Are we safer with a small gene pool of only the most useful genes or with a big gene pool filled with genes we haven't yet seen any value in ?
The world we live in is indeed finite, and this allows us to imagine two extreme earthly biospheres, set along a continuum of numbers of beings from high to low.
One is a biosphere sustaining a trillion trillion trillion tiny microbes and one is a biosphere sustaining a hundred thousand big blue whales.
A tendency towards bigger entities, in a finite world, must always tend to fewer entities compared to a tendency, in a finite world, to see more of the smaller entity.
A single species populating the earth with hundred thousand blue whales represents a very small set of underused genes for a biosphere to meet the crisis of a pronounced trend to hotter climate, leading to the drying up the oceans.
But a trillion trillion trillion microbes probably represents a million distinct species and an enormous amount of underused genes to allow this biosphere to successfully adopt to a much hotter climate.
The 1940s complaint against preserving and even expanding the existing gene pool came down to the philosophic and scientific virtues of simplicity (aka overcoming personal ambiguity anxiety with a PhD) --- it was messy and untidy to have all these junk genes lying about the garage - simply 'pick the best and bin the rest'.
This implied that the future, like the present and the past, was simple, stable, predictable, controllable ---- a notion that you either accepted or rejected.
Most scientists in 1940, perhaps even today, accepted the future was simple and predictable.
Dr Martin Henry Dawson did not ---- his was a messy garage, just filled with junk genes that you never knew might come in handy some day....