Human evolution Flashcards
The order and family humans belong to
Order: Primates
Family: Hominidae (commonly called hominids)
Class that humans belong to and characteristics of this class
Mammalia: Bodies covered in hair Suckle their young Three ossicles in the middle ear
Family Hominidae includes the extant taxa…
Human
Chimpanzee
Gorilla
Orangutan
Current term for bipedal humans and our fossil ancestors
hominins
Genera considered hominins
Ardipithecus
Australopithecus
Homo
The name that refers to the orangutan, gorilla and chimpanzee
Great Apes
Shared characteristics between humans and apes
- opposable thumbs with a power grip
- no tail
- sexual dimorphism between males and females
- brain centers processing hand and eye coordination enlarged
- naked fingertips with flat nails
- long, freely rotating arms
- reduced snout and sense of smell
- stereoscopic vision with forward pointing eyes
- molars and premolars have rounded cusps
Mode of transport difference between apes and human
Apes: knuckle walkers, quadrupedal
Humans: walk on two legs, bipedal
Skull differences between apes and humans
Jawbone: Apes-large, prominent, no chin vs Humans-reduced jaw, developed chin
Cranial and brow ridges: Apes-prominent vs Humans-reduced
Brain size: Apes-smaller vs Humans-larger
Face: Apes-wider, sloping face vs Humans-narrow, flat face
Appendicular skeletal differences between Apes and Humans
Arms: Apes-longer arms vs Humans-shorter arms
Feet: Apes-flat feet, opposable big toe vs Humans-arched feet, forward thrusting big toe
Pelvis: Apes-long and narrow pelvis vs Humans-short and wide pelvis
Legs: Apes-weaker legs and smaller knees vs Humans-stronger legs and larger knees
Spine differences between Apes and Humans
Shape: Apes-C shaped spine vs Humans-S shaped spine
Foramen magnum: Apes-at back of skull vs Humans-central under skull
Evidence for hominid common ancestry
Fossils
Genetic
Cultural
A scientist who studies fossils
Paleontologist
Most commonly preserved parts of hominin skeletons studied by scientists
teeth,
jaw bones,
skull fragments,
long bones,
feet,
hands,
pelvic bones and vertebra are scarce
Particular key characteristics scientists examine in hominin fossils
- bipedalism
- dentition and palate shape
- brain size
- prognathism
- cranial and brow ridges
Prognathism
Large prominent jawbone with reduced or chin lacking
Foramen magnum
The opening for the spinal cord into the skull
Evidence for bipedalism in hominins
- Foramen magnum shifted forward, centrally at the bottom of the skull
- The spine becomes S shaped
- Longer and stronger legs
- Larger and stronger knee joint
- A forward pointing big toe, parallel to the other toes
- An arched foot
- A larger, shorter and wider pelvic girdle to support greater weight in an upright posture
Advantages of bipedalism
- bodies expose smaller surface area to the sun, reduced risk of overheating
- bodies exposed to more wind to assist cooling
- hands free to use tools etc.
- extended vision across landscape to see predators and food
Changes in brain size in hominins
Cranium size increases Chimpanzee has around 400 cm^3
Australopithecus between 440-500 cm^3
Various Homo species 640-1500 cm*3
Humans about 1400 cm^3
Changes in dentition in hominins
- Canines have reduced in size, Apes have protruding canines and they become roughly the same size as the other teeth in hominins
- Diastema (gap between incisors and canines) is reduced/disappears
- Tooth enamel has become thicker
Changes in prognathism in hominins
- From jaws that protruded (a snout) with no chin
- Jaws have become less protruding (flatter) with a pronounced chin.
- The forehead appears more vertical because of this together with the increased cranium.