human evolution

Question 1

human phylogeny - part one

Answer 1

vertebrates : chordates with a backbone

gnathostomes : vertebrates with jaws

tetrapods : gnathostomes with limbs and feet

amniotes : tetrapods with eggs adapted for land

mammals : amniotes with hair and that lactate ( class - mammalia )

Question 2

human phylogeny - part two

Answer 2

Eutherians : placental mammals

primates : eutherians with hands and feet adapted for grasping. no claws, large brain, short jaws, stereo vision. (order)

anthropoids : primates with a somewhat opposable thumb

hominoids : anthropoids with a fully opposable thumb - apes and humans

Question 3

hominins

Answer 3

hominoids more closely related to modern humans than modern chimps, gorillas or orangutans

Question 4

forehead : differences between modern Hominins and Panins

Answer 4

human: steep forehead, flat face
chimpanzee: low forehead, projecting face

Question 5

brain : differences between modern Hominins and Panins

Answer 5

human: large brain (14 - 1600 cc), large cranial size at birth
chimpanzee: small brain (400cc)

Question 6

teeth : differences between modern Hominins and Panins

Answer 6

human: small canines, large molars
chimpanzee: large canines, small molars

Question 7

bipedal : differences between modern Hominins and Panins

Answer 7

bipedal - using 2 legs for walking

human: fully bipedal - foramen magnum under skull
chimpanzee: partially bipedal - foramen magnum at back of skull

Question 8

earliest hominins

Answer 8

three candidate groups of fossils:

• Sahelanthropus tchadensis
• Orrorin tugensis
• Ardipithecus ramidus

very limited material

fossils from 6-4.5 mya

Question 9

Australopithecus

Answer 9

archaic hominins from east Africa
(earliest hominin. - unknown if related to humans)
- several species
- A. afarensis discovered in 1974, Ethiopia
- 4.5 - 4 mya
- 1m tall
- fully bipedal
- but small brained relative to modern humans 400-500 cc

Question 10

bipedal locomotion

Answer 10

• key adaptation in hominids
• anthropoid ancestors were arboreal ( living in trees ) - (30 - 35 mya)
• didnt evolve in one go
• long distance bi-pedalism only evolved 1.9 mya
• a pre-adaptation for other hominid features

Question 11

savannah theory : bipedal locomotion

Answer 11

a hypothesis that human bipedalism evolved evolved as a direct result of human ancestors transition from an arboreal lifestyle to one on the savannas

*widely excepted

Question 12

aquatic ape theory - bipedal locomotion

Answer 12

our ancestors once spent a significant part of their life in water

• not really accepted

Question 13

functional morphology of A. afarensis

Answer 13

• brain bigger than chimp but so is body
• small incisors and big molars suggests diet of tough food (prob. plant based)
• capable of bi-pedal walking but only over short distances
• large zygomatic arches : massive jaw muscles
• rectangular ( or U shaped ) arrangment of teeth
• protruding jaw

Question 14

A. garhi

Answer 14

• east africa 2.5 mya
• even larger chewing teeth
• ‘megadont’ (having larger teeth)
• fossil animal bones with scrap-marks found in same site : first evidence of tool use and de-flehing animal carcases

Question 15

dexterity

Answer 15

performing tasks with hands

manual dexterity in humans:

• power grip
• precision grip

( change to bipedalism allowed selection on hands )

Question 16

australopiths

Answer 16

Paranthropus spp., a robust australopith 2.3 - 1.2 mya, Southern Africa

Australopithecus africanus, gracile australopith 3 - 2.5 mya, Southern Africa, bipedal but possibly arboreal

Question 17

transitional hominins

Answer 17

earliest example of genus Homo

1. Homo habilis
   600-700 cc, ‘handy man’, 2.4 mya Olduvai gorge Tanzania, controversial: may be an australopith, possibility of spoken language based on false assumptions about brain morphology ( Broca’s area )
2. H. rudolphensis
   500-800 cc, bigger wider faltter face, 1.9 mya Lake Turkana Kenya, large chewing muscles, very little known about species

Question 18

pre-modern homo

Answer 18

1. homo ergaster
2. 5 mya - kenya, slender, fully bipedal, low sexual dismorphism
3. homo eructus
4. 2 mya - kenya, ‘peking man’, may be the direct ancestor of modern humans, first ti migrate out of africa 1.5 mya

Question 19

Homo neanderthalensis

Answer 19

• many similarities with modern humans
• upto 1900 cc
• evidence for interbreeding with early H. sapiens in europe
• but modern humans not directly descended from neaderthalensis (share some DNA)
• 0.2 mya - 0.04 mya

Question 20

hominin average brain size

Answer 20

H. neanderthalensis : up to 1900cc
H. sapiens : average 1400cc
H. erectus : average 900cc
H. habilis : average 650cc

Question 21

Homo sapiens : modern hominins

Answer 21

• oldest fossils 185-160,000 years old in Ethiopia - possibly split 365k years ago
• moden humans evolved in africa
• lack heavy brow ridges
• oldest fossils outside africa 100,000 years old
• oldest in new world 15,000 years ago
• the only extant hominin

Question 22

out of Africa hypothesis : the spread of humans

Answer 22

a model for the origin and dispersal of modern humans. The hypothesis contends that humans evolved in East Africa, dispersing to populate the rest of the world from c. 70,000 years ago, replacing, rather than interbreeding with, the archaic hominins that were resident outside of Africa

Question 23

hominin adaptations

Answer 23

hominins are hominoids with:

• full bipedalism
• dextrous hands
• smaller jaws and teeth
• very large brains
• reduced sexual dismorphism
• unique social and cultural behaviour