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The only monkeys you’ll find on the islands of the Caribbean today were brought there (intentionally or not) by people. But just a few thousand years ago, thriving populations of primates existed across the Caribbean. The discovery of exceptionally well-preserved monkey bones in the Dominican Republic is helping researchers better understand the evolutionary history of these now-extinct primates.

In the waning days of summer 1862, Gen. Robert E. Lee lined his Confederate troops along a grassy ridge on the western side of Antietam Creek in the outskirts of Sharpsburg, Md.

Across the stream, Union troops prepared for an attack.

Then, on Sept. 17, in the shadow of the Blue Ridge Mountains, the Battle of Antietam began. The armies blasted each other with gunfire from dawn until nearly dusk. That day proved to be the single bloodiest day of the American Civil War, with more than 23,000 men lying dead or wounded in the valley’s fields by nightfall.