Aliens In Future Histories

In Robert Heinlein's Future History collection, The Green Hills Of Earth, the first person narrator of one short story reminisces about his contacts with Martians whereas the viewpoint character of another short story interacts briefly with Venerians. In Heinlein's Future History novel, Methuselah's Children, the Howard Families meet two intelligent species when they venture beyond the Solar System. These three instalments account for the only four encounters with extraterrestrial intelligences in the Future History.

How much richer is Poul Anderson's Technic History featuring many intelligent species and also many closely observed details like the influence of Planha on Anglic when human beings and Ythrians jointly colonize the terrestroid planet, Avalon. Both human and Ythrian Avalonians fight to remain in the Domain of Ythri and not to be annexed by the Terran Empire. Some human beings serve the Merseian Roidhunate. Some beings of Merseian descent form a minority in the population of the humanly colonized planet, Dennitza, where they are loyal to the Emperor, not to the Roidhun. We read about several of these species often enough to learn what they are like.