Photo: Chimps Get Drunk on Palm Wine

Humans' closest living relatives may have a drinking habit: Scientists spied intoxicated wild chimps soaking up palm wine with leaves and squeezing it into their mouths.

Alcohol consumption is seen across nearly all modern human cultures that have access to fermentable materials. This prevalence led scientists to suggest what is known as the "Drunken Monkey Hypothesis" — that alcohol consumption might have provided a benefit of some kind to the ancestors of humanity, and perhaps also to the ancestors of chimpanzees, humanity's closest living relatives.

Humans and apes share a genetic mutation that emerged about 10 million years ago that helps them break down alcohol and could have helped them eat overripe and fermenting fruit. According to the proponents of the Drunken Monkey Hypothesis, the benefits of such an expanded diet may have even led evolution to favor an attraction to alcohol.

http://www.livescience.com/51146-chimps-get-drunk.html