Early Hominid Predation

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The state of fossil assemblages associated with early hominid remains has lead many to view them as dominant hunters. Earlier on,Raymond Dart presumed that early hominids were responsible for the bone assemblages in caves[1]. He further hypothesized that they were aggressive hunters and called his theory Killer Ape hypothesis. However current evidence is in favour of the concept that early hominins had an ecological role as preys and endured predation from a range of carnivores such as hyenas,crocodiles,leopards as well as birds of prey.[2]

Who were the early hominids ?

Early hominids are constituted by the australopithecines (sensu lato) and their fossil remains have provided important clues in the understanding of the ape-hominid transition. It is therefore important to understand the relationship of early hominids and other major predators which coexisted with the hominids during the Plio-Pleistocene period.[3] The fossil record shows that early hominids evolved in the early Pliocene in East Africa. However, they became widespread during the Plio-Pleistocene period.The first discovery of an early hominid is Australopithecus africanus or the Taung child from South Africa. Other species such as A.(Paranthropus) robustus,and A.afarensis were later discovered in South African caves as well as East Africa.

Early hominid vulnerability

During the terminal phase of the Miocene epoch (around five million years ago), the climate began to shift from wet subtropical to much more arid, grassland conditions[4]. Over the next three million years, the heavy forest cover gradually died out and arboreal hominid ancestors were forced down onto ground. There, they faced the most brutal lineup of predators in the world, including lions, leopards, hyenas, and possibly wild dogs in large packs. Survival in such environments is limited to either predator avoidance or running and hominids such as A.afarensis would have been vulnerable due to lack of swift movements necessary to escape predators. Bipedalism also exposed early hominids to predators by aligning them vertically[4]. They were forced to rely on binocular vision for predatory avoidance, but in cases where a predator was not seen, they were easy prey for ambush hunters. In addition, their plant food diet increased their exposure to predators. The combination of other factors such as smaller body size, and lack of sharp teeth or claws also increased vulnerability of hominids to this fate. Only a few fossilised examples are available; according to the taphonomic studies of Hart and Sussman(2005), 5% of A. afarensis fossils show evidence of having been eaten.

Leopards

In the 1970s Bob Brain came across the skull of an early hominid at the Swartkrans cave. The skull was identified as that of A.(Paranthropus) robustus, while the canine indentations on the pariental region were interpreted as those made by a leopard(Panthera pardus). The size of the tooth marks suggests that the leopard dragged the corpse carrying it by head.[5]The transportation of the kill through dragging is still observable in extant leopards. Therefore, since leopards are not scavengers, Brain(1981) concluded that the animal which dragged the corpse is the same animal which killed A .(Paranthropus) robustus[5].

Raptors

Even though large raptors are known to feed on medium sized mammals,previous taphonomic analysis on hominin-linked accumulations have underrated their role as taphonomic agents. Hominin fossil accumulations have always been attributed to leopard or saber tooths which are known to have killed most members of the Australopithecine clade. However, the Taung bird of prey hypothesis proposed by Berger and Clarke(1995,1996) challenged the popular idea which held leopards responsible for the death of the Taung child. The results of their taphonomic analysis showed that damages on the crania of the Taung child and other animal fossils from the Taung site in South Africa were similar to those caused by modern eagles.[6] These claims were subjected to a lot of debate because Australopithecines were considered to be behaviorally sophisticated and socially organized and too large to be preyed upon by eagles. After a decade of debate, studies on the nest remains of the African Crowned eagle(Stephanoaetus coronatus) provided comparative evidence to affirm the bird of prey hypothesis. [7] The taphonomic analysis showed that feeding damage made by African crowned eagles on monkeys is manifested by punctures and scratches which are similar to those observed on the crania of the Taung child.

Extinct cats

Although a little is known about sabre tooths as hominid predators,there has been a considerable discussion about their role on the accumulation of hominid fossils since they were found on hominid sites.The sabre-tooth or Megantereon was found in Member 4 and 5 of Sterkfontein,Member 3 of Swartkrans as well as Kromdaai. Fossils of false saber tooths such as Dinofelis were also found in the Swartkrans and Kromdaai. Vrba(1976) concluded that some of the bovids remains in the hominid fossil caves were too large to have been killed by leopards. Her implication of sabre-tooths as an agent was supported by Brain (1993).However, the evidence substantiating this view was said to be insignificant by de Reuter and Berger (2000). In his book, Brain(1993) suggested that Dinofelis, the false saber-toothed cat, was a specialist primate killer, picking off hominids and baboons which were then dragged back to its cave lair[8].

Crocodiles

Habitat specificity of crocodiles makes their fossil occurrences good indicators of paleo-wetland settings. Combined with the presence of shed crocodile teeth, crocodile feeding traces on bone indicate landscape settings that are modeled to have provided well-defined hazards for hominins. Hominin body fossils and trace fossils of the Pliocene and Early Pleistocene were recovered from rivers and lake basins which were inhabited by crocodiles(e.g., Afar Triangle and lower Omo River in Ethiopia, Lake Turkana region of Kenya, Olduvai Gorge, Tanzania). [9] The accumulation of bones recovered from Bed I and II of the Olduvai Gorge have been attributed to Crocodylus lloidi. The tibia of an eland sized bovid,femur of a zebra sized equid,OH-7(Olduvai Hominin-7) hominin specimens as well as Oldowan stone artifacts were excavated from a trench which contains shed teeth identified as those of C. lloidi. [10] After studying damaged remains, Davidson and Solomon (1990) concluded that tooth marks on OH(Olduvai Hominin) 7 specimens were made by crocodiles.Recently an examination of the of O.H.8 foot bones from FLKNN level 3 at the Olduvai Gorge revealed that puctures and tooth pits on these specimens are diagnostic of crocodile damage. The calcaneum of OH 35 also bear similar crocodilian toothmarks.[9]

Conclusion

Currently, there is much evidence from the fossilized remains to infer that early hominids met violent deaths often as action of predators. Terrestrial predators such as leopards,hyaenas and possibly saber tooths played a significant role in the accumulation of bones of the Plio-Pleistocene hominids.Other examples are afforded by the crocodilian tooth impressions on the foot of Homo habilis(specimen OH 8)and the taphonomic signatures associated with eagle damage on the crania of the Taung child.[3] The above-mentioned predators have also been inferred by Acsadi and Nemeskeri (1970) as a cause of death in the later members of genus Homo while modern humans are still preyed upon by big cats and crocodiles despite their intelligence.In conclusion, the presented inferential evidence and Bob Brain’s critique of the Killer-Ape hypothesis have provided valuable understanding of the palaeoecological roles of early hominids[5].

Reference

  1. Dart, R. A. 1949. "The predatory implemental technique of Australopithecus". American Journal of Physical Anthropology 7 (1): 1-38.
  2. Hart, D. and Sussman, R.W. (2005) Man The Hunted: Primates, Predators,and Human Evolution.Boulder: Westview Press
  3. 3.0 3.1 Tobias,P.V.(2006) Longevity, death and encephalisation among Plio-Pleistocene hominins. International Congress Series,1296, pp. 1-15
  4. 4.0 4.1 Davenport,C. M.2006. An Essay on Human Evolution[Online].Available: http://home.usit.net/~cmdaven/human.htm#top#top[30 September 2007]
  5. 5.0 5.1 5.2 Brain, C.K. 1993.A taphonomic overview of the Swartkrans fossil assemblages.In (C.K. Brain Ed) Swartkrans, a Cave’s Chronicle of Early Man. Pretoria, Transvaal Museum Monographs 8, 258-264
  6. Berger, L.R. and Clarke, R.J. 1995. Bird of prey involvement in the collection of the Taung child fauna,Journal of Human Evolution 29 pp. 275–299
  7. McGraw,S.W.,Cooke,C. and Schultz,S.2006.Primate remains from African crowned eagle(Stephanoaetus coronatus)nests in Ivory Coast’s Tai Forest:Implications for the primate predation and early hominid taphonomy in South Africa.American Physical Anthroplogy. 131, pp. 151-165
  8. de Ruiter, D.J & Berger, L.R. (2000). Leopards as taphonomic agents in Dolomitic Caves- Implicationas for bone accumulations in the Hominid-bearing Deposits of South Africa. Journal of Archaeological Science (2000) 27, 665-684.
  9. 9.0 9.1 Njau, J.K. and Blumenschine R. J.(2005). A Diagnosis of Crocodile Feeding Traces on Larger Mammal Bone, with Fossil Examples from the Plio-Pleistocene Olduvai Basin, Tanzania. Journal of Human Evolution, 50(2):142-162
  10. Davidson, I. and Solomon, S.,1990. Was OH 7 the victim of a crocodile Attack?In: Solomon, S., Davidson, I., Watson, D. (Eds.), Problem Solving in Taphonomy:Archaeological and Palaeontological Studies from Europe,Africa and Oceania. Tempus, St. Lucia, Queensland, pp. 197-206