calc_definitive_min_ranks_since_last_retained_commonality_with

calc_definitive_min_ranks_since_last_retained_commonality_with(focal: Union[HereditaryStratigraphicColumn, HereditaryStratigraphicSpecimen], other: Union[HereditaryStratigraphicColumn, HereditaryStratigraphicSpecimen]) → int | None

Determine hard, inclusive lower bound on generations since MRCA.

At least, how many depositions have elapsed along the focal column’s line of descent since the last matching strata at the same rank between focal and other?

Returns None if no common ancestor between focal and other can be resolved with absolute confidence.