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Human Biology ATAR > Evolutionary trends in hominids > Flashcards

Evolutionary trends in hominids Flashcards

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1
Q

Hominidae

A
  • = hominids
  • Family name
  • Includes great apes and lesser humans
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2
Q

Homininae

A
  • = hominines
  • Sub-family name
  • Includes gorillas, chimpanzees and humans
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3
Q

Hominini

A
  • = hominins
  • Extinct and modern humans
  • It is used to separate gorillas and chimpanzees from humans
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4
Q

Great apes

A

orang-utans
gorillas
chimpanzees

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5
Q

Lesser apes

A

gibbons

siamangs

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6
Q

How do hominins differ from apes?

A
  • In their appearance, structure and behaviour
  • Hominins are relatively hairless and their structure allows for a fully bipedal stance and gait
  • Hominins have a unique erect posture and striding gait
  • Hominins also have a greater development of the brain, changes in the size and shape of their teeth, development of speech and sexual characteristics
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7
Q

Bipedal locomotion

A

walking on two legs with the body upright

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8
Q

What is an adaptation?

A

Characteristics that help on organism survive and reproduce in its natural environment

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9
Q

Adaptations for an erect posture

A
  • To stand upright and walk with a striding gait, humans require a modified muscular and skeletal structure
  • These are considered adaptations as our erect posture helps our human ancestors to survive
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10
Q

Types of postural adaptations

A
  1. Position of the foramen magnum
  2. Curvature of the spine
  3. Jaw size
  4. Pelvis shape
  5. Carrying angle of the femur
  6. Knee structure
  7. Foot structure
  8. Centre of gravity
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11
Q

Foramen magnum

A
  • Large hole at the base of the skull in which the brain joins the spinal cord
  • In humans, it is directly under the skull
  • In quadrupeds, it is further towards the back of the skull
  • Having the foramen magnum directly under the skull enables the skull to balance on the top of the vertebral column
  • Non-human require much stronger neck muscles to hold the head in position
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12
Q

Spine curvature in non-humans

A
  • Non-humans have their vertebrae arranged in a single (C shaped) curve, causing the body to tilt forwards
  • Their centre of gravity is in front of its hind feet
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13
Q

Spine curvature in humans

A
  • Humans have a double curvature, giving them an S shaped spine which contributes to an upright stance
  • The vertebrae in the lower, or lumbar region are wedge-shaped from front to back, thus forming a forward-jutting curve. This improves body balance in the upright position
  • It enables the head to balance on the top of the neck
  • The curves bring the head directly over the spine, this means that the centre of gravity runs straight through the head and spine
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14
Q

Pelvis shape

A
  • The pelvis in humans is broader and shorter than that of other primates
  • The human pelvis supports the abdominal organs during upright stance
  • Broad hip bones provide space for the attachment of large buttock muscles, which move the legs and keep the upper body erect
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15
Q

Position of the hip joint (humans)

A
  • The hip joint is directly under the head and body trunk (when we walk)
  • This allows the weight of the body to be transferred to the legs
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16
Q

Pelvis and femur structure

A
  • The pelvis is wide with two acetabulum
  • The head of the femur is large and first into the acetabulum
  • Femurs converge towards the knees
  • Femurs are not directly vertical
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17
Q

Carrying angle

A
  • The angle the femur makes with the knee joint
  • Ensures that the weight distribution remains close to the central axis of the body when walking
  • During walking, it enables the body to be rotated about the lower leg and foot, producing a striding gait (instead of swaying from side to side)
  • Weight is transmitted through the outside of the femur
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18
Q

The knee

A
  • The weight of the body is transmitted down the outside of the femur to the knee
  • The knee consists of two ‘hinges’ with the ligaments in between (e.g. ACL)
  • The outer hinge is larger
  • Although the weight of the body is transmitted down the outside of the knee joint, the centre of gravity falls through a lone just in front of the knee (when standing)
  • This force tries to bend the knee backwards, but the knee ligaments naturally resist it
  • Therefore, no energy is required to support the body in a standing position
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19
Q

The foot

A
  • Does not have an opposable toe
  • No longer prehensile
  • Human have both a longitudinal and a transverse arch
  • Non-humans have only a longitudinal arch
  • The arches facilitate a striding gait
  • These two arches have enabled humans to perfect bipedal locomotion
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20
Q

Centre of gravity

A
  • Apes have much longer arms and their legs are relatively short
  • Shorter arms and longer legs in humans lower the human centre of gravity
  • Apes → chest level
  • Humans → pelvis level
  • A lower centre of gravity gives greater stability during striding
  • Longer legs in humans facilitates longer steps when striding
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21
Q

Stance and locomotion

A
  • Hominins have an upright stance and a striding gait

- All homo-genera (habillis, erectus and neanderthalansis) and Australopithecines were upright

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22
Q

Muscle tone

A
  • The partial contraction of many skeletal muscles
  • Facilitated posture
  • Sleep reduces muscle tone
  • Humans require sustained muscle tone to support and upright stance
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23
Q

Areas with muscles that support the upright stance

A
  • Spine
  • Hip
  • Knee
  • Ankle
  • Abdomen
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24
Q

What areas work together to maintain postural equilibrium?

A

The nervous system (sensory tract of the cerebral cortex) and sense organs

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25
Q

Knee extension

A
  • In a striding gait, hominins have their hips and knees fully extended (straightened)
  • Even when bipedal, apes have their knees bent and their bodies bent forward at the hip
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26
Q

Weight transmission

A
  • In a striding gait, the weight is transmitted from the heel along the outside of the foot to the ball of the foot
  • At the final moment of the stride, the weight is transferred to the big toe
  • The toe is parallel, as it is used for weight bearing rather than grasping
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27
Q

Rotation of the trunk

A
  • With each stride, the trunk rotated about the pelvis
  • Arms swing to oppose this rotation keeping the shoulders perpendicular to the direction of travel
  • This reduces the need for energy to reverse trunk rotation
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28
Q

Footsteps

A
  • Each footstep can follow in a straight line
  • Apes lack a wide pelvis and carrying angle
  • When bipedal, apes must swat from side to side so that the weight is over each leg in turn
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29
Q

Average human brain size

A

1350 cm3

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30
Q

Average ape brain size

A

200-500 cm3

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31
Q

Human cerebral cortex

A
  • Large and convoluted
  • Convolutions increase the surface area of the cortex
  • The greatest increase is in the frontal lobe
32
Q

Frontal lobe in humans

A

47% of total cortical surface

33
Q

Frontal lobe in apes

A

33% of cortical surface

34
Q

Endocasts

A
  • An impression made of the inside of a structure
  • Brain endocasts show that Australopithecines had cranial capacities similar to apes
  • The trend after Australopithecines was for a general increase in cranial capacity
35
Q

Dentition

A
  • Human dentition is very distinctive
  • Dental arcade is parabolic, with all teeth very similar in height
  • Apes have parallel sides to their dental arcade, large canines and diastemas
  • The trend is toward smaller, more uniform teeth in hominins
36
Q

Time of earliest life forms

A

3500 MYA

37
Q

Time of the first mammals

A

260 MYA

38
Q

Time of the first primates

A

65 MYA

39
Q

Early hominins

A
  • Lived in a woodland or forest environment
  • Were ape-like, with arms and hands suited to living in a tree
  • Upright locomotion may have been used where gaps in the forest appeared and hominins needed to cross open ground
  • 5-6 MYA, the African environment was changing
  • Temperatures began to fall causing forests to recede, leaving savannah
  • Natural selection favoured bipedalism
40
Q

Advantages of bipedalism

A
  1. Increased range of vision
  2. Increased size (upright) to deter predators
  3. Hands free for carrying and making tools
  4. Higher reach when picking fruit
  5. Improved cooling (less sun and more breeze)
41
Q

Types of hominins (least to most evolved)

A 
-	Australopithecines
o	A. Afarensis
o	A. Africanus
o	P. Robustus
-	Homo habilis
-	Homo erectus
-	Homo sapiens (neanderthalensis)
-	Homo sapiens-sapiens (Cro-Magnon man)
42
Q

A. Afarensis

A
  • 3.5-5 MYA

- Found in East Africa

43
Q

Skull of A. Afarensis

A
  • Brain capacity: 400cc
  • Skull more ape-like than human
  • Jaws were large and forward thrusting with prognathism
  • Upper part of the face was small with a low cranial vault, low forehead, brow ridge, flat nose and no chin
44
Q

Locomotion of A. Afarensis

A
  • 1-1.3m tall
  • Full adapted to upright walking
  • Bipedal
  • 25-30Kg
45
Q

Diet/food resources of A. Afarensis

A
  • Herbivores, feeding on hard objects (seeds and grain, tough chewy plants, large quantities of fruits, seeds, pods, roots and tubers)
  • Canines much reduced, but upper teeth still retain a diastema
46
Q

Selection pressures for A. Afarensis

A
  • Adoption of bipedalism as a means of locomotion to evade predators in open savannah
  • Running required the adoption of an efficient cooling system
    o ↑ sweating ability
    o Hair loss
  • Freeing of hands allowed for the carrying of objects considerable distances
47
Q

A. Africanus

A
  • 2.5-3 MYA
  • Found in East Africa
  • Cranial capacity of 450cc
  • 1.3m tall
  • Fully adapted to upright walking
  • Bipedal
  • 30kg
48
Q

P. Robustus

A
  • 1.5-2 MYA
  • Cranial capacity of 500cc
  • Vary large molars, small incisors and canines
  • Broad cheek bones
  • Sagittal crest
  • 1.5m tall
  • Fully adapted to upright walking
  • Bipedal
  • 70kg
49
Q

Australopithecine culture

A
  1. Nomadic with home bases
  2. Foragers and scavengers
  3. Used and possibly made a range of pebble tools (choppers, scrapers, flakes and chisels) called oldowan tools
  4. Branches, grasses and bushes used as shelter
  5. Omnivorous or frugivorous
50
Q

Homo habilis

A
  • 2.5-1.5 MYA

- Found in East and Southern Africa

51
Q

The skull of homo

A
  • Brain capacity: 650-750cc
  • Cranial vault more rounded, bigger brain and a smaller, narrower and longer face
  • Evidence of a bulge in the speech producing part of the brain that shows that rudimentary speech may have been used
  • Reduced snout
  • Brain shape more human like
52
Q

Evidence for abstract thought in homo habilis

A
  • Tools made from materials some distance away suggested that they ‘planned’ the manufacturing of tools in advance
53
Q

Diet/food resources for homo habilis

A
  • Scavenger/hunter-gatherer of catfish, small animals and plants
  • Diet largely carnivorous
  • Smaller teeth with narrower back teeth
54
Q

Selection pressures for homo habilis

A
  • Increases in brain size selected for

- Increased cooperation required

55
Q

Homo erectus

A
  • 1.5 MYA – 250,000 YA

- Found in Africa

56
Q

The skull of homo erectus

A
  • Cranial capacity:850-1100cc
  • Pronounced, thick straight brow ridge
  • Less prognathic jaw
  • Speech production area and recognition area of the brain show swelling
57
Q

Abstract thought in homo erectus

A
  • More advanced tool making required an ability to plan the shape of the tool before it was made
  • Some evidence of scalping which suggests that some form of ritualism existed
  • First use of fire
58
Q

Diet/food resources of homo erectus

A
  • Systematic hunting of large game had become a major part of hominid life for the first time
  • Largely a carnivorous diet
  • Massive molars
59
Q

Selection pressures for homo erectus

A
  • A marked increase in brain size and complexity suggests that there were strong pressures for increased intelligence
  • Development of tool technology gives a competitive advantage over other predators
  • Selection for improved bipedalism
  • Began to lose body hair
60
Q

Shelter/home of homo erectus

A
  • Created shelter from broken branches, twigs, leaves and reeds
  • Created home bases
61
Q

Homo sapiens neanderthalensis

A
  • Neanderthals

- 200,000-35000 YA

62
Q

Neanderthal skull

A
  • Brain capacity: 1600cc
  • The brain was larger than the average modern human brain
  • Heavy brow ridges, and a very large forward thrusting middle face
  • Has an occipital bun
  • Jaw is stout, usually without a chin
63
Q

Neanderthal’s shelter/home

A
  • Use of caves as shelter by some groups

- Others constructed shelters of wood supported b mammoth tusks and covered with skins

64
Q

Abstract thought in neanderthals

A
  • Individuals were buried on their sides with their knees up around their chest, covered with ochre or flowers and surrounded by skulls or horns
  • Suggests the beginning of a religious ritual
  • They started working in groups to co-operatively hunt large game
  • This required good communication and abstract thought
65
Q

Diet/food of neanderthals

A
  • These people were hunters
  • Plant food would have been unavailable during the cold winter of the glacial period
  • Possessed large molar teeth that were well worn
66
Q

Selection pressures of neanderthals

A
  • Well adapted to the cold glacial climate prevailing: has a stout squat body form
  • Food supply was possibly tenuous at times
  • Had to cope with the cold by developing use of clothing, fire and shelter
  • Became extinct as they were unable to cope with the selection pressures of modern humans
67
Q

Cro-Magnon man

A
  • 40000 – 15000 YA
68
Q

The skull of Cro-Magnon man

A
  • Cranial capacity: 1400cc
  • No overhanging brows
  • Occipital lobe is rounded and low
  • Projecting chin
  • Reduced size of teeth, jaw and associated muscles
69
Q

Diet/food resources of Cro-Magnon man

A
  • Exploited numerous food resources as a hunter – gatherer
  • Later a farmer with domesticated animals and cultivated crops
  • Teeth became smaller as food preparation improved
70
Q

Abstract thought of Cro-Magnon man

A
  • Very fine tool technology
  • First appearance of cave paintings, bone carvings and clay statues
  • Began hunting selected animals e.g. mammoth
71
Q

Types of tools

A

Oldowan tools
Acheulian tools
Mousterian tools
Upper palaeolithic

72
Q

Oldowan tools

A
  • Used by the late Australopithecines (found) and Homo habilis
  • First appeared 2.5 MYA
  • Also called pebble tools
  • Simple river worn pebbles with crudely fashioned flakes removed
  • Often look like a round cobble with the top knocked off
  • Australopithecines: used to exploit their natural environment
  • Homo habilis: hunting, cutting and sharing food
73
Q

Acheulian tools

A
  • Used by homo erectus
  • First appeared 1.5 MYA
  • ‘tear drop’ shape
  • Tools are more sophisticated than the oldowan tools. More blows have removed more flakes from the rock
  • Referred to as a hand axe
  • Used for hunting and butchering prey/animals and possibly skinning
74
Q

Mousterian tools

A
  • Used by Neanderthal man
  • First appeared 150,000 YA
  • Included fine points, sharp knives and scrapers
  • Some stone points were hafted into spears
  • Known as flake tools
  • Differ from Acheulian tools by having more, smaller flakes taken off
  • Used to hunt, prepare animal hides for shelter/tents and clothes in colder conditions
75
Q

Upper Palaeolithic

A
  • Used by late Cro-Magnon man
  • 40,000 YA
  • Sharper, pointier tools
  • Hunting equipment improved by the use of narrow bone or ivory pints for spears
  • Known as blade tools
  • Used for hunting, farming, ornamental use and for tools such as fishing hooks and needles

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