Define ‘Apes’
The family name for the group of primates that do not have tails (humans are part of this grouping).
What does ‘Arboreal’ mean?
Living in/relating to trees.
What is ‘Brachiating’?
And what adaptations do ‘Brachiators’/primates typically possess in order to do this?
A form of locomotion involving movement through arboreal environments via swinging from branch to branch.
Brachiators typically have:
- A short lumbar spine
- Long Curved Fingers
- Reduced Thumbs
- Long Forelimbs
- Flexible Shoulder Joints
- Freely Rotating Wrists
What is ‘Knuckle-Walking’?
And what main adaptation/trait do ‘Knuckle-Walkers’/primates typically possess?
This is a form of quadrupedal locomotion in which the forelimbs hold the fingers in a partially flexed posture that allows the primate’s body weight to press down on the ground through the knuckles as they walk.
- Bones around the knuckle joints are enlarged to enhance stability and weight-bearing (presence of this is used to identify Knuckle-Walking in fossils)
State the types of locomotion typically observed in arboreal primates:
- Brachiation (swinging through the branches)
- Knuckle-Walking (quadrupedal walking)
Suggest two possible advantages of ‘Brachiating’:
Allows for effecient travel through trees from branch to branch, thus allowing primates to adopt an arboreal niche:
Thus;
1) Increased likelihood of avoiding ground-dwelling predators
2)Ability to access otherwise unobtainable food sources
Suggest two possible advantages for ‘Knuckle-Walking’:
1) Allows primates to efficiently travel in terrestrial niches/ground environments during times when ‘Brachiation’ is perhaps not possible (thus expanding range of niches/environments they may occupy)
2) Allows primates to grasp and carry objects while travelling from one location to another
Briefly describe the ‘Cranium/Brain-Case’:
This is the part of the skull that encloses the brain and protects it from injury.
Briefly describe the ‘Brow Ridge’:
These are well-developed bony ridges above and around the eyes.
They help protect the eyes by reinforcing against the powerful forces generated by chewing/biting.
Briefly describe ‘Canine Teeth’:
Large pointed teeth used for holding/killing prey, as weapons, or for aggressive displays.
Briefly describe the ‘Zygomatic Arch’:
This is the ‘arch’ in the ‘cheekbone’ where important muscles utilised for chewing pass through;
(These muscles are then attached to the mandible and skull).
Briefly describe the ‘Nuchal Crest’:
This is an extension towards the base of the skull to which (thick) neck muscles attach.
(These muscles position, move, and stabalise the head and cervical vertibrae).
Briefly describe the ‘Sagittal Crest’:
This is a ridge bone running lengthwise along the midline of the top of the skull.
(Strong jaw muscles attach to it, and thus it reinforces the skull against powerful forces generated by chewing/biting).
Briefly describe the ‘Premolars’ and ‘Molars’:
These are the large flat teeth that are used for shearing and crushing food during chewing.
Briefly describe the ‘Foramen Magnum’:
This is a large hole at the base of the skull through which the spinal cord and spinal arteries enter the skull.
(For Bipeds, it is located centrally at the base of the skull)
(For Quadrupeds, it is located further back at the base of the skull).
Briefly describe a ‘Diastema’:
This is a space between the teeth for which large canines may fit into so that the teeth can come together fully when the mouth closes.
Briefly describe a ‘Prognathism’:
This is a feature when the lower portion of the face markedly projects forward (at an angle).
Give a brief comparison of a Chimpanzee’s jaw area to that of a Modern Human:
1) Chimpanzee:
- More robust/rectangular-shaped jaw
- Narrow ‘U-Shaped’ Dental Arcade
(Post-canine teeth either side of jaw are parallel to each other)
2) Modern Human:
- Wider, Parabolic/’V-shaped’ Dental Arcade
- Smaller teeth
- Less robust/more gracile mandibles
Compare the ‘Sagittal Crest’ for Chimpanzees and Humans, giving a reason for the difference:
- Chimpanzee: Present
- Human: No Sagittal Crest
- Substantial jaw muscles are needed to move a large/robust mandible attach to this skull component. As such muscles are reduced in humans, no crest is necessary.
- Most likely brought about by change in diet over time.
Compare the ‘Relative Size of Canines’ for Chimpanzees and Humans, giving a reason for any difference:
- Chimpanzee: Larger (with associated larger Diastema)
- Human: Smaller/reduced
- Canine Teeth predominantly utilised in aggressive displays, and thus trend of Modern Humans toward less overt displays (ie increased use of language/vocalisations) reduced the need for intimidating dental features
Compare the ‘Shape of Jaw’ for Chimpanzees and Humans, giving a reason for any difference:
- Chimpanzee: ‘U-shaped’, no chin, and presence of Simian Shelf
- Human: ‘V-shaped’, protruding chin, NO Simian Shelf
- Trend towards Modern Humans follows reduction in size and specialisation of human teeth as our diet evolved.
- Less musculature required in Humans, so bone structure could be reduced/become more gracile
Compare the ‘Zygomatic Arch’ and ‘Brow Ridge’ of Chimpanzees and Modern Humans, giving a reason for any differences:
- Chimpanzee: Thick/prominent Zygomatic Arch and Brow Ridges
- Human: Less thick/prominent and more gracile
- Chimpanzees have a ‘tougher’ diet, requiring greater chewing forces to process fibrous plant material, and so need more robust structures for reinforcement/muscle attachments to prevent fractures.
- Humans’ shift toward diet with higher content of ‘softer’/cooked foods meant a removed need for ‘Biologically Expensive Butressing’, and so evolved more gracile structures.
Compare the ‘Foramen Magnum’ of Chimpanzees and Modern Humans, giving a reason for any difference:
- Chimpanzee: Positioned toward rear of skull and angled backwards.
- Human: Centrally located and vertically aligned.
- Humans evolved to be bipedal, and so mostly upright positioning involves skull being situated directly above spinal cord, thus requiring a centrally located Foramen Magnum.
- Chimpanzees are quadrupeds who mostly knuckle-walk as a means of locomotion, so their skulls project forward from a relatively horizontal spine, requiring a Foramen Magnum located more towards rear of skull for support.
Contrast the main ‘Differences in Hand Structure’ for Quadrupeds and Bipeds:
(According to LearnCoach)
Quadrupeds:
- Curved Fingers for Brachiating
- Power Grip (fingers and thumb wrap around an object)
- Less Fine Motor Skills
Bipeds:
- Straight Fingers
- Precision Grip (thumb and finger grip object)
- More Fine Motor Skills
- Better Tool-Use Ability (and ability to acquire food)
- Opposable Thumb!
