Even a Small Population of Humans Can Drive Animals to Extinction: The Tale of the Moa

The moa, completely flightless birds, may have been driven to extinction by far fewer humans than previously thought. Scientists have found that during the time when moa became extinct, New Zealand's human population was just two and a half thousand people at most.

The researchers calculate that the Polynesians, who caused moa extinction in just little over a century, had some of the lowest human population densities on record. In fact, during the peak period of moa hunting, there were fewer than 1,500 Polynesian settlers in New Zealand. That's about one person per 100 square kilometers.

In order to better understand exactly how many people were present during the moa hunting period, the scientists aimed at "book-ending" the moa hunter period with new estimates for when people started eating moa, and when there were no more moa to eat. Starting with the latest estimate for a founding population of 400 people, the researchers then applied population growth rates in the range achieved by past and present populations.

"The analysis showed that the sites were all first occupied-and the people began eating moa-after the major Kaharoa eruption of Mt. Tarawera of about 1314 CE," said Chris Jacomb, one of the researchers, in a news release.

The findings reveal that the total extinction most likely occurred within a decade on either side of 1425 CE, which is barely a century after the earliest well-dated site. These findings, in particular, call into question the notion that a small population can't cause mass extinctions; many believe that people could not have caused the extinction of megafauna in North America since the human population was too small. Instead, it seems that even small human populations can have drastic impacts on their environment.

The findings are published in the journal Nature Communications.