By Robert Hazen, George Mason University
We know that life on Earth evolved by a two-step process. The first step, called chemical evolution, marked the transition from non-life to life. Somehow, by chemical processes, rock and water and air became the first living thing. Then we have biological evolution. Now, how did that take place? Read on to find out.
The Origin of Life
Biological evolution posits, that, at some point on the ancient Earth, a living organism appeared. That organism may have been an inevitable product of some chemical process; it may have been a very rare, improbable event. It may have been a miracle, in fact.
But in any case, life did arise at some place, at some time, in the history of Earth. Science is not yet in a position to answer the question of life’s origins definitively. We don’t know, for example, whether it formed at the surface, at the ocean-atmosphere interface, or whether it might have formed in a deep hydrothermal zone.
Of course, the situation may change if we find life on other worlds, or if life is produced in a simple laboratory experiment. In that case, we’re going to be able to say, with much more certainty, how life arose. Presently, the origin of life remains one of science’s most tantalizing unanswered questions.
This is a transcript from the video series The Joy of Science. Watch it now, on Wondrium.
The First Living Organism
Nevertheless, we do have abundant observational evidence to guide us in our understanding of life’s history since that first living organism, which was at least four billion years ago. The first living organism found itself in an ocean, rich in synthetic nutrients, and had no competition.
Thus, life, we now suspect, spread around the earth in essentially a geological instant. It was gobbling up that free lunch that was the nutrient-rich ocean. For a time, it grew unchecked. One can imagine one cell, one organism, multiplying and becoming two, four and eight, in a geometric progression; gradually filling all the available niches where life might exist.
During biological evolution, it is believed that once life multiplied, it consumed much of the food, and began to compete with itself for ever more limited resources. There’s a universal axiom of complex physical systems that competes for limited resources. This is what brings change and evolution, often with increasing complexity as it progresses.
A Complex, Competitive, Evolving System
This is, in a way, similar to, say, the evolution of cars. The first cars were very primitive, with open carriages and very small motors. Over the years, as more car companies came along and more competition came along, cars became more and more sophisticated, with more pressure each year to produce new and better models; more efficient, safer, more luxurious in styling, and so forth. Cars evolved because of that competitive pressure. We see this tremendously in computers.
Once again, compare the original analog computers, using vacuum tubes, with the modern versions. Again, with lots of competition, along with consumers that want faster computers, that can do more things and are easier to use, computers evolved very rapidly in that competitive environment.
Thus, again and again we see the same patterns emerging in a competitive system. Everybody’s trying to win, so they keep evolving and getting increasing layers of complexity. Needless to say, the same thing is true for the evolution of life. Life is a complex, competitive, evolving system.
Descent From a Common Ancestor
The evolution of life by descent from a common ancestor is the central, unifying theme in biology. This idea is at the root of our understanding of genetic mechanisms of cellular structures, and also the molecular building blocks that are common to all known life forms.
And yet, before examining this compelling evidence, the overwhelming evidence for evolution, one has to think about another idea-one that connects science and religion.
Interestingly, evolution has, over the years, become a very controversial topic. It, more than any other great principle of science, has become a lightning rod for attacks from fundamentalist religious groups, in North America and elsewhere around the world. While there are many different religious beliefs related to life and human origins, the doctrine most at odds with modern scientific theories is called creationism—an aspect of fundamental Christian belief.
Common Questions about the Biological Evolution of Life
The first living organism found itself in an ocean rich in synthetic nutrients and had no competition. Thus, life, we now suspect, spread around the earth in essentially a geological instant.
During biological evolution, it is believed that once life multiplied, it consumed much of the food, and began to compete with itself for ever more limited resources.
The evolution of life by descent from a common ancestor is the central, unifying theme in biology. This idea is at the root of our understanding of genetic mechanisms of cellular structures, and also the molecular building blocks that are common to all known life forms.
