Could Life Be Sustainable On a Planet Without Evolution?

I was thinking a bit about this for some reason and started wondering what other people had to say on the topic so I did a quick google search of the question. As often happens when you google a question one of the results was a Quora entry. Scanning through the various responses I came across one that caught my attention and I want to address it here. First I repost the answer from Quora in its entirety (italics mine).

Drew Smith, PhD in Molecular, Cellular and Developmental Biology from the University of Colorado

Consider the factors that enable evolution through natural selection:

  • Heritability of characteristics
  • Modification of those characteristics
  • Selective advantage of certain modified characteristics

These factors do not merely enable evolution — they make it inescapable. A non-evolving world would have to lack at least one of these three factors.

It’s hard to even imagine what reproduction without heritability of characteristics would look like, so one way to get to a world without evolution would be to have life forms that are immortal and therefore do not reproduce.

A scenario in which heritable characteristics are never modified is probably impossible. This would require error-free maintenance and replication of genetic information. The 2nd law of thermodynamics implies that perfectly (that is, infinitely) accurate replication of information requires infinite energy. So let’s rule that one out.

Abolishing selective advantage is equally hard to envision. Even in a perfectly stable environment, some variations will result in more efficient extraction of resources leading to faster reproduction and thus evolution. Unless you specify that the founding organisms are already perfectly efficient in their utilization of resources (another thermodynamic impossibility) or that there is no biologically feasible pathway toward greater efficiency, then evolution will happen.

Bottom line, evolution is inevitable in any self-reproducing system.

I do not take issue with Dr. Smith’s 3 factors that enable evolution through natural selection. There are others but those three are the major factors I would agree. However, from that point on we differ in several key respects. After listing the three factors he goes on to say a non evolving world would have to lack one of those three factors. This is incorrect. A non evolving world might lack one of those three factors or it might simply have a modified version of one or all of them.

Consider the first, heritability of characteristics. Dr. Smith says that is hard to even imagine what reproduction without heritability of characteristics would look like. The only way around this and thus of finding living beings on a world without evolution is for there to be life forms that are immortal and thus have no need to reproduce. Not having a need to reproduce is not the same thing as lacking in the ability to reproduce or lacking an interest in reproduction thought that has no bearing on my argument here. Interestingly an immortal being would have no need to evolve either though it would seemingly have no reason not too either. I like hard problems and Dr. Smith tells me this is a hard thing to imagine so I have to try. Imagine a being that is what we might define as pure consciousness without a physical body. It exists somehow and is aware of its own existence, it has a finite life span and (passively) absorbs any available energy to maintain its existence until such time as that energy is exhausted and its life span ends. In order to meet the most widely accepted criteria of life it also needs to reproduce. Let us stipulate that our BoCs reproduce by budding in a completely random fashion determined by an arbitrary quantum event about which the BoCs have no knowledge or understanding. Reproduction is what Dr. Smith tells us is hard to imagine without heritability of characteristics. In the absence of a body what characteristics would be considered heritable? Perhaps you would say that personality traits or behaviors would be passed on to succeeding generations. Our beings of pure consciousness have no personalities and do not behave in any way at all. They do not act or react, understand or learn, move or sit still, talk or be silent, they just exist. Occasionally they bud to reproduce but this occurs totally at random and without any intention or even knowledge that it is happening from the BoCs. Simply put they have no behaviors or personality to be inherited. We have just imagined what reproduction without heritability of characteristics might look like and therefore part 1 of Dr. Smith’s argument is invalidated

Authors note added post publication: obviously the above scenario is far fetched and sci-fi like in many respects. Nevertheless I was able to imagine it. I included the example for two reasons. The first, obviously was to use in support of my arguments but the second was as an example to be cautious in choice of words when answering questions of this type. Saying something is “hard to imagine” or “impossible to imagine” sounds nice but it is almost always a suckers bet. It is very difficult to defeat the human imagination. Best to leave it out and/or rephrase when trying to strengthen your position or prove a point.

Let’s now consider the second factor, modification of characteristics. Here Dr. Smith says, “ A scenario in which heritable characteristics are never modified is probably impossible. This would require error-free maintenance and replication of genetic information. The 2nd law of thermodynamics implies that perfectly (that is, infinitely) accurate replication of information requires infinite energy. So let’s rule that one out. I do tend to agree with his rather strong but supported argument that a scenario with zero modification is probably impossible because of thermodynamic constraints. However, I do not think that zero modification of genetic or other information is a requirement for a given world to be evolution free. I see no reason why a very low rate of modification would automatically imply that the processes of evolution will come in to play particularly if the environment is quite (though not necessarily perfectly — see next section) stable. The rate of change of genetic or other information has only to be lower that the rate of change of the environment for natural selection to fall out of the picture as an influence on survivability of any given living being.

We have now dispensed with part 2 of the good doctor’s arguments and can move on to the third and final part abolishing selective advantage. Dr. Smith says this “is equally hard to envision. Even in a perfectly stable environment, some variations will result in more efficient extraction of resources leading to faster reproduction and thus evolution. Unless you specify that the founding organisms are already perfectly efficient in their utilization of resources (another thermodynamic impossibility) or that there is no biologically feasible pathway toward greater efficiency, then evolution will happen. Especially given what we said in the above section on modification of genetic or other characteristics (that it must be very low but not zero, less than the rate of change of the environment) I do not think his statement holds for all situations. With a very low but non zero rate of genetic modification that stays lower than the rate of change of the environment there may never be a situation in which one of the (very rare) changes that occurs in a given being results in an advantage. The environment will presumably already have “moved on” and changed more such that whatever change occurred in the being had it given an advantage if it happened 1000 years ago, would give no such advantage in the current environment. One could plausibly argue that a being that does not evolve at least as fast as its environment does is on a fast track to extinction. I agree, one could, but one would be hard pressed to define exactly how “evolves as fast as its environment” in this sense is to be measured and evaluated. Without those definitions it would be difficult to determine cause/effect in any particular hypothesized extinction scenario.

That pretty much disposes of part 3 of Dr. Smith’s argument. We have now shown flaws or completely invalidated all 3 of the stated factors/reasons why the doctor believes living beings could not survive on a world without evolution. Does that mean we should embrace the alternative, that they in fact could. I am not prepared to go that far yet. Stay tuned. Comments welcome and appreciated as always.

Research scientist (Ph.D. micro/mol biology), Thought middle manager, Everyday junglist, Selecta (Ret.), Boulderer, Cat lover, Fish hater

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