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Life Sciences > Human evolution > Flashcards

Human evolution Flashcards

1
Q

What is a phylogenetic tree?

A

A tree-like diagram representing the evolutionary relationship between groups of organism.

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2
Q

Meaning of phylo + genetic tree

A

Phylo - groups

Genetic tree - evolutionary relationship

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3
Q

Define Hominid

A

group consisting of modern humans, chimpanzees, gorillas and orangutans. It includes all members of the family Hominidae.

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4
Q

Define Hominin

A

group consisting of modern humans, extinct human species and all our immediate ancestors (Homo, Australopithecus, Paranthropus and Ardipithecus)

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5
Q

What are the 4 living genera of the family Hominidae

A
  1. Pongo: orangutan
  2. Gorilla
  3. Pan: Chimps and Bonobos
  4. Homo sapiens
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6
Q

What is the general pattern of human development?

A

Ape-like ancestor 🡪 ape men 🡪 early humans 🡪 modern humans

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7
Q

How many years ago did the first ape-like being appear?

A

38 million years ago

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8
Q

What are our closest living relatives?

A

Chimps are our closest living relatives. We did not evolve from chimps but we share a common ancestor.

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9
Q

Dryopithecine Apes

A

Between 5-25mya the first apes which were believed to be on the same line of development as humans appeared and ranged in size from small gibbons to large modern apes.

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10
Q

Similarities between African Apes and humans:

A
  1. The upper limbs
  2. The brain
  3. Vision
  4. Number of offspring produced
  5. Upright posture
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11
Q

Differences between African Apes and humans

A
  • Fossil evidence: Bipedalism, flat face, shape of jaws, dentition, enlarged brain.
  • Cultural evidence: language, weapons, tools.
  • Genetic evidence: Identical DNA structure, Similar sequence of genes, Similar portions of DNA with no function
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12
Q

Similarities between African Apes and humans - the upper limbs

A
  • Primates have strong upper arms, which they can move freely due to the shallow socket (glenoid cavity) and because the scapulae aren’t attached to the vertebral column. Primates can rotate their forearm at the elbow joint.
  • Primates have flat nails instead of claws which allows for bare finger tips= rich in nerve endings ∴ they are sensitive —> allows for precision grip.
  • All primates have opposable thumbs (work in the opposite direction of their fingers so can have a power grip on branches)
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13
Q

Similarities between African Apes and humans - the brain

A
  • Primates have large brains compared to their body masses ∴ they can make sense of a large amount of information.
  • Parts of the brain that interpret information from the hands and eyes are enlarged. Olfactory centre (smell) is reduced.
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14
Q

Similarities between African Apes and humans - the vision

A

Eyes in front of head – allows perception of depth.

  • -Binocular vision = looking at an object using both eyes.
  • -Stereoscopic vision = observing the solid nature of an object.

Primates have cones (as well as rods) for colour and bright light vision.

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15
Q

Similarities between African Apes and humans - the number of offspring produced

A
  • Primates have fewer offspring than other mammals and their young are dependent on their parents for a long period of time. This allows adults to teach the young essential survival skills.
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16
Q

Similarities between African Apes and humans - the upright posture

A
  • Primates can sit upright with their head held high —> allows a better view of their surroundings and allows the animal to walk on 2 legs so their upper limbs are able to carry things such as food, tools and babies
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17
Q

Differences between African Apes and humans - Fossil evidence: Bipedalism:

A
  • All primates can sit upright or walk on 2 feet occasionally ∴ they are capable of upright posture. - -
  • Humans walk on 2 feet all the time.
  • The position of the foramen magnum must move more anteriorly when an animal displays bipedalism.
  • Bipedalism results in a straightened spine as well as a broader pelvic girdle in order to support body weight.
  • We can look at the position of a foramen magnum on a fossil to determine whether the animal was a biped or quadruped.
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18
Q

What are the advantages of bipedalism

A
  • Hands are free for carrying things
  • Better view of surroundings
  • More efficient movement
  • Faster cooling of the body
  • Display of male sex organs as part of courtship behaviour.
19
Q

What is the foramen magnum

A

the hole in the base of the skull through which the spinal cord passes.

20
Q

Differences between African Apes and humans - Fossil evidence: flat face

A

> Our foreheads don’t slope backwards as much as those of ape men.
Our lower jaws have a well-developed chin.
The bones of the nose and jaws do not stick out as much as those of ape men. We are not prognathous. We have decreased prognathism. Our brow and cranial ridges are also not as pronounced.

21
Q

Define prognathous

A

having a projecting lower jaw or chin.

22
Q

Differences between African Apes and humans - Fossil evidence: shape of jaws

A

> Jaws of apes = U-shaped with parallel sides and a slightly rounded front. Large spaces between teeth.

> Human jaws = parabolic – gently curved. Small spaces between teeth.

23
Q

Differences between African Apes and humans - Fossil evidence: dentition

A

Dental formula on powerpoint slides

24
Q

Differences between African Apes and humans - Fossil evidence: enlarged brain

A

> The ratio of brain size to body mass is greater in primates than in other organisms.
Humans have the largest brain size of all primates. Our brain size ranges from 1200ml to 1800ml with the average brain being 1400ml.

25
Q

Differences between African Apes and humans - Cultural evidence: Language:

A
  • Many modern apes communicate by means of sounds. Gorillas have a range of 22 different sounds and chimps have more. These are considered the natural languages of these apes.
  • Humans have created artificial languages to communicate = This enables humans to work together and pass information from parent to offspring which has led to the development of human culture.
26
Q

Differences between African Apes and humans - Cultural evidence: weapons & tools

A

> Early hominids used stones that were found on the ground as weapons and tools. First tools were made by Homo habilis about 2 mya.

27
Q

Differences between African Apes and humans - Genetic evidence

A

> Identical DNA structure

> Similar sequence of genes

> Similar portions of DNA with no function

  • More closely related species have a greater similarity to each other than distant species.
  • The similarity in the DNA of humans and chimps is greater than with the gorilla so humans are more closely related to the chimp than he gorilla.
  • There is only a 1.4% difference in the DNA nucleotide sequence between humans and chimps.
28
Q

Australopithecine fossils found:

A
  1. Lucy (Australopithecus afarensis)
  2. Taung child (Australopithecus africanus)
  3. Mrs Ples (Australopithecus africanus)
  4. Little foot (Australopithecus africanus)
  5. Karabou (Australopithecus sediba)
29
Q

Lucy (Australopithecus afarensis)

A
  • 3.2 million years old, found in Ethiopia.
  • Weighed between 30 and 45kg, 1m tall.
  • Had an anterior foramen magnum 🡪 bipedal
  • Cranial capacity: 375-550cc. (cubic centimetre)
  • Skull: similar to a chimp but with human-like teeth (smaller canines than modern apes but larger and more pointed than that of modern humans)
30
Q

Taung child (Australopithecus africanus)

A
  • 2.6-2.8 million years old, found in Taung in the NW province by Raymond Dart.
  • Had an anterior foramen magnum 🡪 bipedal
  • Had an ape-like head but the dentition of a human baby. Back teeth were bigger than in afarensis. The teeth and jaws of africanus are much larger than those of modern humans, but they are more similar to human teeth than ape teeth.
  • Brain size: larger than a chimp despite similar body size but not advanced in the areas necessary for speech.
31
Q

Australopithecine fossils: Mrs Ples

A
  • 2.6 my old fossil discovered by Robert Broom in the Sterkfontein Caves.
  • Adult form of Taung Child.
  • Original name was Plesianthropus.
  • In 2002 it was found that Mrs. Ples was actually a male.
32
Q

Australopithecine fossils: Little Foot

A
  • 3.9 to 4.2 my old. Found in Sterkfontein Caves.
    In 1997 only the tibia was found
    In 1998 part of the arm bones and a portion of the skull were found
    In 2006 the entire fossil was brought to the surface.
  • Skeleton was that on an early hominid.
33
Q

Australopithecine fossils: Karabou (‘The Answer’)

A
  • Matthew Berger found the lower jaw and clavicle at the Malapa site in the Cradle of Humankind in 2008. Lee Berger (father) found the skull in 2009. A complete juvenile male and an adult female skeleton were found.
  • Brain size: 420-450ml
  • Height: 1.27m
  • Age: 1.78-1.98my old.
  • Thought to be a transitional fossil between A. africanus and H. habilis or erectus because it is more similar to Homo than any other australopithecine.
  • A. sediba was bipedal with long arms suitable for climbing but had a human-like skull, pelvis and teeth.
34
Q

Define Paranthropus

A

A robust australopithecine (large teeth and muscle attachments on the face)

35
Q

How is the homo habilis similar to the australopithecine?

A

H. habilis appears to be similar to the australopithecines with less pronounced brow ridges, more human-like teeth, a flatter face, a more rounded head and a brain size of 600-750ml.

36
Q

What do scientists believe about australopithecines?

A

Scientists believe that the australopithecines gave rise to many lines or branches of development. Approx 2 mya, one line of development gave rise to the 1st of early humans, Homo habilis.

37
Q

What is the H.habilis referred to as and why?

A

H. habilis is referred to as handy man because these were the first early humans to make and use tools.

38
Q

Trends in human development - what changes took place gradually in the development of humans:

A

> A shift of the foramen magnum to a forward position in the skull 🡪 bipedalism
The development of a more rounded skull
An increase in cranium size 🡪 larger brain
A flatter face due to:
A less sloping forehead
Less protruding jaws (decreased prognathism)
A more developed chin
A more rounded jaw
Increased skeleton size (increase in height)
A change in dentition to the human dental formula

39
Q

The homo species

A
  1. Homo habilis
  2. Homo erectus
  3. Homo neanderthalensis
  4. Homo sapiens
  5. Homo naledi
40
Q

Homo species: Homo erectus

A

> 1.5mya H. habilis gave rise to Homo erectus.
H. erectus had a head like an ape but looked like modern humans from the neck down.
It was as tall as modern humans and had a brain size of 700-1300ml.
H. habilis and the australopithecines are found only in Africa while H. erectus was wide-ranging and has been found in Africa, Asia and Europe.
There is evidence that H. erectus used fire and their stone tools were more sophisticated than those of habilis.

41
Q

Homo species: Homo neanderthalensis

A

> Closest extinct human relatives
Lived 400-40kya in Europe and south-western to central Asia.
Short, stocky bodies (needed for cold environments)
Big brains (sometimes bigger than ours)
Used tools, fire, clothes, marked their graves with flowers.

42
Q

Homo species: Homo sapiens

A

> Homo sapiens arose from H. erectus around 150 000 to 200 000 years ago.
Distinctive features of H. sapiens:
A large brain (1200-1800ml)
Flat faces
Florisbad man (discovered in Florisbad in the Free State in 1932) is considered to be that of an earlier form of H. sapiens.

43
Q

Homo species: Homo naledi

A

> Had a curious mix of primitive (small brain) and modern traits (long legs).
1.5m tall and about 45kg
Was a climber, long distance walker and a tool maker. > Showed evidence of burial of the dead.
Between 236 000 and 335 000 years old.
H. naledi could have come into contact with some H. sapiens before it went extinct.

44
Q

The “Out of Africa” Hypothesis

A

on slides

Life Sciences (5 decks)

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