Friday, 27 June 2014
In "Starfog," the last story of Poul Anderson's History of Technic Civilization, descendants of the Aenean rebels who fled from known space at the end of The Rebel Worlds, have spent so many generations ingesting, and becoming dependent on, heavy metals and becoming tolerant of ionizing radiation that they can no longer interbreed with standard humanity; they are no longer human.
In "Watershed," the last story of James Blish's pantropy series, Earth has changed so much that it will now be colonized by Adapted Men while standard humanity must adapt to the new social role of a racial minority - a historical watershed for the sometimes despised Adapted Men.
These different scenarios have in common the understanding that, over long periods of time, everything changes, from planetary environments to DNA. And there is no unchanging human nature.
Compare and contrast:
James Blish's four "pantropy" stories, collected as The Seedling Stars;
Poul Anderson's four post-Terran Empire stories, collected in The Long Night and again in Flandry's Legacy.
Both these tetralogies are hard sf with interstellar themes:
Blish's theme is artificial adaptation of human beings to extraterrestrial environments;
Anderson's theme is natural adaptations by human beings left isolated in extraterrestrial environments.
When I had explicitated this comparison, I realized why I had been thinking of these two series in parallel.
The pantropy series is a short but complete future history, covering:
an early interplanetary period;
intermediate periods on two extrasolar planets;
longer term galactic hegemony for humanity in its many adapted forms.
The post-Empire stories also cover a future historical period:
post-Imperial anarchy in the mid-fourth millennium;
an intermediate period while the Allied Planets restore interstellar civilization;
longer term, human civilizations have spread through several spiral arms and one is served by the Commonalty.
The main difference is that the post-Empire stories are not complete in themselves but are merely the concluding section of the much longer History of Technic Civilization.