This is a question that has caused great debates amongst scientists and the general public. In a book titled “Power, Sex, Suicide: Mitochondria and the meaning of life” by a Professor of Evolutionary Biochemistry at University College London, Nick Lane addresses this question from a scientific point of view. Through reviewing key ideas and theories of other great scientists the first chapter really does put things into perspective.
To answer this question you must first have an understanding of the origin of life on Earth.
We are all aware from our biology lessons in school and programmes on tv that life first started out as a small simple cell. Putting it simply, that innocent cell developed the ability to form colonies which specialised and cooperated together to become basic organisms. Over millions of years these basic organisms then evolved further and adapted to different environments to create the vast variety of plants and animals we know today.
It’s often wondered, if life played over and over right from the beginning would history repeat itself? In other words, if we wound back time to when the planet was nothing but rock, would evolution lead to mankind every time or would it result in new exotic and strange worlds each time?
Unfortunately, we will not be around to answer this question for sure. However, we and scientists can make an educated guess as to the fate of our planet if life had to start over.
The idea that there would be a unique world each time was fully supported by Stephen Jay Gould in his book “Wonderful life”. This makes complete sense on first glance as for example, if you erased the entire English language and the creators had to start over of course it wouldn’t be the same as we know today - they would come up with different words and it would evolve differently, or would it?
We must consider other important factors like the creators’s environment. The people who first started the English language will be exposed to other languages just the same and their living environment would be just the same. Now if you think about it, it doesn’t seem so likely that the English language would be very different from what we use today.
So, if life was wiped from the planet and everything had to start over it probably would evolve to be similar to as it was before - afterall, they are adapting to live in the same environment.
This is known as convergent evolution, where organisms develop a similar physical appearance and performance regardless of their ancestry and whether they’re related. The reason this happens is because there are only so many possible engineering solutions to the same problems, and only the best solutions will survive and pass the test of time (this is known as natural selection).
However, how large of a role in evolution does chance play compared to natural selection? It’s very difficult to distinguish which features of organisms are present due to contingency (chance) or convergence. For example, was it due to chance that we have four fingers and a thumb, or was it an evolutionary advantage and therefore a necessity?
In his book “Life’s solution”, Simon Conway Morris supports the theory that evolution is ruled by necessity not chance, and that convergence is the driving force of life. The best example of this is the evolution of higher intelligence.
If you evolve to have higher intelligence over other organisms this is of course an evolutionary advantage. To stand a chance in surviving and becoming the dominant species you must have intelligence. Therefore, intelligence is a necessity and hence many organisms will converge on intelligence being the solution to many problems.
Humans have evolved to fill the highest position (niche) because we have higher intelligence so are capable of dominating that position. However, if that position was vacated who would evolve to fill it - bears, the giant squid, monkeys?
It seems it was only by chance that humans became the dominating species because given time many other intelligent species could have evolved to fill the highest niche, just like we did.
So, perhaps evolution is indeed driven by convergence but this is facilitated and helped by contingency and chance. Now, back to the question, who’s to say that intelligent beings won’t evolve anywhere else in the universe?
All of the major innovations of life on Earth have evolved repeatedly for example, flight has evolved independently at least four times (insects, pterosaurs, birds, bats). If higher intelligence is as necessary as scientists believe, it seems unlikely that intelligent life hasn’t evolved anywhere else apart from Earth.
But as far as we are aware life doesn’t exist on any other planets apart from ours so, what is holding life back?
Life on Earth has existed for 3000 million years yet large multicellular organisms have only been around for the last 600 million. It makes sense for many to believe that the ability of individual cells to cooperate together to form these multicellular organisms was what held the evolution of life back.
However, multicellularity is believed to have evolved independently numerous times, for example in plants, animals and fungi. Therefore, it seems it is easy to get cells to cooperate and function together so surely this couldn’t have been holding life back?
Scientists now believe that the key to evolution was the formation of the eukaryotic cell - the type of cell that makes up all multicellular organisms. Think of it this way, if you and your friends are each wanting to build a house you will all find ways to stick everything together, be it through cement, glue or screws. However, if none of you have the bricks in the first place none of you can even start building.
Eukaryotic cells are unique in that they have a membrane bound nucleus and mitochondria. It’s previously been established that the way the cell stores its DNA (whether it’s contained within a nucleus or not) doesn’t significantly hinder its abilities in any way.
All known eukaryotic cells share the same genetic ancestry / are related and have or once had mitochondria. This means the evolution of the eukaryotic cell only occurred once, and the single event that was holding the evolution of life back was the presence of mitochondria within cells.
This single event which made the evolution of complex multicellular organisms possible seems to have been genuine contingency or chance. Therefore, the chances of it or a similar event happening again on another planet is very small.
So, in conclusion, life likely has evolved elsewhere in the universe but unless a similar event such as the creation of eukaryotic cells occurs that life probably won’t evolve to be multicellular. However, although the chances are very small we have no reason to believe intelligent beings won’t evolve elsewhere in the universe - we may not be alone.
Conway Morris, S. (2003). Life's Solution: Inevitable Humans in a Lonely Universe. Cambridge: Cambridge University Press.
Gould, S. J. (1989). Wonderful Life: The Burgess Shale and the Nature of History. New York: W. W. Norton & Co.
Lane, N. (2018). Power, Sex, Suicide: Mitochondria and the meaning of life. 2nd ed. Oxford: Oxford University Press.
**Image by Greg Rakozy on Unsplash**
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