Behavior

What do we know about Australopithecus boisei’s behavior? 

Tool Use

Initially, Nutcracker Man was considered the earliest stone tool user (Woods). This was because stone tools were found in association with Nutcracker Man’s remains (Woods). But just 5 years later, this changed. In 1964, Leakey found the remains of another early hominid, Homo habilis, at the same site as Nutcracker Man (Woods). Homo habilis had a larger brain and its hand bones were recovered that showed a capacity for precision grips (Woods). So, it was assumed that they were the stone tool users, NOT A. boisei (Woods).

Today, most researchers accept that Homo habilis was the ONLY stone tool user at Olduvai (Woods). But, a few believe it was possible that BOTH early hominids were using tools. Evidence supporting Au. boisei as a tool user includes (Woods):

• There is NO evidence that eliminates A. boisei as a tool user (their hand bones have never been found)
• Tools (bone, stone, flake-based) have been found at 2 sites that are believed to have been occupied exclusively by P. robustus, a close early relative to A. boisei

Diet

A. boisei is known for its massive cheek teeth and large chewing muscles. Because of these distinctive features, it was often assumed that the species relied on hard, dense objects such as nuts (Cerling et al). But recent research, suggests this may not be the full picture.

• Dental morphology (Woods)
  • A. boisei’s small incisors and canines suggest that IF they were eating fruit, it was probably small fruit and/or lacked “thick husks and fleshy pulp”
  • Their “hyper-thick” enamel protected against increased crushing and grinding action of the teeth
    • Although there is no consensus about what they were crushing/grinding or how often
• Chemical Analysis (Cerling et al)
  • Recent carbon isotope data shows that A. boisei relied heavily on C4 resources such as grasses and likely ate few hard objects such as nuts
  • This means that A. boisei was a grazer
    • Unlike A. robustus (a closely related species which lived in South America), other early humans, and most living apes who are all browsers (rely on C3 resources like trees and shrubs)
    • Suggests A. boisei was NOT competing against other hominids and apes for food resources, but was likely competing against early horses, hippos and some early cow-like species

Social Structure

Most evidence on A. boisei’s social structure comes from their body size and canine size (Woods). Female size (usually smaller) is compared to male size to give researchers an idea of sexual dimorphism (Woods). Researchers used these ratios and compared them to living primates to predict that A. boisei exhibited a range of social structures including: monogamous polyandry (1 female + many males), polygamy (1 male + many females), and multi-male structures (Woods).

However, the field has recently distanced itself from these type of predictions. This is because they rely entirely on analogies to living apes and because researchers have become increasingly aware of the difficulty of assigning sex to fossil hominids (Woods).

Critique of “HOMINIDS: An agent-based spatial simulation model to evaluate behavioral patterns of early Pleistocene hominids”

Overview

Griffith and Long’s paper was based on a computer simulation, specifically an agent-based model or ABM. These type of models have been used extensively in studying animals, but have not been applied as readily to the study of early humans (Griffith and Long). Griffith and Long started by creating an artificial ancient landscape based on two known occupation sites of hominids: Voi and Turkana. Plant samples, rainfall measurements, and seasonal differences were recorded for both Kenyan sites and used to create a realistic and dynamic ecosystem (Griffith and Long).

Once the landscape was created, computerized versions of A. boisei were added (Griffith and Long). Their foraging patterns, interactions with one another, nesting locations, etc. were observed (Griffith and Long). Ten different A. boisei were used in each location (Griffith and Long). For this paper, the focus was on digging tools and the consumption of underground tubers (Griffith and Long).  So at first,  A. boisei was introduced without tools (and therefore no ability to consume tubers) and then again with tools (Griffith and Long).

Although the focus of this particular paper was somewhat narrow (digging tool use and nesting patterns), many more behavior patterns could easily be studied in the future. Griffith and Long purposely made their software open to all so that other behaviors (interactions with other hominids like Homo habilis,  meat eating capacity, etc.) could be studied in the future.

Results

• In both locations, A. boisei were unable to meet their caloric need during Season 4 (in January and February when conditions are dry)
• Allowing A. boisei to use digging tools (and therefore the ability to eat tubers)significantly increased their chance of meeting their calorie needs during lean times (Seasons 3 and 4)
  • This also resulted in more concentrated activity (foraging activity, nesting activity, etc. ) around the tubers, so that activity was not as randomly dispersed and widespread

    

My Critiques

Overall, I thought Griffith and Long’s approach to studying hominid behavior was very interesting and creative. Unlike many other studies, they did not rely on analogies to living primates (which may be inaccurate stand-ins for early humans). I also appreciated that the made their software open-access, allowing other researchers to run new simulations to study different behaviors. My criticisms revolve around:

• How the virtual ecosystem was designed:
  • The weather patterns, plants, and landscape conditions (flooded, unflooded, or channel) used in the simulation were modeled after contemporary species, contemporary weather patterns, and the contemporary landscape
    • Is it really safe to assume the conditions/plants/landscape of today are similar enough to those in Nutcracker Man’s time (1.75 million years ago)? Can they be used as accurate analogies? Or would the differences have skewed the results?
    •  In a perfect world, I would’ve preferred an attempt to recreate the ecosystem of the Pleistocene
• The hominids had full knowledge about which plants were most profitable and always chose the food items with the highest return rates (cost vs. benefits)
  • I find it unlikely that a hominid would have always known this or known it in advance
• The tubers could only be eaten if the hominid was provided with a digging tool, but was this always necessary?
  • Could A. boisei still have gotten to a tuber with just his or her hands?

References

Cerling TE, Mbua E, Kirera FM, Manthi FK, Grine FE, Leakey MG, Sponheimer M, Uno KT.          2011. Diet of Paranthropus boisei in the early Pleistocene of East Africa. Proceedings          of the National Academy of Sciences 108:9337–9341.

Dean MC, Wood BA. 1982. Basicranial Anatomy of Plio-Pleistocene Hominids from East               and South Africa. American Journal of Physical Anthropology 59:157–174.

Derrico F, Backwell LR. 2003. Possible Evidence of Bone Tool Shaping by Swartkrans                    Early Hominids. Journal of Archaeological Science 30:1559–1576.
Griffith CS, Long BL, Sept JM. 2010. HOMINIDS: An agent-based spatial simulation model                to evaluate behavioral patterns of early Pleistocene hominids. Ecological                              Modelling 221:738–760.