Tony Lucas sent this:Where are all the males? - ancient DNA raises questions about extinct moa populations.
A little more than 700 years ago multiple species of the gigantic flightless birds called moas were still running around New Zealand. They ranged over almost the entirety of the North and South Islands, from the coast to the mountain forests, but when the Maori people arrived in the late 13th century the birds were quickly driven to extinction. Within a few hundred years they were entirely wiped out (along with the immense Haast's eagle, which fed on the moas), but fortunately for scientists these birds left behind vast accumulations of bones.
Two such moa graveyards are the Pyramid Valley and Bell Hill Vineyard sites on South Island. Together they record the presence of four moa species (Dinornis robustus, Emeus crassus, Euryapteryx curtus, Pachyornis elephantopus) over the course of the 3,000 years prior to the arrival of the Maori, and these sites presented scientists with the opportunity to recover ancient DNA from a large sample of bones to investigate the population genetics of the birds, including the sex of each individual. As they collected and analysed the genetic data, however, they found something they were not expecting. In each species and across both deposits, females, which are considerably larger and heavier than males, were significantly more common, with an average of five females for every one male out of a sample of 227. What could could account for this disparity?
PICTURE CAPTION: The skeletons of female (larger, background) and male (smaller, foreground) Dinornis robustus, with a pigeon skeleton for comparison. From Allentoft et al 2010
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Oh, it's simple. The females ate the males after they mated.
ReplyDeleteSeriously, though. It has just occurred to me that perhaps male moa's had features that made then especially susceptible to predation. I reminded most strongly of the male peacock. As i recall, that tail of his was quite the vulnerability to the individual animal, but also quite the necessity for survival of his genetic traits. Perhaps male moas had a similar handicap? There is of course extreme difficultly making conjectures on an extinct species when there is so much more to an animal's existence than skeletal structure, especially behavior. I want to make it clear my understanding of zoology is rudimentary, but this did occur to me.
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