Paranthropus

Paranthropus is an extinct genus of bipedal hominids, native to Eastern and Southern Africa, characterized by great robustness of the jaw and molars. The Paranthropus (robust paranthropes or australopithecines) probably descend from the genus Australopithecus (gracile australopithecines or australopithecines). Some paleontologists consider, however, that robust australopithecines belong to Australopithecus.

The fossils found correspond to species that lived between 2.6 and 1.1 million years before the present, in the Gelasian and Calabrian (early to middle Pleistocene). They are characterized by a specialized chewing apparatus, consisting of large jaws and molars with a very thick layer of enamel, very small incisors and canines and premolars that develop as if they were molars, and powerful facial muscles that are inserted into a crest. sagittal similar to that of the gorilla. Their brains were between 410 cm³, the earliest, and 530 cm³ for the rest, therefore they were smaller in size than the brains of the genus Homo.

Etymology

The word Paranthropus was coined by Robert Broom in 1938, who found fossils and classified them into a new species. It means 'next to man', and indeed, it coexisted with Homo for 1.5 million years.

Species

Three species have been described:

• Paranthropus aethiopicus. It is the first species of this genus (appears about 2.5 m.a). He had a particularly solid face. It is considered that it could lead parallel to the two subsequent species. He lived in East Africa.

• Paranthropus boisei. It had a more robust look. Its cranial characteristics are specialized for the consumption of hard vegetables. They presented a great sexual dimorphism, the body of the male being much larger than the female. Located between 2.3 and 1.2 m.a. He lived in East Africa.

• Paranthropus robustus. It was characterized by particularly thick bones. Head volume between 500 and 530 cm3, high and elongated face. Solid teeth. Located between 1.8 and 1.5 m.a. The Paranthropus robustus coexisted with the Homo for a million years, until it was extinguished. He lived in South Africa.

It should be noted that scientists who reject the existence of Paranthropus as a distinct genus designate these species as Australopithecus robustus, Australopithecus boisei and Australopithecus aethiopicus.^{[citation required]}

Description

Skull

Paranthropus had a massive skull, tall and flat, with a prominent sagittal crest, similar to that of the gorilla, along the midline that anchored the enormous temporalis muscles used in chewing. Like other australopithecines, Paranthropus was sexually dimorphic, with males being noticeably larger than females. They had large molars with a relatively thick dental enamel lining (postcanine megadontia), and comparatively small incisors (similar in size to modern humans), possibly adaptations for processing abrasive foods. The teeth ofP. aethiopicusdeveloped faster than those of P. boisei.

Paranthropus had adaptations in the skull to resist large bite loads while feeding, namely the expansive squamous suture. The remarkably thick palate was once thought to be an adaptation to resist a high bite force, but is best explained as a byproduct of facial elongation and nasal anatomy.

In the P. boisei's jaw hinge was adapted to grind food from side to side (rather than up and down in modern humans), which is better for processing the abrasive starchy foods that probably made up the majority of your diet. TheP. robustus may have chewed in a front-to-back direction, and had less exaggerated anatomical features (less derivation) than P. boiseias perhaps he didn't need them with this type of chewing strategy. This may also have allowedP. robustusprocess harder foods better.

The volume of the braincase was, on average, about 500 cubic centimeters (0.5 L), comparable to that of gracile australopithecines, but smaller than that of Homo. The volume The modern human brain has an average of 1270 cm³ for men and 1130 cm³ for women.

Limbos and locomotion

Unlike P. robustus, the forearms of P. boiseiwere strongly built, which might suggest habitual suspensive behavior as in orangutans and gibbons. A scapula ofP. boisei indicates long infraspinatus muscle, which is also associated with suspension behavior. An ulna ofP. aethiopicus, on the other hand, shows more similarities with Homo than with P. boisei.

Paranthropus were bipedal, and their hips, legs, and feet resemble those of A. afarensisand modern humans. The pelvis is similar to that of A. afarensis, but the hip joints are smaller in P. robustus. Physical similarity implies a similar gait. Their big toe, similar to that of modern humans, indicates a foot posture and range of motion similar to those of modern humans, but the more distal ankle joint would have inhibited the cycle of movement. march of modern humans. Around 1.8 mya, Paranthropus and H. habilis' may have achieved approximately the same degree of bipedalism.

Height and weight

Compared to the large and robust head, the body was rather small. The average weight ofP. robustus may have been 40 kilograms (88.2 lb) for males and 32 kilograms (70.5 lb) for females; and for P. boisei50 kilograms (110.2 lb) for males and 34 kilograms (75.0 lb) for females. In members 1 and 2 of Swartkrans Cave, it is estimated that around 35% of the individuals ofP. robustusweighed 28kg, 22% around 43 kilograms (94.8 lb), and the remaining 43% more than the previous ones but less than 54 kilograms (119 lb). In Member 3, all individuals were approximately 45 kilograms (99.2 lb). The weight of the females was about the same in theH. erectuscontemporaries, but the males of H. erectuswere on average 13kg heavier than males of P. robustus. The sites of P. robustus are strangely dominated by small adults, which could be explained as greater predation or mortality of the largest males in a group. The largest known individual of Paranthropus was estimated at 54kg.

According to a 1991 study, based on the length of the femur and using the dimensions of modern humans, it is estimated that males and females of P. robustusmeasured an average of 132 and 110 centimeters (4' 4' and 3' 7.30'), respectively, and those of P. boisei 137 and 124 centimeters (4' 5_^29/32" and 4'_^4/5 "). However, these latter estimates are problematic, as there were no male femurs ofP. boiseipositively identified at the time. In 2013, it was estimated that a partial skeleton of a 1.34 Ma male ofP. boiseiwas at least 156 centimeters (5' 1_^2/5") and 50 kilograms (110.2 lb).

Pathology

Paranthropus appears to have had notably high rates of pitted enamel hypoplasia (PEH), where tooth enamel formation is irregular rather than largely uniform. InP. robustus, about 47% of primary teeth and 14% of adult teeth were affected, compared with about 6.7% and 4.3%, respectively, in any other hominid species. analyzed. The condition of these holes covering the entire tooth is consistent with the modern human ailment amelogenesis imperfecta. However, since the circular holes covering the enamel are of uniform size, are only present in the molar teeth, and have the same severity in all individuals, PEH may have been a genetic condition. It is possible that coding DNA related to enamel thickening also made them more vulnerable to PEH.

10 cases of cavities have been identified in theP. robustus, indicating a rate similar to that of modern humans. A molar from Drimolen, in South Africa, had a cavity in the root of the tooth, something unusual in fossil great apes. For cavity-creating bacteria to reach this area, the individual would also have to have had alveolar resorption, which is commonly associated with gum disease; or supereruption of the teeth, which occurs when the teeth wear down and have to erupt a little more to maintain a proper bite, and this exposed the root. The latter is most likely, and the exposed root appears to have caused hypercementosis to anchor the tooth in place. The cavity appears to have been healing, which may have been caused by a change in diet or oral microbiome, or the loss of the adjacent molar.