Presentation on theme: "Early Humans: Meet the Ancestors"— Presentation transcript:
1 Early Humans: Meet the Ancestors 2. Archaeological Evidence and the Limits of Knowledge
2 Objectives Look at the scientific investigative tools Stratigraphy Archaeological dating methodsComparative Anatomy of FossilsDNA and Isotope analysisArtefact and Ecofact EvidenceConsider the security of our interpretations.
3 Charles Darwin Origin of Species, 1859 The Descent of Man, 1871 Cartoon from “The Hornet” satirical magazine 1871
4 StratigraphyProvides relative dating – separating the remote past into horizons of greater and lesser age.Boxgrove, England
5 Fauna Assemblages – Environmental Dating Boxgrove excavation era of strata indicated by animal bone assemblagesExtinct rhinocerous,Stephanorhinus hundsheimensisPeriod when Britain had a climate like modern AfricaSites can be given sequence relative to each other but not a date by this method.
6 Radio Carbon Dating Invented c. 1950 Based on the principle that C14 decays at a predictable rateAge calculation made by examining ratio of C14 and C12Relatively short half life c years makes it accurate, but limits its range to about the last 40,000 years
7 Lascaux, S France Accelerator Mass Spectroscopy – very small samples. C14 dating of cave painting, targeting carbon based pigmentsImages date to kyaSome images refreshed over thousands of years
8 Potassium - Argon Dating Less accurate but much greater dating range – suitable for the earliest hominidsUsed to date layers of volcanic rockNoble gas Argon 40 released when rock moltenAny Argon 40 present must have derived from Radio Decay of Potassium
10 Uranium Series DatingBased on ratios between radio active Uranium isotopes and daughter productsUranium products are soluble in water.Thorium and Protractium products are insoluble in water.Calcareous deposits like limestone therefore start their existence with no Thorium or Protractium present.
11 Uranium 238 Series Uranium 238 4.51 billion years Uranium ,000 yearsThorium ,200 yearsRadium yearsRadon daysLead yearsPolonium daysLead stable
12 Uranium 235 Series Uranium 235 713 million years Protractium ,400 yearsThorium daysRadium daysLead stable
13 Vartop Cave, RomaniaLimestone cave Neanderthal occupation dated to 62kya to 97kya by U-series.Footprints Suggests an individual 1.46 m tall
14 Cave Art Creswell Crags, Derbyshire Engraving Church Hole Creswell CragsU-series sampling of flowstone suggests pre- 12,800 BP
15 Equilibrium LevelAs levels of Thorium 230 increase rate at which it is destroyed approaches rate at which Thorium 230 is created by decay of Uranium 234.
16 Comparative Anatomy of Fossils Comparison of cranial capacity
17 Incompleteness Australopithecus Afarensis Best specimen “Lucy” Only 40 % completeNo formal burials from this period.Most bodies dismembered and scattered by scavengers
18 Turkana Boy H. erectus, 1.5 mya Very narrow spinal column Lacked fine control of diaphragmImplications for speachOther specimens fall with range of modern humansMight be an individual with genetic defect.
19 New Species or or Diseased Individual Recent discovery of a new “hobbit” species contestedH. floresiensis skull compared to modern human with the genetic disorder microcephaly.H. floresiensis frontal and temporal lobes highly developed
20 Dimorphism in Australopithecine Suggested Australopithecine dimorphism as compared to modern humansHominids of different sizes now thought to represent different contemporary species
21 Ancient DNA Cheddar Gorge Late Palaeolithic skull 1911 DNA recovered 1990’sAdrian Targett – descendant living few miles from find siteFears of contamination from modern DNA
22 Age EstimationTooth Eruption can give age at death in modern humans very accuratelyAge can also be estimated from the state of fusion of bones of the skull and limbs
23 Errors in estimating age Australopithecene infant “Taung’s Child”Age by comparison with humans 7 yearsAge by comparison with chimps 3 years
24 Comparative Anatomy - Teeth Nakalipithecus nakayamei jaw, Kenya, c 10myaHomo erectus c. 1 myaBroad grinding teeth indicate a fibrous plant diet, smaller teeth of H. erectus indicate an omnivore's diet – high value foods like fruit and meat.
25 Isotopes and DietFractionation of stable isotopes can idicate the origin of food sources.Ratios of C13 and C12 different for terrestrial and marine dietsMesolithic shell midden with human remains, Oronsay, Inner HebridesSuggest protein almost entirely from fish, shellfish and marine mammals
26 Assessing Prey Species Butchered animal bone, BoxgroveHomebase site – resources brought back to a central base.Sequence of cuts and knaw marks suggests human kill later scavenged by other large predators,
27 Tool Use Modern chimps demonstrating tool use. Baringo Basin tools, Kenya 2.6 myaEarlier tools almost certainly being used but impossible to distinguish from naturally broken material
28 Inorganic Artefacts Clacton-on-Sea spear Sharpened and fire hardened shaftEarliest wooden artefact, 290 kyaAssociated with Homo heidelbergensis.Earlier artefacts simply have not survived.
29 Problems Interpretation rests on very partial survival of evidence. Measuring errors – complex procedures to measure very small differences in compositionSampling errors – contaminationMost interesting statements rest on chains of inferenceAll data is subject to a degree of doubt
30 Piltdown Man HoaxDiscovered 1908 gravel pit East Sussex by museum Charles DawsonPublished in the Journal of the Geological Society 1912, named Eoanthropus dawsoniExposed by fluoride absorption test 1949, published 1953 in “Time”Medieval human skull Orang-utan jaw and chimpanzee teeth