It is shown that the latest results from the NMC (CERN) and E665 (Fermilab) groups on F A 2 (x)/F D 2 (x) obtained in the shadowing region bring new evidence of the universal A dependence of distortions made in a free-nucleon structure function by a nuclear medium. The observed universality implies that one can consider separately hard (A ≤ 4) and soft (A > 4) parton distribution distortions. Soft distortions, which result in differencies between the deep-inelastic scattering cross-sections for nuclei with masses A 1 , A 2 ≥ 4, can be explained as a consequence of the nuclear density variation, independent of x in the range 0.001 ≤ x ≤ 0.7.It is found that nuclear shadowing begins at x I = 0.0615 ± 0.0024, independent of A, which is consistent with models that allow for threeparton recombination processes.