Lecture 17 - Turnover Pulse Hypothesis Flashcards
Major Evolutionary Trends @ ~ 2.5 Ma
Homo
- increase in brain size and capacity for tool making
- decrease in prognathism, and postcanine tooth size
- increase in body size
- appear around 2.8 Ma
Major Evolutionary Trends @ ~ 2.5 Ma
Paranthropus
- hypermasticatory complex
- increase in cheek tooth size
- body size similar to Australopithecus
- “robust Australopithecines”
Major Evolutionary Trends @ ~ 2.5 Ma
Early Homo
- larger cranial capacity
- slight reduction in size of cheek teeth; more U dental arcade
- reduced prognathism, more gracile cranium
- anatomically, more similar to Australopiths
- associated with stone tools
- classification as Homo supported by ability to use and make stone tools
Paranthropus
P. aethipicus
- East Africa, 2.7-2.5 Ma
- well developed sagittal & nuchal crests
- heavy chewing
- relatively small brain
- prognathism, dish-shaped face
Paranthropus
P. boisei
- East Africa, 2.3-1.2 Ma
- forward-projecting cheek bones (zygomatics)
- forwardly-placed sagittal crest
- reduced prognathism
anterior dental crowding –> marked reduction in incisors and canines
enlargement of premolars and canines, postcanine megadonty - diet = grasses, starchy roots
Paranthropus
P. robustus
- cousin of P. boisei
- South Africa, 2.0 - 1.5 Ma
- extreme adaptations to heavy chewing, large teeth
- mostly vegetarian, omnivorous
- based on teeth microwear and istopic analysis, heavy tough chew foods but different diets
- diet = nuts, seeds
comparison for dealing with different environments (Paranthro vs Homo)
- split in hominin lineage from Aus. into Homo and Paran. to adjust to environments with different methods
- Paranthro had a hypermasticatory that allowed them to eat nuts, seeds and grind etc.
- Homo developed smaller cheek teeth, more reliant to tools
outsourcing food processing from teeth to tools
Human Evolution & Global Climate
- starting at around 2.5 Ma, seems to be a phase shift
–>relatively warm to much cooler, highly variable climate changes - period of major importance in global climate studies
- shift tends to coincide with split in human evolution (Homo vs. Para.)
how could we determine is climate shift led to evolution
- changes in morphology consistent w/climate shift
- shifts in diet consistent with climate trend
- look for examples in other animals
if global climate change is driving, then humans are not the only species affected
turnover pulse hypothesis
= climate change or ecosystem shifts can cause rapid extinctions and the emergence of new species
- species migrate towards preferred climate through tracking
- because of this ability, we wouldn’t expect to see large-scale lineage turnovers (species extinction/speciation) when climate change is slow enough to track
- the only thing that should lead to widespread extinction + speciation would be climate change (that exceeds species ability to track & migrate)
best evidence for turnover pulse hypothesis
time periods where there are clusters of turnovers & see if they coincide with big climate change
- something like this happens at 2.5 Ma, 8 out of 9 species of antelope go extinct and same amount appear in Eastern African
Vrba, 1998
how does turnover pulse hypothesis relate to savanna hypothesis
savanna relates to one area, TPH is more general
* both realte to evolution of animals in relation to environment
* TPH shows variation of climate, savanna focuses on just forest to grassland shift
