Paleoanthropology
Professor Janaki Natalie Parikh
profjnp@gmail.com
Paleoanthropology
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Paleoanthropology: prefix paleo, meaning?
Ancient, prehistoric…very, very old
The study of human fossil remains
What is a fossil?
Natural record of an ancient life form
Conditions conducive to fossilization
• Do the majority of living things become fossils?
• No. Fossils are RARE & replaced. Most organisms will
decompose, leaving no record
• What conditions facilitate fossilization?
• Encased in lava, volcanic ash, tar, or sap
• Freezing: being encased in ice
• Dry, desert like conditions (natural mummification, a pause
in disintegration)
• Being quickly covered in sediment
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http://vimeo.com/6581503
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http://www.sciencedaily.com/releases/2010/07/100727065647.htm
Contextualizing fossil finds
• Relative dating : nothing to do w/…
A comparative method, doesn’t
provide a specific date
• Main technique: stratigraphy, utilizes process of
superposition,
complicated
due to plate
tectonics, useful
for calibration
Relative Dating cont’d
• Calibration: comparing measurements obtained from 1
device by another measurement of estab. accuracy
• Biostratigraphy: provides approx date by utilizing
plant/animal remains from the site w/ well estab. Time
frames
• Paleomagnetic reversals: Earth’s magnetic field shifts @
irregular intervals, rocks contain evid. of the reversal
Chronometric/Isotopic/Absolute Dating
• 1) Carbon-14: living thing absorb carbon, isotope (14C,
source: cosmic radiation) begins radioactive decay @
predictable rate
• ½ life of 5730 yrs (+/-40 yrs): 14C → 14N
• After ~5730yrs elapse, ½ of orig. amt. is left & aft. Another
5730 yrs, how much?
• ½ of the ½, in other words: ¼, continuing until…
• This method is useful through ~70,000 yrs ago
Chronometric Dating cont’d
2) Argon-Argon & Potassium-Argon: based on decay of 40K →
40Ar (½ life ~1.25 billion yrs) or of 39Ar → 40Ar
• Arg-Arg has mostly replaced Pot-Arg due to higher accuracy
• Can only be used to date volcanic rock or ash
• Such a long ½ life is an advantage, but also means that the
sample must be @ least 500,000 yrs old to use either
technique
Arg-Arg or Pot-Arg
500,000 y.a.
Beg. Of Earth
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Carbon-14
70,000 y.a.
CurrentDay
Chronometric Dating cont’d
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What species originates during this gap?
Modern humans: us!
Is there any way to get accurate dates for our origins?
Yes, by using a combination of relative & chronometric
techniques
• 3) Dendrochronology: counting tree rings. Useful w/in last
~10,000 yrs.
Chronometric Dating cont’d
• 4) Thermoluminescence: measures trapped electrons by
releasing their energy in the form of light (Useful to ~1
m.y.a.)
• Used to date pottery, brick & possibly soil
• 5) Electron spin resonance (ESR): detects magnetism of
trapped electrons
• Used to date: tooth enamel, shells, cave deposits & rocks
• Can be used ~1 mya, most useful
for dates less than 300,000 y.a.
Debate regarding paleospecies
• Review criteria for biological species
• Can the same criteria be applied to paleospecies?
• No. Thus, w/ extinct species, we have to go by similarities
in physical characteristics
• That’s difficult in a species w/ such variability in superficial
physical features/traits
Paleospecies Debate cont’d
• For ex, say in a few million yrs, intelligent life comes to Earth
to excavate
• Will they find remains of millions of us?
• No, let’s say that the most complete remains they find here
are of Rosie O’Donnell & Yao Ming: can we be sure they’d
consider
these 2 the same species?
• Yet, could they successfully
mate?
Yes. On that note…(if they mated)
http://www.youtube.com/watch?v=1Qbt0pEgZOQ
Lumpers vs. Splitters Debate
• Splitters: require very few differences to draw a species
designation
• Lumpers: more conservative about species designations,
require numerous differences
• Vast majority of scientists fall into which category?
• Splitters. Why? Due to what factors?
• Due to notariety & financial considerations, there is pressure
towards splitting