Human Evolution - The Homo Genus Flashcards
Fossil Basics - Trace Fossils (Ichnology)
- Footprints
- Coprolites, tracks, trails, nests
Fossil Basics - Periminerilsation + Petrification
- Chemical process
- Minerals replaced
Taphonomy
- How an animal becomes fossilised and what processes mean it will/won’t
Why are some bones more commo than others?
- Teeth is very common due to very solid material that survives trampling and wethering
- Smaller bones are less likely to be fossilised as they can be crushed
Why are fossils not found everywhere?
- Human fossils aren’t everywhere due to habitat e.g. rainforests
Stratigraphy
- How layers of the earth is formed/what they are made of
Dating
top layer = new, bottom = older?
- not as straightforward as some things sink/ humans bury things in holes / in caves, there is a lack of banding due to flooding etc.
How do you determine a species? - Splitters
Different species unless there is a convincing reason to unite the
- Variation = new species
How do you determine a species? - Lumpers
Same species unless there is a convincing reason to divide them
- Intra-species variation normal e.g. age, sex, disease, genetic variation
Interbreeding
- Different + related species can interbreed
- Often infertile but not always (takes 2 million years of separation from a common ancestor)
Hybrid zones
10% of primate species engage in cross-species hybridization
- can result in a new species
Fossil remains are limited
- Complete skeletons are incredibly rare + can be difficult to identify
- Usually find a mix of fragmentary bones + teeth
- Often impossible to link cranial + post cranial elements
Original definition of Homo genus (compared to previous genus)
- Small, modern teeth compared to ancestors’ large teeth in homo fossil record
- Bipedal
- Tool use - thought this meant intelligence so they are more human
- Brain size
Small teeth not exclusive to Homo genus
- Found before homo species
- Older species (Australopithecus sediba (MH2)) had smaller teeth than homo genus
Being bipedal not exclusive to Homo genus
- Upright posture/ bipedality goes back 7 million years with Sahelanthropus tchadensis
Tool use not exclusive to Homo genus
- Use of tools predated Homo genus (~2.8 Mya)
- ~3.3 Mya ‘Lomekwian’ : Kenyanpithecus platyops
- ~3.4 Mya cut marks on bones: Australopithecus afarensis
Bigger brains not exclusive to Homo genus
- Homo habilis = 500cm^3 on low end while Paranthropus robustus = 550cm^3
- There was a trend towards bigger brain vol over times
- However, variations with ranges overlapping between ancestors of another genus + more modern homonids
Is our definition of Homo wrong & why all these problems with the Homo genus?
- Homo habilis was found with old definition of homo genus but with a small brain
- Debate if it counts as a homonids e.g. they used tools a lot, small teeth, but more like the species before than species later
Genetics + interbreeding : H. sapiens
Interbred with:
- Denisovans (Melanesians & Aboriginal Australians)
- H. neanderthalensis (Eurasians + Africans)
- Also with unknown archaic European pop. + African pop. (in areas with lack of fossil record e.g. West Africa)
Genetics + interbreeding : H. neanderthalensis & Denisovans
Interbred thousands of years ago:
- Female remains from around 90 kya found to have a N mother + D father
Link between climate + evolution of homonids
- Large climatic fluctuations when homo genus evolved
If climate is variable/ severe, you might:
- Die out
- Move to a new area
- Adapt to diff. conditions
Hominin variability = environmental variability
Homo mass migration out of Africa however…
- Absence of evidence is not evidence of absence
- Lack of fossils in regions doesn’t mean there are no homonids
Did Homo habilis leave Africa? - Theories
- Inefficient energetics as they were shorter = shorter strides so more energy not as efficient at moving
- Challenging Northern African habitat - dry + desert condition
- Were scavengers - didn’t actively hunt
However, no evidence that they left Africa
Were Homo erectus the first global species?
Originally considered all individuals:
- Energetically efficient, tall, bipeds
- Had increased brain size
- Known to be morphologically variable
- Behaviourally more capable/adaptable since they’re active hunters - can make tools to problem solve
- Makes it easier to eat while migrating not relying on finding food
