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Scientists finally solve mystery of famed bird’s disappearance
Nine species of large, flightless birds known as moas (Dinornithiformes) flourished in New Zealand for millions of years. Then, about 600 years ago, they abruptly went extinct. Scientists have long wondered what role hunting by Homo sapiens played in the decline of moas, as their die-off coincided with the arrival of the first humans on the islands in the late 13th century. A new genetic analysis of moa fossils suggests that humans are the only cause of the extinction of these giant birds. Were disease and volcanic eruptions causing them to already be extinct when we drove them over the brink? The study contributes to the ongoing discussion about whether earlier humans hunted and lived in a sustainable way or whether they were primarily responsible for the extinction of many species.
Carles Lalueza-Fox, an evolutionary biologist at the Institute of Evolutionary Biology in Barcelona, Spain, who was not involved in the research, says, “The paper presents a very convincing case of extinction due to humans.” “Its not because of a long, natural decline. “.
Scientists have long argued about what caused the extinction of many species of megafauna—giant animals including mammoths, mastodons, and moas—beginning between 9000 and 13,000 years ago, when humans began to spread around the world. Often, the animals disappeared shortly after humans arrived in their habitats, leading some researchers to suggest that we exterminated them by overhunting. 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. But did other natural causes set them on a path to oblivion, as some scientists proposed in a recent paper?
Evolutionary biologist Morten Allentoft of the University of Copenhagen expressed skepticism about this theory. It is known by archaeologists that the Polynesians who initially inhabited New Zealand consumed both the eggs of the birds and moas of all ages. The moa species, which range in size from 12 to 250 kg, provided substantial meals to the birds, who had never before seen a terrestrial mammal. “At archaeological sites, you see heaps upon heaps of bird bones,” says Allentoft. It is impossible for animals to survive if they are hunted throughout their entire life cycle. “.
Utilizing prehistoric DNA from 281 individual moas from four distinct species—including Dinornis robustus, the tallest moa at 2 meters and capable of reaching foliage 3 Allentoft and associates set out to ascertain the moas genetic and population history over the last 4000 years using radiocarbon dating and elevated observation (6 meters above the ground). The moa bones, which ranged in age from 12,966 to 602 years old, were gathered from five fossil sites on the South Island of New Zealand. Utilizing nuclear and mitochondrial DNA extracted from the bones, the researchers were able to assess the genetic diversity of the four species.
Usually, extinction events can be seen in a species genetic history; as the animals numbers dwindle, they lose their genetic diversity. But the teams 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 birds numbers were stable during the 4000 years prior to their extinction, they report online today in the Proceedings of the National Academy of Sciences. Populations of D. robustus even appear to have been slowly increasing when the Polynesians arrived. No more than 200 years later, the birds had vanished. “There is no trace of” their pending extinction in their genes, Allentoft says. “The moa are there, and then they are gone.”
For example, Trevor Worthy, an evolutionary biologist and moa expert at Flinders University in Adelaide, Australia, who was not involved in the research, says the paper presents an “impressive amount of evidence” that humans alone drove the moa extinct. It is inevitable to conclude that these birds were not senescent, not in the advanced age of their ancestry, and not on the verge of extinction. Rather, when humans encountered them and exterminated them, they were robust, healthy populations. However, he doesn’t think that Allentoft’s team’s “robust data set” will end the argument regarding human involvement in the extinction of the birds because “some have a belief that humans would not have” done such a thing.
Regarding Allentoft, he believes that any other group of humans would have eliminated the moas, so he is not shocked that the Polynesian settlers did so. “We prefer to believe that indigenous people coexist peacefully with the natural world,” he states. “But this is rarely the case. Humans everywhere will take what they need to survive. Thats how it works. “.
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