Unit 3 Paleoanthropology and the Fossil Record Paleoanthropology The study of human evolution the hominid fossils and their relations to each other and modern humans There is nothing outside Africa that is even in the running to be a potential human ancestor The most fossils are found in East Africa in the Rift valley several in South Africa and a few in Central Africa Goals o ID the early hominid species consider how they are different from modern age o Establish their relationships to one another o Gain insight to their behavior The big 3 o Culture Religion art ritual etc o Brain Size Primates are more encephalized than other mammals Relative to their body size they have bigger brains Within primates only humans are the most encephalized o Bipedalism Walk habitually on two feet have no other ways of walking There are differences in the skeletons between bipeds and quadrupeds o These three things did NOT happen at the same time Skeletal Adaptations for Bipedalism Skull Spine Pelvis Femur o Foramen magnum The hole through which the spinal cord passes centrally underneath the skull o Curvature o This puts the head directly on top of the skeleton so the head is not out in front o Helps us maintain balance o The great apes have a slight curvature but it s not as great as our curvature is o The ilium ilia are oriented in an anterior posterior direction o This helps position the muscles o We find the pelvis in the fossil record o Bicondylar Angle referring to the angle that the femur makes in its anatomical position from the hip to the knee made from the bottom of femur to hip It is unnatural to stand with our legs hip length apart because of the bicondylar angle o Neck Length The length of the neck is correlated to how far out the femur will extend o Feet In a chimp the neck length is shorter In a biped the neck will be longer Great Apes have an opposable big toe Humans have a derived foot with all the toes being in one line Bipeds have arches in their feet which helps to stabilize weight Great Apes do not have an arch Apes arms are longer than humans o Arboreal Apes have elongated and curved toes and fingers to live in trees Humans do not Apes cannot get a flat band because of a ridge in their wrists so they walk on their knuckles Humans can get a flat hand and do not have a ridge Hypothesis for Bipedalism Have to do with being on the ground and freeing the hands to carry things o Tools food infants carrying o Feeding o Hunting To have a better view of the open country o Seeing over tall grass o Traveling between trees Energy efficiency o Better energy use to walk on two legs as opposed to 4 Family Provisioning o Males providing hunted meat for families o Females providing gathered fruits and nuts o Behaviors Even the experts do not agree on this Lumper paleoanthropologist that want to put all the fossils into fewer categories Splitters suggest that the differences can speak for themselves it s ok to maintain Lumpers and Splitters many different categories East Africa vs South Africa o Geology East Africa known as a Rift valley because it is where two land masses are butting up against each other Resulted in earthquakes and volcanic activity Ideal for getting dates for a site The fossils are generally well preserved because of the volcanic activity South Africa lots of limestone Ground water will erode a fissure in the surface and will either become larger or will form a cave underground Things get trapped in the caves if it was an animal it dies in the cave o Over time a brechia develops Brechia a hard matrix that is composed of sand debris pebbles etc and forms around the fossils Because it is so hard when fossils are found encased in brechia it can be very difficult to remove them The dating of a South African site is by biostratigraphy o Relating it to something else o The South African sites are a lot more general The fossils are found through quarry activities limestone quarries Central Africa more like East Africa Fossils are not found through quarrying activities o Taphonomy the study of something after it dies includes becoming a fossil Miocene Fossils Sahelanthropus tchadensis o Nearly complete skull that is small brained and it has some ape like characteristics o The position of the foramen magnum suggests bipedality so that makes it a great last common ancestor LCA candidate between apes and humans o 6 7 million years old Oldest possible hominid o Geography found in Central Africa Unexpected since most fossils are found in East or South Africa Miocene Pliocene Fossils Orrorin tugenensis o Found in Kenya East Africa o Multiple individuals represented o The teeth are more ape like in their morphology but evidence of bipedality in the femoral neck length Ardipithecus ramidus o They link it to sahelanthropus tchadensis So it is also a great LCA candidate between African apes and humans o Falsifies the idea of a chimp like last common ancestor because it doesn t look like a chimp o Small brained o Bipedal o Also was capable of moving through the trees opposable big toe o Found in East Africa Pliocene Fossils Kenyanthropus platyops o Nearly complete skull that is fairly old 3 2 3 5 mya o flat faced man from Kenya o Small brained o Big brow regions but a flat face o Found in 1999 o Date Australopithecus o Morphology o Not much information on it o Contemporary with another hominid genus Aust meaning it lived at the same time but its features are more human like or derived o Not in the genus homo but it is very similar to later fossils that are o Makes it a better candidate for the human lineage than the Aust o Date derived ancestor Australopithecus A afarensis o 3 9 3 mya o Only found in East Africa o At least 120 individuals found well represented o Skull shows it was small brained o Had a small degree of post orbital constriction o Small to no sagittal crests o Have large brow ridges o Large nuchal crest o Fairly prognothic gives a concave appearance to the face o Teeth ape like very large canines U shaped dentition the sides are parallel to each other o Postcranially evidence of bipedality o No opposable big toe o 3 5 4 feet tall o Long arms o knuckle walking o Size of a chimpanzee o Lucy Found in 1974 A afarensis Single individual that is relatively complete She tells us that afarensis were bipeds 40 complete 3 2 million years old o Selam Not an adult child 3 4 years old when it died Nearly complete juvenile skeleton 60 complete Most complete A child A afarensis Tells us