Darwin and his intellectual kinfolk reluctantly accepted a world in constant "liquid" evolutionary change but then reduced that change to a practical nil by making the liquid to be glass.
Glass is a liquid, technically, and over centuries will flow downward ( a very little) if left as vertical glass window panes.
Darwin saw evolutionary change happening so slowly that effectively the genome passed vertically from grandparent to parent to grandchild would be 99.99% the exact same.
But verticality was also the key to Darwin's entire structuring of reality.
In the lower level hand corner of his intellectual grid, primitive and tiny life had emerged, a long time ago, from the chemical slime.
In the upper right corner - much bigger and much more complex - was Man with an arrow of progress pointing upwards to the right ; ever upward, ever more bigger and more complex.
The lower orders, races and nations were older, smaller ,weaker and simple-minded.
The highest representatives of progress were in the upper classes of the bigger, newer nations and races.
Each stratification in this 45 degree angled vertical representation of progress over time dined with its own kind : commensality that was close, separate and unequal.
The classic representation of Modernity - as Stephen Jay Gould pointed out long ago - was that mural painted on the all of about every museum of Natural History worldwide.
Small creepy crawlies occupy the left part of the mural as civilizied Man strides confidently out of the frame at the extreme right.
In between small horses to the left become bigger horses to the right.
But Gould points out that in fact the smaller and older beings - four billion year old bacteria being the ultimate example - don't go extinct when bigger and bigger beings come along - they continue to occupy biological niches quite successfully along with their bigger pals.
And every time the Earth decides to do so global house-cleaning and kills of most of the species - it is the bigger not the smaller species that disproportionally go extinct !
Henry Dawson was not the first to observe Horizontal Evolution
(HGT : Horizontal Gene Transfer or "Transformation") but he was the first to take it seriously and to study it intensely.
It turns out that bacteria, those poor dumb simple things, have a huge number of ways of adjusting to changing environments (a huge number of genes) - but in no way are all these gene tricks found in all bacteria, because that would be far too much of a nutritional burden for each to maintain.
Instead, when times get tough, some bacteria instantly shed useful genes for dealing with the crisis and other bacteria instantly take them up and put them instantly to work.
Let civilized Man invent an antibiotic and five years later bacteria from around the world can show a newfound resistance to it.
Dawson easily intellectually also absorbed HGT.
It just became yet another color in his already growing palette of the ways the very smallest and weakest, oldest forms of life - the bacteria - manage to co-exist, survive, endure and even thrive against the toughest attacks that Life's biggest and most complex being , civilized Man , could throw at them.
It became apparent that Man and his bacteria had to learn, not to like and admire each other, but at least to agree to accept that both were bound together for all eternity : sharing, albeit reluctantly , in an open and global horizontal commensality.
Weak stupid bacteria in the lower left and big strong bright Man at the upper right framed the entire continuum of vertical stratification of life.
Such as the smaller (in vertical distance apart) but all important stratification between upper class white European protestant males and women, children, negro natives, and the European working class "beneath" them.
For Darwin claimed this apparently unfair hierarchy was a actually a perfectly aligned meritocracy and the European male was on top because he was smarter than anyone or anything else.
But to admit that the humble bacteria could slice and dice genes while the lab scientist could only watch helplessly , threatened the whole elaborate stratification justification.
Maybe genius was as likely to be found in urban testament as in leafy green suburb !
Unthinkable : so Dawson's efforts with HGT were met with icy silence.
But his earlier HGT work does help explain Dawson's seemingly quixotic effort to let SBE 4Fs thrive against the establishment eugenicists using the war as an excuse to hasten their deaths.
In a horizontal world where worth was found everywhere and anywhere, what biological, let alone moral, justification be found to let the 4F die and the 1A thrive ?
Its a very post-modern question to which Modernity had no good answer....