HUMAN EVOLUTION Flashcards
HUMANS IN ANIMAL KINGDOM
- mammalia and into the genus Homo.
SIMILARITIES BETWEEN APES AND HUMANS
- opposable thumbs that allow for power grip
- two hands with five fingers (toes too)
- no tail
DIFFERENCES BETWEEN APES AND HUMANS
H - bipedal, A - quadrupedal
H - large, developed brain, A - small less dev brain
H - narrow flat face, A - wider sloping face
EVIDENCE OF COMMON ANCESTORS
- fossil evidence
- genetic evidence
- cultural evidence
WHAT DOES FOSSIL EVIDENCE LOOK AT
looks at:
- bipedalism
- dentition
- palate shape
- brain size
- cranial and brow ridges
- prognathism
PALEONTOLOGY
study of fossils
BIPEDALISM
- walking upright on two feet
- foramen magnum in the middle of the skull enables bipedalism, as opposed to it being at the back of the skull
ADVANTAGES OF BIPEDALISM
- upright bodies expose less surface area to the sun - less overheating
- hands are free to use tools and hunt
- adaptable - can occupy wider variety of habitats
PALATE SHAPE
- was previously narrow and rectangular, later became more u-shaped and then became wider and more curved in humans
CRANIAL AND BROW RIDGES
- apes have prominent c&b ridges for attachment of chewing muscles
- decreased in size over time and completely reduced in humans
DENTITION
- teeth size decreased with evolution
- apes have prominent canines, but human canines are the same size as other teeth
- tooth enamel thickened over time
- diastema disappeared over time
DIASTEMA
the large gap between the incisors and canines
PROGNATHISM
- when the jaw protrudes and there is no chin (in apes)
- apes have sloping face bc of this
- teeth smaller over time = reduced prognathism
BRAIN SIZE
- cranium size inc in most fossils over time = brain capacity inc as well
- ape cranium is small and elongated, less dev brain
- humans have rounded skull = bigger cranium and larger dev brain
MORE COMPLEX HUMAN BRAIN HELPED WITH
- well developed hand-eye coordination
- the capacity for language
- the use of fire
GENETIC EVIDENCE
- very rare to extract DNA from a fossil
organisms contain: - chromosomal DNA
- mitochondrial DNA
COMPARING mtDNA
- by comparing mtDNA of living hominids, scientists can determine when the evolutionary paths of humans and apes separated
- many diffs = sep occured earlier
- more time for mutations to occur = more variation
CULTURAL EVIDENCE: TOOLS
the production and use of tools (and other cultural practices like fire making and art) are suggested as further evidence of common ancestors for living hominids
TYPES OF TOOLS
- made of stone, sometimes bone and wood
- some sharp stones, others carved blades
- provide access to wider variety of foods
THREE MAIN TOOL CULTURES
- oldowan
- acheulian
- mousterian
MAIN HOMINID GENERA WITHIN THE HOMINID GROUP
- ardipithecus
- australopithecus
- homo
ARDIPITHECUS
- 5,8 - 4,4 mya
- transition between apes and australopithecus
CHARACTERISTICS OF ARDIPITHECUS
- probably bipedal
- long arms for climbing trees
- small brain capacity
- sloped face
AUSTRALOPITHECUS
- first bipedal primates
- lived between 4,5 and 1,4 mya
CHARACTERISTICS OF AUSTRALOPITHECUS
- bipedalism and upright walking
- large brow ridges
- u-shaped palate
- protruding jaw, no chin
FIVE WELL KNOWN AUSTRALOPITHECINES
- Taung child
- Mrs Ples
- Lucy
- Little Foot
- Australopithecus sediba
TAUNG CHILD
- found by Raymond Dart
- was of a 3-4 yr old child
- small brain, human-like teeth, bipedal
MRS PLES
- Robert Broom
- possibly bipedal, no protruding canines
LITTLE FOOT
- Ron Clarke
- bipedal, short arms, similar hands to humans
CHARACTERISTICS OF HOMO
- bipedalism
- flat face
- wide, curved palate
- larger brain
- no brow ridges
HOMO HABILLIS
- smaller body and larger brain than Australopithecus
- fossil found in Tanzania
HOMO ERECTUS
- closer to modern humans than Australopithecus
- large bodies, thick skulls and large teeth
HOMO TIMELINE
- habillis
- erectus
- neanderthalensis
- sapiens
HOMO SAPIENS
- direct ancestors of modern humans
- developed better skills and more advanced technology
- had a large brain capacity
- used tools and wore clothing made of various materials
OUT OF AFRICA HYPOTHESIS
- states that all human life originated from Africa and Homo sapiens migrated from Africa 50000 mya
- resulted in more Hs replacing He around the world
EVIDENCE OF AFRICAN ORIGINS
- genetic links (chro, mit, Y-chro DNA)
- fossils and artifacts of hominins (Africa has largest numbers)
THE USE OF GENETIC LINKS (OOA) mtDNA
- mtDNA of diff pops are compared to determine the extent of genetic variation in a pop
- more variation = more mutations
- high variation in Africa = Africans are the oldest humans
STRUCTURAL CHANGES IN HUMANS IN TERMS OF BIPEDALISM
- the moving forward of the foramen magnum
- the vertabral column in humans is S-shaped for flexibility & shock absorption
- longer arms, shorter legs
- stronger knee-joints
- arched foot, instead of flat
CHROMOSOMAL DNA DEF
occurs in the nuclei of all cells and contains all the genetic information
COMPARISON OF CHROMOSOMAL DNA
determine how closely related they are, more similarities more closely related
cultural changes that distinguishes modern humans from primates
- development of speech and language (improved comm and social interaction) (helped with hunting and defence)
- tools
Oldewan tool culture
- oldest tools found, found in Tanzania
- 2,6 to 1,5 mya
- choppers, flakes, scrapers
- rock, stone
Acheulian tool culture
- more advanced, found in France
- 1,5 mya to 250 000 ya
- hand-axes, picks, cleavers
- stone, wood, bone
Moustertian tool culture
- found in France
- 250 000 to 50 000 ya
- flakes, scrapers, points
- hand axes w carefully shaped blades
what did refined tools help with
- gave access to better food, clothing and shelter
- more comf and complex lifestyles
microliths
smaller blades that formed part of arrowheads and fishhooks
fossils found in Great Rift Valley
h-h and h-e in Kenya
ardi and austra in Ethiopia
the Cradle of Humankind
the richest source of hominin fossils in the world, 40km North of Jhb
importance of CoH
- produced over one third of the world’s hominin fossils
- scientists have concluded that humans originated in Africa
why is it important to know the dates of fossils
- to compare diff fossils and observe evolutionary trends
- determine the order in which different life forms appeared on Earth
radiometric dating
- based on radioactivity, if the age of the rock of the fossil is known, it is assumed that the fossils are the same age
- if fossils are older than 50 000 years
relative dating
- based on the fact that deeper layers of sed rock are older than shallow years
- therefore deeper layers = older fossil
- not very accurate
alternatives to evolution
creationism
literalism
intelligent design
reproductive isolation
occurs by means of various isolating mechanisms which prevent pops from exchanging genes
mechanisms of reproductive isolation
behavioral patterns, physiological processes that prevent diff species from crossbreeding an producing viable offspring
eg.) prezygotic and postzygotic
prezygotic division
occur before fertilization and prevent mating and/or fert from taking place
postzygotic division
after fert and cause abnormal zygote development so that no viable / fertile offspring can be produced
