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In 1871, a farmer abandoned five cows on Amsterdam Island, a 54-square-kilometer French territory lost in the southern Indian Ocean.
That small founding group grew into a herd of thousands of animals that survived for more than a century in extreme conditions. In 2024, geneticists analyzed its DNA —preserved decades before its extinction— and the results dismantled a theory that science had taken for granted.
The study was published in July 2024 in Molecular Biology and Evolution, led by geneticist Mathieu Gautier with researchers from INRAE and the University of Liège.
The team worked with samples obtained from animals in 1992 and 2006, before the last specimen was removed in 2010 as part of an ecological restoration program.
What scientists discovered when they analyzed the DNA of the remote island cows
The genome of the cattle in question showed two clearly differentiated lineages. Most of it, about three-quarters, came from European taurine breeds related to today’s Jersey cattle, historically adapted to cold, wet, and windy climates. The remaining quarter corresponded to Indian Ocean zebus, linked to cattle from Madagascar and Mayotte.
That combination, already present before they arrived on the island, would explain why five animals were able to thrive in such a hostile environment.
The key finding of the study rebuts a 2017 investigation published in Scientific Reports, which claimed the herd had experienced accelerated island dwarfism: a reduction of up to three-quarters of its original size in just over a century.
Genetic analysis found no sign of selection for reduced size. The data indicate that the founders were already small when they arrived, and that their dual lineage gave them from the start the biological tools to adapt to Amsterdam Island’s hurricane-force winds, cold, and scarcity of fresh water.
What the DNA confirmed
- Mixed origin: 75% European taurine (Jersey-type) +25% Indian Ocean zebu.
- No accelerated dwarfism: no genetic signal of selection for smaller size.
- Origin advantage: Genetic diversity was present in the five founders.
- Rapid expansion: the herd grew to nearly 2,000 animals in 1952 and recovered after a disease-driven collapse in 1988.
How they survived 130 years on a remote island with just 5 cows
With so few founders, inbreeding was inevitable for generations. The researchers estimated inbreeding levels near 30%, a threshold that in most animal populations triggers hereditary diseases and can lead to extinction.
However, the herd did not collapse: no signs were detected of an accumulation of harmful genetic variants or population decline.
What prevented collapse was the speed of growth. The herd expanded quickly enough to maintain genetic diversity before inbreeding could erode it.
This analysis was possible because researchers preserved biological samples in the decades before eradication —without any formal preservation program in place when the last animals were removed in 2010— which made it possible, decades later, to reconstruct the complete genetic history of a herd that began with five cows on a remote island.
Why was the herd eliminated?
- The cattle threatened endemic species such as the Amsterdam albatross and the tree Phylica arborea.
- In 1987, a fence was installed, and more than a thousand animals were removed from the southern sector.
- The last specimen was removed in 2010 as part of an ecological restoration plan.
- In 2019, UNESCO declared the French Southern Lands a World Heritage Site.