'Inclusion' - the concept if not the term itself - did have many defenders in late 1940, but they did so on the basis of its ethical and moral worth, not because it had been scientifically discovered to be a crucial survival mechanism.
I don't doubt for a minute that Henry Dawson genuinely cared about the small and the powerless (the big and the powerful are always already included and are never excluded).
Cared about them and wanted to see them included as potential helpers and possibly helpees.
But that hardly made the extremely diffident and un-charismatic Dawson extraordinary enough to credit as the founder of a major scientific and moral revolution.
Today we all routinely give lip service (usually nothing more than that) to words like diversity, inclusion, gene pool as being 'very good things'.
That is because the most confident portion of us are fully post-modernist, in the scientific and culturally sense, and the rest of us reluctantly and silently go along.
But 1940 was the very Apogee of modernity and all these terms were then viewed as being highly negative.
With a hubristique confidence in a simple, stable and predictable future, 1940 modernists confidently picked a few biological winners (upper class male WASPS leading the pack) and equally confidently hoped to quickly bin the rest.
Confidently defining the norm and the normal, the deviant and the decadent and the deficient, they set about to drain - rather than deepen and protect - the gene pools of humanity and of the planet itself.
Intellectually contradicting themselves, something modernists are very good (bad?) at, modernists as investors did talk much about the virtues of holding diversified portfolios and never putting all of one's eggs in one basket.
Advice they totally ignored in the area of applied biology and eugenics --- where excluding most of their society from university admission, politics, the public service, business, the front-of-buses, etc was practically an artform.
Dawson had slowly come to see the explanation for his variant on Fermi's Paradox ("alien lifeforms - where are they ?").
Dawson's Paradox was this : "the small,weak and ancient microbes - why are they still here --- and flourishing ?"
In 1940, most scientists were skeptical that microbes even had a genome let alone genome systems that in many ways were more efficient than that of humanity.
Humanity, for all the glories of its highest civilizations (here cue the glories of 1940's WWII) after all was but a single species and had been around for only a few thousand years as a civilization.
But the innumerable species of microbes, occupying every niche on Earth, despite being invisibly tiny and immobile, had survived four billion years of the worst disasters that the Cosmos could throw at the planet.
This paradox directly contradicted the Central Dogma of modernity : that Evolution was a linear process, proceeding ever upwards from the small simple and the ancient to the new big and complex.
Scientists and intellectuals, via a massive feat of cognitive dissonance, ignored this Paradox but Dawson realized he had the most likely explanation in what he called "bacterial transformation" and what Science today calls HGT (horizontal gift transferring) --- a wide generous horizontal inheritance of genes instead of our narrow selfish vertical inheritance of genes that we humans are limited to .
HGT was a process where highly useful bits of individual microbe genomes are taken up by other microbes even if from widely separated species and put to use to save them from a new environmental crisis their existing genome left them unprepared for.
The metabolic cost of every microbe carrying all the possible genes it might need to surmount unexpected new situations would be impossible to sustain.
But spread over trillions time trillions of individual genomes, microbes held survival kits for every possible crisis.
It allowed all microbes to share one immense genome spread over trillions time trillions of individual microbes each with individually unique personal genomes.
In human terms, such horizontal genetics could be compared to a human social and cultural system with a "Open Source" worldwide library of survival tips, where every single human is potentially both an author and patron.
Humanity's actual vertical genetics is like our current world where 'the suits' tightly and profitably control patents, trademarks and copyrights --- even on lifesaving drugs.
Human selfishness almost assures us that our species will not survive the first big environmental crisis that the Cosmos throws at us.
injecting the science of Inclusion into an exclusionary war
Dawson could see that the microbes' Science of Inclusion was far more evolutionary successful than our human Science of Exclusion.
This led him to his highly success WWII penicillin-for-all project - a project that has benefited ten billion of us since 1940...