Early Humans: Meet the Ancestors

2. Archaeological Evidence and the Limits of Knowledge

Objectives

• Look at the scientific investigative tools

• Stratigraphy

• Archaeological dating methods

• Comparative Anatomy of Fossils

• DNA and Isotope analysis

• Artefact and Ecofact Evidence

• Consider the security of our interpretations.

Charles Darwin

• Origin of Species, 1859

• The Descent of Man, 1871

• Cartoon from “The Hornet” satirical magazine 1871

Stratigraphy

• Provides relative dating – separating the remote past into horizons of greater and lesser age.

• Boxgrove, England

Fauna Assemblages – Environmental Dating

• Boxgrove excavation era of strata indicated by animal bone assemblages

• Extinct rhinocerous,

Stephanorhinus hundsheimensis• Period when Britain had a climate

like modern Africa• Sites can be given sequence

relative to each other but not a date by this method.

Radio Carbon Dating

• Invented c. 1950

• Based on the principle that C14 decays at a predictable rate

• Age calculation made by examining ratio of C14 and C12

• Relatively short half life c. 5740 years makes it accurate, but limits its range to about the last 40,000 years

Lascaux, S France

• Accelerator Mass Spectroscopy – very small samples.

• C14 dating of cave painting, targeting carbon based pigments

• Images date to 30-10 kya• Some images refreshed

over thousands of years

Potassium - Argon Dating

• Less accurate but much greater dating range – suitable for the earliest hominids

• Used to date layers of volcanic rock

• Noble gas Argon 40 released when rock molten

• Any Argon 40 present must have derived from Radio Decay of Potassium

Laetoli, Early Hominid FootprintsVolcanic ash Potassium – Argon suggests 3.6 mya

Uranium Series Dating

• Based on ratios between radio active Uranium isotopes and daughter products

• Uranium 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.

Uranium 238 Series

• Uranium 238 4.51 billion years

• Uranium 234 250,000 years

• Thorium 230 75,200 years

• Radium 226 1620 years

• Radon 222 3.83 days

• Lead 210 22 years

• Polonium 210 138 days

• Lead 206 stable

Uranium 235 Series

• Uranium 235 713 million years

• Protractium 231 32,400 years

• Thorium 227 18.6 days

• Radium 223 11.1 days

• Lead 207 stable

Vartop Cave, Romania

• Limestone cave Neanderthal occupation dated to 62kya to 97kya by U-series.

• Footprints Suggests an individual 1.46 m tall

Cave Art Creswell Crags, Derbyshire

• Engraving Church Hole Creswell Crags

• U-series sampling of flowstone suggests pre- 12,800 BP

Equilibrium Level

As levels of Thorium 230 increase rate at which it is destroyed approaches rate at which Thorium 230 is created by decay of Uranium 234.

Comparative Anatomy of Fossils

• Comparison of cranial capacity

Incompleteness

• Australopithecus Afarensis• Best specimen “Lucy”• Only 40 % complete• No formal burials from this

period. • Most bodies dismembered and

scattered by scavengers

Turkana Boy

• H. erectus, 1.5 mya• Very narrow spinal column• Lacked fine control of diaphragm• Implications for speach• Other specimens fall with range

of modern humans• Might be an individual with

genetic defect.

New Species or or Diseased

Individual

• Recent discovery of a new “hobbit” species contested

• H. floresiensis skull compared to modern human with the genetic disorder microcephaly.

• H. floresiensis frontal and temporal lobes highly developed

Dimorphism in Australopithecine

• Suggested Australopithecine dimorphism as compared to modern humans

• Hominids of different sizes now thought to represent different contemporary species

Ancient DNA

• Cheddar Gorge• Late Palaeolithic skull

1911• DNA recovered 1990’s• Adrian Targett –

descendant living few miles from find site

• Fears of contamination from modern DNA

Age Estimation

• Tooth Eruption can give age at death in modern humans very accurately

• Age can also be estimated from the state of fusion of bones of the skull and limbs

Errors in estimating age

• Australopithecene infant “Taung’s Child”

• Age by comparison with humans 7 years

• Age by comparison with chimps 3 years

Comparative Anatomy - Teeth

• Nakalipithecus nakayamei jaw, Kenya, c 10mya• Homo erectus c. 1 mya• Broad grinding teeth indicate a fibrous plant diet, smaller

teeth of H. erectus indicate an omnivore's diet – high value foods like fruit and meat.

Isotopes and Diet• Fractionation of stable

isotopes can idicate the origin of food sources.

• Ratios of C13 and C12 different for terrestrial and marine diets

• Mesolithic shell midden with human remains, Oronsay, Inner Hebrides

• Suggest protein almost entirely from fish, shellfish and marine mammals

• Butchered animal bone, Boxgrove

• Homebase site – resources brought back to a central base.

• Sequence of cuts and knaw marks suggests human kill later scavenged by other large predators,

Assessing Prey Species

Tool Use

• Modern chimps demonstrating tool use.• Baringo Basin tools, Kenya 2.6 mya• Earlier tools almost certainly being used but

impossible to distinguish from naturally broken material

Inorganic Artefacts

• Clacton-on-Sea spear• Sharpened and fire

hardened shaft• Earliest wooden artefact,

290 kya• Associated with Homo

heidelbergensis.• Earlier artefacts simply

have not survived.

Problems

• Interpretation rests on very partial survival of evidence.

• Measuring errors – complex procedures to measure very small differences in composition

• Sampling errors – contamination • Most interesting statements rest on chains of

inference• All data is subject to a degree of doubt

Piltdown Man Hoax• Discovered 1908 gravel pit

East Sussex by museum Charles Dawson

• Published in the Journal of the Geological Society 1912, named Eoanthropus dawsoni

• Exposed by fluoride absorption test 1949, published 1953 in “Time”

• Medieval human skull Orang-utan jaw and chimpanzee teeth