Why do shared words for spruce suggest a northern homeland for Proto-Uralic speakers?

Linguists use shared cognates to reconstruct the environment of early Uralic languages. The presence of consistent terms for spruce across nearly all Uralic languages—such as Finnish kuusi, Mordvin kuz, and Nenets xādy—serves as evidence for a northern homeland.1

Because the natural range of this specific type of tree is restricted to northern climates, scholars infer that the Proto-Uralic speakers must have inhabited a region where these trees were common. This linguistic evidence, alongside other botanical terms like those for cloudberry, supports the hypothesis that the original homeland of Proto-Uralic was located in the vicinity of the north-central Urals.12

However, researchers exercise caution with this method, as some shared terms for culturally mobile items—such as those for metal or reindeer—could potentially result from later borrowing rather than ancestral inheritance.1