East to West yes but the book asserts that it's the variance North to South that matters because supposedly biomes change far more along that axis than on the East to West one.
Africa and Eur-Asia measure almost identically North to South
> Africa and Eur-Asia measure almost identically North to South
And there's not much room for useful exchange of crops or livestock between Indians engaged in tropical farming and Sami engaged in reindeer pastoralism on the tundra.
The book says that a longer West-East axis means more civilizations can exchange the same crops/animals as the climate tends to be similar, while across the Nort-South axis you have a much harder time moving things, as you end up having to go from cold to temperate to tropical and then back again, effectively stopping movements. I haven't read the book again in many years, but this is something that stuck with me...
Africa and Eur-Asia measure almost identically North to South