Survival of the fittest

I was pondering on the theory of "survival of the fittest" - rightly or wrongly attributed to Darwin - while on the treadmill the other day. I like to ponder, it helps to pass the time at the gym while I clock up the miles. Listening to music or an audiobook doesn´t work for me as the background noise is too loud...

Anyway, as I was saying...my understanding of the theory is that nature ensures the fitter and brighter of each species survive in order to produce fit and bright offspring. Those less able to look after themselves will perish young, taking their poor genes with them. Thus each generation should be an improvement on the one before. A simplistic explanation but I think it captures the essence.

I just wonder why, given how long the human race has been around, we are still producing some specimens who seem to lack any commonsense whatsoever. Take for example the people who climb into wild animal enclosures and are then mauled. There are several cases every year on the news. Or those who fall while trying to take a selfie from a precarious place, or any other of the risky things people seem to do without thinking of the consequences. It´s as if their self-preservation gene is missing. Obviously I´m not talking about people who take calculated risks for adventure etc.

Food for thought, anyway!