Great Brains with Anderson's Artificial Intelligences: two cases of enhanced but abstracted intellect. Ythrians and Seventh Men are two cases of experience enriched by the power and physiology of flight.
With Earth about to be rendered uninhabitable by a falling Moon, the Fifth Men partly terraform Venus, incidentally exterminating Venerians, and partly adapt humanity to the new planet. Since the Venerian land surface is a few islands in a planetary ocean, some human beings become aquatic whereas others become aerial.
The Sixth Men, not fliers but fascinated by flight and living on Venus, worship not a god-man but a god-bird that is conceived in various forms:
the divine sea-eagle, winged with power;
the giant swift, winged with mercy;
a disembodied air spirit;
a bird-god that became man to give men physical and spiritual flight.
The Seventh Men, an artificially produced species:
have feathers, a leathery membrane, hollow bones, internal surfaces functioning as supplementary lungs to maintain high oxidation, hearts that beat more powerfully in flight and a normally feverish state;
experience more vividly and live more richly when flying;
hunt birds and fish and browse an artificially produced food plant that drifts in the upper air;
perform elaborate air dances;
eventually opt to fly together and commit mass suicide when persecuted by their successors, the avian but flightless giant Eighth Men.
This summary suggests the extent to which Anderson is a successor of Stapledon.