Researchers have been able to decode the DNA of a now-extinct Caribbean bird (the Caracara creightoni) using the remains of an individual long since dead. The results have been published in the journal Molecular Phylogenetics and Evolution.
The skeleton had been in its grave for some 2,500 years when it was discovered by cave divers in the Sawmill Sink blue hole on Great Abaco Island. The shadowy depths of the sinkhole provide a fantastic environment for fossils – its dark, oxygen-free surrounds keep them in a relatively pristine condition.
In total, researchers have gathered more than 10,000 remnants from close to 100 species, from birds and bats to crocodiles, tortoises, iguanas, and snakes. That includes the head of a C. creightoni, a type of carrion-eating falcon related to the crested caracara and the southern caracara (both of which are still alive today).
"For birds, having an entire head of an extinct species from a fossil site is pretty mind-blowing," Jessica Oswald, a postdoctoral researcher at the Florida Museum of Natural History, said in a statement.
"Because all the material from the blue hole is beautifully preserved, we thought at least some DNA would probably be there."
But there is a problem: ancient DNA is often fragmented – or missing completely. Bird bones, particularly, are vulnerable to heat, light, and oxygen because they are dainty, hollow things. And so, Oswald's expectations were relatively low. One or two genes, perhaps, but certainly not the 98.7 percent of the mitochondrial genome she found.
"Getting DNA from an extinct bird in the tropics is significant because it hasn't been successful in many cases or even tried," she explained.
DNA analysis reveals the now-extinct C. creightoni shared a common ancestor with its modern relatives sometime between 1.2 and 0.4 million years ago.
The bird went extinct roughly 1,000 years ago, shortly after humans arrived on the island. The species it relied on for food (tortoises, crocodiles, iguanas, and rodents) disappeared – and so did C. creightoni.
"This species would still be flying around if it weren't for humans," David Steadman, a curator at the museum, added. "We're using ancient DNA to study what should be modern biodiversity."
The achievement shows how ancient DNA can be extracted with a smaller amount of bone than previously thought, which has uses beyond the C. creightoni.
"By understanding species that weren't able to withstand human presence, it helps us better appreciate what we have left – and not just appreciate it, but understand that when these species evolved, there were a lot more things running and flying around than we have today," said Steadman.