for National Geographic News
Ancient relatives of eagles not only hunted and ate early humans but also influenced how our species evolved, a new study suggests.
In addition, the research appears to settle a long-running debate over what killed a prehistoric child in Africa 2.5 million years ago.
The findings are based on an analysis of more than 600 modern-day monkey bones collected beneath the nests of African crowned eagles in the rain forests of Côte d'Ivoire (Ivory Coast).
The monkey remains revealed that the eagleswhich typically weigh between 10 and 12 pounds (4.5 and 5 kilograms)frequently kill and eat primates weighing up to 24 pounds (11 kilograms).
The researchers say that they were surprised to find that large monkey species that live on the ground are a common target for the raptors.
The study suggests that birds of prey "have been a selective force in primate evolution for a long time," says lead study author W. Scott McGraw, an associate professor of anthropology at Ohio State University in Columbus.
The study is now online and will be published in the October issue of the American Journal of Physical Anthropology.
"Before this study, I thought that eagles wouldn't contribute that much to the mortality rate of primates in the forest," McGraw added. "I couldn't have been more wrong."
Targeting Ground Monkeys
Evolutionary biologist Susanne Schultz of the University of Liverpool in England collected prey remains from under eagle nests in the Taï rain forest in the southwestern part of Côte d'Ivoire (see map).
The discarded remains included bones and skulls of mangabeys, large, predominantly ground-living monkeys.
"I thought you would see the eagles eating monkeys that mainly lived in the trees, because the birds are flying around the canopy," Schultz said. "But they were actually hitting animals on the ground harder."
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