CHAPTER 10: HUMAN CHANGE OVER TIME Flashcards
1
Q
class mammalia
A
- fur or body hair
- milk-producing mammary glands
- teeth - incisors, canines, premolars
- lower jaw made of one bone
- breathe using lungs
2
Q
order primate
A
- flattened face
- opposable thumbs
- forward - facing eyes
- bicuspid teeth
- large brain relative to the body
- long gestational period
- nails instead of claws
- prehensile or grasping hands
- no single characteristic is diagnostic of a primate but taken together the features can help identify one
3
Q
family hominids/hominidae/hominoids
A
- large brain (cerebral cortex)
- characteristic skull bones
- absence of tail
- relatively long upper limbs
- wider chest
- shoulder joints that permit the arms to be rotated
4
Q
genus homo
A
- homo sapiens are the only existing member of the genus homo
- bipedalism
- large brain
- self-awareness
- use of complex language
- writing and art
- rituals
- use of tools
- culture
5
Q
how can we tell from fossils that an organism was bipedal
A
- evidence of erect or bipedal walking can come from
- position of the hole (foramen magnum) in the base of the skull
- arrangement of the femur and tibia (femur is angled)
- shape of the pelvis (bowl shaped)
- shape of the spine (s shape)
- size of the heel bone and subsequent heel arch
6
Q
effect of bipedalism on hominin behaviour
A
- freed the hands for tool making
- freed the hands for carrying young
- reaching for higher food
- raising head to scan predatores
- cultural behaviour such as ceremony
- enabled them to walk greater distances and migrate
7
Q
trends in hominin evolution
A
- brain size also was increasing (enlarged skull size)
- an increase in the length of feet with more developed arches
- an increase in leg length (a larger leg : arm ratio) - and become stronger than arms
other trends: - a reduction in the size of teeth
- a flattening and shortening of the face, making the face nearly vertical
- a more central foramen magnum
- a smaller zygomatic arch (cheekbone)
- a less prominent brow ridge
- a more parabolic-shaped (or V-shaped) jaw
- the development of a more S-shaped spine.
8
Q
timeline of hominin species
based on when they first arose
A
- A. afarensis
- A.africanus
- Homo habilis - first tool makers
- Homo ergaster(sometimes thought to beHomo erectus ergaster) - only found in Africa
- Homo erectus - first emigrants - migrated out of Africa
- Homo heidelbergensis - diverged into homo sapiens and homo neandethalensis (intermediate features between H.erectus and H.sapiens)
- Homo floresiensis - the hobbit - small on stature
- Homo neanderthalensis - all non-african humans have neanderthal DNA
- Homo sapiens
- The denisovans - home sapiens from oceania and mainland asia have denisovan DNA (unknown when they first appeared)
9
Q
the features of early hominins- the Australopithecines
A
- were able to walk with a bipedal locomotion
- spine shape was beteen c and s shaped
- a rounded jaw but not parabolic
10
Q
trend in brain size
A
- compared to australopithecines, homo sapiens have:
- larger brains relative to their body
- the trend is increasing size with the major exception to this being Homo floresiensis
-
cerebral cortex, cerebellum and areas associated w language expanded at higher rates than other brain regions
- large brains need lots of energy 20% → structural changes
- early homo could not survive on plants - meat → functional changes
- required cooperative hunting - communities → cognitive changes
- use of the brain made only possible because of earlier evolution of opposable thumb and bipedalism → structural changes
- Homo Florensies does not fit the trend (small brain capacity)
11
Q
trend in leg length
hominin evolution
A
- longer legs allow more effective bipedal motion
- longer leg to arm ratio
12
Q
trend in shape of the pelvis
hominin evolution
A
- compared to chimp
- shorter and broader
- compared to australopithecine
- more bowl-shaped
- allow more surface area for muscle attachment
13
Q
trend in foot shape
hominin evolution
A
- enlarged heel
- foot arch
- allow weight to be evenly distributed
- forward facing big toe
- allows us to use big toe for propulsion (to move forward)
14
Q
trend in leg angle
hominin evolution
A
- compared to chimps
- more angle
15
Q
trend in limb structure
hominin evolution
A
- compared to australopithecines, homo sapiens have
- less angle femur-hip joint
- longer legs
- narrower and bowl-shaped pelvis
16
Q
what does a bigger brain allow
A
- Australopithecus
- sexual dimorphism - similar social structures to modern apes
- herbivores
- near forests - grasslands
- simple tool use
- homo habilis
- used tools to prepare food and clothing
- enabled meat in the diet
- homo erectus
- hand axes
- use of fire
- systematic hunting
- travelling
- homo sapiens
- technology
- farming
- caring for aged/ill members of species
17
Q
relate the changes to leg structure to bipedalism
A
- angled femur from hip to knee brings knees closer together under the body’s centre of gravity
- central foramen magnum - head balanced directly over spine - better balance + walking upright
- pelvis - helps maintain stability when walking
- s-shaped spine - helps absorb shock and distribute body weight evenly during walking
- foot structure (arch, non-opposable big toe) - balance, shock absorption, and efficient propulsion during walking
18
Q
how and why the human fossil record has changed over time
A
- the human fossil record is incomplete
- periods of time in the geological record where very few fossils have been found (2-3mya)
- HUMAN FOSSIL RECORD IS ALWAYS CHANGING
19
Q
reasons for incompleteness of the human fossil record
A
- many species of hominins did not live in areas that are conducive to fossilisation
- most hominin species only lived for a very short geologic time
- many hominin species probably practiced burial rituals
- hominin species tend not to leave their dead behind
20
Q
why scientists can have different interpretations of the human family tree despite using the same evidence
A
- imprecision of dating methods
- different intepretations
- new evidence is found
- interbreeding between H.sapiens and H.Neanderthalensis
- evidence of putative homo species
21
Q
how scientists used mtDNA to determine that Neanderthals were a different species to sapiens
A
- small amounts of mtDNA were extracted from Neanderthal fossils
- challenging bc of the degradation of ancient DNA
- the mtDNA was sequenced
- compared w the sequences of modern humans
- neanderthal mtDNA is distinct from modern humans
Compared the mtDNA sequence of the Neanderthals to the mtDNA of H.Sapiens – they identified similarities and difference
This determined there was genetic divergence and that the two were not closely related.
22
Q
evidence that Homo sapiens and Homo neanderthalensis and the Denisovans interbred
A
- modern races of H.sapiens have Denisovan DNA - modern Tibetans have EPAS1 gene - which allows them to breathe easily at high altitudes
- Denisovan DNA accounts for 3-5% of the DNA of Aboriginal Australians
- It accounts for 7-8% of Papuans from Papua New Guinea
- 1-2% of DNA of all people of European and Asian descent is from Homo neanderthalensis
23
Q
the Denisovans
A
- bone fragments found in Siberia in 2010
- a finger bone
- more fossils: teeth, fragment of jaw bone, fragment of arm or leg bone and a fragment of skull bone
- found to be a different species
- DNA taken from the genomes of Melanesian Homo Sapiens revealed they share 4-6% DNA with Denisovans but other human populations do not
- most closely related to H.neandertahlensis
- hypothesis:
- An interbreeding event occurred between the Denisovans and ancient Melanesians
- likely occurred between 15000 - 44000 years ago as the ancestors of Melanesians migrated south through Southeast Asia
24
Q
Homo Naledi
A
- discovered in 2013 - in a cave in South Africa
- small cranial capacity, but a long survuval
- limb + foot structure → partially arboreal (lived on trees)
- bones exhibited characteristics from both the genus homo and genus Australopithecus
- classified into a new species of the Homo genus, Homo naledi
- hand has a similar shape to modern humans but the curved finger and strong thumb are more primitive
25
Q
Homo Luzonensis
A
- teeth and finger bones, part of a foot and part of a femur were discovered in the Philippines (remains came from three diff people)
- lived at least 50000-67000 years ago on an island
- it is classified as Homo
- activity of the species → cognitive ability to make stone tools and hunt w them
26
Q
Homo Floresiensis
A
- discovered in 2003 on Indonesians island of Flores
- 1.1m tall
- small cranial capactiy
- intelligent - used fire, made stone tools
27
Q
out of Africa theory
A
- out of Africa states that homo sapiens evolved in Africa and then left, replacing other human groups
- more evidence to support this hypothesis
- small scale migration: one smaller move 120 000 years ago into the Middle East
- large scale migration: a larger move 60 000-70 000 years ago into all other continents (Europe and Asia then all other continents)
- more evidence to support this hypothesis
- H.sapiens evolved in Africa about 300,000 years ago from H.heidlbergensis
- around 70,000 years ago H.sapiens migrated out of Africa and spread across the rest of the world replacing populations of other hominin species
- according to this theory, all modern humans are descendants of an African population of Homo sapiens
28
Q
multiregional hypothesis
A
- the multiregional hypothesis states that homo erectus left Africa and evolved into homo sapiens in different t locations
- homo sapiens evolved in different parts of the world, in parallel, from populations of Homo erectus
29
Q
ancestor of Homo Sapiens
A
- to trace human migration - assumptions are made
- homo sapiens and Neanderthal evolved from homo heidelbergensis
- homo heidelbergensis evolved from homo erectus/ergaster
30
Q
mtDNA
hominin evolution
A
- can be more useful than nuclear DNA because:
- it is inherited via the maternal line and does not undergo recombination
- the only variation that exists is from mutations accumulating over time
- there is a non-coding region called the d-loop → has a higher rate of mutation than other regions
- the particular mtDNA sequence of the D-loop of each person is called that person’s haplotype
- the various haplotypes worldwide fall into a number of large clusters known as haplogroups
- a haplogroup is a group of people with similar haplotypes who share a common ancestor
- Mitochondrial analysis is more accurate due to a known mutation rate and maternal inheritance. Molecular clock.
31
Q
use of haplogroups in mtDNA
A
- mutations accumulate over time
- mtDNA is more useful than nuclear DNA
- major human haplogroups can be used to track modern human migration across the world
- due to a lack of genetic recombination and a high level of mutation in the D-loop
- each haplogroup represents significant differences in mtDNA
- allow for human populations to be tracked out of Africa
32
Q
the likely route that the ancestors of Indigenous Australians took to travel to Australia
A
- 58,000 years ago, a population of H.sapiens split off from the main population, travelling east through Asia and making it to AUSTRALIA
- as they passed through Asia, they interbred with H.neanderthalensis and Denisovans
- moved out of north-east Africa → the Middle East → Asia and then travelled south to Sahul→ From here different ancestors travelled both east and west
- DNA evidence also suggests that modern hominins reached the Australian around 55,000 years ago from South-East Asia, with distinct groups, from a single initial migration, spreading rapidly down the western and eastern coasts to occupy particular geographical areas.
- the extinction of the Australian megafauna approximately 42,000 years ago is also evidence for the rapid migration of modern hominins across the continent.
33
Q
when did ancestors of Indigenous Australians arrive in australia
A
50 000 years ago
34
Q
how does the analysis of haplotypes allows us to determine where and when human migration occurred
A
- mtDNA is conserved through the maternal lineage there is no recombination
- the only thing that alters it is mutations overtime
- we know the average mutation rate so we can determine the time of migration
- African populations have a much higher genetic diversity likely due to them having more time to accumulate mutations. with this info we can find out approximately when new alleles were introduced occurred and approximately when humans migrated
35
Q
when and where the first fossils of Homo sapiens were found outside of Africa
A
- when: 100,000 - 120,000 years ago
- where: Middle East
36
Q
the importance of ‘country’ to indigenous Australians
A
- due to the length of time they have lived in Australia
- created strong + rich connections to their Country and Place
- hundreds of different tribes (clans/mobs) that have unique languages and connections to their land across mainland Aus, Tasmania and Torres Strait
prolonged connection over time of specific populations in specific areas of the Australian continent
37
Q
evidence to support out of Africa theory
mtDNA
A
-
evidence from mtDNA
- more diversity in mtDNA of modern African populations than the rest of the world’s populations combined
-
molecular genetic studies can be used to determine when lineages separated
- migration of H.sapiens is an example of the founder effect
- beneficial → high known mutation rate (bc it doesn’t have repair mechanisms) → large diff between populations
38
Q
comparative genomics in neanderthals and sapiens
A
- 99.7% of the nucleotide sequences of the modern human and Neanderthal genomes are identical
- comparison of nuclear genomes of modern humans and Neanderthals → 1-4% of the DNA of ALL non-African modern humans came from Neanderthals
- native Africans do not have any Neanderthal DNA
39
Q
challenge with the fossil record
A
- it is difficult to determine patterns when natural variation exists as:
- much of the evidence is only based on fossils and DNA and this evidence is largely incomplete
- hard to definitively prove whether the extinct organisms were able to interbreed (and thus be classified as the same species)
- may be many species in which no fossilisation occurred or fossils are yet to be found
- conflicting dates using different tech -> esp is specimens are old/incomplete
- falsifications of fossils
- difference in intepretation
40
Q
how has mtDNA changed our perspective on when sapiens arrived in Australia?
A
- mtDNA haplogroups are unique to Aboriginal and Torres Strait Islanders peoples diverged from other groups
- the large variation in these haplogroups reflects the large time frame since Aboriginal and Torres Strait Islander peoples diverged from other groups
- large number of haplogroups in Indigenous Australian DNA
41
Q
evidence to support out of Africa theory
fossils
A
-
evidence from fossils
- fossils of H.sapiens older than 70 000 years may have arisen because
- H.sapiens left Africa a number of times since evolution 300 000 years ago but were unsuccessful until 70 000 years
- fossils found in all regions of the world
42
Q
hominin vs hominoid
A
Hominin: the group consisting of modern humans, extinct human species and all our immediate ancestors (including members of the genera Homo, Australopithecus, Paranthropus and Ardipithecus).
Hominoid: the group consisting of all modern and extinct Great Apes (that is, modern humans, chimpanzees, gorillas and orang-utans plus all their immediate ancestors).
43
Q
tribe hominini
A
- humans are part of the taxonomic tribe Hominini
- hominins have adaptations that enable the wrists and hands to manipulate objects and use tools.
- skull differences between hominoids and hominins
- compared with other apes, humans are capable of advanced cognitive capacity, and complex language and belief systems.
44
Q
advantages of using mtDNA as a molecular clock
A
- there are many more copies of mtDNA in each cell
- mtDNA has a known rate of mutation
- mtDNA mutations accumulate or are not repaired
- all changes in nucleotides are a result of mutations rather than recombination
- mtDNA inherited from mother only allowing for a more direct line of relationships to be established.
- less likely to degrade
- used for determining lineage.
45
Q
advantages of whole genome analysis
A
- more bases and therefore information available
- DNA from both parents can determine if interbreeding occurred
- presence of introns can reveal more inherited mutations
46
Q
difference between whole genome analysis and mtDNA analysis
A
- mtDNA is inherited from mother only, whereas nuclear DNA is inherited from both parents
- mtDNA has fewer bases compared to nuclear DNA
- no recombination in mtDNA compared to nuclear DNA
- mtDNA used for lineage/migration compared to nuclear DNA for parentage/relationship between species
- mtDNA has a faster mutation rate / less conserved compared to nuclear DNA.
