Abiogenesis, the origin of life from inorganic matter some 3.5 billion years ago, remains one of the central mysteries of biology. The confounding and engaging nature of how life began is also a question of how (or why) human life began.
The very question seems to destroy something of an implacable binary central to our understanding of the world. It suggests that the relationship between animate and inanimate matter between ourselves and the ground we walk on is more of a continuum than a line in the sand.
An Autocatalytic Reaction
There is a significant debate amongst scientists in the field as to the precise nature of life’s first origins from inorganic matter. Still, most consider one foundational idea to be factual.
Most scientists now believe an autocatalytic chemical system was in play before life began, the existence of which was key to life’s origin.
What do we mean by autocatalytic? In chemistry, a catalyst is a thing that helps engender chemical reactions or allows those reactions to function more quickly (or more efficiently). A catalyst catalyzes. In the human body, several well-known catalysts help keep our bodies healthy and running.
Take lactase, for example. Lactase is a catalyst that the human body produces that helps us break down milk for our consumption. When human beings are lactose intolerant, they lack properly functioning lactase in their body to help break down the milk.
An autocatalytic reaction would be a catalyzing chemical process that produces more catalysts to continue the catalysis. In other words, the autocatalytic system is autonomous because it creates the material required for its perpetual existence.
The autocatalytic reaction theory’s broad acceptance ends at the thought of its existence. Beyond the fact of an autocatalytic chemical reaction engendering life’s origins, scientists have demonstrated two different theories as to the nature of the autocatalytic reaction that began life on Earth.
Theory 1: Replication First
The first theory of autocatalytic reactions that created life is known as “replication first.” In this theory, there are compounds known as oligomeric compounds (some commonly known oligomeric compounds in the human body include hemoglobin and peptide) that helped catalyze the emergence of life through their self-replicating ability.
The self-replicating nature of oligomeric compounds is not under debate and has been a firm establishment for more than 100 years. What is up for discussion with the “replication first” theory is whether or not such replication could feasibly allow life to form from nothing.
Theory 2: Metabolism First
In the second theory, it is not a self-replicating system that allowed for the emergence of life but, as Stuart Kaufmann suggests in Investigations, cyclic metabolic systems formed before the advent of life.
The so-called “metabolism first” theory demonstrates a model of life whereby a system existed via catalysis, creating energy of its own accord. This energy is what stimulated the emergence of a self-replicating life form from the primordial soup.
Theory 3: Metabolism and Replication
The third and final theory for a pre-life system that engendered the existence of life on Earth is a compromise between the first two theories. It states that systems may have simultaneously existed — that is, those of self-replication and metabolism that paved the way for life.
Is Pre-Darwinian Evolution Possible?
A single hypothesis unifies the three theories outlined above: namely, that evolution existed before life. In other words, an evolution not related to the passing on of genetic traits from parent to offspring, but rather a non-competition-based shift that allowed Darwinian evolution to form.
In Marc Tessera’s paper, Is Pre-Darwinian Evolution Possible, he brings to light two significant problems that an autocatalytic self-replicating system would need to address to “evolve” such that Darwinian evolution as we know it would be possible.
The first is the question of heredity. For evolution to exist, Tessera argues that there must be a “passing-down” of genetic information, whereby mutations can occur and progress towards efficiency may be achieved.
The second is the question of chirality. Chirality is a complex topic in biology that is beyond the scope of this article. Still, we may state a simple definition. Chirality describes a molecule whose shape is asymmetrical, but that forms a symmetrical shape when put next to its mirror image.
Though the question of symmetry may seem obscure and unimportant in the grand scheme of life, we can boldly claim that, in fact, life as we know it would not exist without chiral molecules. Most significantly, our genetic material (DNA in humans, although it would have been RNA in the first molecules) is chiral. The fact that they are chiral allows them to replicate. Their replication is central to life.
1, 2, or 3: Choose a Door
With Tessera’s contention that the question of chirality and heredity must be present in a pre-Darwinian system, he brings up problems with all three theories mentioned above in his paper.
- The first theory of “replication first,” Tessera claims, doesn’t appropriately solve the question of chirality, though it adequately addresses the problem of heredity.
- The second theory, “metabolism first,” Tessera claims is the least plausible as it addresses neither the questions of chirality nor heredity.
- The third theory, a combination of the first two, still doesn’t explain how and why chiral molecules first came into being to allow for Darwinian evolution to occur.
Abiogenesis: What We Don’t (Yet) Know
Addy Pross and Robert Pascal have developed a theory concerning a general principle of the origins of life, its continual perpetuation, and its evolution. Their theory, called the Dynamic Kinetic Stability theory (DKS), states that persistent stable self-replicating systems tend to move towards greater stability.
What is significant about this theory is that the stability the authors refer to isn’t the typical stability we think of in the field of thermodynamics. Instead, this theory states that self-replicating systems are more likely to become increasingly complex because this complexity helps to increase their efficiency and thereby their longevity or stability.
What remains beyond our grasp are some key questions. As Marc Tessera points out above, the existence of chirality in a self-replicating system would need to exist for life as we know it to emerge.
One plausible solution would be that nucleic acids (that is, the molecules that make up our DNA) help establish self-replicating networks of the kind we’ve mentioned above.
Nucleic acids can replicate through a process called “template binding,” in which the chiral nature of the molecule is taken advantage of to produce a copy. Scientists are unsure whether template binding is a crucial aspect of an autocatalytic system of the kind we described above or whether such a system could exist without that.
Above, we’ve given just a few of the many unanswered speculations regarding abiogenesis. As you can see, the questions in some way dominate the present answers. However, there is one promising idea presented in Pross and Pascal’s paper.
When Darwin developed his theory of evolution, he merely set a ball rolling. The exact mechanics of evolution, or the “how” of evolution, remained unanswered.
The theory of evolution was nevertheless a breakthrough in scientific thought. It permitted thousands and thousands of scientists throughout the years, from Friedrich Miescher to James Watson and Francis Crick.
It’s similarly possible that the theory of DKS may enable countless chemists and biologists to “hit the lab,” so to speak, and work out the answers to many of our outstanding questions.
Abiogenesis: What We May Never Know
Though it is widely agreed upon that abiogenesis is a description of an actual historical event and that autocatalytic processes were a significant part of this event, the ever-elusive “how?” remains beyond our grasp.
How precisely was it that life sprung from organic matter and began the long cycle of evolution that allows you to read this article that we’ve written? This one question may always remain a mystery.
Furthermore, the biggest mystery of all is how all this matter came to be in one place at one time to allow for the development of chemical processes. All of this is beyond our grasp and likely always will be.
Much of abiogenesis remains a mystery, although we do have the answers to some questions. Here are some of the most frequently asked questions on the web.
What is an example of abiogenesis?
Abiogenesis is also known informally as the Origin of Life (OoL). The only example of abiogenesis that remains scientifically plausible is the emergence of single-celled organisms from organic matter 3.5 billion years ago.
Is spontaneous generation the same as abiogenesis?
Spontaneous generation is the long-debunked idea that in daily life, living beings emerge from non-living entities.
One of the most commonly cited examples of spontaneous generation is the emergence of fly larvae on rotting meat. Random generation holds that these larvae emerged from the meat spontaneously. Science and common sense tell us that flies laid their eggs there.
Abiogenesis, then, is different from spontaneous generation in that abiogenesis describes a historical event whereby life emerged 3.5 billion years ago.
Who disproved abiogenesis for the first time?
Creationists have long disapproved of the abiogenesis theory of the origin of life. It was Antonie van Leeuwenhoek, however, who first disproved spontaneous generation.
Using a single-lens microscope, he documented the development of small animals like fleas in great detail, which eventually led to his disproving of the idea of spontaneous generation of life.
Who first promulgated the theory of abiogenesis?
Long before our present-day microscopes, a man once referred to as “The Master of Those Who Know” promulgated a theory that was a forerunner for the abiogenesis theory. This man’s more commonly recognized name is Aristotle.
Aristotle’s theory was the theory of spontaneous generation. In this theory, he held that flies spontaneously generate from rotting meat. While this has long been disproved, Aristotle’s thoughts in this area went a long way in developing the theory of abiogenesis.
What is the evidence for abiogenesis?
Microfossils found in Northern Quebec suggest that life formed very soon after the oceans. This discovery gives credence to the theory that some historical event enabled the development of the systems whereby single-celled organisms could arise from organic matter.
Why is the theory of abiogenesis just another example of the idea of spontaneous generation?
In short, it’s not. Though the fundamental principles of the two thoughts consist of life arising from organic matter, in reality, the two are entirely different.
Spontaneous generation holds, for example, that maggots come naturally from meat and become flies. This idea is ultimately aversion to the concept of evolution, as rotting meat has minimal genetic similarity to a larva. In contrast, a mother fly has genetic material that is nearly identical to her offspring.
In contrast to spontaneous generation, abiogenesis is a reasonable proposition following everything we know about evolution. In abiogenesis, a pre-Darwinian self-replicating system allowed for the emergence of single-celled organisms which directly inherited their genetic material from this system.
Life sprung naturally from an autocatalytic system that provided energy and mechanics that allowed for the development of single-celled organisms. Though clouded in the fog of time, this historical event remains factual (as far as we can tell).
Beyond that, though, many questions remain a mystery. These questions include: Where did the organic matter come from? What is it doing? For what purpose is it doing it? Do any of the laws of chemistry, biology, and physics even exist?
The greatest mysteries of life, namely who or what are we and why are we here, will always remain matters of speculation. In all of the major religions, living the mystery is a central aspect of practice. In Christianity, this is called faith. In Buddhism, these principles are outlined in the Vajrayana and elsewhere.
As it is almost always appropriate when confronting the mysteries of life, we may conclude by turning to the words of an artist. As Frank Herbert, the author of the acclaimed Dune series, once said, “the mystery of life isn’t a problem to solve but rather a reality to experience every day.”