Chapter 10: Human Change Over Time Flashcards
State the characteristics of mammals
- Fur or hair over their body
- Milk-producing mammary glands
- Teeth comprising of incisors, canines, premolars and molars
- A lower jaw made of one bone
- Breath using lungs
- Three bones in the middle ear
State the characteristics of primates
- Flattened face
- Opposoable thumbs (allows for grip)
- Binocular vision
- Bicuspid teeth
- Short nose
- Large brain relative to body
- Long gestational period
State the characteristics of hominoids/hominids
- Large brain (cerebral cortex)
- Characteristic teeth and skull bones
- Absence of tail
- Long upper limbs
- Wide chest
- Joints that allow arms to rotate
State the characteritics of hominins
- Bipedalism (walking on two hind legs in a sustained fashion)
- Large brain (allows for self awareness, use of complex language, writing and rituals)
- Use of tools
- Culture
NOTE: Hominins refer to modern human groups and their bipedal ancestors.
List the fossil evidence for bipedalism
- Bowl-shaped pelvis and s-shaped spine
- Central foramen magnum on the base of the skull
- Larger feet and heel bone + more prominent foot arch
- The femur and tibia arranged at an angle
List the effects of bipedalism on hominin behaviour
- Enabled them to walk greater distances and migrate
- Freed the hands for making tools and carrying young
- Allowed them to reach for food (e.g. vegetation on trees)
- Allowed them scan for predators by raising their head
- Cultural behaviours such as ceremonies
List the trends in hominin evolution
- An increase in the size of the cranium (indicates that brain size is increasing)
- Longer feet with more developed arches
- Longer legs (a larger leg to arm ratio)
- Smaller teeth
- Flattening and shortening of the face (making the face nearly vertical)
- A more central foramen magnum
- Smaller cheek bones (zygomatic arch)
- Less prominent brow ridge
- More V-shaped jaw (parabolic)
- Development of an S-shaped spine
Outline the timeline of the hominin species
- Australopithecus (A. afarensis and then A. africanus)
- Homo habilis (first tool makers)
- Homo ergaster (only found in Africa)
- Homo erectus (first emigrants, migrated out of Africa)
- Homo heidelbergensis (displays features between H. erectus and H. sapiens)
- Homo floresiensis (the hobbit, small stature)
- Homo neanderthalensis (all non-african humans have neanderthal DNA)
- The denisovans (homo sapiens from oceania and mainland asia have denisovan DNA)
- Homo sapiens (the only extant member of the human species)
NOTE: Homo neanderthalensis were NEVER in Africa.
Describe the features of early hominins (Australopithecines)
- Bipedalism
- Spine was between a c- and s-shape
- Rounded but not parabolic jaw
State the difference between hominins and hominoids
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Hominins refer to modern humans, extinct human species as well as immediate ancestors
- This includes members of Homo, Australopithecus, Paranthropus and Ardipithecus
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Hominoids refer to all modern and extinct Great Apes
- This includes modern humans, chimpanzees, gorillas, and their immediate ancestors
Describe how brain size has changed in relation to hominin evolution
- Brain size (relative to body) has increased from the Australopithecines to Homo sapiens
- Homo neanderthalensis is the exception
- Cerebral cortex and cerebellum (including other areas associated with language) expanded at higher rates compared to other brain regions
Explain the effect of increased brain size
- Larger brains require a lot of energy
- They allowed for tool use, travelling, the use of fire, systematic hunting, farming, caring for ill/elderly members of the species and enabled meat in the diet
Describe the trend in leg length and its relation to bipedalism
- Longer leg to arm ratio
- Longer legs allow for a more effective bipedal motion
Describe the trend in pelvis shape and its relation to bipedalism
- Compared to chimpanzees, our pelvis is shorter and wider
- Allows humans to walk and balance upright without having to shift our weight forwards and use our knuckles for stability
- Compared to australopithecines, our pelvis is more bowl-shaped
- Made the pelvis more stable to support weight (allowing for bipedalism)
- Allows more surface area for muscle attachment
Describe the trend in foot shape and its relation to bipedalism
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Larger heel and larger arch in the foot
- Allows for even distribution of weight
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Forward facing big toe
- Allows us to use the big toe for propulsion (to move forward)
Describe the trend in leg angle and its relation to bipedalism
- Compared to australopithecines, the angle between our femur and tibia is smaller
- This is because australopithecines were shorter (large angle helped bring the centre of mass within the outline of the feet)
Describe how and why the human fossil record has changed over time
- The human fossil record is always changing
- It is incomplete (compete fossils of incomplete specimens or incomplete fossils of complete specimens)
- Classifications are not fixed and may change upon discovering new information
Explain why the human fossil record is incomplete
- Many species of hominins did not live in areas that are conducive to fossilisation
- It is likely that many hominin species practiced burial rituals
- Most hominin species only lived for a short period of geological time
Explain why scientists can have different interpretations of the human family tree despite using the same evidence
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Ancestral relationships are inferred based on limited fossil evidence
- New evidence causes scientists to revise hypotheses
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Dating methods tend to be imprecise
- Some scientists consider genetic dating to have an error margin
- The human fossil record is open to differing interpretations that are contested, refined and replaced when challenged with new evidence
Explain how scientists used mtDNA to determine that Neanderthals were a different species to sapiens
- mtDNA was extracted from Neanderthal fossils
- The mtDNA was sequenced and compared to that of modern humans
- It was found that Neanderthal mtDNA is distinct from modern humans indicating that they are two separate species
Describe the evidence of the interbreeding between Denisovans, Neanderthals and Homo sapiens
- Fossil evidence doesn’t provide a definitive answer of their interbreeding but genome sequencing has shown strong suggestions
- Denisovan DNA accounts for 3-5% of DNA of Aboriginal Australians + Melanesian populations (e.g. Papua New Guinea)
- All non-African modern humans have 1-4% of Neanderthal DNA (only native Africans have no Neanderthal DNA)
State the evidence of the existence of Homo naledi
- Fossilised remains were discovered in a South African cave in 2013
- Showed characteristics between genus Homo and genus Australopithecus
- Classified into a new species, Homo naledi
State the evidence of the existence of Homo luzonensis
- Fossilised teeth, finger bones, remains of a foot and a femur were discovered in the Philippines
- Lived in luzon 50 000 to 67 000 years ago
- Classified as Homo due to their cognitive ability to make and hunt with stone tools
State the evidence of the existence of the Denisovans
- Finger bone found in Siberian cave in 2008
- Most closely related to Homo Neanderthalensis
NOTE: The Denisovans were a small population and only interacted to interbreed with Homo sapiens in the areas they inhabited.