calc_definitive_min_ranks_since_first_retained_disparity_with

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

Determine a hard, exclusive lower bound on generations since MRCA.

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

Returns None if no disparity found (i.e., both columns have same number of strata deposited and the most recent stratum is common between focal and other).