Origin of Life: Spontaneous Proliferation?

How did life originate on Earth? Did life really start from nothing? Was it just luck and magic that created human beings and all the other creatures? These questions provoked a heated debate about the origin of life on Earth. Some believe life appeared as a result of the combination of chemicals on primitive Earth. Others propose that substances from outer space potentially paved the path for life. Still, others think it’s just a mix of serendipities and time. Scientists are not close to knowing the exact answer and they may never find the key to this mysterious door. Yet, knowing more about the origin of life on Earth and better understanding where humans came from acts as a vital part to the whole human race. It is somewhat unmeaningful and hollow to live a life not even knowing the most significant part of ourselves – life or human origin. Led by the question “How did life first start on Earth?”, this article will expand on research done and explore the unknown past. Abiogenesis and biogenesis are both possible based on various pieces of evidence. In the following, an elaboration on several prevalent theories and experiments will be provided as possible explanations of this mystery.

DISPROVAL OF SPONTANEOUS GENERATION

While it appeared that abiogenesis could explain the creation of life on Earth, many theories and experiments refuted spontaneous generation. Spontaneous generation was disproved through the execution of various experiments and verification of significant theories. After cultivating and enhancing the precision of experiments, results consistently showed that life or organisms can’t arise spontaneously.

According to Explore Yeast6, the development of the Germ Theory of Fermentation and Pasteurization aided Louis Pasteur to disprove abiogenesis. The Germ Theory of Fermentation stated that anaerobic organisms or organisms surviving without oxygen caused fermentation. For instance, yeast was able to live in the absence of air and produce alcohol from sugar. In addition, fermentation occurs only when there are living microorganisms, growing due to the spores in air or on food. This discovery also helped develop the renowned process of “pasteurization”. Pasteur implied that if heating killed most of the bacteria, then it’s unlikely for a liquid to be spoiled. In other words, fermentation is not caused due to spontaneously generated bacteria, but due to the surviving organisms that produced acid6.

Furthermore, Pasteur conducted an experiment that further debunked spontaneous generation. He used a swan-necked flask that allowed air to go into the heated broth while keeping bacterial spores out. The result showed no chemical changes or growth of anything in the broth. On the other hand, when Pasteur tilted the flask on its side and allowed access of dust into the heated broth, bacteria growth contaminated the broth. The same would happen if the neck of the flask was broken exposing the liquid to non-filtered air. Overall, this showed that bacteria appearance did not arise from spontaneous proliferation7.

To better illustrate the point, two other experiments consolidated this refutation against spontaneous generation. Firstly, Francesco Redi proposed that maggots didn’t spontaneously generate from rotting meat and supported his opinion with an experiment. Initially, he placed meat in many jars. There were three types of jars, some were left uncovered, some were covered with gauze, and others were sealed with a lid. Gradually, maggots were present in the first two groups of jars but not in the ones that were sealed. He concluded that maggots do not spontaneously arise from meat, because only the ones that flies have access to appeared to have maggots7. Plus, Lazzaro Spallanzani demonstrated that microbes do not spontaneously generate. Since he believed that microbes could move airborne, he contended that the microbes that appeared in an experiment conducted by John Needham (an English biologist in favor of spontaneous proliferation) is due to the broth’s exposure to air after boiling but before the flask had been sealed. Spallanzani then devised an experiment, where he placed the broth in a sealed flask. After that, he eliminated air from the flask and boiled or sterilized the heated broth. As a result, no microbes appeared in the broth. Undoubtedly, this was a huge blow for spontaneous generation7.

Based on the many theories and experiments elaborated above, spontaneous generation seems to be an unfeasible explanation for the origination of life on primitive Earth.

This disapproval theory against spontaneous proliferation is indeed persuasive, but arguments in favor of spontaneous proliferation are also present, such as the instances provided below.

PRIMORDIAL SOUP

In 1940 Russian scientist Alexander Oparin and English geneticist John Haldane hypothesized another theory of how life originates – the theory of the primordial soup. Literally, it means a bowl of soup from ancient times. Alexander Oparin and John Haldane theorized that life started in the primordial ocean. The mix of gases in the atmosphere and the energy from lightning strikes allowed the primitive water to be rich and organic, creating amino acids found in protein (an element that all living things have). Over periods of hundreds of years, life became possible to be created spontaneously in the ocean. Amino acids contain nitrogen and hydrogen, and those 2 elements did appear in the primordial time3. Hence this theory is reasonable.

In 1952 Stanley Miller, a graduate student from University of Chicago, with Harold Urey, a Nobel laureate in chemistry, conducted a famous experiment that proved life spawned from the primordial soup. Miller and Urey put ammonia (NH3), methane (CH4), and water vapor in an enclosed container to simulate the environment in primordial time. Then they put electrical sparks through the container to emulate lightning. Amino acids, which are substances that are found in protein, were soon observed to have formed3. These experiments demonstrated the process of how life potentially formed in support of the primordial soup theory.

HYDROTHERMAL VENTS

Similar to the hypothesis of abiogenesis and spontaneous proliferation is a second postulation of hydrothermal vents. Hydrothermal vents allowed life living in the deep ocean and in extreme environments to produce energy without the energy from sunlight. In other words, with the help of submarine vents, living organisms can be formed deep in an oceanic world with no sunlight and the help of above-sea-level heat.

According to an article published by Heather Scoville4, these types of organisms are extremophiles that can live in the severest of conditions. Hydrothermal vents are structures in the bottom of the ocean, existing in extreme conditions. The vents were capable of making their surroundings extremely hot, hence the word "thermal" in its name. Life forms that live in and near these vents need and have adaptations that enable them to thrive in these harsh conditions of heat and pressure.

Since sunlight cannot reach to the depths of these structures, there had to be another energy source for early life that may have formed there. A potential energy source lurks behind the vents’ chemical compositions. Hydrothermal vents contain chemicals that aid in the occurrence of chemosynthesis—a way for organisms to create their own energy similar to photosynthesis that uses chemicals instead of sunlight to make energy1.

Synthesizing the amount of heat and pressure in these areas, along with the types of chemicals available, life can be created and changed relatively quickly. Scientists further validated this hypothesis by successfully tracing the DNA of all currently living organisms back to a common ancestor of extremophiles that inhabited the hydrothermal vents4.

SEEDED BY METEORITES

A final and third hypothesis of the origin of life is a mix of luck, time, and meteorites. It is helpful to start thinking about these questions: Why do meteorites have the ability to carry life? Why can life be carried by meteorites?

The first meteorite drifted through the universe in the form of a comet. The surface of the comet was covered in ice, which froze and in turn protected the preservation of the carried life. This is also one of the reasons why life did not melt when a comet entered the atmosphere, where intense heat is produced from friction due to movement. When the ice layer on the surface of the comet melted, the remaining un-melted meteorite blocks brought the life forms to Earth from outer space.

Some people may say that life would melt when passing through the atmosphere, but in fact, microscopic lifeforms like bacteria or viruses have the ability to pass through the atmosphere. For instance, a virus has a protective layer on its surface that is hard enough to protect it from destruction or deterioration when passing through the atmosphere.

Yet, even if bacteria and micro-viruses were introduced to earth, how did they evolve into larger life forms without perishing? How did a tiny bacterium affect the global production of life? Life comes from reproduction and transmission. Research has shown that the bacteria stayed and survived for a period of time after arriving on Earth, during which they diffused to their most primitive form. Infection through this conduit gradually increased the number of bacteria that bred microorganisms, which mutated and grew into other organisms5.

AN ONGOING PROCESS OF REVEALING MYSTERIES

In conclusion, life origination is still an unsolved puzzle, where efforts in approaching a possible answer are still being made. Scientists and thinkers proposed different theories and provided their own understandings on this subject. Alexander Oparin and John Haldane theorized that life was first created in the primordial ocean by the combination of energy and gases, which was also later verified by the experiments performed by Miller and Urey. Others contended that organisms are carried to Earth by meteorites or basically arose from hydrothermal vents, where creatures thrived under extreme environments. Against these theories and in contradiction to biogenesis, Louis Pasteur conducted experiments and theories, attesting that organisms cannot arise from spontaneous proliferation. He is renowned for his studies on fermentation and extrapolating conclusions from experiments of previous scientists. The theories explained are just a tiny portion of the iceberg. These scientific investigations prove to be a crucial first step towards an understanding of the origin of life and where the human race came from. The subsequent steps about to be taken require the wider society to remember that “The important thing is not to stop questioning,” as Albert Einstein put it9, p. 64.