Paranthropus boisei

Paranthropus boisei Temporal range: Pleistocene, 2.3–1.2Ma PreЄ Є O S D C P T J K Pg N ↓
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Primates
Family:	Hominidae
Genus:	Paranthropus
Species:	P. boisei
Binomial name
†Paranthropus boisei (Mary Leakey, 1959)
synonyms
Australopithecus boisei (Dart, 1938) Zinjanthropus boisei (Louis Leakey, 1959)

Paranthropus boisei or Australopithecus boisei was an early hominin, described as the largest of the Paranthropus genus (robust australopithecines). It lived in Eastern Africa during the Pleistocene epoch from about 2.3 until about 1.2 million years ago.^[1]

Discovery

First discovered by anthropologist Mary Leakey on July 17, 1959, at Olduvai Gorge, Tanzania, the well-preserved cranium (nicknamed "Nutcracker Man") was dated to 1.75 million years old and had characteristics distinctive of the robust australopithecines. Mary and her husband Louis Leakey classified the find as Zinjanthropus boisei: "Zinj" for the medieval East African region of Zanj, "anthropus" (Gr. ανθρωπος, anthropos) "human being"; and "boisei" for Charles Boise, the anthropologists' team’s benefactor.^[2]

Paranthropus boisei (as the species was eventually categorized) proved to be a treasure especially when the anthropologists' son Richard Leakey considered it to be the first hominin species to use stone tools. Another skull was unearthed in 1969 by Richard at Koobi Fora near the Lake Turkana region, in Kenya.

Morphology and interpretations

Paranthropus boisei reconstruction

Paranthropus boisei - forensic facial reconstruction

The brain volume is quite small, about 500 and 550 cm³, not much larger in comparison to Australopithecus afarensis and Australopithecus africanus or modern day chimpanzees. Unlike the P. robustus, the P. boisei feature a much shorter foramen magnum. Additionally the cranial variation of P. boisei is remarkably high.^[3] The average adult males were larger than females (sexual dimorphism), as was the case in virtually all australopithecine species. Males weighed 49 kg (108 lb) and stood 1.37 m (4 ft 6 in) tall, while females weighed 34 kg (75 lb) and stood 1.24 m (4 ft 1 in) tall.^[1]

It had a skull highly specialized for heavy chewing and several traits seen in modern day gorillas. P. boisei inhabited savannah woodland territories. The back molar teeth were relatively large, with an area over twice as great as is found in modern humans.^[4] The species is sometimes referred to as “Nutcracker Man” because it has the biggest, flattest cheek teeth and the thickest enamel of any known hominin.^[5]

Paranthropus boisei had large chewing muscles accompanied by a strong sagittal crest. Due to the fact that their face is so wide P. boisei also featured enormous cheek teeth, four times the size of modern humans.^[3] Although they have such enormous molar and cheek teeth the frontal teeth are much smaller than similar species.

Some argue that the craniodental morphology of this taxon (e.g., large postcanine dentition, thick enamel, robust mandibles, sagittal cresting, flaring zygomatic region) are indicative of a diet of hard or tough foods such as ground tubers, nuts and seeds.^[6] However, research on the molar microwear of P. boisei^[7][8] found a microwear pattern very different than that observed for P. robustus in South Africa which is thought to have fed on hard foods as a fallback resource.^[9] This work suggests that hard foods were an infrequent part of its diet. The carbon isotope ratios of P. boisei suggest it had a diet dominated by C4 vegetation unlike P. robustus in South Africa.

Fossils

Cast of the skull sometimes known as "Nutcracker Man", found by Mary Leakey in 1959, with jaw discovered by Kamoya Kimeu in 1964

In 1993, A. Amzaye found fossils of P. boisei at Konso, Ethiopia. The partial skull's designation is KGA10-525 and is dated to 1.4 million years old. It is the biggest skull specimen ever found of P. boisei. The oldest specimen of P. boisei was found in Omo, Ethiopia and dates to 2.3 million years old, classified as (L. 74a-21) while the youngest specimen from Olduvai Gorge dates 1.2 million years old, classified as OH 3 and OH 38.

Other well preserved specimens

• OH 5 Zinjanthropus, "Zinj" or "Nutcracker Man" was the first P. boisei specimen found by Mary Leakey at Olduvai Gorge, Tanzania belonged to an adult male (circa 1.75 mya).
• KNM ER 406 is a small partial cranium discovered by Richard Leakey and H. Mutua in 1969, found at Koobi Fora, Kenya, which displays large zygomatic arches, and a cranial capacity of 510 cm³ (circa 1.7 mya).
• KNM WT 17400 is a partial cranium, with similar characteristics as KNM WT 17000 "Black skull" belonging to Paranthropus aethiopicus, and was found at West Turkana, Kenya (circa 1.7 mya).

Lifestyle

Stamp of Uzbekistan, 2002

Diet

The diet of any taxon speaks to the different types of food and drink that the specific organism relied upon for nutrition. Almost all the research into the diets of extinct hominins focuses primarily on the foods that they consumed, because all relied upon water for drink. Almost all primates and hominins were generalists, meaning that they ate a wide variety of foods and did not rely on a single, specific food source.^[10]

The most widely agreed upon theory of what foods Paranthropus boisei ate while it was living is that it relied upon hard-object feeding for its primary source of nutrition.^[11] Strong jaw muscles are believed to be an evolutionary adaptation of Paranthropus boisei for a diet of nuts, seeds and hard fruit.^[12] It is clear in analysis of the molars of Paranthropus boisei that the wear on the teeth is indicative of constant chewing of small, hard food items, like nuts and seeds. Through the use of carbon dating techniques scientists are able to determine the foods that Paranthropus boisei would have been ingesting while it was alive.^[12] Further proof of the diet of fruits and nuts that Paranthropus boisei would have eaten is its classification as a cosmopolitan species, meaning that its wide geographic range would result in a diverse diet of different foods.^[12]

Along with fruits and nuts, it has been determined that Paranthropus boisei ate large quantities of grass and sedges. Through the analysis of stable isotopes located in the fossils of Paranthropus boisei it is clear that it ate large quantities of the C4 biomass that existed during the time that it was alive. In fact, it has been determined that Paranthropus boisei ate larger quantities of plant matter than any other hominin studied to date.^[13] One study concluded that the diet of Paranthropus boisei actually consisted mostly of grasses and sedges such as tigernut and that it rarely ate fruits and nuts.^[14][15]

Behavior

After surviving in two distinct ecological settings, P. boisei developed different expression of survival strategy. It is also important to note that the addition of 'tubers' into their diet has made it more likely for P. boisei to meet their daily calorie requirement.^[16]

Carbon isotope data on Paranthropus boisei suggest that their diet was primarily based on C4 resources, probably grasses or sedges. The data also suggest that this C4 resource centered diet was present over a wide range of period and region.^[12]

They further disprove various theories about the diet patterns of Paranthropus boisei; Paranthropus boisei diet pattern was not similar to that of African Apes, and it was not focused on nuts and hard fruits. This data suggests that this C4-resource-centered diet was present over a wide range of period and region.^[17]

Based on carbon isotope data and dental microwear, it is probable that Paranthropus in eastern Africa and southern Africa had different diets as well.^[18]

Dentition

Paranthropus boisei is known for having large, smooth, and thick enameled cheek teeth. The teeth of P. boisei seemed as if it was imitative, so it was thought that it was specialized in its diet. The micro wear pattern of P. boiseis unique and strong teeth led many to believe its diet consisted of hard foods; this is how the P. boisei got the nickname of the "Nutcracker Man". P. Some analysis of P. boisei show light wear of the teeth, the wear patterns showed fine striations.^[13] P. boisei is considered to be one of the largest consumers of hard objects. Thicker enamel is one main characteristic of evolution of the hominins. There is a possibility that a link exists between thickness of enamel and adaptation for eating certain foods.^[19]

The dental micro wear of P. boisei has been under close studies since the 1980s because the eating habits of these hominins are unknown. When studying micro wear, scientists are able to study the patterns in the wear of the teeth to see what dietary class this hominin falls into. When a P. boisei died, the pattern in their teeth from their last few meals would harden into the enamel, so scientists are able to see what they have possibly eaten.^[20]

See also

• List of fossil sites (with link directory)
• List of human evolution fossils (with images)
• Olduwan

References

External links

Wikimedia Commons has media related to Paranthropus boisei.

• Archaeology Info
• MNSU
• Paranthropus boisei - The Smithsonian Institution's Human Origins Program
• The first skull of Australopithecus boisei, Gen Suwa et al., letters to nature, Nature, Vol. 389, 2 October 1997
• American Museum of Natural History illustration of P. boisei by Jay Matternes

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