Unfortunately, scientists aren't so sure that an actual intelligent alien would be so benign. In a recent interview with El País, famed physicist Stephen Hawking posited that an alien visitation would put Earthlings in the same position as Native Americans when Columbus landed on their shores.
"Such advanced aliens would perhaps become nomads, looking to conquer and colonize whatever planets they can reach," Hawking speculated.
The likelihood that intelligent life is out there is up for debate; less discussed are the conditions necessary to evolve a life-form that's both smart and nice. But the lessons from Earth suggest that intelligence and aggression might evolve hand-in-hand.
No one really knows how humans got to be so clever. What's clear is that hominin brains began expanding wildly about 2 million years ago. (Hominins include those species after the human lineage — the genus Homo — split from the chimpanzee lineage.)
By around 100,000 years ago, humans made the never-before-seen leap to inventing language. And by at least 40,000 years ago, our ancestors were making art.
"We have brains that are three times bigger than those of our closest relatives," said Mark Flinn, an anthropologist at the University of Missouri who has researched the emergence of human intelligence.
Humans have unprecedented abilities to think about each other's thoughts and motivations, he said, to play out social scenarios in their brains and to think about the past and future.
"The general presumption is that this is just sort of a natural outcome of the evolutionary process, but that's really giving short shrift to the very special circumstances of human evolution," Flinn said.
Huge brains are expensive.
They take an enormous number of calories to grow and function (up to 50 percent of intake in infancy and childhood, Flinn said) and make humans basically helpless for years after birth. Read More: