While we were smart enough to ask questions and consider our existence, we wondered where we came from. Discovering evolution through natural selection led us part of the way to the answer when he explained how life changes over time, but cannot cope with the origin of life itself.
So far, the only answers we have to this last question come in the form of our fiction. In the 2012 sci-fi horror movie Prometheusdirected by Ridley Scott, the crew of the titular ship sails across the space seas to the alien moon LV-223 in search of the origins of mankind.
There they find the remains of an alien species known as the Engineers, who gave birth to human life in the distant past. The journey manages to discover the beginning of humanity, but it may also have triggered events that will end our species. The idea of life on Earth sown elsewhere in space may sound like science fiction, but is there any use to it? Let’s start over, so to speak.
Generally speaking, there are two leading hypotheses about the origin of life. The first is that of abiogenesis (modern Latin means spontaneous generation), which is the process by which life could have arisen from previous inanimate matter.
There is no doubt that our bodies are created and maintained by complex chemical processes, but there is something innately different even for an ordinary single-celled organism and an inanimate molecule – not to mention more complex multicellular life. Both are chemistry at work, but one is much more complicated and much harder to wrap around our heads.
IN central idea behind abiogenesis is that chemical systems, which become more complex over time, may eventually become able to use energy to do work and do things, even copies of themselves. A molecule, no matter how simple, that can use energy, move through the environment and reproduce, meets the most widely accepted definitions of life. How this paradigm shift from non-life to life can happen remains an open question.
Some evidence in support of abiogenesis is the knowledge that the necessary components of life were present on early Earth.
In 1952, Stanley Miller and Harold Yuri performed what would become known as the Miller-Yuri experiment. They tried to recreate the conditions of the early Earth to see if the chemical precursors of life could have originated in this environment.
To simulate the environment of the primordial Earth, they added methane, ammonia and hydrogen to the water, then gave it a spark to simulate energy from a lightning strike. Their later observations confirmed the presence of amino acids and nucleobases, providing further evidence that early Earth conditions might be conducive to the spontaneous emergence of life. Subsequent experiments repeating the process also found that the minerals from the beakers themselves may have facilitated the reactions and that these minerals were present in the rocks and were available for early chemistry. In short, all the necessary ingredients were present, the only question is whether or not they found a way to put them together properly. To date, we are not sure. Of course, a different origin is possible.
We now come to the second hypothesis about the origin of life on Earth, which laid the foundation of Prometheus. It is possible that life did not originate on Earth at all, but instead was delivered to our planet from elsewhere. To be clear, the hypothesis does not necessarily require some extraterrestrial mind to be responsible for this delivery – chance, not the deliberate actions of engineers, could do the trick.
In essence, there is evidence that some of the same processes that may have occurred on early Earth (abiogenesis) may actually occur in interplanetary space. In fact, some studies show this space can be a better place to build biomolecules from the environment that Miller and Yuri replicated in their experiment. Molecular clouds, where stars and planets are born, can also build peptides and other organic molecules.
The more we look at our universe, the more we discover that chemistry obviously wants to organize itself in ways that have the potential to lead to life. To date, of course, we have found life in only one place and you are looking at it. However, it does not seem so far away that once life appears in one place, it can spread at least to its close neighbors. It may not be unreasonable to wonder if the life you see all around you actually began on Mars or one of Jupiter’s moons and reached Earth through celestial delivery from an asteroid impact.
Such a trip would not be the most convenient, but experiments show that some microbes do well in the vacuum of space, even for long periods of time. In fact, microbes have been exposed to space for several years outside the International Space Station survived well.
The experience of being expelled from their home world and the fiery re-entry into Earth may be a different story, but if there is one thing we have learned, it is that life wants to live on. If possible, he finds a way. Either way, it all comes down to the same thing. Panspermia just kicked the organic can out of the way. Life still had to emerge from non-life somewhere. Maybe one day we’ll find out how it happened.