I was wondering if we could think about experiments to falsify natural selection . According to this wiki : we could invalidate natural selection
“...if it could be shown that selection or environmental pressures do not favor the reproductive success of better adapted individuals”.
So, to test this hypothesis we would have to:
- Have different individuals that are defined as more or less adapted to a given environment
- Put them in that environment
- See if the better adapted individuals have a better reproductive success. (I will avoid the word fitness because one can consider it already contains the principle of natural selection)
But is it possible to define a priori that an individual is more or less adapted? Of course, we could suppose a priori that because of some or other trait (higher longevity, higher stress tolerance, or whatever), an individual carrying that trait will be more adapted. But if we find out this individual does not have a better reproductive success in that environment, we could conclude it was just not the right trait to be better adapted and it would not invalidate natural selection.
Isn’t it, on the contrary, the fact that some individuals have a better reproductive success which allows defining them as better adapted a posteriori? There would then be some kind of a vicious circle.
Ok, so one could say that we do not need to define a priori better or less adapted individuals. We could just put individuals in an environment and see if at least some have a better reproductive success. That would mean that they are better adapted –and so that natural selection occurs-. But suppose we find no significant differences in individuals reproductive success: that could indeed mean that natural selection does not exist. But, well, that could also just mean that there was no selection pressure in that environment.
So if we want to test natural selection existence, we need either to get individuals that are a 100% sure better adapted than others; or environmental conditions that 100% sure exert selection pressures on organisms ; and we need to know this a priori. But, it seems to me that considering an individual as “adapted” or an environment as “selective” can only be done a posteriori if we already accept the idea of natural selection.
That’s why, to me, it is difficult to think of an experiment that would falsify natural selection. Is natural selection falsifiable ?