Paranthropus boisei
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30-04-2014, 10:01 AM (This post was last modified: 30-04-2014 01:27 PM by ghostexorcist.)
Paranthropus boisei
The following is a paper that I wrote for my ATH 355 (Fossil Evidence for Human Evolution) class. I literally wrote it in a single day because I was strapped for time. I'm sure I could have done a better job with more time, but I think it's not bad.

Adopt-a-fossil: Paranthropus boisei (OH 5)

By Jim R. McClanahan

Humans once took pride in the knowledge that we were specially created by God. We were unique among his earthly creations. Animals were just mere beasts of burden and sources of food to us. They shared no qualities with humans other than having a common creator. Then that pesky Charles Darwin came along and ruined everything. With the publishing of his On the Origin of Species (1859), he showed that it was not the hands of some omnipotent being that molded life into its many forms, but the unguided, natural forces of the environment and the choice of female mates that explained life’s diversity. It wasn’t long after that we learned humans were not alone. Scientists began to discover human cousins who had either lived alongside us or roamed the earth long before our coming. This meant that we were not solely unique, but one of a crowded family line that just so happened to survive into the present. This paper details Paranthropus boisei, one of these human cousins. I will cover the political climate of early paleoanthropology, where the first P. boisei fossil was found, who found it and what it looked like, and the hominid’s evolutionary lineage, feeding patterns, possible tool use, and social organization.

The most recent human cousin, the Neanderthal (Homo neanderthalensis), was first discovered in Germany in 1856 (King, 1864), three years prior to Darwin’s magnum opus. This discovery was soon supplemented by Homo erectus (then known as Pithecanthropus erectus) in Java (1892) and the first of the Australopithecines, the Taung child (Australopithecus africanus) in South Africa (1925) (Dubois, 1892; Dart, 1925). At this time a war raged over the original homeland of mankind. Was it Europe, Asia, or Africa? Asia was an attractive option preferred by many professional and amateur scientists working during the 19th- and early-20th-century. For instance, Eugene Dubois, the discoverer of H. erectus, wrote: “And thus the factual proof is provided of what some have already conjectured, that the East Indies was the cradle of the human kind” (Dubois, 1864, p. 14). Despite promising finds in the 1920s and 1930s, Africa didn’t become a budding area of research until a monumental discovery in 1959.

One hundred years after Darwin published his landmark study on Natural Selection, the paleoanthropologist Mary Leakey discovered an almost complete cranium eroding out 22 ft. down from the top of Bed I in Olduvai Gorge, Tanzania. Geological forces caused minimal damage to the skull, the few damaged areas (around the nose and on the cranium) later being glued back on. The hyper robust skull has buttressing in several areas, such as around the frontal bone, the arched zygomatic bone and process, and the sagittal crest at the crown of the skull. These features are meant to reinforce the skull against the massive torquing forces that would have been created by the chewing of the robust molar teeth. They are three times larger than the size of humans, and the premolars are also so large that they have essentially been molarized. The incisors are miniscule in comparison. The face is dish-shaped, with the eye orbits and maxilla sticking out further than the extremely recessed nose opening (Leakey, 1959, p. 492).

Due to the hyper robust nature of the skull, Mary's husband Louis, who was also a noted researcher, initially wanted to name the specimen Titanohomo mirabilis (“miraculous giant man”) (Johanson & Edgar, 2006, p. 168), but he later settled on Zinjanthropus boisei. The first half means “African man” and the second is in honor of Leakey’s benefactor Charles Boise (Leakey, 1959, p. 492). Its catalog number is OH5 (Olduvai Hominid 5). By placing it in a new genus, Zinjanthropus, Leakey was making the claim that the new specimen was separate from the gracile and robust australopithecines previously discovered in South Africa. Yet, oddly enough, he recognized it as a member of this group due to morphological affinities, such as a larger cranium and a more recessed maxilla. What truly set “Zinj” apart from its paleoanthropological forerunners, Leakey believed, was that this was the culprit responsible for making the noted Olduvai tools, the oldest of the recognized lithic technology (Leakey, 1959, p. 491). Leakey later amended his view when the remains of more human-like specimens with dexterous hands were discovered in Olduvai Gorge. These specimens were subsumed into the new genus Homo and the species habilis (“handy man”) (Leakey, Tobias, & Napier, 1964). Robinson (1960) suggested that Zinj should be absorbed into the genus Paranthropus, which has remained a well-used taxon.

Several debates over the specimen’s exact evolutionary lineage have raged for several decades. OH 5 was originally the first fossil to be dated using the then novel radiometric potassium-argon method. Volcanic tufts from the various soil layers containing the specimen (Bed I), as well as those above and below, were used to provide a date of 1.75 million years (MY) (Leakey, Evernden, & Curtis, 1961). Although the fellow East African species Paranthropus aethiopicus predates P. boisei at 2.3 MY, some researchers believe there is enough continuity between the two to absorb the former under the title P. boisei sensu stricto (in the strict sense). This would distinguish both as being a separate evolutionary lineage from P. robustus, a South African robust Australopithecine dated between 2 and 1.2 MY. If true, this would mean the similarity in robusticity between the eastern and southern regions is an example of homoplasy, or convergent evolution (Constantino & Wood, 2007). Yet, some researchers have tried to determine whether the similarities are the result of a monophyly, a group consisting of descendants and their ancestor. For instance, Strait, Grine, and Moniz (1997) proposed that a hypothetical ancestor of all species of Panaranthropus (a monophyly) shared a hypothetical ancestor with Homo, and that this ancestor was descended from Australopithecus africanus (3-2.4 MY). In a previous study, Skelton and McHenry (1992) proposed that P. aethiopicus and a hypothetical ancestor (a monophyly) shared ancestry with A. afarensis (3.6-2.9 MY). Furthermore, they suggested that the hypothetical ancestor of P. robustus and boisei (another monophyly) shared a common ancestor with Homo, and that this ancestor was descended from A. africanus. Even though its exact evolutionary lineage is still not clear, the available evidence shows that P. boisei is a human cousin and not a direct ancestor.

Discoveries and/or analyses within the last ten years have given insight into the diet and feeding behavior of P. boisei. Moyà-Solà et. al. (2007) reanalyzed the fossil hand attributed to the H. habilis holotype (OH 7) first discovered by Leakey. The specimen was compared to the appendages of extinct and extant groups. The former included several species of fossil baboons, P. robustus, A. africanus, H. erectus, and H. neanderthalensis. The latter included H. sapiens, Pan troglodytes (chimpanzees) and several species of modern baboons. The robustness of the OH 7 pollical distal phalanx (the last digit of the thumb) was found to best match that of P. robustus, while the distal trochlea of the middle phalanges (the area where the third digit meets the knuckle) shares similarities with the sample of robust and gracile Australopithecines. The same can be said with several other measures of OH 7 phalange robusticity. Therefore, the authors contend that the hand specimen should instead be attributed to P. boisei. However, instead of attributing tool-making skills to the species, they believe the evidence for pad-to-pad precision grasping points to a pattern of manual grazing similar to modern baboons. A reason to suggest a similarity to baboon grazing patterns is because both subsist(ed) on similar C4 carbon fixed foods such as grasses and tubers (a.k.a., underground storage organs or USOs). Subsequent research has supported this affinity with these primates.

Macho (2014) studied the feeding habits of yearling baboons in Amboseli National Park in Rift Valley Province, Kenya for two reasons. First, the dietary requirements of young baboons are much greater than adults, thus paralleling similar elevated requirements of the larger bodied hominid. Second, the location of the park overlaps with the range historically roamed by P. boisei, the Somalia-Masai steppe region. Macho found that yearlings spent 53 of 88 minutes feeding on corms (tubers). When scaled up to a roughly 34-49 kg (75-108 lbs) individual, the author found that P. boisei would have had to eat for 283 minutes to meet their calculated daily 9,700 kilojoule requirement. If the greater corm extracting ability of a larger individual is taken into account, Macho found that the hominid would have only needed 150 to 133 minutes (or 42% to 33%) out of their total feeding time to meet their daily nutritional requirements.

One way that P. boisei could have extracted corms more easily was tools. While the Moyà-Solà et. al. (2007) study claims it’s more likely that the species didn’t use tools, I think the authors focused too heavily on lithic technology. Paranthropus boisei and robutus may have lived in two different regions, but their dietary regimens and hand morphology are at least similar enough in my opinion to imply similar methods of food extraction. Isotopic analysis shows that both relied heavily on C4 foods, with P. robustus eating more C3 foods (fruits and leaves) in comparison (Lee-Thorp, 2010; Sponheimer et. al., 2006). One study found bone tools in association with P. robustus fossils, and after a comparison with bone tool usage by Bantu-speaking tribal groups, the authors suggested the artifacts were most likely used by the species for foraging for termites. Although, digging for tubers and processing thick-skinned fruits were also possible uses (Blackwell & d’Errico, 2008). Likewise, P. boisei could have used some kind of digging implement. As I previously mentioned, they have the manual dexterity needed for precision grasping. Plus, a recent survey shows that the makers of the Olduvai tools have more in common with apes than Moyà-Solà et. al. (2007) acknowledged in their study (Wynn et. al. 2011). Whether this maker was P. boisei is still unclear, but the fact remains that modern chimpanzees, which do not have the same hand dexterity, use “sticks, fragments from fallen logs, and tree bark” to dig for tubers (Wynn et. al. 2011, p. 183). Therefore, I suggest the lack of tools in association with the robust Australopithecine is linked to the impermanent nature of wood.

The type of food that P. boisei ate and the fossil layer in which the specimen was found (Bed I) gives insight into the type of environment in which they lived and the type of fauna that they coexisted with. C4 foods make up 40-60% of the biomass of Beds I and the lower level of Bed II (1.8 MY), and such foods are prevalent in freshwater swamps (Van Der Merwe, 2013, p. 1). Kappelman’s (1984) review of previous research confirms a closed, moist environment. Instead of relying on isotopic information, the author used fossil evidence consisting of aquatic bovids (including hippopotami) and insectivorous rodents to show the habitat of Bed I “consist[ed] of a closed canopy probably with isolated patches of grassland and marsh” (Kappelman, 1984, p. 185). In addition, he used pollen and geological data to show that there was a drastic shift towards a drier climate in the proceeding Bed II layer. Given the P. boisei’s reliance on C4 foods, this climactic shift may have put a strain on their living conditions.

Whereas hand morphology and isotopic data gives information on the diet and feeding behavior of the hominid, a recent discovery of a partial P. boisei skeleton sheds light on their size and social organization. Dominguez et. al. (2013) discovered teeth, arm bones (a left humerus and right radius) and leg bones (a right femur and unspecified tibia) in Bed II of Olduvai Gorge. Collectively known as OH 80, the material has been attributed to the species due to its pronounced robustness, which is more in line with P. robustus in the south than with H. habilis or modern humans. It has been dated to 1.338 ± 0.024 MY using the argon-argon method, making it younger than OH 5. With the exception of the radius, all skeletal material is only partial in nature, having been, the authors suggest, the result of the taphonomic process of carnivore feeding. Based on a reconstruction of the femur, the individual was an estimated 156 ± 3.91 cm (61.4 ± 1.5 in.) tall and weighed 61.7-50 kg (136-110.2 lbs).[1] The authors go on to compare these findings with previous research that used KNM-ER 1500, a proposed P. boisei female cranium discovered in Koobi Fora, Kenya in 1973, to show that the species had a large degree of sexual dimorphism. This might suggest that the P. boisei social organization involved a fair amount of competition for females. However, Constantino and Wood (2007) cautions that this is not a valid hypothesis since the species has almost nonexistent canines. Therefore, there are no living primate groups that can be successfully mapped onto them (p. 58).

In conclusion, Paranthropus boisei is a human cousin that was discovered in Olduvai Gorge, Tanzania in East Africa by the paleoanthropologist Mary Leakey in 1959. The cranium is quite robust, with buttressing throughout and massive molar teeth. It is notable on two accounts. First, the academic political climate of the day favored Asia as the origin of mankind, but the find shifted the focus to East Africa. Second, it was the first fossil to be dated (1.75 MY) using the then novel potassium-argon radiometric method. Its phenotypic similarities with another robust Australopithecine from South Africa, P. robustus, is thought to be an example of convergent evolution. Although, several models for its exact evolutionary history have been proposed that relates it either to all robust Australopithecines directly or some more distantly. Despite the possibility of convergent traits, there are enough similarities between P. boisei and robustus hand morphology and feeding behavior to suggest that the former may have used some kind of wooden implements to dig for the C4 carbon fixed tubers that isotopic analyses shows that they subsisted on in their swampy habitat. In addition, recent skeletal finds support previous research that shows there was a fair amount of sexual dimorphism between male and female specimens of the hominid. But considering the lack of prominent canines, there are no living primate groups that can be successfully mapped onto them. This means their social organization is still a mystery.

Notes

[1] The upper limit is significantly heavier than the weight given in the previously mentioned Macho (2014) study, but these measurements were based on research conducted prior to the skeletal discovery.

Bibliography

Backwell, L., and d’Errico, F. (2008). Early Hominid Bone Tools from Drimolen, South Africa. Journal of Archaeological Science 35: 2880-2894.

Constantinto, P. and Wood, B. (2007). The Evolution of Zinjanthropus boisei. Evolutionary Anthropology 16: 49-62.

Dart, R. (1925). Australopithecus africanus: The Man-Ape of South Africa. Nature 115: 195-199.

Dominguez-Rodrigo, M., Pickering, T. R., Baquedano, E., Mabulla, A., Mark, D.F., Musiba, C., Bunn, H.T., Uribelarrea, D., Smith, V., Diez-Martin, F., Perez-Gonza, A., Sanchez, P., Santonja, M., Barboni, D., Gidna, A., Ashley, G., Yravedra, J., Heaton, J.L., Arriaza, M.C. (2013). First Partial Skeleton of a 1.34-Million-Year-Old Paranthropus boisei from Bed II, Olduvai Gorge, Tanzania. PLoS One 8 (12): 1-10.

Dubois, E. (1892). Palaeontologische onderzoekingen op Java. Verslag van het Jijnwezen, Third Quarter: 10-14.

Johanson, D. C., and Edgar, B. (2006). From Lucy to Language. New York: Simon & Schuster.

King W. (1864). The Reputed Fossil Man of the Neanderthal. Q. J. Sci. 1: 88–97.

Leakey, L.S.B. (1959). A New Fossil Skull from Olduvai. Nature 184: 491-493.

Leakey, L.S.B., Evernden, J.F., and Curtis, G.H. (1961). Age of Bed I, Olduvai Gorge, Tanganyika. Nature 191: 478-479.

Leakey, L.S.B., Tobias, P.V., and Napier, J.R. (1964). A New Species of the Genus Homo from OIduvai Gorge. Nature 202: 7-9.

Lee-Thorp, J.A., Sponheimer, M., Passey, B.H., de Ruiter, D.J., and Cerling, T.E., Stable Isotopes in Fossil Hominin Tooth Enamel Suggest a Fundamental Dietary Shift in the Pliocene. Philosophical Transactions 365 (1556): 3389-3396.

Macho, G.A. (2014). Baboon Feeding Ecology Informs the Dietary Niche of Paranthropus boisei. PLoS One 9 (1): 1-8.

Moyà-Solà S.A., Köhler, M.A., Alba, D.M., and Almécija, S.C. (2008). Taxonomic Attribution of the Olduvai Hominid 7 Manual Remains and the Functional Interpretation of Hand Morphology in Robust Australopithecines. Folia Primatologica 79: 215-250.

Robinson, J.T. (1960). The Affinities of the New Olduvai Australopithecine. Nature 186: 456-458.

Skelton RR, McHenry HM. 1992. Evolutionary Relationships among Early Hominids. Journal of Human Evolution 23: 309-349.

Sponheimer, M., Passey, B.H., de Ruiter, D.J., Guatelli-Steinberg, D., Cerling, T.E., and Lee-Thorp, J.A. (2006). “Isotopic Evidence for Dietary Variability in the Early Hominin Paranthropus Robustus.” Science 314 (980): 980-82.

Strait, D.S., Grine, F.E., Moniz, M.A. (1997). A Reappraisal of Early Hominid Phylogeny. Journal of Human Evolution 32: 17-82.

Van Der Merwe, N.J. (2013). Isotopic ecology of fossil fauna from Olduvai Gorge at ca 1.8 Ma, compared with modern fauna. South African Journal of Science 109 (11/12): 1-14.

Wynn, T., Hernandez-Aguilar, R.A., Marchant, L.F., McGrew, W.C. (2011). "An ape's view of the Oldowan" Revisited. Evolutionary Anthropology 20: 181-197.
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30-04-2014, 11:00 AM
RE: Paranthropus boisei
Good job, reads very well.

[Image: dobie.png]Science is the process we've designed to be responsible for generating our best guess as to what the fuck is going on. Girly Man
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30-04-2014, 11:28 AM
RE: Paranthropus boisei
I liked it, was easy to read and follow and flowed well.

The requirement of evidence to back your claim does not disappear because it hurts your feelings, reality does not care about your feefees.
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30-04-2014, 11:46 AM
RE: Paranthropus boisei
You know some stuff and now I know it too Thumbsup

Like the others said it reads well, thanks for sharing!

“I am quite sure now that often, very often, in matters concerning religion and politics a man’s reasoning powers are not above the monkey’s.”~Mark Twain
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30-04-2014, 01:41 PM
RE: Paranthropus boisei
Thanks for the kind remarks. I purposely chose this specimen because of my planned study abroad in Olduvai Gorge, Tanzania. I wanted to know basic information about it just in case we stumble upon some of its remains.
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08-05-2014, 02:41 PM
RE: Paranthropus boisei
I ended up getting a 98 on the assignment. I'm pretty happy considering the short amount of time I had to research and write it. The paper apparently has advanced my professor's own research because I found some references that she was not aware of.
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21-07-2014, 07:32 PM
RE: Paranthropus boisei
(30-04-2014 10:01 AM)ghostexorcist Wrote:  Dominguez-Rodrigo, M., Pickering, T. R., Baquedano, E., Mabulla, A., Mark, D.F., Musiba, C., Bunn, H.T., Uribelarrea, D., Smith, V., Diez-Martin, F., Perez-Gonza, A., Sanchez, P., Santonja, M., Barboni, D., Gidna, A., Ashley, G., Yravedra, J., Heaton, J.L., Arriaza, M.C. (2013). First Partial Skeleton of a 1.34-Million-Year-Old Paranthropus boisei from Bed II, Olduvai Gorge, Tanzania. PLoS One 8 (12): 1-10.

Many of the people involved with this paper were at my field school. Manuel Dominquez-Rodrigo, the lead author, was in charge of the entire thing. Audax Mabulla, the head of antiquities in Tanzania, gave us lectures on lithics, took us to go see rock art, and even helped me with a personal project. Charles Musiba and Henry Bunn were not officially a part of the field school since they were busy with their own field school in Laetoli (home of the famous 3.7 million year old Australopithecus trackway). They did stop by the camp once, though. Fernando Diez-Martin gave us more advanced lectures on lithics. Doris Barboni gave us lectures on paleobotany. Both Gail Ashley and David Uribelarrea took us around the gorge and gave us lectures on geology. I briefly shared a dorm room with Jose Yravedra. Those are all of the names I readily recognize at the moment.

Here is a group picture with Manuel (center), David (far left with the sun glasses), myself (the light bulb next to David), and most of the other field school students. It was taken at the Olduvai Gorge Museum.

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