Like other members of the Paranthropus genus, P. boisei is characterized by a specialized skull with adaptations for heavy chewing. A strong sagittal crest on the midline of the top of the skull anchored the temporalis muscles (large chewing muscles) from the top and side of the braincase to the lower jaw, and thus moved the massive jaw up and down. The force was focused on the large cheek teeth (molars and premolars). Flaring cheekbones gave P. boisei a very wide and dish-shaped face, creating a larger opening for bigger jaw muscles to pass through and support massive cheek teeth four times the size of a modern human’s. This species had even larger cheek teeth than P. robustus, a flatter, bigger-brained skull than P. aethiopicus, and the thickest dental enamel of any known early human. Cranial capacity in this species suggests a slight rise in brain size (about 100 cc in 1 million years) independent of brain enlargement in the genus Homo.
Where Lived: Eastern Africa (Ethiopia, Kenya, Tanzania, Malawi)
When Lived: About 2.3 to 1.2 million years ago
Paranthropus boisei lived about 2.3 to 1.2 million years ago.
Year of Discovery: 1959
History of Discovery:
Paleoanthropologists actually found the first fossils belonging to P. boisei in 1955, but it wasn’t until Mary Leakey’s 1959 discovery of the ‘Zinj’ skull (OH 5) that scientists knew what they had found was a new species. ‘Zinj’ became the type specimen for P. boisei and, soon after, arguably the most famous early human fossil from Olduvai Gorge in northern Tanzania.
Males: average 4 ft 6 in (137 cm); Females: average 4 ft 1 in (124 cm)
Males: average 108 lbs (49 kg); Females: average 75 lbs (34 kg)
Height & Weight Supplemental Information:
If you compare a male P. boisei individual to a male Au. africanus who lived during a similar time period (3.3–2.1 Mya), you’ll see why the species Paranthropus got the name ‘robust.’ While both males are on average 4 ft 6 inches tall, the average male P. boisei was 18 pounds heavier than a male Au. africanus of the same height. Even P. boisei females were slightly larger and heavier than what scientists had seen before in the fossil record of other early humans.
Male and female P. boisei individuals were closer in body size than individuals of other species of early humans preceding them, but this species still had a fairly high level of sexual dimorphism.