Dating Techniques: AMS Carbon Dating Decay Law: N(t)=N 0 (e λ t ) Previous Technique –Larger Sample –Measure Activity Comparison of 14 C/ 12 C ratio Accelerator Mass Spectrometry –Smaller Sample Send atoms through accelerator – Separate Isotopes – Obtain very accurate atom-by-atom count for 14 C/ 12 C ratio RANGE: Present 40,000 BP
Dating Techniques: AMS Problems… Event Horizon: 40,000 BP –Contamination –Low amounts of remaining 14 C Fluctuation of 14 C/ 12 C ratio Correction by dendrochronology
Procedure –Crystalline structured material absorbs radiation which is released when heated. –Heating the sample releases the captured energy which can be measured, thus revealing the age. History Dating Techniques: Thermoluminescence RANGE: 2,000 500,000 BP
Measures radioactive decay following uptake of uranium into the carbonate as it forms. Use decay rates for uranium and thorium. Useful in European caves. Dating Techniques: Uranium-Series RANGE: 5,000 350,000 BP
A. afarensis 3.9-2.9 mya Bipedal Lucy 3.2 mya Our Story: Early Hominids A. boisei/robustus 2.3 mya Larger brain Huge teeth (gorilla-like) Discovery led to thoughts of co-existence of two hominid species
Our Story: Early Hominids H. habilis 2 mya Possibly rudolfensis as well (2.4 mya) Larger brain First to make tools H. Erectus 1.9 mya Ergaster is early African erectus. Even Larger brain. Shorter face, arms Human proportions. CENSORED
Our Story: Who is Neanderthal? Basic Characteristics Short stature Great muscle mass Large boned skeleton Heavy build Males: 1.7 m tall 84 kg Females: 1.5 m tall 80 kg
Skull Description Low forehead region Prominent brow ridge Large nasal cavity Forward-projecting cheek and nasal regions Our Story: Neanderthal Traits Non-projecting jaw Space behind third molar 1500-1600 cm 3 cranial capacity
Stereotype is wrong! Walked fully upright Had some thought of the hereafter –Burial sites/graves Made own tools –Stone flints –Was human; distinction from animals Our Story: Dimwitted Brute?
Whence came modern man? How did Neanderthal and Cro-Magnon interact? Our Story: Theories of Origin Out of Africa 1 Out of Africa 1 –1.7 million BP –Homo erectus leaves Africa and spreads across Eurasia
Modern man: all groups have evolved from Erectus groups spread across the continents. Our Story: Multiregionalism Gene flow accounts for similarities we observe today. Favored by racists in the past to account for a superior race.
Neanderthals develop from Erectus population Our Story: Out of Africa 2 2 nd Exodus from Africa 70,000 BP Population replacement wipes out other hominids: including Neanderthals Modern man developed independently in Africa 200,000 BP
Application: AMS Carbon Dating Could Cro-Magnon and Neanderthal have mixed after Out of Africa II? When did they disappear? 30,000 BP Evidence of co-existence for up to 10,000 years in some areas! 1998: Lagar Velho –Dates to about 25,000 BP –Skull displays mix of Cro-Magnon and Neanderthal characteristics!
Neanderthals (in the full sense) disappeared from Portuguese region 5,000 years before Lagar Velho was born. In many places (France, Russia, Balkans) it looks as if Cro-Magnon man wiped out Neanderthal Lagar Velho shows that in some cases they were not wiped out: they were mixed into Cro-Magnon society! Big Questions: How many other Lagars are there? Do we have significant Neanderthal heritage? Application: Lagar Velho
Hélène Valladas and team Kebara –Results of TL-dating: flint tools were ~60,000 years old Qafzeh –Results: skeleton would be ~92,000 years old Application: Thermoluminescence
Amud Cave Burnt flints in ash layersBurnt flints in ash layers 19 were able to be tested19 were able to be tested 14 in upper two levels14 in upper two levels –44,000-70,000 BP –70% were 50,000-60,000 BP 5 from lower layer5 from lower layer –55,000-76,000 BP –4 were 65,000-76,000 Results/ConclusionResults/Conclusion –Normal intra-species variation Application: Thermoluminescence
Application: Uranium-Series Pontnewydd Cave in Whales. –Found bones, teeth, flint, stone axes, scrapers, & arrowheads –Dated to 250,000 BP Uncovered Neanderthal hunter-gatherer & his children