The bottomline re:Darwinism

Darwinian Evolution Fails Cost-Benefit Analysis

Ann Gauger September 2, 2015 3:57 AM |

Imagine what would happen if (1) many corporate executives started research departments, but only one department survived cost-cutting. (2) One of the working scientists in that department stumbled on an innovation with some promise, but none of the scientists survived the next round of layoffs. The innovation was discovered again by a new hire and this time (3) he had a lucky idea but was ignored by management because the idea yielded no profit. He, along with the other scientists, was let go again. (4) Everything started all over. Eventually (a very long time later) a series of scientists rediscovered a pathway to the same idea without being laid off, and a scientist saw a way to implement it. The big payoff arrived.

Starting from the beginning, the odds of having that innovation occur would be small. In the scenario I described, no reward was seen at any stage until stage four, so for bottom line-driven management it was more cost-effective to lay off the staff than to keep paying them. The question is, could the innovation make it through the constant pruning. I set the scenario up so the payoff was realized, but in reality each scientist could have been cut at any time and the information gained in previous steps could have been lost. Only the last step had a big payoff, so once it occurred, management would see it as an innovation worth keeping.

So what is this strange scenario about? It's not about bashing management. Instead, it illustrates the difficulty of preserving an unrealized future innovation from blind cost-cutting processes.

Bacterial populations are much, much larger than my management scenario (there are 10²⁰ E. coli on the planet at any one time) and the pruning due to cost-cutting reduces things only partially. But because bacteria live in boom-and-bust cycles (they eat their resource until they run out, then die; the lucky few recolonize), this is another source of pruning and a mutation has to yield a significant benefit for cells carrying it not to be lost due to random processes. This means that any non-beneficial accumulated mutations are likely be lost at each cycle, even if they lead to a beneficial adaptation.

Now what if there had been only two steps to reach the goal, with a small benefit for the first step and a large benefit for the second? That would seem to be easy, right? Darwinian evolution would predict that this two-step pathway should be well within reach of mutation and selection, and occur readily. Yet it wasn't. In a previous post I reported that the odds are that onlyone in a trillion cells would take that two-step adaptive pathway to a high function rather than have the relevant genes deleted or broken, all due to the high (in this case, extremely high) cost of making the currently useless proteins. Cells stopped at the first adaptive step and eliminated the proteins rather than follow the two-step path to a big payoff. This surprising fact has a profound effect on the likelihood of evolutionary success.

In our experiment the cost of making useless proteins was very high. In nature the cost of making useless proteins is unlikely to be as high, but it's still enough to cause loss of new potentially useful mutations. Experimentshave shown that bacteria tend to ditch genes (and proteins) they don't need. By our calculations, because of this and other factors involving population dynamics, any pathway requiring more than three neutral steps will be beyond the reach of purely unguided processes, even in bacteria. Bottom line: the cost of expression can definitely impede the pathway to Darwinian evolution.