Darwin descends into accepting Galton and Spencer as converts

Herbert Spencer - it must be said - got Darwin's Theory of Evolution just half right, as did Francis Galton.

Spencer

But Spencer got the bigger, more important, more fundamental part , right.

Spencer accepted that Evolution - all on its own - would get the mix of humans sorted right to best benefit the survival of the human species as a whole (albeit at a horrible cost to some individuals).

He thought 'the fittest' would reproduce more while 'the un-fittest' would reproduce less and in the long run would disappear.

He didn't fully consider Darwin's theory in its more subtle points.

Such that there might just be a thousand different variants of human 'fitness' , each varied for wildly different biological niches : the well-suited-to-ice arctic dweller failing to thrive under the hot desert sun.

Instead - and it was very evil-producing "instead" - he wasn't always intellectually consistent with this acceptance of evolution's main point.

So he also fretted that modern civilization's charity was letting 'the unfit' survive,  compared to their chances in much earlier times .

Spencer didn't fret that modern civilization was also allowing 'the fit' to survive in greater numbers , compared their slim chance out in the wilds of early cave life.

He was one of the many many supposedly intelligent people -then and now - who thought that if the beavers sheltered their young inside houses that was part of biological Nature, but if humans did the same , it was not.

Or if deer moved about in massive herds, to help keep their young, elderly and weak alive this was part of biological Nature but charity hospitals to do the same for us was not.

Galton

Galton, by contrast and despite being Darwin's half cousin and being a very good physical scientist, didn't get the evolutionary point that natural selection , all on its own , would always ensure the strongest survival of the human species.

(Unless a sudden massive catastrophe wiped all the species out !)

So he wanted the human elite to artificially ensure that the fit had more children and the unfit had less.

He only shared his bodily fluids with Spencer to the extent that he too worried that modern civilization's charity was keeping too many unfit alive.

I can only repeat it also kept the fit alive as well.

Which is why late 19th century humanity had almost two billion people, while back in those wonderfully bracing early cave days, it probably dipped to only 200 (obviously very fit) people !

Darwin

Darwin garnered support for his theory by accepting many strange camp followers and frequently biting his tongue.

So while he did discuss - obliquely - these two opposing theories in his later book "THE DESCENT OF MAN" , he failed to rebuke his two disciplines for not really getting his theory .

Galton , for not accepting that natural selection worked , and worked accurately because it had the widest possible variety of human capabilities to select among.

Because Galton's theory of "EUGENICS" was only going to reduce the current human gene pool, by keeping only the 'most fit' based only on current environmental conditions -- and so weaken the species as a whole as it tried to face new unknown environmental conditions.

Spencer's theory of SOCIAL DARWINISM had a number of evolutionary failings.

For a start, it failed to understand that evolution's selection worked only on inherited (genetic) capabilities, not on skills gained during life itself.

(Children of skillfully trained carpenters did not automatically become skilled carpenters at birth.)

More dangerous for the perhaps two hundred million people murdered in the name of Social Darwinism during the 20th century, Spencer tended to think of fitness as  'one size fills all' - a fit person was fit for all time and in all biological niches.

That is he tended to render fitness as a static condition (being 'fit' as we use it today to mean being in good physical shape) not dynamic (as being 'fit for this but not that').

This meant if the Germans saw all of themselves as fit for everything and everywhere and every time and the Jews as the reverse, they could meld Galton and Spencer's seeming opposing ideas together and start building a lot of gas chambers....