Darwin's dilemma: Bizarre ancient animal identified through DNA
What do you get when you cross an elephant, a llama, a camel, and a rhinoceros? If you have no idea, don't feel too bad – it puzzled Charles Darwin too, when he stumbled on the fossilized bones of just such a creature in 1834. Known as Macrauchenia patachonica, the enigmatic, extinct animal has evaded classification ever since, but a new DNA study has finally found where it fits on the family tree.
The Macrauchenia was first discovered by Darwin while on a research trip in Argentina. It's general body shape is that of a camel, but it had hooves like a rhino, a long neck like a llama and most strikingly, a short trunk like an elephant. This cobbled-together creature likely lived across South America before dying out about 10,000 years ago, and with such a mishmashed morphology, it was hard to pin down exactly what legacy it left behind.
To solve the problem, researchers from the University of Potsdam in Germany and the American Museum of Natural History studied a sample of its mitochondrial DNA, extracted from an 11,000 year old fossil. The first problem with this technique is the fact that DNA tends to degrade over time, so there were a few holes in the sequence. Normally, these are patched up by comparing the genome to that of the creature's closest living relatives.
But therein lies the second problem: Macrauchenia is an evolutionary dead end, having no modern relatives. So the team created a new technique that compared the genomes of a range of modern animals, and using those as reference points, they were able to recover about 80 percent of the 17,000 genes that most likely made up the Macrauchenia. That allowed them to slot it into Panperissodactyla, a large group of mammals that includes horses, rhinos and tapirs.
"The new study shows that the line that led to Macrauchenia separated from the lineage of the equids (the horse family) before 66 million years ago, just before the extinction of the dinosaurs," says Michael Hofreiter, one of the study's authors. "Because of this distant kinship, it was particularly difficult to reconstruct the DNA sequence."
The research was published in the journal Nature Communications.