@doctor db - Just a minor, very pedantic point You are right that Herbert Spencer is credited with coining the term, "survival of the fittest" ( as I mentioned in my own post on the previous page).
Its wrong to say that Darwin never used the phrase though. From wiki
"Darwin first used Spencer's new phrase "survival of the fittest" as a synonym for natural selection in the fifth edition of On the Origin of Species, published in 1869.[2][3] Darwin meant it as a metaphor for "better adapted for immediate, local environment", not the common inference of "in the best physical shape".[4] Hence, it is not a scientific description"