Part II: Chapters 12 and 13

Chapter 12: Behavior and Evolution of Early Hominins

The Archaeology of Stone Tools

Instead of stone tools being studied as the focal point within a system of typologies, or types of types, the study of artifacts within a context of subsistence strategy has become the current trend. Archaeologists study artifacts including chipped stone tools as a method of determining not only individual tool function, but they use their analysis to answer larger methodological questions relating to subsistence practices. One way of determining function is by practicing the methods and techniques that were used to create the original artifact. This type of research is called experimental archaeology. There are 5 modes of defined stone tool assemblages: Mode 1. Oldowan (chopping tool), Mode 2. Acheulean (uniformly flaked bifaces), Mode 3. Prepared Core (Levallois-micro flaking), Mode 4. Blade ( Upper Paleo, Later Stone Age), and Mode 5. Microlith(Mesolithic, small, delicate tools). The different modes of stone tool technology appear at different periods, but often continue to be utilized in later stone tool assemblages. Simple chopping tools of the Mode 1 kit can be found in the archaeological record up until the late historic periods in North America. Tool kits like the Oldowan and the Acheulean have a persisting utility based on their multiple functions and ease of preparation.

The Earliest Known Tools-

At approximately 2.5 mya, the oldest recorded stone tool artifacts appear in the archaeological record. They have been recorded at several sites, but the technology is named after the Oldoway Gorge in Tanzania (Those Leakeys are everywhere). Four categories of stone tools were created from Mary Leakey’s research: tools, utilized pieces, waste, and manuports. It is important to point out that the assemblage variety attributed to the Oldowan are more of a result of opportunistic production (p.312); artifacts tend to blend in one another typologically as a result. Utilized pieces tend to resemble waste, and scraper tools and choppers are often the product of flake production through various types of percussion. Manuports are pieces of rock that have been carried to a site, but have not been modified. They are frequently comprised of materials that could be used as percussion tools or could be percussion flaked into a chopper or scraper. Early hominins may have used a variety of materials such as antler, bone, or wood, but preservation in the archaeologicical record is poor for those material types. The stone tools associated with early hominin use have wear patterns indicating they were used for a range of subsistence activities such as butchering, wood-working, and plant processing (p.315). The broader implication for the Oldowan technology is nothing short of one of the most significant technological revolutions that may have contributed to further encephalization (p.315).

How has the discovery of Homo Floresiensis redefined the correlation between brain size and tool production capabilities since they had a tiny brain yet potentially created advanced stone tools?

The Kanzi Experiment: Oook oook oook!

In addition to the debate that pits Australopithecus against early Homo, a debate exists over whether apes have the physical and cognitive ability to create stone tools. The cognitive demands and physical structure of the arms, wrists, and hands were studied in Kanzi, a captive bonobo. Although Kanzi was able to produce stone tools, the lithic product differed from the Oldowan assemblages. The studies failed to determine if Kanzi’s poorer performance reflected differences in cognitive ability or anatomical constraints (p.317).

A frequent argument resides regarding the identity of the hominin responsible for early stone technology. The two representative and contemporaneous hominins are Homo and Australopithecus. By comparing hand morphology, pro-Australopithecus advocates such as Randall Susman conclude that later robust australopithecines had the manipulative ability based on hand morphology to create stone tools (p.318-319). It is possible that both species were able to produce stone tools and something led to technological expansion in the genus Homo.

Tool technology appears to have expanded, but did not necessarily originate, along a parallel gradient with the brain. What different hypotheses might be able to account for this parallel expansion? What adaptive strategies (e.g., resource intensification, niche exploitation, predation defense, warfare…) would have been well-suited for the implementation of stone tool technology?

The Pattern of Early Hominin Evolution-

The understanding of early hominin evolution continues to be elusive, but what is clear is early the early phase of hominin evolution was not a straight path to Homo sapiens (p.320). Rather, it was a result of a series of adaptive radiations in which early hominins expanded geographically, adapted to and exploited different habitats and niches, and underwent varying specializations including evolutionary reversals. The origin of the hominin clade is currently established somewhere between 7 and 5 mya and may have been the result of an earlier adaptive radiation of the African apes. A second radiation was likely responsible for the diversification and geographic expansion of gracile australopithecines in Africa. A third dispersal may have resulted in the emergence of the robust australopithecines. The fourth potential radiation may have been linked to early species of Homo. The resulting picture of early hominin evolution is that of a bush (p.323); it represents a continuity of events where several dispersals led to multiple species coexisting throughout Africa during different periods. This would be a fine example of punctuated equilibrium.

Homo represents an example of a reversal in the evolutionary trend of megadonty although the causes for this reversal remain contested (p.326). Other evolutionary trends that help create the clade include larger cranial capacity and reduced dentition. More recent analyses (p.326) indicate when other factors are included with a more focused cladistic method, the adaptive shifts that signify the Homo genus actually occurred later with Homo ergaster. Homo habilis and Homo rudolfensis would actually be more cladistically similar to Australopithecus. This would create a definitive gap that may signify a major adaptive change that led to the evolutionary success to later species of Homo. If the turnover-pulse hypothesis is correct, major climate shifts would have lead to origination/extinction events, and major climate changes would have resulted in detrimental/opportunistic changes in ecological relationships. In the paleontological/archaeological record, adaptive radiations in early hominins reflect adaptive strategies from an ecological perspective. During particular periods associated with events of adaptation, early hominins adjusted to and exploited ecological niches through adaptation and specialization in terms of geographic distribution, behavior, and diet.

What underlying factors could be responsible for the multiple adaptive radiations and specializations that occurred in African apes and early hominins? The authors provide a few potential factors for each radiation. Can you think of any other potential factors and/or related specializations? The turnover-pulse hypothesis argues that extinction occurs after origination. Is there any evidence in early hominin evolution that supports/debunks this argument?

Chapter 13: Africa and Beyond: The Evolution of Homo

Evolutionary Patterns-

The species Homo erectus has undergone several name changes since its discovery in 1887 by Eugene Dubois on the island of Java (p.332). Initially regarded as the “missing link” in human evolution, Dubois named the fossil specimens considered to be from the same individual Anthropithecus erectus. He changed the name to Pithecanthropus erectus after believing the “missing link” had been discovered based on cranium measurements (p.333). The classification as the link between apes and humans was based off a single top of a hominin cranium and a complete femur although the femur is now thought to be that of a later species Homo sapiens (p.334). Peking man was discovered in 1927 by Davidson Black and was subsequently named Sinanthropus erectus (p.334). In 1951, both species were combined in to a single genus and species Homo erectus because of their greater similarities to Homo sapiens (p.335).

The oldest known and most complete fossil specimens have been recovered in the Lake Turkana region of northern Kenya and are around 1.8 million years old (p.336). Of significance is the brain size which is larger than Homo habilis by approximately 210cc at 850cc.

One of the most important discoveries for Homo erectus was the complete skeleton of a H. erectus boy on the west side of Lake Turkana. The importance is two-fold: many of the postcranial elements of Homo erectus had not been discovered, and it allows for overall body proportions and their relationships to be scrutinized (p.337). The anatomical relationships allowed paleoanthropologists to make inferences about ecological and behavioral factors attributed to the species such as life-history, subsistence, and language capacity (p.337).

Changing Views: Dates and Evolutionary Pattern-

Two views of Homo erectus have appeared as a result of the quantity of fossil specimens that have been collected (p.339). The first conclusion is that anatomical variations initially observed in Asia seem to quickly spread everywhere. The second conclusion declares that Homo erectus originated in Africa around 2 million years ago and dispersed outside Africa around 1 million years ago. The possibility that H. erectus took around 1 million years to disperse provides an important puzzle in the history of H. erectus (p.339). One of the reasons for delay may be considered on technological terms. It is suggested (p.339) that Homo erectus lacked sufficient technological development needed to expand their geographic range outside of Africa until the development of the Acheulean industry around 1.4 mya.

What are the implications of the gap in time between Homo erectus’s appearance and eventual expansion out of Africa? Current evidence (p.339) suggests that either there was no delay between evolution and dispersal of Homo out of Africa, or Asia was the origin of H. erectus at 2 mya. Recent analysis of the Modjokerto skull from Java determines the age to be between 1.8 and 1.6 million years old and is highly suggestive of an Asia origin although the actual provenance of the skull is in question (p.340). Another find in China in 1988 may also offer a precursor to H. erectus dated close to 2 mya (p.340). Both of these finds reinforces the hypothesis for an “out of Asia” origin tale of H. erectus although most still consider that H. erectus is descended directly from Homo habilis/rudolfensis approximately 2 mya in Africa (p.341).

Changing Views: Anatomy and Evolutionary Pattern-

Many anthropologists support that Homo erectus may represent multiple species based on variation viewed between separate geographically distributed populations (p.342). Homo ergaster is the new species in which the earliest African specimens have been assigned. The relationship between ergaster and erectus is considered to that of an ancestor and a descendant (p.342). This analysis continues to support the hypothesis for the origin of Homo from Africa and it attributes the appearance of H. erectus in the archaeological record in Africa as a second later dispersal from Asia back to Africa (p.342).

Some of the key anatomical elements observed in H. ergaster/erectus that differ include several differences but two appear to be significant. The first trait is the increase in brain size over time from ergaster to erectus between 850 and 1100cc. It appears to be a significant increase, but the body size increased from ergaster to erectus as well indicating that the relative brain size may have only increased minutely (p.342).

The second trait has implications for the understanding of behavior such as subsistence strategy (p.343). Homo erectus marks the initial appearance of a human nose with the nostrils facing downward which permits moisture to condensate from exhalation which would have been important in active subsistence on in a warm, arid environment (p.343).

Several other behavioral inferences can be made through the larger body size, decreased sexual dimorphism, a more robust and heavily muscled structure (compared to modern humans), and the absence of an expanded neural canal in the lower thoracic vertebrae indicate the following: Homo ergaster/erectus was subjected to routine heavy exertion, possessed an broader-ranged subsistence pattern, had less male competition, and did not possess spoken language (p.343-344). All of these traits may assist in the understanding of the behavioral ecology of H. ergaster/erectus. What sort of ecological model would be sufficient in accommodating the aforementioned trait? The authors (p.343) mention the possibility that H. ergaster/erectus may have participated in male-male cooperation. What significance would this have on the origins of modern human behavior and social structure?

Changing Patterns of Behavior-

A number of changes occurred within the genus Homo during the period that ergaster/erectus lived. The following is a list of behavioral adaptations attributed to the initial appearance and subsequent existence of ergaster/erectus (p.344):

• The first appearance of hominins outside of Africa, although other evidence may argue for Asian origins (p.340-341).
• The first appearance of systematic hunting (broader subsistence patterns and decreased male-to-male competition are possible evidence).
• The first appearance of early “Home bases”( May mark an increased sedentism, intensified resource tethering, increased social behaviors e.g. cooperation).
• Toolmaking becomes systematic (indicates increased cognitive ability and manipulation (p.345)).
• The initial use of fire.
• The first indication of an extended childhood (smaller birth canals, earlier births resulting relatively unformed brains, and the demand for social learning are factors).

In addition, life histories change from being an apelike pattern to more towards modern Homo sapiens although H. ergaster is considered intermediate of the two (p.345).

An increase in the frequency of faunal and lithic evidence in the archaeological record from early Homo through H. erectus occupations indicates hunting activity (p.345). One of the significant developments attributed to the appearance of H. ergaster/erectus is the intensification and innovation of stone tool production evident in the Acheulean Industry (mode 2 technology). The teardrop or ovate shaped handaxe is the flagship for the Acheulean tool industry (p.346). Larger tools also appear that appear to be more specific in function. What is important in the Acheulean kit is the systematic flake reduction and core preparation process as it reflects a higher level of both cognitive and manipulative ability in the conception, process, and finished product (p.346). The Acheulean technological period represents a long period of continuity with a wide geographical distribution lasting from approximately 1.4 mya to 200,000 years ago (p.346; 348).

The Movius line is a boundary between the distribution of bifaces and non-bifaces lithic tool industries (p.349 see figure 13.15). It geographically separates Africa, western Asia, and Europe from eastern and southern Asia. Bifacial reduction is nearly exclusive to the west half (observe the hybrid zone in fig. 13.15). Bifacial reduction of a stone tool means that lithic material has been removed from both dorsal and ventral sides of a core or large flake from a core. Usually this is done in some observable and systematic fashion ending in a thin, finely flaked tool. What potential causal factors can be responsible for this line?

Subsistence Practices and Settlement Patterns: Behavioral Ecology

Several hypotheses have been developed regarding early hominin subsistence development and strategies including the home-base hypothesis, the food sharing hypothesis, the scavenging hypothesis, and the advanced scavenging hypothesis (p.351-359). There is a debate that focuses on “hunting versus scavenging,” or “Man the Hunter” versus “Woman the Gatherer.” It appears that advanced scavenging may have been more feasible from both a technological and an ecological standpoint for hominins although they would have differed from the concept of modern hunter-gatherers (p.359).

Cutmarks and percussion fractures on fossil bones observed in the archaeological record and sites indicate early hunting or scavenging practices associated to the earliest signs of meat processing and consumption as early as 2.5 mya (p.359). The increased consumption of meat is considered an important factor in human evolution (p.360). Did dietary changes lead increased social behaviors such as material transport, resource intensification, and new subsistence strategies? Does the increase in modified faunal remains associated with lithic material suggests cooperation in resource procurement visible in the archaeological record as “kill sites,” or does it represents Homo as a scavenger?