These series represent the decay chain products of long-lived primordial U-238, U-235, and Th-232, respectively.
However, each of them also occurs, to some extent, as primordial isotopes that were made in supernovae, rather than radiogenically as daughter products.
The shape of this curve is the same for the radioactive decay of all isotopes.
The amount of actual time in a half-life is unique to each parent/daughter pair, however.
The samples are processed to prepare Pb activities.