From geological data, we know that life appeared relatively quickly, as soon as the environment of our planet became stable enough to support it. We also know that the first multicellular organism, which ultimately gave rise to modern technological civilization, developed much longer, about 4 billion years.
But, despite the knowledge of when life first appeared on Earth, scientists still do not understand how life came about, which has important consequences for the likelihood of finding life elsewhere in the universe.
In a new article published today in the News of the National Academy of Sciences, David Kipping, an assistant professor at the Columbia Department of Astronomy, shows how analysis using a statistical method called Bayesian probability can shed light on how complex extraterrestrial life can develop in alien worlds. .
“The rapid emergence of life and the late evolution of humanity in the context of the timeline of evolution certainly suggests,” said Kipping. “But in this study, you can really determine what the facts tell us.”
For his analysis, Kipping used the chronology of the earliest evidence of human life and evolution. He asked if life and mind would reappear if the Earth’s history repeats itself, restarting the Earth’s clock again.
He formulated the problem with four possible answers: life is common and often develops to intelligence, life is rare, but it often develops to intelligence, life is common and rarely develops to intelligence, and finally, life is rare and rarely develops to intelligence.
This Bayesian inference method is used to update the probabilities of this hypothesis as evidence becomes available or new information becomes available.
For these four hypotheses, Kipping used Bayesian mathematical formulas to map models to each other. “In the Bayesian inference, you always need to choose the previous probability distribution,” Kipping said. “But the key result here is that when comparing the“ rare life ”and“ ordinary life ”scenarios, the ordinary life scenario is always at least nine times more likely than the rare one.”
The analysis is based on data indicating that life arose within 300 million years after the formation of the Earth’s oceans, found in zirconium deposits depleted in carbon-13, which is a very quick start in the context of Earth’s life. Kipping emphasizes that this ratio of the appearance of life is at least 9: 1 or higher.
Kipping’s conclusion is that if planets with similar conditions and evolutionary timelines like Earth’s are common, then analysis shows that life should not have any problems spontaneously arise on other planets. The likelihood that these extraterrestrial life can be complex and reasonable according to Kipping is 3: 2 in favor of intelligent life.
This result is associated with the relatively late appearance of mankind in the inhabited window of the Earth, which indicates that its development was neither an easy nor guaranteed process. “If we replay the history of the Earth, the emergence of intelligence is actually unlikely,” he said.
Kipping indicates that the chances of the study are not guaranteed, being close enough to 50:50.
“An analysis cannot provide certainty or a guarantee, only by statistical probability based on what happened here on Earth,” Kipping said. “Nevertheless, it is gratifying that the universe, teeming with life, is becoming closer. The search for intelligent life in worlds outside the Earth should in no case be discouraging. ”
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