Researchers at Bournemouth University have solved a 150-year-old palaeontological mystery by using ancient DNA to prove that the supposedly extinct giant crane, named Grus primigenia, was actually a larger variant of the modern European common crane that still survives today.
Alphonse Milne-Edwards and the 19th-Century Discovery of Grus primigenia
The puzzle began in the nineteenth century when French biologist Alphonse Milne-Edwards examined unusually large bird bone fragments recovered from caves in southern France. Dating back to the end of the last ice age more than 20,000 years ago, the leg bones were notably broader across their width than those of modern avian counterparts. Comparing the remains to contemporary species such as the common crane and the sarus crane, the nineteenth-century biologist concluded that the physical differences were too stark to belong to living birds. He established a distinct, extinct prehistoric species known as Grus primigenia, an enormous crane that supposedly vanished alongside other ice-age fauna.
For generations, the scientific community accepted that the giant bird had once roamed Europe before dying out. Early researchers relied exclusively on bone morphology, examining only the size and shape of skeletal remains to classify ancient animals. However, a team led by John Stewart suspected that those nineteenth-century assumptions overlooked simple biological variation within a single resilient species.
DNA Analysis from 18 Crane Bones Across Europe
To test whether the ancient giant crane ever truly existed as a separate species, researchers partnered with the Centre for Palaeogenetics in Stockholm, Sweden. The team extracted genetic material from 18 ancient crane bones discovered across England, Wales, France, Germany, and the Balearic Islands. By extracting genetic material to determine which species the birds actually belonged to, the scientists bypassed the limitations of bone shape alone.
The genetic results showed that the ancient giant cranes were members of the same species as modern European common cranes (Grus grus). The researchers were unable to test Milne-Edwards’ original type specimen housed at the Muséum national d’Histoire naturelle in Paris because the historic fossil is too precious to drill into, leaving a tiny possibility regarding its identity.
Sexual Dimorphism and Why the Ice Age Birds Grew Larger
The historical misclassification stemmed from a fundamental biological trait of the birds themselves. Modern cranes exhibit marked sexual dimorphism, featuring large males and smaller females. Researchers believe this natural size gap contributed to earlier speculation that the fossil record captured two distinct species living side by side rather than normal intraspecies variation.
With the identity of the bones resolved, the research team is turning its attention to a new chronological puzzle. Investigators want to understand why European common cranes gradually shrank in size between the end of the last ice age and today. While scientists suspect that habitat transformations such as wetland drainage and human land use changes drove the reduction, the team emphasizes that this explanation remains speculation requiring further study.
Implications for Past Extinctions and Museum Specimens Worldwide
The findings published in Royal Society Open Science carry consequences that extend far beyond a single avian species. The crane study suggests that science may have overestimated the number of extinctions in the past by relying on skeletal dimensions alone.
Some animals previously classified as extinct may simply represent historical size fluctuations within living lineages. Additional genetic investigations could reveal that several species thought to have vanished completely are actually surviving animals that simply grew larger under past environmental conditions.
While it is true that many species of birds are vulnerable to human actions today, it may be that we have overestimated the number of extinctions in the past. Some of these may instead represent size changes to living species.