of the jaw) because they most often swallow their food whole. That’s no small feat; an aardvark may use its sticky tongue to lap up as many as 50,000 ants and termites in a single night!
Like VERY early mammals, the aardvark has a sort of proto-gizzard (an organ passed down to modern day reptiles and birds, and thought to have been present in many dinosaurs) that grinds up the food mechanically, essentially doing the work of teeth.
But the strongest proof that the aardvark just hasn’t evolved?
Its genes.
The aardvark has highly conserved chromosomes, which means its DNA looks more like the DNA of very early mammals than the vast majority of species.
Does it look exactly like it would have 50-odd million years ago? Probably not. But it looks much more like animals that were around then, genetically-speaking, than almost any other living mammal.
Sometimes nature keeps revising her creations…
…and sometimes, you can’t build a better aardvark.
