Continuing the discussion from How Does Drift Contribute to Adaptive Evolution?:
How could drift not contribute to evolution? But “drift” is the wrong term to use here – I’ll come back to that later.
I think I’ll make this a new topic.
I’ll use part of Newtonian science as an analogy.
The Newtonians defined length. But they were basing it on traditional ways of measuring length with a portable measuring rod. They set up a platinum rod in Paris as an international standard for the unit of length.
Let’s imagine what would have happened if they had not set that standard. Maybe we would just use our own measuring rods or rulers. And as the old rulers wore out, we would create new ones. But without a standard, the new ones might be a tad different in length from the old ones. As this process repeated, we might expect the unit of length to change with each new generation of rulers. It would change only slightly. You might call that drift. But, again, “drift” is the wrong term here.
At a time when there was relatively little international travel, we might expect that the “drift” in France would be a bit different from the “drift” in England and a bit different from the “drift” in Russia.
You get “drift” because there is no standard. But actually, there was a kind of standard. The ruler that was being used would be a kind of local standard – a standard for the population that shares its ruler technology. We can think of that as an internal standard. There would be “drift” because of the lack of an external standard.
Philosophy of science
A note about science is appropriate here. The Newtonians were smart enough to understand the importance of standards. So they set international standards for just about everything that they measured.
Here’s my puzzle about philosophy of science. I’ve read a number of books on philosophy of science. And I don’t recall seeing any mention of the importance of standards. To me, this seems a serious flaw in philosophy. The philosophers of science apparently want to concentrate on things like laws of physics. Apparently, coming up with justified true beliefs is fundamental to them. But this seems to miss the point of how science works.
Back to drift
Let me mention some examples of the kind of “drift” I am talking about. An obvious example is the divergence of languages. This “drift” may start as dialect. And as the dialects get further apart, we begin to recognize them as separate languages.
Another example is currency (money). There is no external standard for the value of the unit of currency. So the value will “drift”. We call this “inflation”. In principle, we could see both inflation and deflation. But we mostly see inflation, because the politically powerful find that more acceptable, so they manage to bias the “drift” toward inflation.
What’s wrong with “drift”?
For my example of measuring length, it looks as if the unit of length will drift. But it only looks that way to us, because we are used to thinking in terms of external standards. If we were part of a population where the unit of length were drifting, we would not notice any drift at all. Everything would be in accordance with the only standard that we would know.
Maybe we could say that there would be change over time. But again, we think of it as change only because we think in terms of external standards. I’m inclined to think that the proper term is “evolution” rather than “drift”.
Adaptation
Getting back to science, for the moment, I’ll note that we don’t really have external standards. We have international standards. But the standards of science are not external to the human population. They all depend on human choices.
The Newtonian scientists did their best to provide standards. So they used the freezing point of water as a temperature standard. And they used a platinum rod as a standard of length. These standards weren’t really external, but they did anchor our internal standards to some reasonably stable aspects of reality.
In the case of an evolving (or “drifting”) population, natural selection tends to anchor the internal “standards” of the population to what will allow that population to thrive. So the internal “standards” are anchored to the environment, and will “drift” and the environment changes. And that “drift” will be such as to tend to keep the population well adapted to the “drifting” environment.
A final comment
The usual account of evolution is in terms of genes and genetic change. That sort of account is sometimes said to be “bottom up”. I think I have just given an outline of a “top down” account of how evolution works.