Answer:
Well to me it means a challenge that only those that are physically , mentally and emotionally (even spiritually ready ) ready can overcome.
But the real meaning originated from Darwinian evolutionary theory as a way of describing the mechanism of natural selection.
In his ( Darwinian ) terms the phrase is best understood as "Survival of the form that will leave the most copies of itself in successive generations."
Explanation: to be honest i dont really understand the last sentenceof my answer
Hope it helps :)
