As far as we can determine bacterial-like microbes were the earliest primitive #cells on this planet. One favorite theory suggests that as the hot, primitive earth cooled over millions of years a point was reached when it became possible for liquid water to exist on its surface. Gradually, over eons of time, as the skies poured rains upon the steaming rocks, water accumulated into lakes, rivers and oceans. For tens of millions of years these waters remained hot, only slowly cooling. The high temperatures extracted minerals from the rocks and accelerated chemical reactions. The minerals, along with the carbon dioxide, nitrogen, ammonia, sulfur, methane, carbon monoxide and other gases in the fiery primitive environment interacted chemically in a billion billion different ways to produce a cornucopia of chemicals that formed a chemical soup in the earth's oceans and ponds. The prebiotic earth can be viewed as a massive chemical beaker in which compounds were continuously forming, breaking down and reforming again in new and varied configurations. This chemical soup was also bombarded, throughout the ages, with powerful UV radiation and with lightning from massive storms that raked earth for millions of years. The energy from these sources induced additional bizarre chemical reactions causing a mixture of chemicals to rain from the sky. As a result of these activities every chemical compound allowed by natural law formed, was destroyed and formed again, each time with a new mix of other chemicals. With time, as the earth continued to cool, more and more chemicals that were stable at the cooler temperatures accumulated giving the chemical soup a new character. As a particular mix of chemicals began to accumulate the energetics of concentration (mass action) drove the formation of additional, complex polymeric compounds from the concentrated precursors. Because of the concentration of carbon on earth and the special chemical nature of the carbon bond, organic compounds were common in what has become known as the "organic soup" that virtually covered the earth. Since many of these unstable complex compounds tended to be larger molecules (#polymers) there was a gradual amassing of larger, more complex molecules many of which stored energy in #weak bonds. As these macromolecules grew in variety and complexity those that gained additional stability by taking on #shapes that augmented their survival further accumulated in the primeval organic soup. In other words the normal course of events were driving the chemistry in the direction of increasing complexity and size. Many molecules took on configurations or shapes that caused them to bind with various degrees of affinity to other molecules, which led to additional stability and to new types of chemical interactions and still another level of complexity. The actual sequence of events that produced what we would recognize as a living organism seem, in their complexity, beyond comprehension. However, considering the time scale involved; i.e., even though 10,000 or more years might pass between each of the individual steps leading to life, that period is but a tiny fraction of the millions of years available for something to happen. Further, as there was no life to digest the complex organic molecules that formed, they could remain available for extended periods, during which they could interact with billions of other molecules until, quite by random chance, a successful combination was stumbled upon. Fueling chemical variations was the continuous influx of energy from the planetary fires and the warming sun. This supply of energy provided ample fuel for endless chemical processes to occur.

As the number and variety of complex, interacting molecules increased in the organic soup the rate of molecular interaction grew apace due to the multiple possibility of #interactions built into large molecules. A form of molecular evolution occurred. On a cooler earth millions of unique environments of temperature, light, mineral concentration and other variables developed, each condition imparting its affect on the activity and character of the abundant organic molecules. A crude form of natural selection occurred, selecting and reselecting which molecules would survive in each environment. Some of these complex molecules took on the characteristics of organic catalysts, what we call #enzymes, in that they catalyzed the breaking or forming of specific chemical bonds. Molecular evolution favored those molecules that performed reactions that eventually produced more of themselves (e.g. by raising the precursor's concentration). This organic sea would contain #hydrophobic lipid-like, molecules that spontaneously clustered together forming #lipid membranes which, when shaken vigorously as in the action of waves, formed tiny hollow balls, inside of which were trapped a mix of other molecules present in the water when the ball or vesicle was formed. #Hydrophilic molecules that couldn’t penetrate the lipid barrier were entrapped and isolated from the chaotic external environment in these closed vesicles. In this milieu randomly isolated molecules were concentrated under conditions that would allow them to interact with each other without interference by other molecules. In short, such vesicles could be considered proto-cells. One characteristic of lipid vesicles is that they easily fuse, mixing the contents of each and then subsequently break apart by mechanical action forming the equivalent of daughter proto-cells. This situation offers the possibility of separate, but limited molecular interactions occurring in billions of lipid vesicles over millions of years that would repeatedly fuse and split apart. Molecular evolution would inevitably lead to the increased survival of vesicles that contained molecules that would interact with the lipid membrane in ways that would stabilize it. Over time the random fusion and separation would bring together numerous, but limited, molecular groups. Some of these would interact in unexpected ways, one of which would be to improve the stability of the vesicle. Thus a form of super vesicle would gradually develop as tiny, incremental random additions led to the accumulation of survival characteristics.

Further speculation as to the order of the events that ultimately led to the first living cell is not profitable here. However, it is reasonable to assume that the first cell was probably woefully inefficient (by today's measurements) at everything it did. That is, compared with the lean, mean, competitive cellular machines of today, C-prime wouldn't last 10 seconds; it would be as a lamb among famished tigers. But no matter, as C-prime's advantage over chaos was monumental and might be likened to that of a sighted person in a land where everyone else is blind. Consider that C-prime found itself in a rich medium, a virtual world-wide cornucopia of organic wealth, that it had only to float through while plucking the occasional molecule it required. This Eden-like existence could not last, as physical demands would require that some form of reproduction occur, if for no other reason than to limit the size of the growing C-prime, gorging itself at the worldly table of goodies. The resulting daughter cells that broke off would, in turn (as children are prone to do), demand their share of the organic Eden. Random mutations would inevitably lead to mutant cells that regulated their reproduction and other biochemical activities so as make them MORE EFFICIENT. These mutants would be at a competitive advantage in that odd small (or large) puddle with its limited supply of organic goodies. Once this path was taken it was impossible to stop as mindless competition for increasingly limited resources invariably leads to the brutal application of the "survival-of-the-fittest" natural law (natural selection). Thus as the daughters of C-prime spread across earth into billions of different environments countless contests for survival occurred as each cell sought, through the blind chance of random mutations, to gain an advantage in the ceaseless struggle for life. Once taken there was no way to leave this path and live; the rule was: COMPETE SUCCESSFULLY OR DIE.

FAQ: "If the formation of life on earth was inevitable, given the unique environmental conditions and the long time available, did it happen more than once?".

ANSWER: While that possibility can not be precluded, life probably didn't arise more than once. However, proto-life may have arisen frequently, only to be snuffed out by random events (e.g. meteors). Even the most ardent evolutionist would admit that while the formation of life might be inevitable, given the time frame, the randomness of the events leading to life would make it highly unlikely that two such independent events would occur close together (e.g. within a million years of each other).   It is also assumed that C-prime would hold such an advantage over any following living cell (C-late-comer) that its ascendancy would doom any subsequent, less robust, life form to an early extinction. However, some have proposed that life developed numerous times during the earth's existence, but that it was destroyed by various cataclysmic events, only to pop up again. What appears abundantly clear from the life that currently dominates the planet is that it (including MANKIND) arose from one common ancestor which subsequently evolved into the multitude of life-forms we see around us today. So even if life did develop more than once during the history of our planet, one form won the evolutionary jackpot (i.e., it ATE its competitors).

FAQ: "Can we create life in the lab?".

ANSWER: Starting with a flask containing the components of the primitive earth (the contents of which we don't know for certain), probably not, unless we plan to follow it for several million years or so. Even then we could never repeat the exact environmental conditions that were crucial to the formation of life. But what would happen if we fudged a bit and started out with a mixture of the known organic makings of life; like say grinding up a rat or two, removing all forms of life (don't forget the inevitable viruses) and putting this mixture in a sealed flask and stirring for a while? Frankly, I don't have a clue, but I do suspect that it would be difficult to get money for such a project.

FAQ: "How do you know that GOD didn't create life if you can't recreate it in the lab?"

ANSWER: Obviously, science can't prove that GOD did or didn't create life, making this a circular argument. All the reproducible data we have supports the contention that the universe operates on unbreakable laws. Everything we have learned about life indicates that it works within the framework of these natural laws; i.e., it is not "miraculous". Science does not deal with the origin of the natural laws, but only with identifying what the Natural Laws are (in this universe) and understanding how nature works within their confines. If people wish to believe that GOD wrote these natural laws, so be it. There is no credible SCIENTIFIC data to indicate that GOD has broken any since they were first "written". In this case GOD might be viewed as a coach who wrote the rules to the game but who now sits in the stands as a spectator.

The emphasis in this course is on bacteria, which seems appropriate since they are the life form that has been around the longest. In this sense it seems only fitting that they should receive the lion's share of our attention. After all, being the first they are our ancestors in every sense. All subsequent forms of life can correctly be viewed as variations and/or modifications of the bacterial theme. Viewed this way, the study of bacteria is a study of ourselves, for whatever abilities we have, including our ability to think and reason, arose in a primitive form first in the bacteria and has only been modified and augmented over time to meet the changing needs of evolutionary adaptation. For example, many bacteria sense specific wavelengths of light ; i.e., they see colors. Our eyes are simply an expansion (albeit a significant one) of that ability.

For another perspective visit this site.

Copyright © Dr. R. E. Hurlbert, 1999.
This material may be used for educational purposes only and may not be duplicated for commercial purposes.
SCIENCE HALL, ROOM 440CA
PHONE: 509-335-5108
FAX: 509-335-1907
E-mail address: hurlbert@wsu.edu or hurlbert@pullman.com