Not exactly the best example, since that's not a typical behavior but a result of poor scientific practices. Mantises only take that action when extremely stressed, which is frankly a lesson we should be carefully considering.

Or humans being able to live well past their ability to bear children. It might not make sense for an individual to live that long, but it's better for a species, since it means that you have members that aren't having their own kids, but are capable of helping care for them while the parents do other things.

yeah for us thats purely recreational.