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With emergence of Homo erectus in East Africa before 1.8 mya, key questions about the behavior of this species emerge that we can address with archaeological evidence:
Rick Potts: "Variability selection"
How did Homo erectus respond to...?
- trend: cooler and drier
- pattern: wider swings of variation
Habitats in space & time:
Question Anatomical Evidence Archaeological evidence? Locomotor behavior? robust, efficient walker carrying of raw materials? Life History Patterns
& social behavior
altricial births (dependent offspring)
less sexual dimorphism than previous hominids
food sharing behavior?
survival into old age?
adapted for hot, dry environments
high quality diet, less chewing
sites in wider range of habitats?
evidence for tools to process foods?
more reliance on meat? tubers?
Intelligence? larger brain more planning or design in tools?
survival strategies more adaptable?
Some of the different sources of archaeological evidence to address this question:
Changing Technology and Ranging Patterns in Rift Valley ESA:
Between 1.8-1.5 million years ago we see:
- - technological innovation
- better flaking techniques?
- more selectivity & curation
- more tool types (Karari, Developed Oldowan)
- - shift in ranging patterns (Rogers et al)
- wider range of habitats
- longer travel distance
- coincides with appearance of Homo erectus (a.k.a. Homo ergaster) in East Africa @ 1.8 million years ago
Olduvai Beds I and II
at Olduvai, Mary Leakey detected new types of tools appearing at the top of Bed I in some sites.... things like subspheriods, spheroids, and "protobifaces"... she called this the "Developed Oldowan" and suggested that it was a separate industry... "cultures" or "toolkits" ?
In Bed II, Mary Leakey started to find sites with handaxes contemporary with the Developed Oldowan sites. An example of an Acheulian site at Olduvai is EF-HR.
Bed I sites restricted to lake-margin deposits and concentrated along eastern margin of lake... freshwater streams?
By Bed II (1.7 - 1.15ma) (H.habilis at bottom, H.erectus at top, A.boisei. all through) the environment is significantly more open, and sites become increasingly widely distributed once the lake gets trapped in the graben (much smaller) and sites increasingly found in alluvium and gravels of major drainage ways
stone transport: most sites in Bed I and II have local raw materials... available within 2 km... some a little further away (4km). However, almost every large site, with a large number of artifacts, contains a small proportion from more distant sources... 8-10 km away (e.g. green lavas from Sadiman volcano, phonolite (vitric tuff) from Engelosin outcrop, Kelogi gneisses, etc)
Sites around modern Lake Turkana (Rogers et al article)
changes in the types of sites that formed in the Turkana basin through time -- initially small sites with local raw materials in a restricted range of habitats. (cf Rogers et al article). But by 1.6 mya, sites found in a much wider range of habitats; sites are larger concentrations, and sites include evidence of:
Fire is difficult to pin-down -- you have to demonstrate that it is not just a naturally-occurring fire. Randy Bellamo has tried to do this. Has shown that (1) the things burned in antiquity (with geomagnetic data); (2) that they were contemporary with artifacts (which have been heat alterred) and has also calculated that (3) they were "managed" fires because they burned at a higher, sustained temperature than is typical of burning stumps or bush fires.
Earliest sites: ca. 2.3 mya (Omo Member F, Lokalalei )
Perhaps stone tools were used only sporadically at this time -- e.g. seasonally? expediently? Found stones at places where marginal streams intersect major ("axial") river.
Made by early Homo?? and/or Australopithecus boisei ?
ca 1.9 - 1.8 mya (all around Turkana Basin, including Koobi Fora and Fejej)
So, perhaps stone tools becoming more important? (carried into new environments like lake shores... certainly vegetation different near lake, compared to riverine veg near ancient Omo -- probably more open/grassy. Note that CLIMATE becoming drier/cooler at this time -- conditions becoming more open (both from isotope evidence and from bovids)
ca. 1.7-1.5 mya
sites found associated with two different types of riverine environment...
Raw materials being carried further -- lots of gravels, etc, near basin margins (upstream on small channels), but few down on floodplains of major river -- locality with cutmarks only suggests that stones curated -- not always just discarded on spot.
Stones flaked more systematically -- and new toolforms appear, e.g. "Karari scrapers"
Lots of sites are BIG = huge concentrations of bone/stone, plus burnt patches = controlled use of FIRE????
In what ways would controlling/using fire have been useful to hominids? (adaptive advantage)
In East Africa, evidence for burning has been suggested for several sites:
FxJj20 (1.5 ma) (East Turkana) + A.boisei
Chesowanja (1.4ma) (Kenya) + A.boisei (clasts of baked clay... disturbance)
Gadeb (1.5-0.7ma) & Middle Awash (Ethiopia)
Important facts to ascertain when judging evidence for fire:
localized discoloration of earth + deep (not superficial) chemical alteration (=oxidation)
paleomagnetism (intensity and direction suggest hotter temperatures and re-burning of same spot)
thermal alteration of artifacts
SWARTKRANS, South Africa:
Member III: 5 meters of deposit... probably 1.5 - 1.0 mya
A. robustus fossils, some intrusive handaxes, stone tools and cutmarked bones, bone tools (worn to points) and 270/59,000 pieces of burnt bones suggest FIRE use (including 2 of bone tools)
- discolored (black)
- presence of free carbon (carbonized bone) "char"... = 200-500 degrees C
- histological alteration (lamellar structure pronounced... destroyed & cracked, plus re-crystallization of apatite can be seen via x-rays
- (note that bones won't char like this when covered in meat)
New tool type > 1.5 mya = Bifaces (handaxes, cleavers, knives)
An interesting set of issues revolve around the artifact variation found in Early Stone Age Assemblages.
- How many handaxes need to be present at a site before archaeologists call it "Acheulian"?
- What is the relationship between Developed Oldowan sites and Acheulian sites?
Key interpretive principles include: variation due to learned tradition, variation due to activities or functions, variation due to taphonomic processes.
Early Acheulian Sites
We discussed last time how Acheulian sites are recognized by the presence of handaxes, but the assemblages are variable, in terms of proportions of "types" of different tools -- raising interesting issues of interpretation of what the variation in Acheulian (and Developed Oldowan) assemblages MEANS. This is an issue for all Acheulian sites, from the earliest to the latest.
Today we are going to review early Acheulian sites in East Africa... sites between 1.5 and 700,000 years. 700,000 years is a chronological marker because this is the boundary of the Matuyama Reversed paleomagnetic period ... If a site comes from sediments that are reversed, it must be AT LEAST 700,000 years old. This is how many Acheulian sites have been dated. Though, a number of sites in East Africa have been dated with K/Ar and Ar/Ar techniques as well.
Early BIFACES appear at sites in east Africa before 1.5 mya, at several sites, including Olduvai Bed II site EF-HR, and an early site in Ethiopia called Konso-Gardula. For example, at the site of Peninj by Lake Natron (Tanzania), handaxes occur sandwiched between two dateable layers: under a lava flow dated to 1.3 mya, within REVERSED sediments, and over sediments that are NORMAL = Olduvai Normal Event (1.6-1.8 mya). This site contains lots of lava unifaces and bifaces, particularly cleavers, made on large lava flakes with minimal secondary trimming. (Note that a famous mandible of A. boisei was found in layers just BELOW the handaxes at Peninj...).
Also found in East Turkana sequence (Kenya)very early along the "backslopes" of the Karari escarpment, occurring between tuffs dated @ 1.6 mya and 1.3 mya -- there they are more "UNIFACES" really just shaping a large flake with minimal trimming. (slide of FxJj63) and photo illustrates how handaxes can become "tipped" in sediments
Another site > 700,000 years old in Kenya highlands north of Nairobi is site of Kariandusi containing many bifaces, many out of obsidian. Diatomite quarry -- site in stream deposits leading down to lake. But probably a disturbed context (few small pieces, bifaces alligned with stream motion) and no bones.
Olorgesailie Kenya is one of most famous early Acheulian sites in east Africa. A series of sites lying at the base of a volcano, Mt Olorgesailie, in a small lake basin in the Rift Valley (near modern Nairobi). The site was first discovered in 1942 by Leakeys (competition between Louis and Mary over whose site had the most handaxes....). Work continued by Glynn Isaac in 1960's, and faunal studies in 1980's... eg. a hippo butchery site (no handaxes). Recent new excavations by Rick Potts.
14 sedimentary levels "members" originally thought to be 500,000 years old, but new Ar/Ar laser fusion dates put Member 1 at 0.99 mya, and Member 14 at 0.500 mya.
DE89/B site is one of most famous at Olorgesailie (in Member 7) because it contains many artifacts associated with bones of over 50 individual giant gelada baboons. Bones are pitted from smashing, butchery. Often interpreted as evidence for cooperative hunting. Questions: were all baboons killed at single time (a catastrophic death)? Or was it an assemblage that accumulated more slowly "attritional death"?
Member 1 was a stable land surface followed by Potts along 4-5 km of exposure. He found an Elephas reckii skeleton at Site 15 with mostly flakes (no handaxes, but includes some "biface trimming flakes" that suggest resharpening of handaxes on the spot). Also found many small sites, and some places that look like carnivore dens, with no artifacts.
Overall at Olorgesailie, one sees a differential distribution of tool types across landscape. Potts found, in his studies that lake margin assemblages contain < 5% handaxes. channel sites are often dominated by handaxes (62%).
Expedition to Olorgesailie
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Last updated: 16 October, 2000
Copyright Jeanne Sept 2000 : do not cite without permission
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