From the NY Times:
HUMAN beings are social animals. But just as important, we are socially constrained as well. We can probably thank the latter trait for keeping our fledgling species alive at the dawn of man. Thus could our ancient forebears cooperate, prosper, multiply — and pass along their DNA to later generations. But these same lifesaving social instincts didn’t readily lend themselves to exploration, artistic expression, romance, inventiveness and experimentation — the other human drives that make for a vibrant civilization. To free up those…
We needed beer.
[The] alcohol would have had far-ranging effects, too, reducing the strong herd instincts to maintain a rigid social structure. In time, humans became more expansive in their thinking, as well as more collaborative and creative. A night of modest tippling may have ushered in these feelings of freedom — though, the morning after, instincts to conform and submit would have kicked back in to restore the social order.