Nature must want us to be bad at understanding black swans. (I am still, sort of, listening to The Black Swan.)
The guy who discovered that carrots are edible didn’t really think, “Hmm, there is a small chance that this is a strange variety of hemlock and I will die and thus my family will die as I won’t be there to feed them, but the odds are that I will be fine”*. The man who ate the first carrot was playing Russian roulette, like the guy who lived across the way from Nero Tulip.
Evolution is playing her own game and worries more about the species rather than the individual. Hence, it is in her interest to instil into us a blissful ignorance for hidden risks and a strong hope for hidden rewards. She stands to lose, what, just a few individuals? – but to gain a carrot-induced reproductive boost! And of course, our enterprising caveman introduces carrots to the wider populace, takes a nice cut for himself and his genes.
It’s like that old adage they pass around in finance classes: what is the best way to make money in the casino?
Answer: own it.
* It’s quite possible that his other option was certain death by starvation, which legitimises his decision entirely.
** Just something that came out of a reddit debate:
It is more correct to replace the word “species” with “kin group” and my point still stands (and I guess a species is just a large kin group). Any group that produced the risk-taking individual (phenotype) is likely to still have those genes in its gene pool (genotype). Thus, if it benefits the group, they expand in number. If such a group were basal to all modern humans, it would explain why we view risk in a way that the average insurance broker would disagree with. Consider 2 options, A and B, where A has a higher expected value. A would seem to be the right choice, but if B has a huge payoff, then an individual who does the WRONG thing and gets lucky will be selected for and expand his lineage very quickly. Yes it will be disadvantageous in the long run, but i) nobody said humans are built for the long run and ii) if he has extinguished his rivals’ lineage by sheer weight of numbers by the time luck runs out, and then there is a mutant descendant that corrects his “genetic mistake” and becomes risk averse, it doesn’t matter if all the other descendants do badly, he has still propagated his genes into the future in a way he would not have been able to had he evolved to always make the correct decision based on expected value.
If you don’t think that eating carrots is an evolutionary jackpot, think about rice. The man who discovered rice did very well genetically. But how many like him died eating random stuff?
Btw, I am not attributing a metaphysical guiding hand to evolution.