Will humans slowly evolve to become more rational, and will there be a limit to their rationality? This question is interesting, as the rationality of our decisions affects everything from daily lifestyle choices to the political decisions that catalyze war. Further, if humans do reach perfect rationality, then would are they acting in a rational way relative to their own desires or those of society? Would this form an optimal society?
The first relevant question that anyone seeking an answer to may ask is simply, what is rational behavior? While it is definable for a situation where everyone has the same goals and information, this will certainly never be the case. So how can rationality even be measured if a person’s desires or the extent of their awareness of their situation cannot be measured. This could make it extremely difficult (if not impossible) to even apply any other predictive system to this question, unless major assumptions were made (eg. everyone wants the same thing, everyone can learn the same amount of information about their surroundings).
If these issues could somehow be overcome, then only an observational study of humans performing the same lab tests to measure their rationality over hundreds of years (or long enough for society to change drastically) could actually evaluate whether any change was achieved, but would be rather useless for prediction.
It may be possible to predict whether the population would get slowly more rational over time by some computer simulation involving a genetic population was ran many times. However, besides these results having to be extrapolated greatly to even apply to humans, it would be heavily dependent on a single evaluation/fitness function measuring rationality over an entire lifetime, which is difficult as some decisions are significantly more influential than others (eg. choice of career vs choice of favorite color) in the outcome of an individual’s life, so creating a weighting scheme for these choice requires further simulation (and then brings more error).
It would be interesting if we could argue humans are becoming more rational from historical records qualitatively, but it could almost certainly not be proved quantitatively. Further, to argue that it will continue to improve would again be extrapolating greatly.