An extinct species would never have existed for 150 years. The case begins with a single leg bone unearthed in a cave in southern France and judged too massive to belong to a known crane. From this observation sprang a giant phantom crane, which ancient DNA is now dissolving.
- In 1870, Milne-Edwards had classified a leg bone too massive as evidence of a giant extinct crane, Grus primigenia.
- A DNA study conducted on eighteen ancient bones reveals there is no genetic difference between G. primigenia and the common crane Grus grus, the size gap explained by sexual dimorphism.
- The study also reveals that European cranes have shrunk since the 11th century, a phenomenon possibly linked to climate change or drainage of wetlands, but still unexplained.
- An unusually large bone: how a 1870 error created a phantom species
- Ancient DNA that dismantles 150 years of scientific certainties
- Why European cranes have shrunk since the 11th century, a mystery still unresolved
An unusually large bone: how a 1870 mistake created a phantom species
It all begins with Alphonse Milne-Edwards, a French biologist who, in the 19th century, studied a leg bone discovered in a cave in southern France. The bone belongs to an ancient crane, and something about it immediately seems off to him.
He compares this specimen to the leg bones of the modern cranes of his era, the sarus crane and the common crane, the latter now known by its scientific name Grus grus. Verdict: the bone is too wide to match either of these species.
For Milne-Edwards, the conclusion then naturally follows. He decided that these Late Pleistocene bones represented an extinct giant crane species that lived at the end of the last glacial period, and he named it Grus primigenia.
A species was born, based on a single morphological clue. For a century and a half, it appeared in classifications as a vanished relic of glacial megafauna.
Ancient DNA that dismantles 150 years of scientific certainties
It took the advent of genetic analysis to reopen the case. A new study, published in Royal Society Open Science and led by paleoecologist John Stewart of Bournemouth University, tackles the question head-on.
The research team gathered eighteen bones from ancient cranes, coming from England, Wales, France, Germany and the Balearic Islands. Among these samples are bones classified as G. grus as well as others attributed to G. primigenia.
The result is decisive: there is no significant genetic difference between the two groups. All these bones, however massive or slender they may be, actually belong to the same species, Grus grus.
The explanation offered by the researchers hinges on a single word: sexual dimorphism. In cranes, males are generally larger than females, a size gap large enough to mislead a viewer accustomed to recognizing separate species rather than individual variations.
One detail worth noting: the type specimen described by Milne-Edwards himself, carefully preserved at the National Museum of Natural History in Paris, could not be tested. It is considered too important to have any fragment taken, which adds a certain irony to the case.
Why European cranes have shrunk since the 11th century, a mystery still unresolved
If Grus primigenia disappears from the species register, another intriguing finding emerges from this study. European common cranes appear to have reduced in size since the 11th century AD, a phenomenon that researchers have not yet fully explained.
Two avenues are suggested, without firm certainty. Climate change could have played a role, as could changes in human land use, notably the drainage of wetlands where these birds find their natural habitat.
These two hypotheses are not mutually exclusive. Fewer wetlands available, a changing climate: these factors could have influenced crane size over time, though no established scientific certainty exists to date.
This question remains open, and that is precisely what makes it interesting. Unlike the Grus primigenia case, it has not yet yielded a definitive answer.
This story nicely illustrates how paleontology evolves with its tools. An isolated bone, no matter how large, is no longer enough to establish a species when ancient DNA allows hypotheses to be tested at the molecular level. Grus primigenia thus fades from textbooks, but the mystery of the shrinking cranes continues to fuel research into the recent history of this very much alive species.
Article prepared with the help of AI · Our method
