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physical anthropology ⋆·˚ ༘ * > ˗ˏˋ hominins ´ˎ˗ > Flashcards

˗ˏˋ hominins ´ˎ˗ Flashcards

1
Q

what is a hominin?

A

modern-day humans and extinct bipedal ancestors.

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2
Q

what is a last common ancestor (LCA)?

A
  • hypothetical final ancestor (or ancestral population) of two or more taxa before their divergence
  • humans and chimpanzees
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3
Q

what are paleoanthropologists?

A

people who study human evolution.

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4
Q

what is morphology?

A

study of the form, size, or shape of things.

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5
Q

what is the east african rift system (EARS)?

A
  • refers to the rift valley expanding from malawi to ethiopia
  • active geological structure is responsible for much of the visibility of the paleoanthropological record in east africa
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6
Q

what is a site?

A

a place in which evidence of past societies/species/activities may be observed through archaeological or paleontological practice.

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7
Q

what was one of the first traits for hominins to evolve?

A

our bipedal locomotion.

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8
Q

what did early relatives have?

A

small brains and apelike dentition.

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9
Q

what is encephalization?

A
  • expansion of the brain
  • while bigger brains are a hallmark of hominins, a large brain doesn’t automatically equate intelligence
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10
Q

what is taxonomy?

A
  • science of grouping and classifying organisms
  • primarily based on morphology (in the past)
  • now related to molecular phylogeny (e.g., based on DNA)
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11
Q

what are cladistics?

A

groups organisms based on shared derived traits.

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12
Q

what are clades?

A

a grouping based on ancestral relationships; a branch of the evolutionary tree.

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13
Q

what are lumpers?

A

researchers who prefer to lump variable specimens into a single species or taxon and who feel high levels of variation is biologically real.

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14
Q

what are splitters?

A

researchers who prefer to split a highly variable taxon into multiple groups or species.

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15
Q

what is a paleoenvironment?

A

an environment from a period in the earth’s geological past.

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16
Q

what are faunal assemblages?

A

collections of fossils of the animals found at a site.

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17
Q

what does reconstructing global environments look like?

A

using marine soil data and pollen grains.

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18
Q

what is the savannah hypothesis (or aridity hypothesis)?

A
  • suggests that the expansion of the savannah (or less densely forested, drier environments) forced early hominins from an arboreal lifestyle (one living in trees) to a terrestrial one where bipedalism was a more efficient form of locomotion
  • proposed by charles darwin
  • popular
  • idea that the LCA of humans and chimpanzees was a knuckle-walking quadruped like chimpanzees and gorillas
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19
Q

what is aridification?

A

becoming increasingly arid or dry, as related to the climate or environment.

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20
Q

what is arboreal?

A

one living in trees.

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21
Q

what is the evidence and interpretation for the savannah hypothesis (or aridity hypothesis)?

A
  • evidence: cooling, drying conditions in africa about 6-8 mya
  • interpretation: these things happened within our species at the same time as aridification (diversification
    and bipedalism)
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22
Q

what is the turnover pulse hypothesis?

A
  • climate change is associated with high faunal turnover (e.g. ungulates)
  • ugulates: hoofed mammals—e.g., cows and kudu.
  • faunal turnover: the rate at which species go extinct and are replaced with new species
  • proposed in 1985 by palentologist elisabeth vbra
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23
Q

what is a generalist?

A

a species that can thrive in a wide variety of habitats and can have a varied diet.

24
Q

what is a specialist?

A

a specialist species can thrive only in a narrow range of environmental conditions or has a limited diet.

25
Q

what is the evidence and interpretation for the pulse turnover hypothesis?

A
  • evidence: quaternary ice age (2.5 mya - 3 mya), faunal turnover in east africa and south africa, turkana basin indicates multiple instances of faunal turnover and extinction events, in which global climatic change resulted in changes from closed/forested to open/grassier habitats at single sites
  • interpretation: debates about application to hominins and there were specialist hominin species that thrived as well as the generalist homo sapien.
26
Q

what is the forest hypothesis?

A
  • forested environments influenced bipedalism
  • proposed by r.j. rayner and colleagues
  • says that the LCA of chimpanzees and humans was more arboreal like orangutans, rather than knuckle-walkers like gorillas
27
Q

what is the evidence and interpretation for the forest hypothesis?

A
  • evidence: pollen evidence (south africa) and a closed habitat (referring to a woodland, or tree-filled, environment)
  • interpretation: better conditions for fossilization
28
Q

what is the variability selection hypothesis?

A
  • hominin groups would experience varying degrees of natural selection due to continually changing environments and potential group isolation
  • would allow certain groups to develop genetic combinations that would increase their ability to survive in shifting environments.
  • these populations would then have a genetic advantage over others that were forced into habitat-specific adaptations
  • proposed by richard potts
29
Q

what is the evidence and interpretation for the variability selection hypothesis?

A
  • evidence: large climatic variability and greater survival among generalists than specialists
  • interpretation: flexible interpretations of evolution of bipedalism and evolution towards greater variability
30
Q

what is the pulsed variability selection hypothesis?

A

proposes that the east african rift system (EARS) and changes in deep lakes are key drivers of diversification during early human evolution.
- EARS first developed about 10 mya and is responsible for the creation of large super lakes (e.g., lake baringo and lake turkana) within east africa
- affected by monsoons and solar precessional cycles: cyclical changes in earth’s axis rotation that have global climatic effects

31
Q

what is the evidence and interpretation for the pulsed variability selection hypothesis?

A
  • evidence: three humid phases in east africa and diversification in diet and adaptations
  • interpretation: high levels of species diversity
    and allopatric speciation
32
Q

what is the postcranium?

A

skeleton from below the head.

33
Q

what is obligate bipedalism?

A

where the primary form of locomotion for an organism is bipedal.

34
Q

what are the origins of bipedalism?

A
  • that early hominins descended from trees, and so we were a product of an arboreal last common ancestor (LCA) (most likely given skeletal morphology)
  • that our LCA was a terrestrial quadrupedal knuckle-walking species, more similar to extant chimpanzees
35
Q

what are the proposed selective pressures for bipedalism?

A
  • energy conservation: modern bipedal humans conserve more energy than extant chimpanzees, which are predominantly knuckle-walking quadrupeds when walking over land
  • thermoregulation: maintaining body temperature through physiologically cooling or warming the body
  • bipedalism freed up our ancestors’ hands such that they could more easily gather food and carry tools or infants
36
Q

what is mosaic evolution?

A

the concept that evolutionary change does not occur homogeneously throughout the body in organisms.

37
Q

what is sahelanthropus tchadensis?

A
  • 7 mya (earliest dated hominin find)
  • discovered in chad in 2001 by ahounta djimdoumalbaye
  • announced in nature in 2002 by a team led by french paleontologist michel brunet
  • small cranial
  • larger canines than homo
  • possibly bipedal
38
Q

what is orrorin tugenesis?

A
  • 6-5.7 mya
  • kenya
  • small cheek teeth (hind dentition, molars and premolars)
  • thick enamel
  • apelike canines
  • bipedal adaptations (post-cranium)
39
Q

what is ardipithecus ramidus?

A
  • 4.4 mya
  • found in ethiopia
  • small brain
  • bipedal
  • had ancestral traits (pposable hallux, or big toe)
  • had derived traits (pelvis)
  • large sample size of over 110 specimens
40
Q

what is ardipithecus kadabba?

A
  • 5.2-5.7 mya
  • found in the middle awash region (ethiopia)
  • post-crania: push-off ability of big toe
  • name means “oldest ancestor” in the afar language
41
Q

what is the importance of teeth?

A
  • preserves very well
  • can show diet
  • can reveal environment
  • can show relations to other species
  • can demonstrate sexual dimorphism
  • tells about social structure
  • a reduction in teeth and a more generalist dental morphology could also indicate an increase in softer and more variable foods, such as the inclusion of more meat
42
Q

what are general dental trends?

A
  • dental formula of 2:1:2:3
  • large, flat incisors that occlude (teeth from the maxilla come into contact with the teeth in the mandible)
  • incisiform: referring to a canine that app ears more incisor-like in morphology
  • reduced canine size
  • reduced/eliminated canine diastema
  • hind dentition indicates generalist diet
  • u-shaped dental arch
  • enamel and cusps
43
Q

what is the genus australopithecus?

A
  • varyrying degrees of arborealism and bipedality
  • includes gracile australopithecus and robust australopithecus
  • gracile: slender, less rugged, or pronounced features
  • robust: rugged or exaggerated features
  • large posterior dentition
  • large chewing muscles
44
Q

what does the gracile australopithecus include?

A
  • east afrirican australopithecines: anamensis, afarensis, and garhi
  • south african australopithecines: africanus and sediba
45
Q

what is australopithecus anamensis?

A
  • gracile
  • 4.2-3.8 mya
  • found in kenya, ethiopia
  • small/medium sized brains
  • large canines
  • projecting cheekbones
  • primitive ear-holes
  • bipedal: tibia, femur
  • primitive traits (upper limbs, arboreal)
46
Q

what is australopithecus afarensis?

A
  • gracile
  • 2.9-3.9 mya
  • found in tanzania, kenya, ethiopia
  • “lucy” (3.2 mya)
  • reduced canines, molars (vs. apes), prognathic face, strong chewing muscles
  • sexual dimorphism
  • bipedal: pelvis, lower limbs, footprints (laetoli)
47
Q

what is australopithecus garhi?

A
  • gracile
  • one of the highly contested/debated species
  • 2.5 mya
  • found in ethiopia
  • 450 cc (larger brain)
  • primitive stone tools
  • often compared to gracile australopithecines: larger hind dentition, longer limbs
48
Q

what is australopithecus africanus?

A
  • gracile
  • taung Child (discovered 1924)
  • 3.3-2.1 mya
  • 400-500 cc brain
  • small canines, no diastema
  • postcranial: bipedalism
49
Q

what is australopithecus sediba?

A
  • gracile
  • 1.97 mya
  • had mosaic features: 420-450 cc (larger brain), gracile mandible, small teeth and postcrania (arboreal and bipedal traits)
50
Q

what is the cradle of human kind?

A

limestone caves with well-preserved fossils.

51
Q

what is paranthropus “robust” australopithecines?

A
  • includes aethipicus, boisei, and robustus
  • large, broad, dish-shaped face
  • cheekbone arches that are forward facing, including a large mandible with extremely large posterior dentition
52
Q

what is paranthropus aethiopicus?

A
  • robust
  • 2.7-2.3 mya
  • found in tanzania, kenya, and ethiopia in the EARS system
  • sagittal crest
  • aproximal tibia indicates bipedality and similar body size to au. afarensis.
53
Q

what is paranthropus boisei?

A
  • robust
  • 2.4-1.4 mya
  • found in countries in east africa at sites such as kenya, malawi, tanzania, and ethiopia
  • tools dated to 2.5 mya in ethiopia have been argued to possibly belong to this species
54
Q

what is paranthropus robustus?

A
  • robust
  • 2.3-1.0 mya
  • the only taxon from the genus to be discovered in south africa
  • less derived, more general features that are shared with both east african species (e.g., the sagittal crest and zygomatic flaring)
55
Q

what are fallback foods?

A

foods that may not be preferred by an animal (e.g., foods that are not nutritionally dense) but that are essential for survival in times of stress or scarcity.

56
Q

what is knapping?

A
  • the fracturing of rocks for the manufacture of tools
  • earlier stone age technology (ESA): 3 mya - 300,000
57
Q

what is a techno-complex?

A
  • encompassing multiple assemblages that share similar traits in terms of artifact production and morphology
  • lomekwian (kenya) techno-complex, 3.3 mya
  • oldowan (tanzania) techno-complex, 2.6 mya, earliest stone-tool industry consisting of simple flakes and choppers

physical anthropology ⋆·˚ ༘ * (23 decks)

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