Lecture 6- Hominid evolution II Flashcards
What is the evolutionary tree of Homo sapiens?
-
What is the Hominin diversity like?
• Over 20 species of fossil hominin described including – Australopithecus (≈5 species) – Paranthropus (3 species) – Homo (≈7 species) -• 4 new genera in last 20 years! • Are we the last remaining species of a once diverse group? • Or, has their been too much enthusiasm in claiming the discovery of unique new fossils?
What are the main changes in the human lineage (inferred from the fossil record)?
• Walkingupright • Flatter face profile – Less prominent jaw – More prominent forehead • Teeth differences – Reduction in canine size – Increase in enamel thickness • Increase in brain size (some: chimpanzee= 400 cc, us= 1400 cc) • Greater tool use – More complex ‘carved’ tools
Was our ancestor chimp-like? Or did chimps ‘lose’ some of these traits?
-probably the ancestor would have been chimp-like, since the selection would drive the advantageous traits
What is the Australopithecus diversity and when and where did these exist?
- 4 or 5 species
- 4.5-2.5Mya
- Spread over much of East Africa
- fossil remains tend to follow the rift valley= as the environment is goof for fossilisation
- clearly austr. spreading out through africa
- australopithecus is mostly in the south region
What are the characteristics of Australopithecus anamensis?
• 4.2 Mya - North Kenya/Ethiopia • Lived at same time as Ardipithecus • Had thick tooth enamel (like humans) but big canines (like chimps) • Lived in open savanna/scrub • Bipedality uncertain (only part fragment of tibia) • Most probably a chronospecies (direct ancestor) of Australopithecus afarensis…
What are the characteristics of Australopithecus afarensis?
-“Lucy” -• 3.2 Mya - Ethiopia • Small ape (30-45kg; 1.2m tall) -1st species that was bipedal for most of the time -top of the femur, articulation point -pelvis more bowl like • Bipedal • Range of environments - Open savanna - Scrub, scattered trees - Thick woodland • Possibly good tree climber - Short legs - longer arms - divergent big toe
What is some of the evidence suggesting that Australopithecus afarensis was bipedal?
• Bipedal footprints from Laetoli, Tanzania (3.5MYA) attributed to Australopithecus afarensis. • Bipedal hominid, A. afarensis remains found nearby • Footprints are heel to toe - walking like humans • Two individuals (parent and child?) walking side by side
What was different in Australopithecus afarensis? (bone -wise)
- Change in limb articulation and pelvis shape
- austr= better able to bear the weight than the chimp
- not as good as homo but better
- if chimp walks upright for a long time= all the weight on the knee
- in humans are on the pelvis, close to the hip
What was the Australopithecus afarensis skull like?
- Slightly flatter profile than chimps but no forehead.
- Eyebrow ridges and small sagittal crest.
- Ape-like cranial capacity
- Reduced canines (but, males have bigger canines than females – sexual dimorphism)
- shifts in the skull as well, still no forehead though (we have big ones, chimps none)
- saggital crest= muscle attachment bit for jaw muscles, australopithecus
- canines are smaller
Did Australopithecus afarensis have families?
-several A. afarensis skeletons in one place • Discovered 1975 • 3.2 Mya (Ethiopia) • Up to 17 individuals – 9 adults, 3 adolescents, 5 children • All killed together? – Flash flood, big cats, food-poisoning or attacked? -evidence of first family? -unlikely that it was flood, probably poisoning or an attack
What are some of the more recent Australopithecus species?
-• Australopithecus survived through to about 2 Mya • Two species, A. africanus (South Africa), A. garhi (Ethiopia) • Both had flatter profiles than A. afarensis. Also had smaller canines & thicker tooth enamel • A sediba (approx 2 Mya) – putative ancestor of Homo -survived through to 2 MYA -remeber the major transitions -africanus and garhi= flatter profiles than afarensis, jaw is coming in much more flat -sediba= no major shifts
What is Paranthropus and its characteristics?
• Paranthropus (3 species) descended from Australopithecus but not on the human lineage • 2.5 - 1.5 Mya, Eastern Africa, South Africa • More robust skulls, sagittal crest prominent, very thick enamel • Lived in arid grassland environments • Teeth wear suggests ‘tough’ foods - nuts, seeds, grasses. Different niche to Australopithecus -offshoot= looks less like us, more like apes, they are the extinct group from the australopithecus lineage -very different niche to austr. so dramatic changes in morphology
When did the first Homo appear?
- First Homo species appear 2.8-2.4 Mya:
- Homo rudolfensis (Kenya)
- Homo habilis (Olduvai, Tanzania) – 2.4 Mya
- Homo habilis (Afar, Ethiopia)
– 2.8 Mya
- debated when this happened,
- rudolfensis probably not direct but on the tree
- our direct ancestor most likely homo habilis -from australopithecus to homo habilis is most likely
What were some of the changes in the first Homo that appeared?
- Show first signs of increased cranial capacity › bigger brain › more prominent forehead -But, protruding jaws - limb bones indicate bipedal -But, good climbers (close relative of Australopithecus?) -homo habilis= means handy man -now bigger brain, more prominent forehead -however still share the austr. features= protr. jaws, limb bones indicate bipedal but still good climbers
What was the evolution of tool use in Homo?
- Homo habilis used simple stone tools
- Tools became more sophisticated over time
-the mousterian stone tools= suggest that more advanced hunting skills
Do Chimp use tools as well?
-Chimps use tools as well -chimps are pretty proficient at using tools, even tough they split from us 6 MYA -Last common ancestor probably used tools -eg. Stick to eat ants, Nest building, Using stone to break open palm nut
What is so special about tool use in humans?
• Humans use percussive techniques to shape tools into sharp points • Creates stress on hand joints • Have adaptations in their hands to deal with these • Shape and proportion of hand increases performance when striking with fist – advantage in competition over mates! -big knuckles, some of our muscles are specially adapted muscles for percussive techniques -the hands maybe better for males to compete?
What is the longest enduring Homo species?
• Homo ergaster - earlier species 1.9-1.5Mya
• Homo erectus - later species 1.89Mya- 143,000ya
- Earliest fossils - East Africa 1.9 MYA
- Much more modern human features
- height = 1.6-1.8m, long legs - flatter facial profile
• Found in areas of open savanna, not associated with trees
- blending between ergaster and erectus
- ergaster didn’t last very long
- erectus= the longest occuring species of homo
- overlap with homo sapiens and neanderthals
- turkana boy= long legs, walk more, (know since they moved from africa), no longer arboreal
Did Homo erectus walk?
-Homo erectus walked just like modern humans • 1.5 Mya footprints, found in Kenya • Foot shape and pressure pattern almost identical to modern humans
Why is Homo erectus termed the world traveller?
-Homo erectus found in Africa, Europe, Asia (as far east as Indonesia and China) -the big thing about erectus= migration over the world
What are some of the Homo erectus characteristics that are different from us?
Differences from modern humans • Brow ridge • Lack of chin • Rapid development • More sexual dimorphism -differences from us= some but not many -still no chin or very little -1.6 m at 13 years of age, the development was more rapid in this species than in us -attain full height at 13, in us much later
What are the Dmanisi fossils?
-Homo erectus? -Dated: 1.77-1.78 MYA -Traits: -Narrow jaw (reduction of third molar)- Brain size = 600-700cc -Height = 140-150cm -Tools = primitive -some want this as a new species, subspecies… etc. -much more human like, in the jaw, but small brain, the height is also smaller than the later homo erectus and the tools are very primitive too (in erectus usually very sophisticated)
Did Homo erectus use fire?
-Homo erectus also used fire .Evidence from South Africa (1.5 Mya), Israel (700,000 ya) & numerous European sites (>500,000 ya) -Remnant of burnt grain seed
