Sex and death. It reminds me of the maintenance/reproduction axis.
You mean r selection vs K selection?
That wasn't what I had in mind, but you are right: natural selection does tend to play off one against the other. And a member of H.sap. does sometime find verself in one situation or the other, so it is natural that our psyche's would be comfortable with either approach, depending on circumstances.
The r/K thing is a teensy bit different. That is more to do with offspring quality - with many vs few offspring.
The idea (from dietary energy restriction) is that organisms face resource-investment tradeoffs between self-maintenance and reproduction - and that circumstances and diet can affect where that tradeoff is made. If there isn't enough dietary energy to support reproduction, what resources are available are devoted to maintenance - so the organism can live to reproduce another day.
It is a bit like K-selection taken to an extreme where no babies a...
Update: This post has also been superseded - new comments belong in the latest thread.
The second thread has now also exceeded 500 comments, so after 42 chapters of MoR it's time for a new thread.
From the first thread: