Is life a gamble? Scientist models universe to find out
Scientists suspect that the complex life that slithers and crawls through every nook and cranny on Earth emerged from a random shuffling of non-living matter that ultimately spit out the building blocks of life.
Even so, the details to support the idea are lacking.
But researchers recently got creative in figuring out the probability of life actually emerging spontaneously from such inorganic matter — a process called abiogenesis.
In the study, Tomonori Totani, a professor of astrophysics at the University of Tokyo, modeled the microscopic world of molecules across the epic scale of the entire universe to see if abiogenesis is a likely candidate for the origin of life. He was essentially looking at whether there were enough stars with habitable planets in the universe at the time to allow complexity to arise. His results, published Feb. 3 in the journal Nature, show the betting odds for life emerging are not good, at least for the observable universe.
Related: 7 wild theories on the origin of life
"I hoped to find at least one realistic path of abiogenesis, to explain abiogenesis by words of science," Totani told Live Science. "Sometimes people claim that abiogenesis probability is incredibly low and that the origin of life cannot be understood by science. I, as a scientist, dreamed to find a scientific explanation of why we are here."
Totani's study looks at a leading hypothesis for abiogenesis, that life as we know it began in what researchers call an RNA world. This hypothesis suggests that before the evolution of proteins and the double-stranded genetic molecule called DNA, or deoxyribonucleic acid — which today provides the instructions for life on Earth — the world was dominated by similar but less efficient molecules called RNA, or ribonucleic acid.
In an RNA world, RNA was the first molecule capable of copying and storing information, and of starting and accelerating chemical reactions — two essential characteristics of life on Earth. This world would be a more primitive molecular world to the DNA-protein based chemistry that defines life today.
Although primitive, RNA is made up of many chemicals called monomers that link together to form a polymer. Particularly, RNA is made up of a chain of nitrogen-based molecules called nucleotides. Researchers think that in order for RNA to perform its essential function of copying itself, it needs to be composed of a chain of nucleotides longer than 40 to 60 nucleotides.
So, how would these RNA molecules made up of at least 40 to 60 nucleotides have popped up on their own? Nucleotides have been shown experimentally to randomly organize into RNA given enough time and under the right conditions. But these experiments show that the abundance of RNA rapidly decreases with the length of their chains and none of the experiments could consistently produce strands longer than 10 monomers.
"It has been experimentally confirmed that RNA polymerization can occur by a basic random process," Totani said. "Some experiments claimed that more than 50 (monomer long) RNA were produced, but these are not reproducible. One problem is that aggregates are easily mistaken for a long RNA polymer."
Totani's model uses the most conservative method of RNA polymerization, where each monomer is attached randomly one-by-one until a chain of monomers is formed. Scientists have suggested that polymers (each made up of multiple monomers) could attach to each other to speed up the process, but Totani said such a process is "highly speculative and hypothetical."
Life as we know it
Scientists think life emerged on Earth around 500 million years after the planet formed. Given that there are an estimated 10 sextillion (10^22) stars in the observable universe, it may seem that the odds of life popping up in the universe should be good. But researchers have found that the random formation of RNA with a length greater than 40 is incredibly unlikely given the number of stars — with habitable planets — in our cosmic neighborhood. There are too few stars with habitable planets in the observable universe for abiogenesis to occur within the timeframe of life emerging on Earth.
"However, there is more to the universe than the observable," Totani said in a statement. "In contemporary cosmology, it is agreed the universe underwent a period of rapid inflation, producing a vast region of expansion beyond the horizon of what we can directly observe. Factoring this greater volume [of stars with habitable planets] into models of abiogenesis hugely increases the chances of life occurring."
After our universe flashed into existence some 13.8 billion years ago during the Big Bang, it underwent a period of rapid expansion that continues today. If we think of the universe as a loaf of bread baking in the oven, our observable universe is like a bubble of air trapped in the dough, where the walls of the bubble are the farthest distance light can travel since the Big Bang. As the loaf rises (inflation), our bubble grows while other pockets of air within the bread get farther away. Our observable bubble of air is all that we can see, even though the rest of the loaf is out there.
Related: From Big Bang to Present: Snapshots of Our Universe Through Time
It is estimated that the whole universe could contain more than 1 googol (10^100) stars. When Totani factored in this new abundance of stars, he found that the emergence of life was no longer improbable, but very likely.
This may be good news for the RNA world hypothesis, though it could also mean that the search for life in the universe is a hopeless pursuit.
If life first got its start in RNA, "life on Earth was created by a very rare chance of producing a long RNA polymer," said Totani. "Most likely, Earth is the only planet harboring life in the observable universe. I predict that future observations or explorations of extraterrestrial life will yield no positive results.
If by chance, life is discovered elsewhere in our cosmic neighborhood, Totani believes it would likely be of the same origin as life on Earth. Life may have hitched a ride from comets and asteroids across interplanetary or interstellar space, seeding the local universe with life from a single origin event.
Totani's work is far from an answer to one of science's most existential questions but it may guide further research on the origins of life. Whether we are alone in the universe still remains unanswered, but if Totani's numbers tell us anything, you shouldn't bet on it.
- The 18 Biggest Unsolved Mysteries in Physics
- The 11 Biggest Unanswered Questions About Dark Matter.
- The 15 Weirdest Galaxies in Our Universe
Originally published on Live Science.
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By Ben Turner
By Robert Lea
As for the article at hand, if this author is right that life may be a one-off in the observable Universe, imagine how improbable INTELLIGENT life with a potential for highly developed technological civilization is even in the entire Universe.
I'm not a scientist, but in my mind, if the universe is infinite in size, then all possibilities in nature (provided they obey the laws of physics) are being played out somewhere in the universe. The more probable they are, the more frequently they show up in any given finite part (observable) of the universe.
Figuring out how may take us some time, but our mere existence says our existence is possible. Our rarity indicates how improbable our existence or another like ours in our observable is. Maybe in someone else's observable, there are multiple beings interacting with one another (in a galaxy far, far away).
Or, God did it.
I don't know why you felt it necessary to take a gratuitous shot at my profession, but it is typical of online posts. My profession has allowed me to observe brand new babies for decades, I am simply saying that the traditional scientific explanation for life doesn't quite work for me. I haven't replaced it with a guy in the clouds you know. It's all speculation on everyone's part. I have read the scientific record all my life and I find it inadequate to explain cellular life.
Until scientists actually create LIFE in a lab, there is only FAITH in their theories. And evolution itself *IS* miraculous *EDIT*. Complex biological entities that are programmed to improve themselves through genetic mutation of their offspring, whose predecessors came from basic non living elements *sounds like fantasy,* For anybody to say that anybody's ideas or theories on *the origins of life* are in the realm of the supernatural, mythical, or religious, is total hypocrisy. I'm not religious, and I definitely don't condone the idea of scientists simply saying "god did it"...on anything. Yet I find high value in the fact that a scientifically minded and educated medical professional can still be amazed by a new born baby.
But living molecules have choice. The un-predictability of this choice, has led to the concept of probability and randomness........even though that choice was not random.
Our existence is within an unbreakable order.
At the present time the fields of Archaeology and Paleontology are dominated by the dogma of Darwinian Evolution. Modern observations have shown that many nanomachines cannot be explained by evolution. Also, the Cambrian Explosion proves that evolution did not occur. What you are missing is what our beautiful doctor is saying to you: there is something miraculous about the origin of life, a miracle that he has witnessed in his profession. You think you may know something, well, tell me if you comprehend what it means for the universe to be as many as 100 billion light years in diameter. If you claim that you comprehend such a distance, I would suggest that you are fooling yourself. You need to appreciate what the good doctor is saying to you.
Attaboy, Dr. Dave. You have experienced the birth of life personally and your experience is wonderful to hear about. Unfortunately, Darwinism has created secular humanism, which demands a materialistic explanation of life and the universe. Why was Socrates a Wise Man: Because he knew that he did not know.