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
-
Hominins refer to modern humans, extinct human species as well as immediate ancestors
- This includes members of Homo, Australopithecus, Paranthropus and Ardipithecus
-
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
-
Larger heel and larger arch in the foot
- Allows for even distribution of weight
-
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
-
Ancestral relationships are inferred based on limited fossil evidence
- New evidence causes scientists to revise hypotheses
-
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.
Explain the “out of Africa” hypothesis
- The hypothesis states that Homo sapiens evolved in Africa and then left, replacing other human groups
- It proposes that the migration of modern humans occurred in two waves
- A first small-scale migration starting 120 000 years ago (into the Middle East)
- A second large-scale migration starting 60 000 years ago (to Europe and Asia and then to all other regions)
- Potential reasons for migration include availability of resources, environmental changes and curiosity
NOTE: This theory suggests that all modern humans are descendants of an African population of Homo sapiens.
Explain how mtDNA provides evidence in support of the “out of Africa” hypothesis
- There is higher genetic diversity in the mtDNA of modern African populations compared to the rest of the world
- Homo sapiens have lived in Africa for 300 000 years which has allowed more mutations to accumulate overtime
- Their later migration outside of Africa has left less time for mutations to occur which explains the less diverse mtDNA of modern non-African populations
NOTE: This is an example of the founder effect. New populations (outside of Africa) have a smaller gene pool compared to the original population.
Explain the multiregional hypothesis
- The Multiregional hypothesis states that Homo erectus left Africa and evolved into Homo sapiens in different locations
State when and where the first fossils of Homo sapiens were found outside of Africa
- When: 100,000 - 120,000 years ago
- Where: Middle East
State when Indigenous Australians arrived in Australia
- 50 000 years ago
Explain mitochondrial DNA (mtDNA)
- mtDNA is present in all individuals
- It is maternally inherited, so no recombination occurs
- They contain a non-coding region known as the D-loop
- The D-loop has two DNA sections that undergo mutation quicker than the rest of the molecule
NOTE: The greatest variation in mtDNA is observed within African populations.
Define haplotypes and haplogroups
- Haplotypes refer to the particular mtDNA sequence of an individual’s D-loop
- Haplogroups are the various haplotypes worldwide that fall into a number of large clusters
- Individuals in the same haplogroup share a common ancestor and have similar haplotypes
State how mtDNA haplogroups can be used
- Haplogroups can be used to track modern human migration across the world due to the lack of genetic recombination and high level of mutation in the D-loop
Describe the difference between mtDNA and nucleur DNA
-
mtDNA is maternally inherited, so no recombination occurs
- Have higher mutation rates due to lack of repair mechanisms
- Provides evidence for maternal lineage and migration
- Contains smaller amounts of genetic material
-
Nuclear DNA is inherited from both parents, so recombination occurs
- Have lower mutation rates due to presence of repair mechanisms
- Provides evidence for maternal and paternal lineages + interbreeding across species
- Contains larger amounts of genetic material
List the advantages of mtDNA and nuclear DNA analysis
-
mtDNA
- Faster to sequence
- Known or constant rate of mutation
- Less likely to degrade compared to nuclear DNA
-
DNA
- More genetic material (information) available
- Can be used to determine interbreeding between species
- Presence of introns can reveal more inherited mutations
Outline the likely route that the ancestors of Indigenous Australians took to travel to Australia
- It is proposed that their ancestors moved out of north-east Africa through the Middle East and Asia, and then travelled south to Sahul
- From here, ancestors travelled east and west
NOTE: Sahul is a paleocontinent made up of the present-day landmasses of Australia, Tasmania, and New Guinea.
Explain the importance of “Country” to Indigenous Australians
- Aboriginal and Torres Strait Islander populations are part of the longest living cultures in the world
- Due to the length of time they have lived in Australia, they have created strong and rich connections to their Country and Place
- They exemplify their care for Country by traditional land management practices (e.g. traditional burning and fishing traps), allowing them to live sustainably in Australia
List reasons for why DNA evidence for interbreeding may or may not be found
- Reasons for DNA evidence being found
- DNA has been obtained from older hominin fossils
- Other hominin DNA has been found in the genomes of different hominin species, suggesting interbreeding occurred
- Reasons for DNA evidence not being found
- DNA degrades quickly and may not be found in very old fossils
- Low chance that a fossil of an interbred individual will be found
Explain how ancient cave drawings provide evidence of cultural evolution
- Cave drawings show passing of information through generations
- Cave drawings become more complex over time
- Cave drawings show evidence of change in cultural practices, evidence of complex thought or evidence of symbolic representations
Identify features of primates that distinguish them from other mammal groups
- Prehensile/grasping hands
- Forward facing eyes
- Relatively large brain volume to body
- Nails instead of claws
