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How evolution shaped passenger pigeons' DNA — and their fate

Martha, the last known passenger pigeon before dying in 1914, can be seen at the Smithsonian's Natural History Museum. Photo: Susan Walsh / AP

A new study suggests passenger pigeons, which once covered North America with massive flocks before their extinction in the early 20th century, may have maintained stable populations for thousands of years until human hunters came along, per The Washington Post. That counters previous research that found the species had already taken a downturn by that time.

The double whammy: Besides the sudden influx of human predators, the birds' genome had been tuned to the size of its population. It had surprisingly low genetic variation in some parts of its genome, which "provided few avenues for the bird to respond to human pressures, which ultimately drove it to extinction," according to the study, published Thursday in Science.