Primate ancestors and human origins Flashcards
What are the anatomical differences in the two types of suspensary species?
fast and slow species.
Often the thumb is reduced or gone completely to aid with brachiating. But thumb is used for grooming, so species compensate by cuddling instead.
What are the anatomical adaptations of primates?
- Pendactyl limbs
- Prehensile hands (Knuckle walkers have less prehensile hands)
- Opposable big tow
- tails are often present (Tails can be used as another limb or they’re just used as a balance)
- Sensitive tactile pads with ‘fingerprints’ on fingers/toes
- flat nails on hands and feet in most species.
Where can specialisations of primate species often be seen?
Forelimb or facial morphology
What species forelimb morphology is similar to homo sapiens?
Macaques hand is very similar to ours. They are specialist generalists. Can survive in lots of environments like humans.
What are the anatomical adaptations of an arboreal quadruped?
- Long tail
- Narrow thorax
- Laterally placed scapula
- Long Olecranon process
- deep ulna
- grasping foot
Arboreal primate’s skeletons reveal that they have a lot more stored energy for travelling across canopy.
What are the anatomical adaptations of a terrestrial quadruped?
- reduced tail
- narrow thorax
- restricted shoulder movement
- Posteriorly extended olceration process
- robust radius
- short digits
- long, similar-length forelimb and hindlimb
What can be determined by studying the skull and mandible of a primate?
Can discover a wide range of diets; -herbivores (including folivores and gumnivores)
- omnivores
- obligate carnivores
molars are relatively unspecialized
Visual sense is highly developed. Eyes are large and forward facing, permitting stereoscopic vision.
Post-orbital bar (strepsirrhines) Enclosed orbits (haplorhines)
Unspecialised olfactory apparatus (greatly reduced in diurnal species)
Brain large compared with brains of similar sized mammals.
What are the main mating units for primates and give examples of species that use the mating strategy.
Promiscuity (many:many)
e.g; chimpanzees
Polygamy (one:many)
- Polygyny (1 male:many females) e.g; baboons, langurs, howler monkeys, gorillas.
- Polyandry (1 female:many males) e.g; small new world primates like the marmosets and tamarins.
Monogomy (one:one)
e.g; gibbons, titi monkeys, indris.
What is a Hominoid?
Anything in the homo genus. Any species that contributed to human evolution.
List the differences between apes and monkeys
Monkeys:
-climb on tops of branches using hands and feet to grip, tail to balance.
- long trunks
- arms and legs similar length
Apes:
-swing from branch to branch often hang whilst feeding, no tail.
- short trunks
- long arms
- flexible shoulder joints.
Describe the features of a hominoid skeleton
- ‘braincase’ - frontal, temporal, parital, occipital
- ‘face’ - frontal, maxilla, nasal, zygomatic (jugal and squamosal)
- ‘jaws’-maxilla, mandible, dentition
- ‘skull base’-basicranial bones
(Male gorilla has big sagittal crest for jaw muscle attachment. )
(Humans have no sexual dimorphism in the skull.)
Describe the features of an appendicular hominoid skeleton
Pectoral girdle - clavicle, scapula
‘upper arm’ - humerus
‘lower arm’ - radius, ulna
hand - manus; carpals, metacarpals, phalanges
Pelvic girdle - innominate - ischium, ilium, pubis
‘upper leg’ - femur
‘lower leg’ - tibia, fibula
foot - tarsus; tarsals, metatarsals, phalanges
Name the 4 anatomical planes
median
sagittal
coronal
transverse
What factors are related to hominoid morphological variation?
body size
brain size (encephalisation)
locomotion
ecological niche
Where are the main cranial differences found in hominoids?
- cranial height
- nuchal crest
- sagittal crest
- supraorbital torus
- prognathism (Humans have no prognathism at all. We are perfectly balanced for bipedalism. )
- Orthognathism (having a face that lies beneath the anterior cranial fossa
What differences can appear in dental arch morphology?
Rectangular or parabolic
simian shelf or external chin
canine size
What differences can appear in hominoid limb proportions?
Limb proportions - intermembral index - the length of the humerus and radius relative to the length of the femur and tibia.
In humans = <100
Brachiating primates = >100
What differences can appear in hominoid the vertebrae column shape?
Humans have an S shape spine to balance for bipedalism. Humans have a lower centre of gravity from standing upright and back problems occur because this has evolved over only 2 million years.
What are the main differences in postcranial anatomy in humans compared to other hominoid species?
Humans have an oval thorax to allow arms to swing while we walk. Where other primates have a cone shaped thorax.
Human pelvic is much stockier and robust to hold the increased pressure and weight in comparison to chimps and bonobos. This gives an indication what species are bipedal. Big fundamental difference in humans is large glutes to help move legs, which is very significant.
Hand anatomy differs depending on niche. Brachiatirs will more likely have longer, curved phalanges.
Humans have lost the opposable toe which created the foot arch for a ‘springy’ more efficient step.
Give a summary of the evolution of hominid bipedalism
The evolution of hominid bipedalism, which began in primates about 4 million years ago, or as early as 7 million years ago with Sahelanthropus, has led to significant morphological alterations to the human skeleton.
These changes include the arrangement of the bones in the foot, pelvis size and shape, knee cap size, length of leg and the shape, the orientation of the vertebral column and skull shape.
What are the four major divisions of hominoid locomotion?
- Facultative quadrupedalism
- Obligate quadrupedalism
- Facultative bipedalism
- Obligate bipedalism
What are the major differences between quadrubeds and bipeds? Use two species to illustrate your answer.
Chimpanzee:
- skull attaches posteriorly
- spine slightly curved
- arms longer than legs and also used for walking
- long narrow pelvis
- femur angles out
Australopithecine:
- skull attaches inferiorly
- spine S shaped
- arms shorter than legs and not used for walking
- bowl shaped pelvis
- femur angled in
What are the trends in the human skeleton, locomotion and posture?
- Knees are aligned under the body’s centre of gravity, because the femurs are angled inwards.
- Human legs straighten completely when walking
- Human spinal column has additional curves, keeping the centre of mass of the head and torso aligned.
- Big toe (hallux) not opposable, allowing for arched foot.
- ratio of legs:arms greater in humans than in other apes.
- broad pelvis
What are the 3 main areas of change in transition to bipeds in skull anatomy?
- inferior position of foramen magnum
- loss of prognathic features
- loss of ridges and crests
