In 1871, a farmer left five cows on a remote island, 130 years later, scientists studied their DNA and found something that stunned them

In 1871, a farmer named Heurtin sailed to Amsterdam Island, a lonely, wind-swept speck of land in the Southern Ocean, with five cows and big plans. The attempt at settlement fell apart within months. Heurtin got out. The cows didn't.

What followed is one of the more quietly remarkable stories of survival in modern biology. Those five animals, stranded on a 21-square-mile island buffeted by near-hurricane winds, with little freshwater and no veterinary care, went on to make a feral herd that peaked at about 2,000 animals more than a century later. Not a cowboy. No fences. No food. Just five cows and the genes they carried with them.

So a 2024 study finally turned to their DNA for answers, and found more than they bargained for.


What the DNA revealed
The study, published in the journal Molecular Biology and Evolution, was led by geneticist Mathieu Gautier at INRAE in partnership with the University of Liège, who reconstructed the herd's genetic history from preserved samples from 18 cattle collected in 1992 and 2006. Eight animals were subjected to whole-genome sequencing, a deep genetic read mapping nearly the entire genetic code.

The results looked magnificent. The researchers found that the herd was descended from two separate lineages: about 75% of the herd was descended from European taurine cattle, related to the modern Jersey breed, and 25% from Indian Ocean zebu, hardy heat-tolerant cattle found throughout Madagascar and on neighboring islands. That mixed background probably means the founding five had a lot more genetic variation than you'd expect from such a small number. The more diverse the gene pool, the more tools you have to survive.

The study also found that the cattle may have been pre-adapted, with their European ancestry tracing back to populations of cattle from cool, wet, windy climates. In other words, the biology of the two species was not entirely alien to the harsh environment of Amsterdam Island.

The inbreeding problem, and how they didn't die out
A species with five animals involves a lot of inbreeding. Individual inbreeding levels were around 30%, the kind of number that usually sends alarm bells ringing: relatives passing on the same deleterious mutations, genetic diseases building up over successive generations, populations spiraling to collapse.

That did not occur here, but the researchers think the bottleneck was intense but short-lived, because the herd grew so fast in its early years that it prevented long-term loss of diversity. Previously, field observers reported that the animals were in excellent health.

Genome scans also revealed something unexpected: the most dramatic evolutionary changes seemed to have been in genes associated with the nervous system and behavior, rather than physical characteristics. The cattle have re-programmed themselves psychologically more rapidly than their bodies have changed; they have become more independent, more alert, better adapted to feral life.

The argument of shrinking
The size question has been a scientific bone of contention. In a 2017 paper in Scientific Reports, the researchers argued that the Amsterdam Island cattle had shrunk to about three-quarters of their original body size in little more than a century, a classic case of “island dwarfism,” the well-documented tendency for large mammals to shrink when isolated on islands.

This made the Amsterdam herd one of the fastest recorded cases of dwarfing in large mammals, which usually takes place over thousands of years.

The 2024 genetics study refutes that interpretation. That suggests the founders were probably small-statured breeds to start with. Both Jersey cattle and Madagascar zebu are relatively small animals, so the herd may never have been large.

A herd that no longer exists
The story ends with a complicated footnote. By 2010, all of these animals had been wiped out in the name of protecting the island’s native species, including the endangered Amsterdam albatross and the rare Phylica arborea tree. This is now part of a UNESCO World Heritage site.

The genetic study can only happen because DNA samples were collected before the eradication and stored well enough for modern analysis. The herd is gone, but its genome lives on and continues to tell us about resilience, adaptation, and what living things are capable of when circumstances call for it.