The notes above provide an in depth summary of the Hominid Studies section of the Life Science Syllabus required by the IEB.
These notes have been used in the completion of the Final Matric Exams with confidence and ease.
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Human Evolution
Classification of Hominids
Members of the Hominidae are hominids.
Hominins refer to humans and their fossil ancestors.
Hominids are bipedal animals that show human-like and ape-like features.
Anatomical similarities between African Apes and humans
➔ Opposable thumbs:
◆ Allow monkeys to have power grip.
◆ Allows humans to have power grip, as well as a precision grip (fine motor
ability.
➔ Two hands with 5 fingers.
➔ Two feet with five toes on each.
➔ Long arms that rotate freely.
➔ Naked fingertips and toes end in flat toenails.
➔ Reduced snout length with weakened sense of smell.
➔ 3D vision
➔ Colour vision.
➔ No tail.
➔ Sexual dimorphism (male and females clearly distinguished).
➔ Have molars and premolars with rounded cusps.
Anatomical differences between African Apes and humans
, African Apes Humans
Quadrupedal Bipedal
Long and narrow pelvis Short and wide pelvis
Smaller, less developed brain Larger, more developed brain.
Thin tooth enamel Thick tooth enamel
Prominent cranial and brow ridges Reduced cranial and brow ridges
Flat feet Curved foot arch
Evidence of common ancestors for living Hominids
Humans did not evolve from chimps or the gorilla but they do share a common
ancestor.
There are three main lines of evidence that indicates hominids may have shared a
common ancestor:
➔ Fossil Evidence.
➔ Genetic Evidence.
➔ Archaeological Evidence.
Fossil Evidence
● Fossils provide more information about the structure, movement, lifestyle and
environment of a particular species.
● Hominid fossils indicate how changes occurred over time.
● Many hominid fossils are not complete.
○ Most fossils contain Teeth, jaw bones or skull fragments.
○ Remains of feet, hands, pelvic bones or vertebral columns are scarce.
● Palaeontologists look at the following features of fossils to identify a common
ancestor:
○ Bipedalism.
○ Dentition (Teeth).
, ○ Palate shape.
○ Brain size.
○ Prognathism.
○ Cranial and brow ridges.
Bipedalism
● The greatest observation between apes and humans are the differences in
posture and method of locomotion.
● Apes are four-footed/ Quadrupedal with some (Gorillas) demonstrating
particular manner of walking like knuckle walking.
● Humans are bipedal and walk upright.
● Fossils show evidence of transition from quadrupedalism to bipedalism.
● Advantages:
○ Upright bodies expose smaller surface area to sun= Reduces risk of
overheating.
○ Hands are free to prepare food, use tools and hunt.
○ Vision extends further over tall grass.
○ Adaptability to occupy a wider range of habitats.
● Early hominid’s skeletons changed drastically in order to become bipedal.
● Changes in structures:
○ In bipedal humans, the foramen magnum shifted forward so that the
skull rests on top of the vertebral column and eyes could face forward.
■ The foramen magnum is positioned centrally at the bottom of the
skull.
■ In quadrupedal animals the head is positioned in front of the
vertebral collum and foramen magnum is at the back of the skull.
● The human vertebral column is S-shaped (flexibility and shock absorption) and
the colum of apes is C-shaped.
● Humans have shorter arms and longer legs while apes have shorter legs and
longer arms.
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