There are lots of little things we rarely think about that this rings true for.
Like how children tend to climb trees for example.
They think it's fun, but really its a safety measure against predators. Also seen in cheetahs and grizzly bears. For these three species tree climbing is rare in adulthood, but the youngsters can't stay out of the trees. Unlike most play, it is not a form of training for adulthood but rather an evolved defensive behaviour.
Many young animals die falling out of trees while playing, and yet the behaviour remains because obviously at some stage the threat that accompanied staying on the ground was far greater.
If you've ever been a kid thrilled to climb a tree you've experienced vestigal instinct in its rawest form.
Its interesting how dishonest nature is. Tricking you into behaviour by rewarding you with happiness. Not that these behaviours are things we'd be opposed to necessarrily, but we don't get the message straight, its trickery, its brilliant really. Same could be said for sex, only recently have some organisms started consciously deciding to have children. All used to be, and most still are, tricked into reproducing.
Even the people deciding to have children are being tricked really, by their instincts, unless they're doing it to rip off the government or something. Just wanting children and not being sure why are you're instincts romanticising the concept in your mind.
People rarely have children for logical reasons.
Errandir you busted me on the society thing.
I'm not really sure what the deal is with suicide. Its an odd behaviour to be sure, I think if someone acknowledged the sneaky nature of nature I just mentioned and then came to the conclusion they won't be natures slave and committed suicide. They would be displaying behaviour that can only be described as transcending that of traditional living organisms. They might be the first people to have an argument when saying they are "above" animals.
But I'm not aware of any suicide notes explaining these motives, usually its trivial crap, indicating they are still animals, not fighting their instincts but rather cooperating with them.
So really nature tells some people to die, in the same way it tells kids to get up trees, why I don't know.