Paranthropus (“ape that lived alongside humans”) (2.7–1.2 MYA). The bipedal paranthrops probably descended from gracile australopiths but took a decided turn to the muscular.
Paranthropus had a robust anatomy, with massive jaws, sturdy bones, and strong muscles. Paranthrops lived off vegetation and possibly grubs, resorting to chewy fare only when starving.
Paranthrops were sexually dimorphic. While there was some size variation in the different paranthropic species, males were 1.2–1.4 meters, weighing ~68 kg, while females were 0.9–1.0 meters, 40–45 kilos. Males had a sagittal (cranial) crest (shades of Au. afarensis), but the smaller females did not. Like Au. africanus, Paranthropus were patrilocal.
P. aethiopicus lived 2.7–2.3 MYA; P. boisei: 2.6–1.3 MYA. P. robustus: 2.3–1.2 MYA.
Paranthrops’ brain size was that of a chimp today, ~40% that of a modern human; but paranthrops had significantly larger braincases than australopiths.
P. robustus had a hand adapted for a precision grip and tool use. It is unclear the extent to which paranthrops crafted or used tools. Paranthrops are thought to have preferred living in wooded areas, not grasslands.
Paranthropus were unrelated to the lineage that led to humans: hominids, not hominins. Paranthrops were on an evolutionary path that led to extinction.
The tough build of Paranthropus may have disguised a hominid poorly adapted to the demands of changing climate, at least compared to the upstart Homo genus that prevailed.