Early Hominins Flashcards
Au. aethiopicus (the Black Skull)
- good candidate for ancestor of later robust species (Au. boisei & robustus)
- typical chewing adaptations (masticatory) seen in robust australopiths (large jaw, sagittal crest)
- only skull found
- understanding evolution of chewing features in early human relatives
🌟earliest robust
Au. afarensis
- fully bipedal, mix of human-like & ape-like body (mosaic anatomy)
- sagittal crest (suggests strong chewing muscles)
- small brain compared to humans
- likely vegetarian
- sexually dismorphic: males larger than females
- lived in groups
🌟 includes Lucy - shows early evidence of bipedalism with primitive traits.
🧠 shows how walking upright evolved before big brains
Au. africanus
- South African fossils, hard to date, found in breccia (cement-like rock)
- slightly larger brain than afarensis, no sagittal crest
- clear signs of bipedalism
- preserved endocast (brain imprint) -> insight to early brain development
🌟Tuang Child (first Australopithecine discovered) - proved human ancestors came form Africa
🧠shows continued evolution toward modern humans: bigger brains, flatter faced, bipedal
🌉bridge gap between earlier (afarensis) and later homo species
Au. anamensis
- lived in a forested environment, not open savanna
- thick tibia = bipedalism bc more weight placed on legs
- primitive dentition (large canines, U-shape jaw)
- sometimes confused with Au. afarensis, but more primitive & most likely its ancestor
🌟earliest known Australopithecus
🦵tibia shows upright walking = bipedalism began in the hominin line
Au. bahrelghazali
- known from a single fossil: jaw (mandible) fragment w/ 7 teeth
- discovered in Chad, Central Africa
- slight diff jaw than afarensis
- regional variation of Au. afarensis
🌟confirmed early hominins werent confined to East Africa -> across continent too
Au. boisei
- 1969, Olduvai Gorge, Tanzania
- Fossils found in Tanzania, Kenya, Ethiopia (skull & body parts)
- Brain size similar to robustus
- extreme chewing adaptations (huge molars, sagittal crest, strong jaw)
🌟peak of robust chewing adaptations, highly specialized in tough, plant base diets
🌟shows robust australopiths coexisted with early Homo species
🌟most specialized robust
Au. garhi
“unexpected southern ape”
- Ethiopia
- small brain, large canine molars, sagittal crest, human like limbs like longer legs than arms
- found stone tools & animal bones = possible tool use despite primitive features
🌟could be the link between Australopithecus and Homo, more advanced body proportions, early tool use, potential transitional species?
Au. robustus
- South Africa
- shape of the nasals, brow ridge and presence of bony pillars next to the nose make it different from other robusts
- clearly bipedal and true hominin
- diet w animal protein
🌟robust australopiths evolved separately in south africa w/ own traits than east african relatives (boisei)
Au. sediba
- south africa
- brain size slightly larger than earlier Austalopiths
- shared both Australopithecus & homo traits, homo-like dental, austa face, pelvis = bipedalism & climbing
🌟transitional species between Australopithecus & early homo, evolved in southern africa not just east
cohabitation
- multiple hominin species (2-3 at a time) lived in the same regions of Africa
- natural selection reduced direct feeding competition- different diets/feeding strats
- like how chimpanzees & gorillas coexist
Lucy
- Au. afarensis
- one of the most complete early hominin fossils
- fully bipedal, small brain
🌟clear evidence of bipedalism before large brains evolved
Paranthropus
- genus of robust, mostly vegitarian hominins
- p. aethiopicus (east africa, primitive)
- p. boisei (east africa, specialized)
- p. robusts (south africa, flexible diet)
- big jaws, molars, sagittal crests, adapt for heavy chewing of plant material
- extinct lineage
Prognathism
- forward projection of jaw & face
- common in Australopithecus & paranthropus
- how early hominins adapted facial features to diet (robust jaws for tough plants)
sagittal crest
- bony ridge along top skull & attached jaw muscles
- supports chewing for tough food
- found in robust australopiths and paranthropus
Taung Child
- first fossil of Au. africanus
- proved humans came from Africa
- first evidence of bipedalism & origin of humankind
Why is it that dates for South African hominins are often less reliable and harder to discern than for those in East Africa?
- South African sites are often fissure fills
❓ Problem: sites lack volcanic ash used for absolute dating
✔️instead use relative dating like stratigraphy and faunal correlations = less precise than East African sites where volcanic deposits are more reliable
What are the main differences between
the possible ancestor-descendant
relationships within Australopithecines?
1️⃣Gracile Australopithecines:
- more human like features, likely ancestors of Homo bc bipedalism & early tool use
- generalized diet
2️⃣Robust Australopithecines
- large molars sagittal crests, chew tough plant material
- side branches in hominin evolution but not direct ancestors of Homo
- specialized diet
Could the currently identified australopithecines be the ancestors of modern Homo?
- Yes some gracile species like AU. afarensis and africanus are most likely ancestors from:
- bipedalism, human-like anatomy (pelvis, legs, feet), brain size, tool use
- robust probs not bc theyre extinct
What are the general anatomical features that differentiate
Australopithecines from Homo?
- A = smaller brains, H = larger brains
- A = more prognathic (projecting face) bigger jaws and teeth , H = flatter face, smaller jaw, teeth
- A = bipedal & apelike pelivs legs, curved fingers and toes, some tree climbing ability, H = bipedalism, longer legs than arms, bowl pelvis for walking
