what did uncovery of the piltdown hoax initiate?
systematic excavation in Africa - scientists rediscover Huxley/Darwins contention that humans are most closely related to african apes and evolved in Africa
what did Dart and Broom discover?
that there is two forms of australopithicene
what are the two formss of australopithicene?
1) gracile - A.africanus - Taung boy
2) Robust - A.robustus - thick jaws and prominant teeth
who are the Leakey family?
family of scientists who have dedicated their lives to studying the rift valley in Africa and human fossils found there
what did Mary leaky discover in the olduvai gorge, Tanzania
Australopithecus boisei (1.75ma)
- prominent cheeks and jaw
- big and strong
- eat a heavy diet (ridge on head where jaw muscles attach)
describe Homo habilis (1.75ma) discovered by the Leakeys in Olduvai gorge
- first to be put into the same genus as humans
- dating showed that autralopithecens co-existed with homos (until then it was assumed that the ancestor -australopithecus- evolved into the descendent -homo erectus
what did the homo habilis discovery signify?
that evolution wasnt a linear progression it is actually a bushy evolutionary tree
- realised there was actually multiple hominid species around at the same time
describe Lake turkanya, Kenya
classic rift valley lake - changed size regularly depending on the climate (expanding and contracting)
- sediment piles up on the side in terraces
- well dated by layers of ash from volcano explosions also layered in the lake
- can look at pollen and reconstruct vegetation at the time
what was the major breakthrough discovery in 1970?
‘lucy’ A.afarensis(3ma) - found 40% complete - pelvis intact, limb dimensions - tell how she walked etc
- found in Ethiopia
what did the A.afarensis footprints tell us?
- two animals recorded walking
- both bipedal
what are 2 major fossil findings which stand out on the timeline of discoveries?
1) 6.0-7.0 ma - Sahelanthropus tchadensis - chad (2002)
2) 3.0-3.5 ma - Australopithecus bahrelghazali - chad (1995)
what is significant about the two findings in chad?
- chad is beyond the rift valley (rift valley is often seen as the cradle of human kind) - but these finds prove humans moved out the rift valley
- sparked the thought that the rift valley is influencing our thinking by a huge bias n the fossil record due to its sediment deposits
what is the issue with working out relationships in human evolution?
- people tend to come up with non scientific phylogenies based on hunches while other people take a more cladistic approach - however its very hard to prove anything
- lots of different scenarios have been proposed - inexact discipline with a bad fossil record
what does the rift valleys environment indicate about Australopithicenes?
- pollen cores show the rift valley had a constantly changing environment - so they must have been adapted to a variety of different conditions e.g. life in trees, life on savannah etc
between 3-2ma how many homini species coexisted?
6 - either australopithecine’s or homo
- inhabiting a mixture of environments
summary of australopithecines
- essentially bipedal apes with modified dentition (ape like from the neck up and human like from the neck down)
- walked in a bent knee bent hip style
- thought they spent alot of time climbing trees - mixture of characteristics for climbing and walking
- evidence of sexual dimorphism and lived in groups
what do you observe when comparing chimps, humans and australopithecines?
- australopithecines have long fingers and good rotation adaptations for tree climbing - also short hindlimbs and long forelimbs with alot of movement in should joints - all indications that they were tree dwellers but could walk better than chimps
what are the main differences between gracile and robust australopithecines?
- lies mainly in their dental and facial adaptations to chewing
- robust forms = robust jaws, more bulky chewing muscles and more prominent muscle attachments - thought that meat was only scavenged, mainly ate vegetation and nuts
- little difference in size or brain size
what is the debate over tool use in homo and australopithecines?
tools found - debate wether australopithecines copied homo or stole tools
- recent evidence of tools found in sites where only australopithecine’s have been found