Retrocontinuity

The author(s) of an established future history can inform us about earlier periods of the history in two ways:

(i) installments written later can be set earlier - prequels;

(ii) installments written later can be set later but can divulge for the first time information about earlier periods.

(i) Robert Heinlein described DD Harriman's death before he recounted how Harriman "sold the Moon."

Poul Anderson described Dominic Flandry's career before writing the Young Flandry Trilogy and also described interstellar exploration before interplanetary exploration.

(ii) Heinlein reveals that the Howard Families have existed throughout his Future History, that some Howards were involved in the revolutionary Cabal and that Andy Libby is a Howard.

The Last Flandry novel reveals the existence of the Dakotian and Zacharian communities and also recapitulates some earlier events from a different perspective.

In Jerry Pournelle's and SM Stirling's "The Asteroid Queen," two characters encountered earlier, a United Nations Space Navy general and an oyabun in the Alpha Centauri System, turn out to be members of a Grail Brotherhood that has suppressed knowledge of the Slavers for three centuries. How plausible is this? (Some people think that this is how society is run.) If "The Asteroid Queen" is a canonical part of Larry Niven's Known Space future history, then this Brotherhood exists in the background of every other installment even though not explicitly referenced.