Nagging Questions about Evolutionary Drift and Preferred Reference Systems

Usually when I think I’ve gotten something right I stop thinking about it. So it was irritating to start wondering if I had said enough about evolutionary drift. Oh well. Evolutionary drift is what we call it when a trait seemingly (and to the best of our knowledge, randomly) just ‘drifts’ into prominence. So can we tell what has happened due to natural selection and what is just drift? If we think that the trait provides some adaptive benefit we can argue on those grounds but many times we just don’t have enough data to back that claim up (think fossils). In ‘Consequences of Relativity in Evolutionary Biology‘ I argued that the phenomenon of drift was an artifact of relativity: we cannot tell in principle whether or not something is drift or naturally selected because what we count to be a mutation depends on our perspective. I believe this to be correct, but I think that others may be less convinced than I.

To remedy this more needs to be said about preferred reference systems. A reference system is a point of view in physics and a preferred reference system is what it sound like: a preferred point of view. Relativity denies that there is a reference system that is better than any other. This means that there is no one way to look at the universe. So, if you want to, you are free to declare that the earth is stationary at the center of the universe. You are free to declare the sun to be stable. You are free to declare that whatever is at the center of the Milky Way is the stable center and you are free to declare whatever it is outside the Milky Way to be the actual unmoving center, etc. It all depends on you, though explaining certain phenomena becomes more difficult depending on your choice, e.g. believing the earth to be the center of the universe worked (and still works) pretty well for almost all applications that we ever engage in. It took careful astronomical measurements of the movements of the planets that could not be easily explained with the earth at the center that caused Copernicus to move the center of the solar system to the sun (which made all the movements easily explainable).  The scientists of the day had come up with elaborate epicycle schemes to explain the motions of the planets to some success. It was that Copernicus was so much more successful at accounting for more phenomena that his account was accepted.

Now when it comes to adaptation, fitness and the like most of us really only have one perspective: our own.  We believe we know what makes us successful, what makes us smart, why we are better than the other animals.  This inherently colors our perspective on the fitness of other animals: we didn’t realize bats used sonar to navigate until after we had discovered sonar in a lab.  I guess we just thought that bats flew around blind in the dark before our advent of sonar.  This is all to say that the majority of us are currently in a geocentric, or more accurately anthropocentric, view of the biological universe.

Now I do not want to be seen as saying everyone is this way.  I suspect that there are biologists that can ‘see’ things from the perspective of other species.  The point is that when we study the changes in species most of us are limited in our perspective.  We are trying to figure out why certain mutations have occurred adding epicycles on epicycles to account for the data.  That is, we take some feature of a species, compare it to our own features, and then modify and tweak it to fit it in with what we already thought.  This isn’t wrong, but it is limited.  Recently I read a news story of a study that proposed a novel way in which birds can navigate: apparently birds can see Earth’s magnetic field . If this is correct, it would allow us to reinterpret features of birds in the same way that our discovery of sonar in bats affected our interpretation of their biology- as significantly different from our own.

Finally (again) drift: how are we to distinguish what is drift and what is natural selection?  I think the above discussion makes the distinction even harder to properly distinguish the two.  We have limited knowledge of ourselves and other species and some small change in an organism’s biology that at first glance looks irrelevant and a candidate for drift may yet enable some other feature that we are completely oblivious to. Birds see the magnetic field, squirrels’ tails heat to scare (only) predators who use heat sensing, who knows what’s next.  And who knows whether what we think one day is drift will not be natural selection the next depending on a new perspective.  But, again, this is nothing to worry about.