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6.3: Methods

Last updated

Nov 17, 2020
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- 6.2: Trends
- 6.4: Pre-australopithecines

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The methods of paleoanthropology are basically the same as paleontology: find a fossil or a gene, and then compare and contrast it to every other fossil, bone, or gene currently known. It is very detail oriented work on all fronts, with surprisingly few "aha!" moments, and many of the debates often come down to the interpretation of statistics.

Taphonomy

Taphonomy comes from the Greek “taphos” or death, and it basically means the study of what happens to you after you die. The study of rotting and decay, and especially important for us, the study of how fossils are formed. This is a big problem because when we try to recreate an image of the past our data is sketchy. For example, we have a ton of pig fossils, and can talk in exhaustive detail about the evolution of pigs, but when it comes to human ancestors we have less to work with. We would love to find DNA from early hominids but the same capacity for unzipping for replication and protein synthesis makes it a fragile molecule that is unlikely to survive more than 100,000 years.

Fossils

Remember that fossils are not bones, they are casts of bones.

Exercise $\PageIndex{1}$

READ DENNIS O'NEIL ON FOSSILS

Dating

Getting the dates right is crucial, but we hardly ever get an exact date, like something you could use for a time machine, usually it's just a statistical approximation.

Exercise $\PageIndex{2}$

READ DENNIS O'NEIL ON DATING OVERVIEW
READ DENNIS O'NEIL ON RELATIVE DATING
READ DENNIS O'NEIL ON CHRONOMETRIC DATING 1
READ DENNIS O'NEIL ON CHRONOMETRIC DATING 2

Paleoecology

Along with the hominin species that we find, we want understand what kind of world it lived in. We try to recreate the ecology.

Human ancestors had many predators, including crocodiles CSI: Olduvai Gorge. The work of Jackson Njau [scroll through the different pages]
Hyenas crushed human skulls

Paleoclimatology

Read Dennis O'Neil's intro to climate change and hominin evolution
Climate change and paleoanthropology

Molecular Paleontology

Genetics gives us two major lines of evidence, existing and ancient. Our own DNA gives us many clues to our evolution. We can compare ourselves to other living primates, and other humans, and the differences will suggest pathways to evolution. Ancient DNA has only been found in the most recent hominids

Review of molecular paleontology

In several recent hominids (such as Neandertals and Denisovians), DNA is preserved, and we can see more than just the skeleton. The DNA tells us what proteins were produced and hints at soft tissue and behavior.

Article on genetic evidence for the difference in brain size between humans and other apes

Vocabulary

anthropogeny
absolute dating
relative dating
site context
in situ
paleospecies
chronospecies

Taxonomy

Linnaeus put all life into a huge family tree and correctly included humans on the primate branch. One of the goals of paleoanthropology is to fill-in as many details as possible for all the twists and turns of how that branch leads to us. The family tree metaphor can sometimes be misleading, Stephen J. Gould described taxonomy as more of "luxuriant bush", but for this introductory class, it is useful to minimize the groupings so we don't get overwhelmed. When paleoanthropologist find a fossil they try to fit it into the existing taxonomy, and there a two broad strategies: 1) f you call it another example of an existing group, you are a "lumper" (you're lumping them all together) or 2) if you call it a brand new species you are a "splitter" (you're splitting the branch into two). Splitters tend to get more attention on the news, but for this class we'll lean towards lumping hominid fossils into fewer manageable groups: pre-australopithecines, australopithecines, the genus Paranthropus, early genus Homo, later genus Homo, anatomically modern Homo sapiens (us).