The Odds of Intelligent Life in the Universe

by Nancy Atkinson on April 19, 2008

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When it comes to contemplating the state of our universe, the question likely most prevalent on people’s minds is, “Is anyone else like us out there?” The famous Drake Equation, even when worked out with fairly moderate numbers, seemingly suggests the probable amount of intelligent, communicating civilizations could be quite numerous. But a new paper published by a scientist from the University of East Anglia suggests the odds of finding new life on other Earth-like planets are low, given the time it has taken for beings such as humans to evolve combined with the remaining life span of Earth.

Professor Andrew Watson says that structurally complex and intelligent life evolved relatively late on Earth, and in looking at the probability of the difficult and critical evolutionary steps that occurred in relation to the life span of Earth, provides an improved mathematical model for the evolution of intelligent life.

According to Watson, a limit to evolution is the habitability of Earth, and any other Earth-like planets, which will end as the sun brightens. Solar models predict that the brightness of the sun is increasing, while temperature models suggest that because of this the future life span of Earth will be “only” about another billion years, a short time compared to the four billion years since life first appeared on the planet.

“The Earth’s biosphere is now in its old age and this has implications for our understanding of the likelihood of complex life and intelligence arising on any given planet,” said Watson.

Some scientists believe the extreme age of the universe and its vast number of stars suggests that if the Earth is typical, extraterrestrial life should be common. Watson, however, believes the age of the universe is working against the odds.

“At present, Earth is the only example we have of a planet with life,” he said. “If we learned the planet would be habitable for a set period and that we had evolved early in this period, then even with a sample of one, we’d suspect that evolution from simple to complex and intelligent life was quite likely to occur. By contrast, we now believe that we evolved late in the habitable period, and this suggests that our evolution is rather unlikely. In fact, the timing of events is consistent with it being very rare indeed.”

Watson, it seems, takes the Fermi Paradox to heart in his considerations. The Fermi Paradox is the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilizations and the lack of evidence for, or contact with, such civilizations.

Watson suggests the number of evolutionary steps needed to create intelligent life, in the case of humans, is four. These include the emergence of single-celled bacteria, complex cells, specialized cells allowing complex life forms, and intelligent life with an established language.

“Complex life is separated from the simplest life forms by several very unlikely steps and therefore will be much less common. Intelligence is one step further, so it is much less common still,” said Prof Watson.

Watson’s model suggests an upper limit for the probability of each step occurring is 10 per cent or less, so the chances of intelligent life emerging is low — less than 0.01 per cent over four billion years.

Each step is independent of the other and can only take place after the previous steps in the sequence have occurred. They tend to be evenly spaced through Earth’s history and this is consistent with some of the major transitions identified in the evolution of life on Earth.

Here is more about the Drake Equation.

Here is more information about the Fermi Paradox.

Original News Source: University of East Anglia Press Release

About 

Nancy Atkinson is Universe Today's Senior Editor. She also is the host of the NASA Lunar Science Institute podcast and works with Astronomy Cast. Nancy is also a NASA/JPL Solar System Ambassador.

javier varela May 20, 2008 at 3:58 PM

you also ot to think that even though we may one day be able to find a planet with life trillions of light years away or so, they may not evn be there any way, light travels fast, but not fast enough tht we know if there is any civilization out there still, so to another civilization billions, or trillions of light years away, to them also we may still appear to be in the triassic period or so on

poopenhimer June 27, 2008 at 4:56 PM

Reading these comments i have a lot to say. First of all even though there are a lot of greedy nasty people in the world, humanity as a whole defies the natural feeling of greed. It is our intelligence that seperates us from all other forms of life on this planet, and it is our intelligence that makes it possible for us to repel selfish thoughts.

there was a study done on toddlers and chimpanzees that showed the distinct difference between humans and there closest relatives. The first test was done on a group of toddlers where an adult would purposley put him or herself into a situation where they would be in need of help. Every toddler in the room was willing and eager to help its fellow human.

A similar situation was set up for chimpanzees. They put one chimpanzee in a room where the center was divided by metal bars. Food was placed in the middle of a long board just out of reach of the chimp on the other side. Each end of the board had a string attached to it that traveled through the bars to the side of the room where the chimp was being held. Alone, the strings where to far apart for the chimp to successfully pull the board close enough to him to reach the food. The chimp was then faced with the option to open a door on his side of the room where a fellow chimp was being held. The door was opened and with the help of the second chimp, the original was able to reach the food. But being the dominate chimp, the orignal chimp did not share the bounty with his companion. The test was tried again but this time when the chimp opened the door for help, the second chimp refused to do work with no profit.

Selfishness is what drives evolution. An organism is wired to do anything to survive. We are the exception. If any other animal was given the technollogy and the means as humans what would you think the world would be like. Now this doesnt mean we can become better as a society and help regrow our environment but thats for another day.

Secondly if we find other forms of life, the chances of it being carbon based is extremely high. Carbon is the element that most easily bonds with any other element. It is the most efficient means to the biulding blocks of life and this will never change anywhere throughout the whole universe.

p.s. dolphins arent that smart. Unless they somehow evolve to walk of land, which would probably never ever happen being so well adapted for the water and might have evolved from land into the water, dolphins, even if it wasnt for human intervention, would have never evolved into anything like humans or as succesful. HEED THY WORDS! BEWARE THE FUTURE WHERE ELEPHANTS RULE THE WORLD! THERE TRUNK TRIGGERED GUNS WILL OBLITERATE US ONE DAY!

Dansk1 December 4, 2008 at 8:36 PM

Consifering what I have experienced over a period of 80 years, mingling among those homo-sapiens, I earnestly ptay that there is intelligent lifeform out there, because there sure is’nt any here on Earth. My life savings were confiscated by pseudo-Christians at Sun City Hilton Head, back in March 1995.
Since then, every day on this sphere has (and continues to be) an obvious challenge.
Forget about overseas Internet crooks, like those in Nigeria, worry about the folks right in your neighborhood, or the Del Web Mafia.

Landon January 9, 2009 at 10:00 AM

CANDY BARS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

mc February 5, 2009 at 5:01 PM

poopenhimer Says:
Selfishness is what drives evolution. An organism is wired to do anything to survive. We are the exception. If any other animal was given the technollogy and the means as humans what would you think the world would be like. Now this doesnt mean we can become better as a society and help regrow our environment but thats for another day.

I don’t believe we are an exception. We will do anything to survive. It’s just in this modern age in first world countries, we don’t have an issue of survival. Right now we are more worried about getting fat because we have too much to eat. We are worried about overpopulation because too many of us survive. Once resources start dwindling, do you think we all will just die of starvation without trying to stop it? How many people out there harm other people without an issue of survival? We are just as prone to evolution as any other species, just we are a bit smarter. Also, I would argue the intelligence to some degree. There is such a variation of intelligence from people like einstein to people who can’t wipe their own a” at 30 years old.

javier varela Says:
May 20th, 2008 at 3:58 pm
you also ot to think that even though we may one day be able to find a planet with life trillions of light years away or so, they may not evn be there any way, light travels fast, but not fast enough tht we know if there is any civilization out there still, so to another civilization billions, or trillions of light years away, to them also we may still appear to be in the triassic period or so on

The definition of a light year is the distance travelled by light in one year. The actual speed of light is approximately 3*10^5 m/s. Consdering that about 14 billion light years is all we can see in any direction of the universe, it would be impossible to see something that is anywhere near a trillion light years away. This is where scientists get the idea that the universe is only 14 billion years old. There are alot of holes in this age. First, you have to assume that space does expand faster than the speed of light. Second, you have to assume there is nothing past that 14 billion light year mark. If the universe is 14 billion years old, then we should theoretically be able to work the the paths of these supergroups of galaxy backward until a point where they were all together, which should add up to 14 billion years if correct.

As for the odds of intelligent life on other planets, we don’t know enough at all to even make an estimate. One of this guy’s arguments is the complication of evolution. We don’t consider the fact that life could flourish in some conditiones that we haven’t considered. Or even solar systems with gas giants that have many moons and are close enough to the parent star for liquid water. Until we can get samples from at least a small section of the universe, we won’t be able to provide a statistic for how many civilizations that are out there. As far as we know it could be 0 or it could be 10^20000

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