Human Evolution 02 Flashcards
how are the relationships btw. humans, chimpanzees and gorillas?
Humans and chimps closer than gorillas
What does the X chromosome tell us?
Initial speciation => hybridization (very long) => final differentiation
On what is old evolutionary taxonomy based?
Morphology
What does genomic analysis/ cladistic taxonomy state?
Homo closer related to Pan than these are to other great apes
What defines us as hominins?
Bipedal locomotion
Short face (viscerocranium)
Large brain (neurocranium)
What are possible types of locomotion of the last common ancestor?
Suspensory
Climbing/bridging
Arboreal quadrupedalism
Knuckle walking
Terrestrial digitigrade quadrupedalism
Why did bipedal locomotion evolve?
Adaption to ecosystem
• lower surface => solar radiation
• free sight over high grass (but many not in Savannah)
Free hands (but bipedal locomotion before tool use!)
• tool and weapon use
• carry food
Widening of ecological niche
• climate change
• large home range
• feeding from bushes
Energy efficient locomotion
• traveling between trees
“Aquatic Ape”: lacustrine predation/ gathering
Climate in Miocene
Global cooling & short time climate fluctuations
Scarcer forests
Increased seasonality
Less rainfall => drying up of mediterranean
Hypersalinity
Formation of highest elevations
Oxygen isotope analysis
16O and 18O (heavier)
ratio correlates with temperature: the lower the temp, the less 18O evaporated and precipitated
=> 16O depleted, 18O rich oceans
Australopithecus africanus
Skull of child, might have been killed by eagle
Closer to humans than chimps
Smaller canines
Steeper front
No superorbital structure
More central foramen magnum
Sulcus sylvii (parital/frontal lobe border)
Lunate sulcus (Affenfurche) (but probably other suture impression) => divides visual cortex, in humans more posterior than in chimps
=> implies reorganization of brain (language more important)
Later adult australopithecans
Piltdown hoax
Large canine (Orang-Utan)
Quadrupedal
Large brain before bipedalism
=> supported ancient split but wrong!
Modifications required for bipedalism
• Lumbar lordosis
• shortened hipbone
(Approximation of iliosacral and hip joint) => reduces lever arms in pelvis?
• angle btw ilium and iscium
Little Foot
mobile great toe, rest of foot quite human like
Whole skeleton excavated after 25 years => most complete skeleton of australopitecine
2.2 (Uranium dating of flowstone) or 3.67 (cosmogenic dating)
=> flowstone intrusive, might be younger than skeleton
Dating of fossils from karstic caves
Complex
• Paleomagnetism => reversed polarities
• Fauna dating => comparison to other fossilized species
• Potassium-Argon dating based on volcanic ash
• Uranium-series dating of stalagmites and stalactites
• new cosmogenic aluminium and beryllium dating of breccia
Australopithecus sediba
Cranially directed shoulder joints => climbing
Thunnel shaped thorax
short pelvis
Narrow lower thorax
Primitive rearfoot, longitudinal arch
