Ancient Monkey Transformed into a 'Sloth' When It Arrived in Jamaica

[Judi Lynn]

By Brandon Specktor, Senior Writer | November 13, 2018 06:58am ET

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The weird Jamaican sloth-monkey (X. mcgregori) was most closely related to the titi monkeys, like this red titi monkey, Callicebus cupreus.
Credit: ZSL

About 10 million years ago, a family of monkeys left the South American mainland on a cruise to Jamaica and, as is still the case for so many tourists today, swiftly fell for the lazy pace of island life. Over many generations, the primates' legs evolved for slow climbs up tropical trees, their mouths grew a few giant molars at the expense of other, tinier teeth and — apparently unburdened by natural predators — the chilled-out tree dwellers spent their days living more like sloths than monkeys.

These strange Jamaican sloth-monkeys, better known as Xenothrix mcgregori, are real (at least, they were; they've been extinct for at least 900 years). And while there is no scientific dispute that these primates were among the oddest ever to grace the Western Hemisphere, there is little consensus on how they got there in the first place, and who their ancestors were. [Wipe Out: History's Most Mysterious Extinctions]

Now, a new study published Nov. 12 in the journal Proceedings of the National Academy of Sciences offers the first major evidence that the ancestors of Jamaica's X. mcgregori monkeys may have been accidental colonists from South America.

In the new study, an international team of zoologists from the U.K. and the U.S. analyzed DNA samples taken from two X. mcgregori leg bones dated to about 1,500 years ago. With help from the Natural History Museum in London's Ancient DNA Laboratory, the researchers mapped the X. mcgregori's genome and compared it with a selection of other extinct Caribbean primates as well as monkeys still living on the South American mainland.

More:
https://www.livescience.com/64070-jamaican-monkeys-turned-into-sloths.html