Add Yahoo as a preferred source to see more of our stories on Google. The Sun's distance from Earth allows it to be habitable for life. DrPixel/Moment via Getty Images A popular model of evolution ...

What took so long for humans to appear on Earth? The Earth is 4.6 billion years old, and life began about 4 billion years ago, yet humans—the only intelligent, technological species we know of in the ...

Over hundreds of thousands of years, humans somehow evolved a type of intelligence found nowhere else in the animal kingdom, at least on Earth. According to the most famous theory describing the ...

For decades, many scientists have relied on the "hard steps" model to suggest that intelligent life is rare — the improbable result of a series of unlikely evolutionary leaps. But new research by ...

A new model increases the probability of intelligent life elsewhere in the universe, upending the decades-old “hard steps” theory that intelligent life was an incredibly improbable event on Earth. Are ...

For decades, scientists assumed that life on Earth emerged through a chain of highly improbable flukes. But a new theory suggests it may have instead arrived just in time. The emergence of human life ...

Some of the greatest evolutionary biologists of the 20th century famously dismissed the prospect of humanlike intelligence beyond Earth. Elen11 Elen11/Getty Editor’s note: The Focus on Research column ...