Warm Little Pools: How Did Life On Earth Begin?
In these articles, I try to stick to theories that are already widely accepted. One of the core strengths of the scientific method is the ability to exactly reproduce studies. With this possibility on the table, strong and weak theories are separated over time, by the careful work of the people who act as the cells of the scientific superorganism.
This article is an exception to that rule. Occasionally, a theory will slap us in the face with intrigue, as a candidate for answering a question that had previously seemed impossible. Going against a strictly scientific mindset can be justified by the sheer awe brought on by the idea. What we encounter today will get its opportunity to go through the ringer of history. For now, let's just explore it.
We have previously learned that the mark of a good scientific theory is testable predictions. The work summarized here provides just such predictions, for a massive question: what is the origin of life on Earth?
When we begin comparing mysteries, life's existence is on par with the existence of the universe itself. For all of the wonder that the universe inspires, there are many distinctions that argue for life as the pearl to its oyster. Life is threatened by extreme heat and cold, impacts from space debris, and harmful radiation. The universe enables all of these threats with its apathy towards all things living. We can appreciate this delicacy because we see it in ourselves. It's unclear how likely or unlikely it is that the universe has come to exist. Now that it has, however, it appears monolithic in a way that makes life appear as a champagne flute on the streets of Pamplona.
To see where this all began, we're going back to a time when our planet looked incredibly alien. The oceans were full of iron, more closely resembling coffee than water. A rust orange sky sat where we now see ours aquamarine. Acid rain and asteroids pelted barren mountains. How did our sensitive biology arise from such conditions? If Bruce Damer and David Deamer of the University of California at Santa Cruz are correct, life emerged just as Charles Darwin once hesitantly speculated: from a 'warm little pond.'
Warm Little Ponds
The specific ponds we are talking about are small hydrothermal pools. They are likely located on or near a volcano, and are fed by a natural geyser or hot spring. What makes these pools ideal for this proposed hypothesis? Several factors, including:
the geothermal heat source, as a constant input of energy into the pools
the inflow of water from the geyser/hot spring, to refill them when after they evaporate
the mineral surfaces containing the ponds, the importance of which will soon be revealed
the small size, relative to larger bodies of water (oceans, lakes, etc.)
This idea of having all the necessary parts for life assemble over time in one place, before eventually combining in some way, is not a new one. One famous experiment, the Miller-Urey Experiment, simulated the supposed conditions at the time when life arose, in test tubes and glassware. Their method for combining these elements into the necessary compounds for primitive life was through a spark, intended to simulate a lightning strike. They were able to show that this method could indeed produce amino acids, one of life's primary building blocks.
One key similarity between the Miller-Urey Experiment and Damer and Deamer's hypothesis is the test tubes containing the chemical solution, and the small pools. Many theories about the origin of life put forth the idea that it occurred in the ocean. This is problematic for two reasons. First, the chemical solutions that could eventually become amino acids are far more likely to dilute or drift apart in the ocean than in an isolated pond. Second, salty conditions are not conducive to life flourishing, as is shown by our inability to drink salt water to survive on a desert island. For these reasons, a small pool is proposed as the ideal site of life's origin.
Damer and Deamer's hypothesis differs from the Miller-Urey Experiment in one primary way. They don't think that a lightning strike was the catalyst behind the origin of living entities. Their idea revolves around a cycling process. The warm little pond is hydrated and dehydrated over and over, with the chemical building blocks for life slowly accumulating, and eventually entering a form of chemical evolution.
'Life' Cycles and Protocells
The cycling process of the pool filling with water, and then evaporating, worked to assemble the ingredients for life. As the pools filled, minerals and chemical elements accumulated in the pool. When the water evaporated, these materials accumulated close together. With the pool empty, a chemical film formed on the sides of the pools, like soap suds in a drained bath. The interactions between the chemicals in the film led to the creation of more complex molecules, called polymers.
Polymers are important in the development of life because of their ability to perform functions. Functions are one of the main differences between life and inorganic chemistry, like rocks. Life adapts to its environment in many ways, while rocks are resigned to their fate. To promote the development of functions, polymers had to assemble together. The rehydration of the pools was an obstacle to this, as the close-knit chemical film would be dispersed throughout the pool.
This issue was solved by the formation of 'protocells.' Thin membranes of lipids, or fats, encased the soup of polymers during the pool's empty phases. When the pool was filled via the natural hot spring, the protocells kept the polymers contained. During the next dehydration phase, the chemical film became more concentrated, as existing protocells interacted with the influx of new minerals and elements. As the cycle continued, the increasing concentration of protocells helped our new 'system of life' gain more functions and complexity.
The Path To Chemical Evolution
Increasing levels of functionality and complexity are one of life's constants, from these warm little ponds to the incredible diversity we see today. Wings, brains, thumbs, and organs are all ridiculously intricate machines. They each perform their functions with great precision and reliability. In the beginning, what passed for functionality was far below modern standards. Life hadn't yet developed the great tools that make nature so awesome. Survival was based upon the ability of these chemical soups to cling together, for dear 'life,' so to speak.
These protocells were put under great strain by the hydration-dehydration cycle. One of the primary traits that separated the 'survivors' from the 'deceased,' was the strength of the protocell membrane. Constant pressure from the pool's cycling tested the protocells' stability. Weaker membranes would been torn apart, scattering polymers. Strong membranes rode the cycle like a bull, towards their next opportunity to interact with other protocells in the chemical film. In these repetitive interactions, we find the beginnings of evolution and natural selection.
While the functions that these primitive polymers would have performed may seem irrelevant today, they would have been crucial in the warm little ponds. This primitive form of chemical evolution would have come down to factors such as membrane strength, and perhaps some kind of ability to attract other protocells. What was most important was that the groups of polymers, with their potential for functionality, were protected. Over the massive numbers of cycles in the pools, the recombination of protocells in the chemical film increased the likelihood of new, useful polymer combinations. These combinations would lead to more complex chemicals made of amino acids, including RNA. RNA has many similarities with DNA, the genetic instructions through which all life forms unfold. In this drawn out yet simple way, a quality like membrane strength in protocells is ultimately responsible for the development of our brains. All from a simple water cycle acting on warm little ponds.
Cooperation, Not Competition
Have we really found the origin of life? That remains to be seen. What we have learned about here constitutes an intermediate phase between the inorganic and organic worlds. In layperson's terms, Damer and Deamer may have found the missing link between non-life and life. At least on paper. Now begins the ringer of history. This theory will undergo rigorous experimentation. The scientific superorganism will test every point of it for cracks, like an immune system for falsehood.
Why is this theory on the origin of life different from the many other speculations that have floated around? We must go back to testable predictions. Damer and Deamer have provided a theory that is not only testable in the lab, but even in the field. Considering the time period involved here (roughly 4 billion years ago), the fact that there still exists hot springs like those proposed is incredible. We will be able to examine sites such as northern California, Western Australia, and Russia's Kamchatka Peninsula as potential scenes of this vibrant crime.
This rich resource base is one of the main reasons that I felt comfortable putting forth something without the track record of a quantum mechanics or Darwin's evolution. It also has the claim of being one of the most coherent and complete theories for the origin of life. When such a plausibly tight potential answer appears, for a question that has stumped so many scientists, it deserves our attention at least, and probably our respect and interrogation as well.
We now have a better idea of what this theory proposes about how life began. We can also find value in considering what it reveals about why we are the way we are, as well as how we should behave. Damer and Deamer's theory proposes that life started through a cycle of cooperation, not competition. The warm little ponds were arenas for collaboration. In the dehydrated periods, the protocells mingled in their polymer soup, undergoing the chemical evolution process. These periods weren't a time to fight over scarce resources. Rather, these were times of mutual support, albeit of a random nature. Any stability or function that could be gained always supported both protocells. Their relationships became those of teamwork rather than predation. Our bodies are still composed of cells in systems that work symbiotically. We should also recognize the helpful bacterial culture in our microbiome, without which we would quickly perish.
If this really is how life began, we need to use it as our new barometer for our view of nature. Many of our evolutionary images come from 19th century biologists, viewing predatory relationships like the lion and gazelle. This view of nature aligns well with capitalism. 'Survival of the fittest,' and justifying the domination of another person or business, is much easier when the urge seems to stem from this grim, bloody baseline. However, we are beginning from the wrong point. Our warm little ponds housed a struggling community of our earliest ancestors, supporting each other in an unconscious drive for 'survival' through 'natural selection.' At our present moment, with the ability to provide basic resources to everyone on the planet, we now have a scientific argument for indulging the urge for community, charity, and humanity that we all feel.
You can read the full version of Damer and Deamer's paper at: http://www.mdpi.com/2075-1729/5/1/872/htm