Archaeology Field Methods and Early Human Evolution sep 9

Survey and Excavation Fundamentals

  • Archaeology integrates artifacts, features, and their associations to reconstruct complex past behavior and the archaeological record.
  • Two core field activities: site survey (finding sites over large areas) and excavation (systematic uncovering of sites on smaller scales).
  • Discovery mechanisms: a mix of accidental findings, informant reports, and purposeful design surveys (targeted search). The goal is to identify where humans left material remains and where those remains are exposed in the ground context.
  • Context matters: the visibility of artifacts depends on exposure in the geological context (surface visibility vs. buried contexts) and this controls how easily artifacts are found.
  • Artifacts and features are marked in place and mapped; modern tools include GPS units and total stations to record precise positions.
  • Context and association are central: understanding how artifacts relate to one another within a site (spatial and stratigraphic relationships) to infer past activities.
  • Site survey often covers very large areas (example: a three-year survey across Rocky Mountain National Park, including alpine zones up to >12{,}000\ \,\text{ft} above sea level), revealing archaeology across the landscape.
  • Excavation moves from broad spatial scales to focused, finer-scale work (more laborious and expensive as scope shrinks).
  • Excavation strategies:
    • Horizontal excavation: broad, shallow exposure to understand relationships across a site; useful when materials are near the surface or not deeply buried. Example: coastal French/Spanish settlement off South Carolina with walls and pits (cooking and storage pits) revealing site function.
    • Vertical excavation: deep, down-going exploration to reveal changes through time; challenging to gain a broad view but essential for diachronic understanding (stratigraphy and deposition processes).
  • Case example of vertical deposition: Foster site, Southern Illinois — >9{,}000\ \,\text{years} of occupation with >19 cultural layers; includes an early dog burial illustrating long-term human-dog associations.
  • Excavation decisions guided by research questions and preservation: well-preserved stratigraphy helps select how to sample and what to excavate.
  • Large horizontal approaches are useful when materials are near surface; vertical approaches reveal diachrony and changes in occupations.
  • Example site: coastal SC settlement shows walls (yellow) and features interpreted as storage pits and cooking pits; the circular features are features (not animal burrows).
  • Features are central: features are remnants of human activity that are removable and provide the behavioral core of a site (e.g., cooking pits, ovens, storage pits).
  • Cooking features and ovens: a red rind (oxidation) around the feature marks the edge of the heating area; the center contains charcoal/fuel; heat-resistant rocks are used to regulate heat and create microwaves of cooking for long periods.
  • Visual of an excavation: top-down view shows a square grid with features and surrounding bone deposits; many bones cluster near pits, indicating site activities around cooking and food processing.
  • The site interpretation emphasizes a crime-scene like approach: gather all types of evidence (artifacts, features, bones) and assess their co-associations to infer what happened at the site; debate about interpretation is common and healthy in archaeology.
  • Ethical and methodological considerations: integrity of the scene, extent of disturbance, and proper mapping are critical; not all sites yield equally robust interpretations.
  • The field process (survey → shovel testing → excavation → analysis → interpretation → publication) is foundational; this will be revisited in paleoanthropology.
  • The lecture ties into paleoanthropology by extending similar nuts-and-bolts methods to fossil records and deeper time contexts.

Large-Scale Survey vs Focused Excavation: Methods in Practice

  • Survey covers very large areas to identify candidate sites; excavation then tests hypotheses and clarifies function and chronology.
  • Shovel testing as a sampling method: using multiple, evenly spaced test pits (e.g., every 10 m) to expand the tested area and detect subsurface remains.
  • Example of shovel tests: a grid where test pits are placed to follow clues from surface artifacts; deeper digging yields artifacts or screening results that guide further excavation.
  • In field reports, the excavation area may include many small probes and screens; volume and density of recovered artifacts help prioritize areas for more intensive digging.
  • The Flinty area example shows how screening yields small, typical artifact categories (stone tools, pottery sherds, ecofacts) and how the distribution informs site function.
  • A typical small test may be reported as “bone fragments” or “pot sherds” from specific stratigraphic levels; these inform the dating and cultural attribution of the site.

Pottery, Technology, and Experimental Replication

  • Cord-marked pottery: exterior has a cord-wrapped texture (cord-marking) achieved by pressing a cord-wrapped around a stick into the clay surface; interior surfaces show finger impressions.
  • Surface texture described as undulating lines reminiscent of a “ruffled potato chip” texture.
  • Pottery studies include comparative analysis with other regional ceramic traditions to infer exchange, contact, and cultural affiliations.
  • Experimental replication: researchers (e.g., Cherilyn Gaber) reconstruct original pottery using clays from the area; compare to archaeological examples to understand manufacturing techniques and uses.
  • A large, common vessel type at the site is described as a “giant crock pot” used for long cooking of stews and foraged foods, illustrating daily life and food processing.
  • Other vessels show variation in forms and techniques, indicating different pottery traditions and production methods within the site’s cultural context.

Features, Cooking, and Food Processing

  • Features are central and removable; they provide the behavioral epicenter of the site, similar to a classroom’s central role.
  • Cooking features typically include a ring of stones and a central fire or pit with charcoal; heated rocks help retain heat (ovens) for long cooking times of food and fruit processing.
  • Visual cues for cooking features: red rims or oxidation lines indicate heated edges; the dark center usually contains charcoal/fuel; surrounding rocks help retain and distribute heat.
  • Dense concentrations of bones around pits indicate food processing areas where bones were burned or processed after meat removal.
  • The layout of features and bones allows researchers to reconstruct cooking activities, food preparation, and social organization around meals.
  • Contemporary crime-scene thinking is applied: a site’s integrity, completeness, and spatial relationships are critical for credible interpretations.

From Field to Theory: Interpreting Evidence and Scientific Practice

  • The field-to-laboratory workflow involves collecting, mapping, analyzing, and interpreting artifacts, features, and bones; eventual publication follows.
  • The instructor emphasizes debates about interpretations and the evolving nature of archaeological and paleoanthropological knowledge.
  • Interdisciplinary collaboration is essential: geologists for stratigraphy; zooarchaeologists for animal bones; experimentalists for replication; dating specialists for chronologies.
  • Training and outreach: interlabs and casts allow students to engage directly with material culture and to gain hands-on experience.
  • Infrastructure and development can disturb sites (e.g., railway construction); ethical considerations include documenting disturbances and preserving site integrity where possible.
  • The field’s iterative nature is a strength of science: new findings lead to revised interpretations and updated models.

Paleontology, Deep Time, and the Evolutionary Record

  • Paleontology integrates fossil records with geological context to understand deep time and human origins.
  • Geological timescales relevant to the course: Miocene, Pliocene, and Pleistocene epochs, with major transitions:
    • Late Miocene: approx. 7.3\times 10^{6}\ \text{to }5.3\times 10^{6}}\text{ years ago}; emergence of early hominids from common ancestors with great apes; not a direct line but a branching process.
    • Pliocene: notable diversification of hominids in Africa; emergence of bipedalism and early stone tool use; environmental shifts from forests to more open habitats begin here.
    • Pleistocene: ice ages; long-term climatic cycles; human dispersal out of Africa and expansive settlement across the globe; entry into the Western Hemisphere within roughly the last 2.5\times 10^{5}\ \,\text{to }10^{5}\text{ years}.
  • The Miocene–Pliocene divergence between humans and the chimpanzees is estimated around 6\text{ to }8\times 10^{6}}\text{ years ago} (some estimates say 5\text{ to }7\times 10^{6}}\text{ years ago}).
  • Evolution is not linear; the fossil record shows multiple genera coexisting in Africa across different landscapes and climates; isolated populations can diverge and interact over time.
  • The dating and dating methodologies include potassium-argon dating and other radiometric methods; dating strategies are integrated with stratigraphy and paleontological context.

Africa’s Fossil Record: East Africa and South Africa

  • East Africa as a hotbed of paleoanthropology: rich fossil sites in the Great Rift Valley; volcanic ash deposits preserve remains; early hominins and tool use emerge here.
  • East Africa's tectonics: the Rift Valley exposes deep sediments and allows rapid burial and subsequent exposure; volcanoes contribute ash layers that preserve materials and provide datable horizons.
  • South Africa’s karst cave record: limestone karst systems preserve bones and artifacts in caves and cracks; erosion and sediment movement can deposit material in caves.
  • Notable East African locales discussed:
    • Olduvai Gorge (Oldavai Gorge) in Tanzania: a premier paleoanthropological site with a long history of excavation led by researchers like the Leakey family; the gorge exposes eroded sediments with abundant fossils and artifacts.
    • Olavai/Olavai Gorge (as named by the lecturer): illustrates how terrain and erosion shape fossil exposure and site planning.
    • Olavai Gorge terrain shows erosion-resistant blocks amid badlands; the landscape helps researchers identify promising stratigraphic sections for excavation.
  • Dr. Michael Mate (Mate) and paleoanthropology in East Africa: a contemporary leader working in Olavai Gorge; emphasizes collaboration and training local scientists in East Africa (Kenya, Tanzania) to foster regional expertise and capacity building.
  • 3D mapping and UAVs: graduate students use drones to map the gorge and build digital elevation models (DEMs) to locate and plan excavations; this modernizes site survey in paleoanthropology.
  • HWKEE site (in East Africa context):
    • Age: approximately 1{,}700{,}000\ \,\text{years old}.
    • Seven years of excavations on a hilltop; preserves long-term sediment accumulation and stratigraphic integrity across multiple layers.
    • Geochronologists date deposits; layers above and below a tagged surface provide dating targets for guided excavation.
    • Excavations reveal both fossils and artifacts; bones and tools are recovered from multiple levels, reflecting a deep timeline.
    • Faunal remains include diverse mammals (e.g., zebras, lions, gazelles) and evidence of tool use (cut marks) on bones.
    • High-resolution surface scanning reveals cut marks vs tooth marks and percussion marks; cross-sectional analysis distinguishes stone-tool cut marks (often V-shaped) from animal-induced marks.
    • The site demonstrates early hominin meat processing strategies and tool-use behaviors; the combination of bones and tool marks provides a strong interpretation of hunting, scavenging, or meat processing activities.
  • Fossil analysis process:
    • Fossils are compared to modern and extinct fauna to determine species; zooarchaeology is used to interpret the faunal assemblage.
    • The field collects diverse evidence (bones, tools, coprolites) that require cross-disciplinary analysis to reconstruct behavior.

Key Fossil Discoveries and Interpretive Milestones

  • Lucy (Australopithecus afarensis, Hadar region, Ethiopia): a well-represented specimen (52 major elements; about 40% of the skeleton) includes ribs, vertebrae, limbs, pelvis, and hip; indicates early bipedalism through functional morphology of the hip and femur.
    • Height about 3.5\ \text{ft} (roughly 1.07 m) and small stature; Lucy’s skeleton provides crucial evidence for upright walking.
  • The First Family of Anthropology (Mary and Louis Leakey, later Richard Leakey): foundational excavators in Kenya and Tanzania; contributions to our understanding of early hominins and site contexts.
  • Laetoli trackways (Tanzania): dated to 3.6\text{ to }3.7\times 10^{6}\text{ years ago}; footprints preserved in volcanic ash cemented by moisture; show bipedal locomotion in Australopithecus afarensis.
    • Footprints indicate at least two individuals; differences in stride depth suggest possible carrying of items or differential weight; trackways provide direct behavioral evidence beyond skeletal morphology.
    • The trackways occur in the Rift Valley environment, where ash deposition from volcanic activity created delicate preserve conditions for footprints.
  • Ardipithecus ramidus (Ardi), Ethiopia (~4.5\times 10^{6}\text{ years ago}): forest-dwelling hominin with opposable big toe; suggests a form of bipedalism but not fully modern locomotion; environment reconstructed as woodland; offers insight into the ecological context preceding habitual bipeds.
  • Australopithecus afarensis (Hadar, Ethiopia): early bipedalism; bipedal adaptations first clearly visible in functional morphology; diversity of specimens across Hadar demonstrates early hominin variability.
  • The Diogenes-like complexities of the record: the fossil record shows multiple lineages coexisting, some going extinct while others emerge; our understanding evolves with new discoveries and revised interpretations.

Trackways, Bipedalism, and the Emergence of Human Traits

  • Trackway evidence (Laetoli) supports upright walking during the Pliocene; stride length, depth of prints, and relative weight suggest locomotor patterns consistent with bipedalism.
  • Bipedalism as a key early human trait: likely emerged around 4.5\text{ to }5.0\times 10^{6}\text{ years ago}; the shift to bipedalism would have required coordinated changes across multiple anatomical systems (pelvis, femur, foot, spine, musculature).
  • Hypotheses for the selective pressures leading to bipedalism:
    • Carrying: free hands to carry tools, food, or offspring (though this is debated since tool-use predates certain bipedal adaptations).
    • Predator detection/avoidance: standing upright to see farther; however, chimps also adjust posture to scan surroundings, so bipedalism might not be solely for predator detection.
    • Habitat changes: transition from forested to more open savannas during the Pliocene favored long-distance travel and energy-efficient locomotion.
  • Limitations of early interpretations: bipedalism likely arose in a mosaic fashion, with multiple anatomical changes over long periods; sometimes modifications happened before technologies like stone tools emerged.
  • The interplay of biology and culture: early hominins adopt new ecological niches; later cultural innovations (stone tools) reinforce and complement anatomical changes, creating feedback loops that support further adaptation and expansion.

Human Evolution: Synthesis and Open Questions

  • Humans and chimpanzees share a distant common ancestor; subsequent lineages diverged roughly in the window [6, 8]\times 10^{6}\text{ years ago} (range estimates vary by study).
  • The fossil and genetic records are continually revised with new discoveries; the course emphasizes critical evaluation of evidence and the necessity of multiple, independent dating and dating-context sources.
  • The study of human evolution requires integrating:
    • Fossil morphology (functional anatomy, locomotion, and relationship to other primates)
    • Paleoenvironmental reconstruction (habitats, climate shifts, vegetation)
    • Chronology (radiometric dating, stratigraphy, cross-site comparisons)
    • Cultural behavior (tool use, cooking, social structure) as inferred from artifacts, features, and traces on bones.
  • The field promotes questions about what it means to be human, pushing beyond imagery to understand essential characteristics: cooperative behavior, bipedalism, tool use, complex social organization, and the capacity for symbolic thought and culture.
  • The class emphasizes that science evolves through debate and revision; new data may shift consensus views or refine timelines and relationships.

Reflections on Method, Ethics, and Real-World Relevance

  • The field integrates ethical considerations about the disturbance of sites, respectful treatment of human remains, and collaboration with local communities and countries of origin for major sites (e.g., East Africa).
  • Archaeology and paleoanthropology have direct relevance to understanding human origins, our place in the natural world, and the relationship between biology and culture.
  • The study of deep time informs perspectives on evolution, biodiversity, climate change, and the interconnectedness of ecosystems across millions of years.
  • Students are encouraged to engage critically with evidence, recognize uncertainties, and consider alternate interpretations in light of new data.

Quick Reference: Key Dates and Terms (LaTeX-formatted)

  • Late Miocene dating: 7.3\times 10^{6}\ \text{to }5.3\times 10^{6}\ \text{years ago}
  • Divergence of humans and chimpanzees: 6\text{--}8\times 10^{6}\ \text{years ago} (some estimates 5\text{--}7\times 10^{6}))
  • Australopithecus afarensis (Lucy): about 3.18\times 10^{6}\ \text{years ago}
  • Laetoli trackways: 3.6\text{ to }3.7\times 10^{6}\ \text{years ago}
  • Ardipithecus ramidus (Ardi): about 4.5\times 10^{6}\ \text{years ago}
  • HWKEE site age: 1.7\times 10^{6}\ \text{years old}
  • Large-scale survey example: site surveys across ecosystems up to 12{,}000\ \text{ft} elevation
  • Excavation unit sizes: about 1\text{ m} square blocks or 50\ \text{cm}$$ squares for test units
  • Pottery terminology: cord-marked pottery (cord-marking from wrapped fibers); exterior texture shows undulating lines; interior shows fingernail impressions; replication by Cherilyn Gaber
  • Cultural-analytic terms: features (removable), screenings, shovel testing, horizontal vs vertical excavation, stratigraphy, law of superposition

Next topics preview

  • Deeper exploration of paleoanthropology: fossil record interpretation, dating methods, and evolving models of human evolution; more on trackways, tool use, and cognitive evolution.
  • Continued comparison of archaeological and fossil records to answer questions about when and how humans became human, and how humans interacted with changing environments.