planet earth outer space

New research on Earth suggests there was only a tiny chance of intelligent life developing

New paper says Earth’s intelligent life is probably ‘rare’

American astronomy professor David Kipping calculates that the chance of Earth developing intelligent life is rare.

planet earth outer space

New research on Earth suggests there was only a tiny chance of intelligent life developing

An American astronomy professor has calculated that if one goes back in time to repeat history, the chance of Earth developing intelligent life is probably rare.

Prof David Kipping’s scenario looks at Earth starting over, winding time back to the moment right after the land cooled from hot magma and giant meteor showers stopped devastating the planet.

This in turn leads to the following questions: Would life rise again on this planet? And would that life ever become intelligent?


A new paper published on 18 May in the journal Proceedings of the National Academy of Sciences offers an answer. Life likely spawns quickly and easily under Earth-like conditions. However, intelligent life is probably rare and slow to emerge, suggesting it might not reappear even if conditions are similar.

The author David Kipping, a Columbia University astronomer, kept his focus on Earth and his paper leaves questions about other planets unanswered.

Kipping used a statistical method called Bayesian analysis to study the handful of data points available, landing on the conclusion that we are probably lucky to exist at all.


Bayesian analysis closely resembles the way human beings actually think.

“The approach forces researchers to examine the assumptions involved in the questions they’re asking and their confidence in those assumptions,” astronomer Pauline Barmby said.

Astrophysicist Will Farr said: “Bayesian analysis is just a way of describing and updating beliefs or information content when you see some piece of data.”


Kipping’s paper took the handful of data points that have been collected on how long it took life and intelligence to emerge on Earth, as well as estimates of how long Earth will be habitable, based on the sun’s life cycle.

“Run Earth’s history over again, and there’s a decent chance that we, or creatures like us, never emerge,” says Dave Kipping.

He then used a Bayesian approach to figure out the odds of whether each event is a “rapid process” or a “slow and rare scenario”.

Kipping wrote: “If life’s emergence from inanimate stuff was fast, we’d expect that on an Earth rewound and rerun, life would probably happen at some point in our planet’s billions of habitable years. But, if that emergence was slow, life might have been a lucky break. The same caveats apply to the emergence of intelligence. Run Earth’s history over again, and there’s a decent chance that we, or creatures like us, never emerge.”


In response, Farr said: “Kipping’s paper is a very good statistical analysis of the very limited information we do have about our planet alone. So what?”

“What you have is: Life emerged a few hundred million or maybe almost a billion years after Earth stopped being bombarded with massive objects,” continued Farr.

“Humans showed up close to the 4-billion-year mark. And Earth will probably be habitable for another billion years or so. That is absolutely useful information. You might ask, if those numbers stayed the same, but Earth was orbiting a different type of star, how would that change things?”


Other authorities have also given their views.

“While Kipping’s paper makes reasonable assumptions and simplifications about how life works, it’s important to recognixe that they are assumptions and simplifications,” biologist and archaeologist Isabelle Winder said.

“Sure, intelligent life probably can emerge only some time after life itself, and life itself probably requires a habitable planet, and so on.

“But Kipping’s paper only looks at when life first emerged and when intelligence first emerged after the planet became habitable. The paper doesn’t care if life and intelligent life emerged more than once, though they might have. The paper also doesn’t care what form those life-forms take.”


Before the Cambrian explosion 541 million years ago, life appeared to have been relatively simple. The fossil record suggests Earth was inhabited by just individual cells or small colonies for billions of years.

Life rapidly diversified during the Cambrian explosion. Within tens of millions of years nearly every current animal body plan, including that of vertebrates, emerged.


Kipping told Live Science: “This exact date of intelligence appearing in human history doesn’t matter that much to this model”.

“Give or take a couple of hundred million years, the conclusions are pretty much the same, just as they don’t change much based on the debate about when precisely life emerged in Earth’s history,”  Kipping said.

On whether it would change his model to introduce uncertainty about how many times intelligence evolved, Kipping said there was no simple answer.

“Here it will matter and, frankly, I can’t give you a simple answer without repeating a complicated series of numerical integrations.”

Kipping said it probably should not matter much given that the odds of intelligence emerging are not so long.

“It’s a slight preference but obviously not a slam dunk significance preference, so however you define intelligence, it’s going to remain fairly ambiguous and diffuse.

“As for whether there is intelligent life elsewhere in the universe, that remains a grand mystery. The best thing to do is to keep looking for hints of intelligent life out there.”