For millions of years, nine species of large, flightless birds known as moas (Dinornithiformes) thrived in New Zealand. Then, about 600 years ago, they abruptly went extinct. Coincidentally, their extinction was directly aligned with the arrival of the first humans on the islands in the later 13th century. Of course, scientists have long wondered what role hunting by Homo sapiens may have played in the moas' die-off or decline. But other scientists have pointed to natural causes, including volcanic eruptions, disease, and climate change at the end of last Ice Age, as the key reasons for these species’ demise. The moas present a particularly interesting case, researchers say, because they were the last of the giant species to vanish - and they did so recently, when a changing climate was no longer a factor.
A new genetic study of moa fossils points to humankind as the sole perpetrator of the birds’ extinction. The study adds to an ongoing debate about whether or not past populations lived and hunted sustainably, or if they were to blame for the extermination of numerous species. Morten Allentoft, an evolutionary biologist at the University of Copenhagen, used ancient DNA from 281 individual moas from four different species, and radiocarbon dating, in an effort to determine the moas’ genetic and population history over the last 4000 years. The moa bones were collected from five fossil sites on New Zealand’s South Island, and ranged in age from 12,966 to 602 years old. The researchers analyzed mitochondrial and nuclear DNA from the bones and used it to examine the genetic diversity of the four species.
The paper presents an “impressive amount of evidence” that humans alone drove the moa extinct, says Trevor Worthy, an evolutionary biologist and moa expert at Flinders University in Adelaide, Australia, who was not involved with the research. Usually, extinction events can be seen in a species’ genetic history - the animals’ numbers dwindle and they lose their genetic diversity. But Allentoft and his team’s analysis failed to find any sign that the moas’ populations were on the verge of collapse. In fact, the scientists report that the opposite was true: the bird's numbers were stable during the 4000 years prior to their extinction.
Read more about their study here.
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