* “Other things being equal, density of lineages is substantially greater at low latitudes than at high latitudes.” (Nichols 1990:484)
* “Other things being equal, the coastal area of a continent will generally have substantially greater lineage density than the interior. Not every coastal area is high in lineage density, but the extensive areas of high density are all on or near coastlines. … [Because of its richer resources, the] seacoast offers the possibility of economic self-sufficiency for a small group occupying a small territory.” (ibid. pp. 484-5)
* “The discrepancy in the lineage density of coastline and interior is most pronounced where the interior is relatively dry … . (ibid. p. 485)
* “The cause of high lineage density in mountain areas is generally attributed to the fact that mountainous geography naturally isolates populations, resists large-scale economic integration, and creates refuge zones.” (ibid. p. 485)
* “Density of lineages is low in areas dominated by large-scale economies,
higher in areas with smaller-scale economies. … Reduction of lineage
density in response to increased scale of economy is not immediate, as
shown by the ancient Near East.” (ibid. p. 486)
As far as I can tell, "lineage density" means the amount of language variation.
Anyone want to nominate fantasy writers for getting this sort of thing especially right or wrong? I'm not enough of an expert on Tolkien to do a detailed evaluation and I realize he was working from the knowledge available in his time, but how close did he get?
Link thanks to thnidu.