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.
很简单：几千年前， 我们发现如果我们继续 做同样的事情，我们就死不了。 因为我们以前所做的， 肯定让我们生存下去， 所以只要我们继续这么做， 我们就没事， 不去尝试新事物是很合理的， 因为新事物可能会杀了你。