In 1870, identifying species was a matter of looking closely at their appearance. If two creatures had the same physical features, they must be the same species, scientists thought.
So when French biologist Alphonse Milne-Edwards studied a very large, ancient crane leg bone from a cave in southern France, he compared it to those of modern cranes.
The ancient leg bone was so much broader across its width than those of the sarus crane (Antigone antigone) or the common crane (Grus grus) that Milne-Edwards decided they could not possibly be the same species.
He decided these Late Pleistocene bones represented an extinct species of giant crane that lived at the end of the last ice age, and named it Grus primigenia.
The identity of G. primigenia has been debated many times over the last 150 years, but now, we have a much clearer answer.
New analysis of ancient DNA suggests that Grus primigenia actually never went extinct: It just got smaller.
It was Grus grus all along.
“Previous studies had merely used the size and shape of the bones to attempt to understand these large birds,” explains paleoecologist John Stewart of Bournemouth University in England.
“The use of DNA analysis has given us a more accurate picture of what they represent.”
Stewart and his team’s results are published in Royal Society Open Science.
In the history of science, ancient DNA analysis is a relatively recent development.
Researchers across the world are eagerly revisiting old museum specimens to see what this new technology can tell us about long-dead animals.
There’s a lot of material to work through, and cases of mistaken identity abound.
The process involves drilling into the bone to collect a small amount of clean powder from within. Then, the scientists use that powder to extract and amplify the DNA.
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Stewart and team used 18 ancient crane bones discovered across England, Wales, France, Germany and the Balearic Islands, including G. grus bones of varying sizes, and a couple of bones previously classified as G. primigenia.
Unfortunately, they were unable to do these tests on Milne-Edwards’ type specimen, now housed at the Muséum national d’Histoire naturelle in Paris, since it’s too precious to drill into.
That leaves a tiny possibility that G. primigenia may still have legs, but that seems unlikely.
There were no clear differences in the DNA of any of the sampled specimens: They were all G. grus, in spite of their physical differences.
“We suspected that these large cranes were not extinct and instead represented larger, modern European common cranes,” Stewart says.
“Cranes have large males and smaller females and we think this contributed to previous speculation that there were two different species – the living, common crane we see today and the extinct, larger species.”
This raises a new question: why, after the 11th century CE, did common cranes gradually become smaller overall?
“It is tempting to conclude that the size change seen in the common crane is owing to climate change and/or human land use change such as wetland drainage, but for now this remains speculation,” the team writes.
The research has been published in Royal Society Open Science.
This article was fact-checked by Rebecca Dyer and edited by Rebecca Dyer. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.
