alt Hacker News> Maybe, most animals evolve towards larger sizes.
Animals tend towards whatever size lets them maximise survival. This is based on available niches and other selective pressures.
> Except on smallish islands, where they tend to become smaller.
Island syndrome leads to both gigantism and dwarfism.
> Animals tend towards whatever size lets them maximise survival.
Evolution is a filter that removes unfit, it does not select the best fit. So a lot of mutations that slightly decreases fitness for the environment stay as they do not make an organism too unfit. This results in a gen pool diversity in a population that helps to survive if the environment changes as previously somewhat harmful mutations can be essential for survival in the new situation.