It's very simple: Many thousands of years ago, we discovered that if we carried on doing the same things, we wouldn't die, because the things that we've done before by definition didn't kill us, and therefore as long as we carry on doing them, we'll be okay, and it's very sensible not to do anything new, because it might kill you.
Es muy simple: Hace miles de años, descubrimos que si continuábamos haciendo las mismas cosas no moriríamos, porque las cosas que hicimos antes por definición no nos mataron, y por lo tanto si seguíamos haciendo eso, estaríamos bien, y era muy sensato no hacer nada nuevo, porque podría matarnos.