Temporal Variation and Microevolution in Paranthropus robustus Based on Newly Discovered Crania from Drimolen Main Quarry, South Africa

The DrimolenDrimolen Main Quarry (DMQ) paleocave deposits have yielded the second largest number of Paranthropus robustusParanthropusrobustus fossils from South AfricaSouth(ern) Africa. The 2018 discovery of two presumed adult male P. robustusParanthropusrobustus crania (DNH 152 and DNH 155) indicates that the P. robustus crania from DMQ (including the presumed female DNH 7DNH 7 cranium) share a suite of primitive and derived traits, distinct from all other hominins. Comparisons between the DMQ crania and those from SwartkransSwartkrans Member 1 Hanging Remnant and KromdraaiKromdraai B Members 4–6 indicate that morphological differences between these fossils cannot be attributed to sexual dimorphismSex(ual) dimorphism alone, as previously suggested. The three well-preserved DMQ crania share morphological features with one another, which they do not share with those well-preserved crania from the other two sites. We instead argue that the DMQ sample represents a discrete, early segment of the P. robustus lineage dating to between ~ 2.04 and 1.95 Ma. Thus, the differences between DMQ and the SwartkransSwartkransand KromdraaiKromdraai B assemblages are likely due to microevolutionMicroevolution within the species over perhaps 200,000 years.