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Science 14 December 2001:
Vol. 294. no. 5550, pp. 2266 - 2268
DOI: 10.1126/science.294.5550.2266b
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News of the Week

MAMMALIAN EVOLUTION:
Placentals' Family Tree Drawn and Quartered

Elizabeth Pennisi

On page 2348, researchers report using a nearly 240-year-old statistical technique to sort out the evolutionary history of the broad class of mammals that give birth to live, fully developed young. The researchers place placental mammals in four major groups, proposing that these groups arose in large part because of the breakup of the giant landmasses that predated modern continents, and that placental mammals in what is now Africa have the most ancient ancestors. Those conclusions are likely to prove controversial, however.

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Science. ISSN 0036-8075 (print), 1095-9203 (online)