“You see heaps and heaps of the birds’ bones in archaeological site. If you hunt animals at all their life stages, they will never have a chance.” –Morten Allenton, an evolutionary biologist at the University of Copenhagen

By Tony Orman

Exterminating the giant bird

The rapid extinction of the several moa species from New Zealand has long been debated. Some, in defence of the early Polynesian migrants who had arrived about 1250, have said the flightless bird numbers were already in decline. The Polynesian migrants were conservationists it was claimed. 

In 2014, scientists investigated further and concluded humans were the sole factor in wholesale killing of the birds and in destruction of habitat. Strangely their findings received little media coverage at the time.

But the reality was that moa were obliterated in a geological “blink of the eye” — just one or two centuries.

The end for the moa was devastatingly fast.

Yet before that, for probably 50 or 60 million years, nine species of large, flightless birds known as moas (Dinornithiformes) thrived in New Zealand. About 600 years ago, moa suddenly became extinct. Their disappearance had coincided with the arrival of the Polynesian migrant humans to New Zealand somewhere in the late 13th century. 

Scientists since have long wondered what influence humans played in the decline and extinction.

Others argued the moa was on the way out — naturally — and humans were not responsible. 

But the question nagged. Were humans the principal factor?  Even the one and only factor?

Then again, or were moa numbers in decline and moa doomed to extinction anyway due to disease and volcanic eruptions? Scientists went into study mode.

Moa cover 300ppi.jpeg

A recent and very impressive book on the moa by publishers Potton and Burton of Nelson. (The book was first published in 2012.)

Convincing Case

The conclusions were summed by a Spanish evolutionary biologist. They were emphatic.

“The paper presents a very convincing case of extinction due to humans,” said Carles Lalueza-Fox, an evolutionary biologist at the Institute of Evolutionary Biology in Barcelona, Spain. “It’s not because of a long, natural decline.”

One of the researchers Morten Allentoft, an evolutionary biologist at the University of Copenhagen, outlined the logic behind the research group’s conclusions. Archaeologists know that the Polynesians who first colonised New Zealand, ate moa of all ages, as well as the birds’ eggs. 

“You see heaps and heaps of the birds’ bones in archaeological sites,” Allentoft said. “If you hunt animals at all their life stages, they will never have a chance.”

Using ancient DNA from 281 individual moa from four different species, including Dinornis robustus (at 2 metres, the tallest moa, able to reach foliage 3.6 meters above the ground) and radiocarbon dating, Allentoft and his colleagues set out to determine the moa’ 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 analysed mitochondrial and nuclear DNA from the bones and used it to examine the genetic diversity of the four species.

The research team’s analysis found no sign that the moa’s population had already been collapsing when the Polynesian colonists settled New Zealand. Indeed, the scientists concluded that the opposite was true – bird numbers were stable during the 4,000 years prior to extinction.

Populations of D. robustus even appeared to have been slowly increasing when the Polynesians arrived. 

Yet in less than 200 years later, the birds had gone. “There is no trace of their pending extinction in their genes,” Allentoft said. “The moa are there, and then they are gone.”

Humans alone killed off the moa

Trevor Henry Worthy is an Australia-based paleozoologist from New Zealand, known for his research on moa and other extinct vertebrates.

He commented that the Copenhagen University paper presented an “impressive amount of evidence” that humans alone drove the moa extinct. Trevor Worthy, an evolutionary biologist and moa expert at Flinders University in Adelaide, Australia, was independent i.e. not involved in the official research. 

“The inescapable conclusion is these birds were not senescent, not in the old age of their lineage and about to exit from the world. Rather they were robust, healthy populations when humans encountered and terminated them.” 

At the time he expressed doubts that even the Copenhagen University’s team’s “robust data set” would settle the debate about the role people played in the moa’s extinction, simply because “some have a belief that humans would not have” done such a thing.

Human Tendency

Copenhagen University’s Morten Allentoft, said he was not surprised that the Polynesian settlers killed off the moa. The reality is any other group of humans would have done the same, he suspected. 

“We like to think of indigenous people as living in harmony with nature,” he said. “But this is rarely the case. Humans everywhere will take what they need to survive. That’s how it works.”

In late 2014 New Zealand scientist Richard Holdaway, (a specialist in extinction biology), Copenhagen University’s Morten Allentoft and four other scientists completed a study entitled “An extremely low-density human population exterminated New Zealand moa.”

They concluded: “New Zealand moa (Aves: Dinornithiformes) are the only late Quaternary megafauna whose extinction was clearly caused by humans. Polynesians exterminated viable populations of moa by hunting and removal of habitat.”