No matter what kind internal inconsistency or awkward external evidence flies up in their faces, supporters of that ever elastic science Eugenics (big shoutout to J Carroll !) always seem to find a ready explanation, helped by the fact that their's is a very undemanding faith.
Darwin's Evolution said that the fittest species & individuals in Nature were those that produced the most descendants --- and that humanity was fully part of Nature.
Eugenicists fully agreed with that definition - until they had to explain to themselves why they also believed that the 'strongest' humans were becoming practically sterile and that the most 'feeble' humans were having the most children.
Then it turned out that, to eugenicists, humanity was - actually, ahem - both fully in Nature and fully out of it : an atheist echo perhaps of 'Son of Man but also Son of God' ?
So eugenicists decided that Mother Nature demanded humans selectively thrown out all the humanitarian bits of human civilization, while keeping keep the other good stuff, like automobiles and telephones.
Eugenicists were even willing to keep civilization's hospitals - but only for those able to pay for them.
For those who couldn't afford hospital care, these feeble-because-poor were to be figuratively banished to live out in the dark wild woods, there to be winnowed out of existence by Mother Nature's tough love mantra of 'root hog or die'.
Civilization, the eugenicists claimed, only kept the feeble alive because of misguided Christian concepts like charity to the weak ---- and then the ingrates dared to breed like rabbits.
Then eugenicists claimed that modern civilization also offered such seductive temptations to the best of men and women that they tended to enjoy themselves rather than make babies to secure the future of 'the race'.
This explanation satisfied the undemanding eugenicists but in reality, Darwin's Theory of Evolution was of the universal and eternal sort and did not really tolerate species deciding to step in and out of its dictates on mere whim.
So Dr Henry Dawson wondered (and wondered productively : see penicillin and DNA) why the microbes, supposedly the very feeblest of beings and those who should therefore be at the very back of the race for reproductive success, were actually the most fecund of beings.
They were hardly being kept alive only thanks to misguided Christian charity, were they ........