The Cambrian Explosion

2007/07/21 · by · in Bio, Ideas

Today I watched the Evolution section of a Discovery program about the 100 Greatest Discoveries. In it Bill Nye talked about the Cambrian Explosion and the Burgess shale. I remember that back in High School I had an argument with a Creationist friend about the sudden explosion of life in that era, and though I never backed down from my belief in Evolution, I couldn’t think up a reason for such an event to occur.

Now, 10 years later, with exposure to many more ideas, I independently came up with the following explanation:

  • Evolution is composed of natural selection, and relies upon variation within a population. It is a process relying upon feedback.
  • Feedback can lead to exponential returns

I argue that before the explosion there must have been plentiful unicellular organisms of many different types, all sharing their genes in a horizontal fashion. When one day along comes a means of forming a multicellular collection, benefiting it’s unicellular components. Eventually this leads to even more variation of life than had existed previously. But until the time that life ceases to share genes in a horizontal fashion things will proceed more or less the same. That is all creatures of all types will bear very close resemblance to each other.

Once an organism viciously breaks this horizontal transfer mechanism, it can then proceed to evolve along it’s own path, always with respect to its environment. Suddenly it’s descendants will inherit both advantageous and disadvantageous traits while the rest of earth microbes get nothing. Natural selection will weed out the disadvantageous lines, and genetic recombination will experiment with the more successful lines. Now we enter the feedback loop. As these genetically selfish organisms change over time, more and more ecological niches open up for more evolution to occur. Changes begin to accelerate, and suddenly we have the Cambrian Explosion.

Had life stayed with the horizontal gene transfer mechanism, we would never have evolved. Any beneficial changes made by an organism would be spread directly back into the population at large. The microbes are not genetically in competition with each other. Once privatization of genes occurs, there begins a direct competition, a riposte and parry, that jumpstarts the process of evolution.

I am not alone in this observation, apparently the eminent Ray Kurzweil has argued about accelerating change, using the Cambrian Explosion as a particular example. (just remember, I thought of it second.)