Paleoanthropology Professor Janaki Natalie Parikh

Paleoanthropology 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

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 irregular intervals, rocks contain evid. of the reversal

Chronometric/Isotopic/Absolute Dating 1) Carbon-14: living thing absorb carbon, isotope ( 14 C, source: cosmic radiation) begins radioactive predictable rate ½ life of 5730 yrs (+/-40 yrs): 14 C → 14 N 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 40 K → 40 Ar (½ life ~1.25 billion yrs) or of 39 Ar → 40 Ar 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 least 500,000 yrs old to use either technique Beg. Of Earth CurrentDay ? Arg-Arg or Pot-ArgCarbon ,000 y.a. 70,000 y.a.

Chronometric Dating cont’d 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)

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