Lecture 6- Hominid evolution II

Question 1

What is the evolutionary tree of Homo sapiens?

Answer 1

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Question 2

What is the Hominin diversity like?

Answer 2

• 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?

Question 3

What are the main changes in the human lineage (inferred from the fossil record)?

Answer 3

• 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

Question 4

Was our ancestor chimp-like? Or did chimps ‘lose’ some of these traits?

Answer 4

-probably the ancestor would have been chimp-like, since the selection would drive the advantageous traits

Question 5

What is the Australopithecus diversity and when and where did these exist?

Answer 5

• 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

Question 6

What are the characteristics of Australopithecus anamensis?

Answer 6

• 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…

Question 7

What are the characteristics of Australopithecus afarensis?

Answer 7

-“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

Question 8

What is some of the evidence suggesting that Australopithecus afarensis was bipedal?

Answer 8

• 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

Question 9

What was different in Australopithecus afarensis? (bone -wise)

Answer 9

• 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

Question 10

What was the Australopithecus afarensis skull like?

Answer 10

• 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

Question 11

Did Australopithecus afarensis have families?

Answer 11

-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

Question 12

What are some of the more recent Australopithecus species?

Answer 12

-• 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

Question 13

What is Paranthropus and its characteristics?

Answer 13

• 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

Question 14

When did the first Homo appear?

Answer 14

• 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

Question 15

What were some of the changes in the first Homo that appeared?

Answer 15

• 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

Question 16

What was the evolution of tool use in Homo?

Answer 16

• Homo habilis used simple stone tools
• Tools became more sophisticated over time

-the mousterian stone tools= suggest that more advanced hunting skills

Question 17

Do Chimp use tools as well?

Answer 17

-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

Question 18

What is so special about tool use in humans?

Answer 18

• 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?

Question 19

What is the longest enduring Homo species?

Answer 19

• 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

Question 20

Did Homo erectus walk?

Answer 20

-Homo erectus walked just like modern humans • 1.5 Mya footprints, found in Kenya • Foot shape and pressure pattern almost identical to modern humans

Question 21

Why is Homo erectus termed the world traveller?

Answer 21

-Homo erectus found in Africa, Europe, Asia (as far east as Indonesia and China) -the big thing about erectus= migration over the world

Question 22

What are some of the Homo erectus characteristics that are different from us?

Answer 22

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

Question 23

What are the Dmanisi fossils?

Answer 23

-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)

Question 24

Did Homo erectus use fire?

Answer 24

-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

Question 25

What are some more contenders for new species?

Answer 25

Denisovans (400,00-44,000ya) - Fossils(two teeth,finger&toe bone) from a cave in Siberia -Cave inhabited by Homo sapiens and Homo neanderthalis -DNA analysis revealed that distinct from both Neanderthals and modern humans (but also shared genes with both). -Interbreeding with H. neanderthalis?

Question 26

What is the Homo floriensis and its characteristics?

Answer 26

• the hobbit • Discovered in 2004, on Flores, Indonesia • 95-17,000 ya (VERY recent) • Thought to have descended from Homo erectus ancestor -overlapping entirely with homo sapiens -unusual as it is tiny, resembling a chimp, back to australopithecus • Tiny skull and skeleton hence nicknamed the ‘hobbit’ • Island dwarfing? Disease?

Question 27

What is the Homo heidelbergensis and its characteristics?

Answer 27

• 700,000-200,000ya
• Lived in colder climates
• Neanderthal ancestor?

Question 28

When did Neanderthals first appear and what was their range?

Answer 28

• Homo neanderthalis • 200,000 – (28-40,000) ya -Range across Europe (except Scandinavia) - reduced to Mediterranean in Ice Age

Question 29

What were the differences between Homo sapiens and the Neanderthals?

Answer 29

• Stockier body – Shorter legs – Broader shoulders, hips – Barrel chested – Less slender hands, feet
• Adaptations to reduce heat loss? (Allen’s rule)
• very different morphology compared to us
• maybe to reduce heat loss= in cold climate, if stockier= less heat lost
• Skull has bigger nasal cavity
• Prominent eyebrow ridges
• Bigger cranial capacity

Question 30

Is there evidence of culture in Neanderthals?

Answer 30

-yes • Make-up? • Music?

Question 31

Did humans and the Neanderthals interbreed?

Answer 31

• Homo sapiens overlapped with Neanderthals • Fossils rarely found together • Share up to 99.5% of genes • DNA sequencing of Neanderthal bones argues against inter- breeding (sometimes) • However, there have been claims of hybrid fossils -we don’t know, rarely found together -DNA sometimes suggests yes and sometimes no -the offspring unlikely to be very fit

Question 32

What happened to the Neanderthals?

Answer 32

Hypotheses: 1. Assimilation with Homo sapiens 2. Extermination by Homo sapiens 3. Climate change/small population size 4. Out-competed by Homo sapiens 5. High infant/maternal mortality during childbirth?

Question 33

When did the first Homo sapiens appear?

Answer 33

-• First Homo sapiens fossil appeared between 190- 160,000 years ago • Nickname ‘Omo I’, found by the Omo River, Ethiopia • Cranial capacity = 1300ml

Question 34

Why do we have smaller canines?

Answer 34

• Primates with smaller canines tend to have wider faces • Inhumans,menhave wider faces than women • Womenprefermenwith wide faces (and prominent cheeks) • Sexual selection against long canines

Question 35

Example questions from this lecture:

Answer 35

• What are the similarities and differences between Australopithecus & modern man? • What do comparative studies & the fossil record tell us about the evolution of tool use by humans? • Discuss the diversity of the genus Homo - why do you think that Homo sapiens is the only remaining member of the genus?