Dougal Dixon's After Man: A Zoology of the Future (1981) was an exhilarating exercise in non-fact speculation, presented as a popular text of 50 million years hence. The quirks of evolution and selection pressure become alarmingly vivid when today's stable-seeming species are seen as mere transitional forms. One colourful section imagined a long-isolated bat colony, diverging to fill all available niches: vaguely seal-like divers, flightless plains predators hunting by sonar, and so on.
In that book, interfering humanity was assumed to have long since become one with the dodo and Tyrannosaurus rex. This time Dixon contemplates not merely what evolution might do to us but what, armed with the toolkit of genetic engineering, we could quite rapidly do to ourselves.
Which brings future possibilities queasily close to home, as changes in "mere animals" did not. An adapted vole of 50,000,000 AD is less bothersome than the reminder that we might not be so very stable or special. Long ago, H.G.Wells in The Island of Dr Moreau and Jonathan Swift with his Yahoos both played with this instinctive dread. Man After Man works it out it in imaginative, sometimes depressing detail.
Like an SF author contriving a setting where his beloved plot will work, Dixon fudges his speculations somewhat. If human descendants could be made aquatic, one agrees they might resemble the imagined creature here (not something I'd care to meet in a dark swimming pool), but would such engineering actually be performed? SF often speculates about adapting people for spaceship life – the major visible change usually being extra hands replacing feet to aid zero-gravity agility, as in Brian Stableford's and my The Third Millennium – but Dixon goes further with a genetically and surgically revamped "vacuumorph" designed to work in space without protection. Would we really opt to manufacture a slave race of these grotesques in their spherical exoskeletons (sorry – a speciesist remark), reliant on high technology to keep them alive, and unable to live on Earth? Well, we're a funny lot... but spacesuits seem more economical.
The biggest question-begger of all is the idea of repopulating a polluted Earth with adapted humans who lack intelligence. Dixon forces this card on us because intelligence mucks up the selection process he plans to display (a bright race adapts the environment and not vice-versa). Plain-, tundra- or tree-dweller, social animal, symbiote: Homo dumbo is convincingly shown as changing and diversifying to fit every handy niche. The initial premise once accepted, this is good, striking stuff – imaginary developments vividly illustrating real science.
(As for unreal science, I note some passing references to "telepathy". In general this actually denotes communication/control by direct nerve contact – perhaps feasible. In one case, though... a specialized social human with remote-viewing powers so great that eyes and ears have atrophied? Naughty, naughty.)
This is a superior coffee-table production, illuminating and fun rather than strictly realistic. Buy it as a present, not as a textbook.