In 1954, Robinson suggested that the heavily built skull of "Paranthropus" (at the time only including "P. robustus") was indicative of a specialist diet specifically adapted for processing a narrow band of foods. Because of this, the predominant model of "Paranthropus" extinction for the latter half of the 20th century was that it was unable to adapt to the volatile climate of the Pleistocene, unlike the much more adaptable "Homo". It was also once thought "P. boisei" cracked open nuts and similar hard foods with its powerful teeth, giving OH 5 the nickname "Nutcracker Man".