Life is abundant on Earth. To date, we have identified more than a million life forms, but this pales in comparison to the vast majority of species still undiscovered. The number of extinct life forms is few thousand times more than the total number of life forms that presently exist. Over time, we have observed that the life can survive even in extreme conditions, like in the hottest volcanic springs, below the coldest ice of Antarctica, in the rocks below the sea floor, in barren deserts, in acidic conditions, and in places lacking oxygen. Even a cen- tury ago, such statements would be considered laughable.
Among all the existing life forms man takes pride in think- ing he is the most intelligent. Man’s ability to generate new knowledge and to pass it on to the next generations has given the human species an immense advantage over other life forms. He grew stronger as time passed and successfully ex- ploited nature to his gain. His hunger for knowledge is in- finite. He found answers to many complex riddles posed by nature. Even in his efforts towards finding an answer to the origin of life question, man has made many discoveries and come up with theories that have helped shape the different fields in a variety of ways.
One important theory on the origin of life stands apart un- til the end of 19th century: spontaneous generation. Until the beginning of 20th century, spontaneous generation was the prevailing theory for the origin of lower life forms. Generation of higher life forms, like humans, were not studied exclusively in science. Those who tried to find an answer for the genera- tion of higher life forms mostly relied on either religious texts or spontaneous generation.
The theory of spontaneous generation began because the existence of microorganisms was unknown. When an animal or plant appeared from no visible seed, then the first natural instinct was to attribute it to spontaneous generation. This simple thought led the first investigators to find a recipe for creating each new plant or animal. They tried to set up a con- trolled environment, and observe how life generates out of non-life, or from a putrefying body. Life appeared, but inves- tigators could only fathom what they could see.
All the investigators were so busy in identifying such recipes that they could not shift their thoughts from it when a breakthrough came from Anton Van Leuwenhoek in the 17th century. Microscopes opened the doors for the new world of microorganisms. But most people, including Leuwenhoek, failed to consider the role of microorganisms in putrefaction or fermentation. Instead, most scholars were more comfort- able with the age-old idea than to a fundamental shift in their worldview.
Moreover, many other ideas, in nature very similar to the theory of spontaneous generation, continued to boost it. Vitalism and Miasmata are examples for such theories. Inter- estingly, none of these theories had any credible scientific evidence in the modern sense, but they continued to support one another. To understand how this worked, let’s consider an experiment devised to test a theory ‘A.' Investigators would interpret the outcome of the experiment by taking another theory ‘B’ for granted. If theory ‘B’ is wrong, then the inter- pretation of the experiment is erred. It means theory ‘A’ still has no credible evidence.
Outside the scientific community, theories supporting the origin of life on Earth by natural means found support, or opposition, from scholars in other schools of studies such as theology and philosophy. Theologians and philosophers asso- ciated such theories with God. The general line of thought suggested that if the life generated on Earth through a natural process, then it would remove the need for a creator. Few ex- ceptions took a different line of argument suggesting that it was God’s wish for the generation of life to happen naturally.
In 18th century philosophy, the idealistic thought became popular, which suggested a teleological principle for all life and opposed any explanation involving a natural means for the origin of life on Earth. But revolutions across Europe by the end of the 18th century resulted in strong support for the materialistic views. Skeptical materialist philosophers sup- ported the theories attributing the origin to a natural means, such as spontaneous generation.
Another proposal for the origin of life on earth went al- most unnoticed until the end of 19th century. This theory, now called panspermia, suggested that life exists throughout the universe. From this, an implication was derived suggesting the seeds of life from space, most likely through a meteorite, must have reached earth. The nature of these seeds of life reaching the earth was not discussed by the proponents of this theory in the 19th century. Also, this might solve the prob- lem of the origin of life on earth, but it will still open another question before us, the origin of life in the universe.
As we stepped into the 20th century, spontaneous genera- tion had been rendered irrelevant in the wake of atmospheric germ theory. And panspermia had never gained the popular- ity that spontaneous generation did. There was a desperate need for new efforts and a new direction to understand how all life began. One of the most debated scientific theories in the history, Darwin’s theory of evolution by natural selection, gave this much-needed direction. Darwinism changed the way people looked at the life in general, and it affected everything that came after. Scientists took the idea derived from Darwin- ism forward and tried to form a strong hypothesis about the beginning of life. The discovery of double helix structure of DNA by James Watson and Francis Crick took this research to a whole new level, as scientists now tried to identify the process leading to the first building blocks of life. These ef- forts took two distinct directions. One, to identify the chem- ical process in early Earth conditions that could have resulted in the first building blocks of life. And two, to find evidence of life in space and confirm the method by which it came to early Earth. Both these efforts depended on Darwinism to ex- plain how that first life led to every other life form on Earth.
When we learn all these efforts, one of the major com- plaints pointing to the lack of a conclusive answer for the big question takes a back seat, and our appreciation for the feasi- bility of different scientific proposals will only grow.