Explanation

Poul Anderson, The Man Who Counts IN Anderson, The Van Rijn Method (Riverdale, NY), pp. 337-515.

At the end of Chapter XIX and the bottom of p. 491, Nicholas van Rijn begins to address Diomedeans. At the beginning of Chapter XXI, half way down p. 497, he finishes speaking. Chapter XX on pp. 492-497 is an essay on Diomedean evolution. For summaries, see Alien Evolution. Van Rijn has imparted the same information in simpler words.

In response to environmental changes, a small arboreal carnivorous glider became a large intelligent migratory flier. Two factors stimulated intelligence:

flying between many diverse environments;
the intense natural selection of the annual migration.

In Diomedeans, exertion causes mating. Migrators mate once a year after migrating whereas settled equatorial populations work strenuously and therefore mate continuously. Each regards the other as bestial and van Rijn must explain that they are one species and can therefore do business. He is almost a savior of Diomedes as Flash Gordon was of Mongo. (The diverse intelligent species of Mongo cannot unite against Ming because he practices divide and rule. Only an outsider, Flash, can unite the opposition.)

Sometimes a hard sf writer must devote a chapter to explanation. Chapter XX could have presented the explanation in terms of van Rijn's malapropisms and Spoonerisms but Anderson opted instead to summarize the necessary background information by addressing the reader directly. When, discussing a settled community, he writes:

"Drak'ho Fleet was one of several which have now been discovered by traders." (XX, p. 496) -

- we realize that we are being addressed not by an omniscient narrator but by an observer living a short while later within Technic civilization.

In a screen dramatization, the adaptation of Chapter XX would show us the highlights of the development from the arboreal carnivore to Flock and Fleet with a voice over.