There'd be no such thing as a "cat lady" in Australia were it not for European explorers, a new study argues. Domestic cats aren’t native to the continent, and had to arrive from either Europe or Asia, though when exactly they arrived and from where has been a matter of debate. 

In order to figure out how long cats have been in Australia, and where they came from, a team of German, American, and Australian researchers traced the genetic history of the continent’s feral cat populations. In a study published in BMC Evolutionary Biology, they examined the genetics of cat populations in six different places on the Australian mainland and on seven different Australian islands, comparing their genetic makeup to DNA data from European and Southeast Asian cat populations. 

They found that cats probably arrived from Europe in the 19th century. European explorers, whalers, and sailors may have had cats on their ships as a form of rodent control, and colonists brought them along for their new settlements, too. 

Since there was no population of cats whose DNA could be traced solely back to Asia, they probably did not initially arrive from there. One alternative history of Australia's feral cat populations postulates that they came with Malaysian sea cucumber fishermen (trepangers) in the 1650s, but this analysis shows that to be implausible. Though the researchers did find genetic sequences associated with Asian cats, those may have arrived in Australia later, or mixed with European cat populations before traveling down under.

Cats are far from the only invasive species in Australia. The continent’s flora and fauna were isolated from the rest of the world for millions of years, and with a few exceptions like the dingo, there weren’t many new species entering the region until Europeans began to settle there. When Europeans arrived, they brought with them familiar animals and plants from home, both intentionally and by accident, including rabbits, horses, foxes, and several types of rats. Over the years, many of these new species have become pests, destroying the native ecology of the region, and, per a 2004 government report, costing more than $5.2 million a year. By dating feral cat populations’ arrival, researchers can also track the subsequent decline of other species, helping establish exactly what kind of impact these invasive species have on local ecology.