Spencer put forward the concept of fitness: “This survival of the fittest, which I have here sought to express in mechanical terms, is that which Mr. Darwin has called ‘natural selection’, or the preservation of favoured races in the struggle for life.”. Thereafter, this was clearly the concept of Darwin that has been exploited by to euthanize ethnic minorities and to sterilise “unfit co-citizens”. How much of the harm could have been avoided if Spencer would have chose just another word. For example if he would have called the fittest the most pogliwolli.
Fitness as a term is misleading since it has two meanings: We associate fitness with bold and strong people pedalling rapidly on virtual mountains in a fitness club. Pogliwolli (fitness in a Darwinian sense) is associated with having lots of offspring (and providing probably sufficient support for these to reach the maturity to breed).
Now pogliwolly and fitness are two quite different things. In a Spencer-Darwinian sense the muscular people on a spinning bike and one child and two dogs at home are not fit. An undernourished father of four in the African Sahel, however, would be fit or pogliwolli.