Parallel Future Histories

The "Cold Lairs" in Kipling's The Jungle Book, which are referenced in Poul Anderson's Starfarers, 20, reminded me of something in Poul Anderson's Technic History which turned out to be the "Cold Valleys" mentioned by Ruethen of the Long Hand near the beginning of "Hunters of the Sky Cave" although, since it seems that Ruethen's tribe inhabits these valleys, maybe they can count as "lairs"? 

We cannot read one future history without thinking of others. They occupy parallel timelines. And we should never forget Robert Heinlein's Future History which was the inspiration for Anderson's Psychotechnic History. Volume I of the Future History is The Man Who Sold The Moon, a collection of six stories including two about the title character, DD Harriman. The opening volumes of Anderson's Technic (not Psychotechnic) History were Trader To The Stars and The Man Who Counts, three stories and one novel about the title character of both volumes, Nicholas van Rijn. Since van Rijn reappears in four subsequent volumes, he becomes a much more rounded and colourful character than Harriman and sponsors several substantial successors. The Future History needed to have been much longer than it became which I think was the original intention.