Evolution of intelligent life on earth may not have been so unlikely Premium

A popular model of evolution concludes that it was incredibly unlikely for humanity to evolve on Earth, and that extraterrestrial intelligence is vanishingly rare.

A popular model of evolution concludes that it was incredibly unlikely for humanity to evolve on Earth, and that extraterrestrial intelligence is vanishingly rare.

But as experts on the entangled history of life and our planet, we propose that the coevolution of life and Earth’s surface environment may have unfolded in a way that makes the evolutionary origin of humanlike intelligence a more foreseeable or expected outcome than generally thought.

Some of the greatest evolutionary biologists of the 20th century famously dismissed the prospect of humanlike intelligence beyond Earth.

This view, firmly rooted in biology, independently gained support from physics in 1983 with an influential publication by Brandon Carter, a theoretical physicist.

In 1983, Carter attempted to explain what he called a remarkable coincidence: the close approximation between the estimated lifespan of the Sun – 10 billion years – and the time Earth took to produce humans – 5 billion years, rounding up.

He imagined three possibilities. In one, intelligent life like humans generally arises very quickly on planets, geologically speaking – in perhaps millions of years. In another, it typically arises in about the time it took on Earth. And in the last, he imagined that Earth was lucky – ordinarily it would take much longer, say, trillions of years for such life to form.

Carter rejected the first possibility because life on Earth took so much longer than that. He rejected the second as an unlikely coincidence, since there is no reason the processes that govern the Sun’s lifespan – nuclear fusion – should just happen to have the same timescale as biological evolution.