Covered by a lot of rock, so this can be hard

- Fossil evidence must be taken with a grain of salt, very rare that the oldest + youngest fossils are the oldest + youngest species
Dating fossils
- Radiometric dating
- Slow decay: K-Ar dating
- Wouldn't use this that often
- Fast decay: C14 dating
- Used often
- Anything younger than 40 thousand years
- In between: Thermoluminescence dating (TL), Electron spin-resonance dating
- Magnetic dating
- Earth's magnetic field reverses itself (N is S, S is N)
- When rocks formed, record the direction of the earth's magnetic field at the time
- We know when these reversal events happened
- Relative dating
- Association with other known species (extinct or appear by certain age)
Assembling the data
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💡 How do the fossilization process, modern dating methods, and the vagaries of discovery shape the narrative of human origins we tell today?
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- Our origin stories aren't 100% accurate and are instead a combination of assumptions and estimations
- Discovery is not simply the chance of finding something, but support is also need (monetarily)
- The narrative that we tell often ignores the indigenous perspective (WHICH IS IRONIC AS FUCK LOL)
- The evolution of primates...that began in the America
- Bias of environmental preservation
- Fossils might not have preserved in certain locations

Focusing on the last 20 million years
-
20 mya: Wet, grassy, green areas
-
10 mya: subtropical and tropical forests
-
5 mya: becomes cooler and drier
- Forests → open space (deserts)
-
2 mya: glaciation + hot, dry dessert areas (period of extremes)
-
East Africa: Forests → open grass lands & savannas