Evidence for Human Evolution Flashcards
(86 cards)
Modern Humans
Kingdom:
Phylum:
Class:
Order:
Family:
Genus:
Species:
Animalia
Chordata
Mammalia
Primates
Hominidae, subfamily: homininae
Homo
Homo Sapiens (H. sapiens)
what are some other primates? (7)
chimpanzees, orangutangs, monkeys, gorillas, apes, lemurs, tarsiers
common primate characteristics: (13)
1) unspecialised body and limbs
2) nails instead of claws
3) grasping fingers and toes with friction ridges for gripping (finger prints)
4) first digit opposable
5) pentadactyl limb (5 digits)
6) poor sense of smell
7) forward facing eyes = stereoscopic vision (most primates can distinguish colour)
8) incisors in each jaw
9) large, complex brain with cerebrum size increased (indicating more highly evolved primate)
10) non-restricted breeding seasons
11) rhythmic sexual cycles (eg: ovulation)
12) usually 1 offspring per pregnancy
13) long period of parental care for the child
characteristics of great apes: (7)
1) larger, more complex brain compared to other primates (increased cognitive ability)
2) arms that freely rotate about shoulder
3) wide, shallow chest cavity
4) no external tail
5) appendix present
6) active during day (diurnal as opposed to nocturnal)
7) 5 cusps in molar teeth of lower jaw
what is bipedalism and what are the benefits?
Bipedalism is the type of mobility where an organism walks on 2 legs. Opposed to quadrupedalism, which is when an organism walks on 4 legs. The benefits of being bipedal include being able to hold things with hands while moving, and it conserves more energy while moving, as all structures fall over centre of gravity, making bipedalism more efficient.
what is the foramen magnum?
the foramen magnum is the hole at the base of the skull where the brain joins the spinal cord
talk about the foramen magnum in non-human apes:
The FM is further back on the skull. This means that when knuckle walking, the face can look forward. There is larger attachment area for larger neck muscles which are needed to hold head in position.
talk about the foramen magnum in humans:
the FM is more central on the skull. This means that the weight of the skull is borne by the spinal cord. When walking on 2 legs, the weight in centred over 2 feet.
talk about the curvature of the spinal cord in humans:
The spine forms an S-shaped curve in humans. The 4 main curves help balance the body, and absorb the shock of walking. The cervical region is where the neck allows the body to be directly under the skull. The lumbar region is the inward curve produced by the lumbar vertebrae being wedge-shaped from front to back.
talk about the curvature of the spinal cord in non-human apes:
The spinal cord in non-human apes is one smooth C-shaped curve. The thoracic and lumbar regions curve upwards.
talk about the pelvis in non-human apes:
The pelvis in non-human apes is longer and narrower. it is tilted in the skeleton - less upright orientation than humans.
talk about the pelvis in humans:
The pelvis in a human is broader, shorter, and bowl-shaped. This pelvis supports abdominal organs when standing, provides stability during bipedal locomotion by having broad hipbones that provide space for the attachment of large buttock muscles, and also supports the developing foetus during pregnancy.
what is a carrying angle?
the angle the femur makes with the vertical.
talk about the carrying angle in non-human apes:
In non-human apes, the carrying angle is more vertical. This is because the weight of the body falls inside the femur. This is why apes sway side to side when walking.
talk about the carrying angle in humans:
The increased breadth of the pelvis necessitates the need for an inward angle from the head of the femur to the knee. This angle keeps weight distribution close to the central axis when walking.
talk about the foot in non-human apes.
The non-human apes are prehensile (graspable) with an opposable big toe. They only have one longitudinal arch. Their feet are not specialised, as they have varied locomotion techniques.
talk about the foot in humans:
Human feet are not prehensile, meaning they have no grasping ability. The large big toe is aligned with other toes on the foot. The metatarsals form 2 arches, one longitudinal and one transverse. The transverse arch is unique to humans as it is specialised for bipedal locomotion.
talk about the skull features of non-human apes:
Non-human apes have prognathism, and a larger jaw. This requires larger muscles to balance more heavier bones. They also have a larger, heavier, and prominent brow ridge.
talk about the skull features of humans:
Humans have a decreased prognathism. This ensures that the skull is better balanced and the centre of balance is over the feet. We also have flatter facial features, including an orognathic jaw decreased in size which offers better balance with less muscular effort. We also have a smaller brow ridge.
talk about the centre of gravity in humans:
Humans have an S-shaped spine and a broad pelvis that positions the centre of gravity over the feet for balance during bipedal locomotion.
talk about the centre of gravity in apes:
Apes have a straighter spine and a narrower pelvis, keeping their centre of gravity forward, which is suited for quadrupedal locomotion.
talk about the muscle tone of humans:
humans have well-developed gluteal and leg muscles for upright posture and bipedalism.
talk about the muscle tone of apes:
apes have stronger upper body muscles for climbing and crawling and less developed lower limbs, making bipedal walking more challenging.
talk about the striding gait of humans:
Humans walk with a heel-to-toe stride that is energy-efficient for long distances. Due to broader hipbones, human’s walking bipedally without swaying side to side. Apes have a flatter foot placement and a less-efficient waddling gait when walking. Due to their features, they sway side to side when they walk.
