There were once nine species of wingless moas in New Zealand, all of which were large herbivores. The largest moas — Dinornis robustus and Dinornis novaezelandiae — were around 12 feet high, and weighed around 510 pounds. The birds went extinct roughly around the time that the Maori arrived in New Zealand in the 13th century, but scientists and researchers were never sure what the cause was. Was it climate change? The spread of disease? Volcano eruptions? Or was it simply humans?
In the report "Extinct New Zealand megafauna were not in decline before human colonization” in the Proceedings of the National Academy of Sciences of the United States of America (PNAS), researchers determined that humans were the cause of the moa extinction. In the report’s abstract, the researchers wrote, "We sampled 281 moa individuals and combined radiocarbon dating with ancient DNA analyses to help resolve the extinction debate and gain insights into moa biology. The samples, which were predominantly from the last 4,000 years preceding the extinction, represent four sympatric moa species excavated from five adjacent fossil deposits. We characterized the moa assemblage using mitochondrial DNA and nuclear microsatellite markers developed specifically for moa. Although genetic diversity differed significantly among the four species, we found that the millennia preceding the extinction were characterized by a remarkable degree of genetic stability in all species, with no loss of heterozygosity and no shifts in allele frequencies over time.”
When a species is in decline, their genes show it, which wasn’t the case with the moa. The moa population was actually on the rise by the time humans found their way to New Zealand. And, as with most meetings like this, the birds ultimately lost. "The extinction event itself was too rapid to be manifested in the moa gene pools,” the researchers wrote.
In fact, the researchers point out, the moa may have been the most rapidly human-caused extinctions to date
A moa bird by Lionel Walter Rothschild, 2nd Baron Rothschild, in the book "Extinct Birds."
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