HUMAN EVOLUTION 26 AUGUST 2015 Section A: Summary Content Notes

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1 HUMAN EVOLUTION 26 AUGUST 2015 Section A: Summary Content Notes Evidence of common ancestors for living primates, including humans We looked at the use of fossils as evidence for evolution in the previous chapters. We can now use that knowledge to explain the origin of modern humans Humans share a common ancestor with two closely related groups of African apes, namely chimpanzee and bonobos. This common ancestor lived about seven million years ago and gave rise to humans and their direct ancestors (homnins) A common ancestor is an ancient species that gives rise to two or more new species. The new species are descended from the common ancestor. The phylogenetic tree below shows that gibbons, gorillas, orang-utans, chimpanzees and humans descended from a common ancestor that lived 35 million years ago A phylogenetic tree for apes and humans Scientists use different kinds of evidence to construct a phylogenetic tree. One kind of evidence is to compare anatomy of two closely-related living species. Similarities in the anatomy were probably present in the ancestor Differences have evolved since the common ancestor divided into two new species

2 Anatomical similarities between African apes and Humans Enlarged and more complex brain relative to body size Reduced snout with reduced sense of smell Eyes in front of skull- stereoscopic vision Eyes have cones Two hands five digits Mobile opposable thumbs Digits with flat nails Long, slender limbs that rotate freely at shoulders and hips Sexual dimorphism male and female clearly distinguished Have molars and premolars with rounded cusps Anatomical differences between African apes and Humans When we look at the differences you must be able to compare the following: o Bipedalism (foramen magnum, spine and pelvic girdle) o Brain size o Teeth (dentition) o Prognathism o Palate shape o Cranial ridges o Brow ridges o

3 There are three main lines of evidence that that indicate hominids have a shared common Fossil evidence Genetic evidence Cultural evidence 1. Fossil evidence Palaeontologists study fossils to provide more information about structure, movement, lifestyle, and environment In search for a common ancestor for hominids, palaeontologists look at the following features Bipedalism Dentition (teeth) Palate shape Brain size Prognathism AFRICAN APES TYPE OF MOVEMENT Quadrupedal knuckle-walkers/ walk on all fours HUMANS Bipedal walk upright on two legs Foramen magnum at back of skull Foramen magnum closer to front of the skull C-shaped vertebral column S-shaped vertebra column Long and narrow pelvis Short and wide pelvis BRAIN SIZE Smaller less developed brain Large well developed brain TEETH (dentition) Large prominent canines Smaller canine Thin tooth enamel Thick tooth enamel PROGNATISM Large prominent jaw bone with no chin (prognathism) Rounded jaw with developed chin Wider, sloping face Narrow flat face PALATE SHAPE Narrow rectangular palate Wider more curved palate CRANIAL and BROWRIDGES Prominent cranial and brow ridges Reduced cranial and brow ridge

4 2. Genetic evidence DNA comparisons are made between living hominids, as DNA breaks down in dead cells and its very rare to extract DNA from a fossil Organisms have two types DNA o Chromosomal DNA in the nucleus o Mitochondrial DNA (mt DNA in the mitochondria) 3. Cultural evidence Tools Oldowan, Acheulian, Mousterian Fire-making, burial rites, art and hunting techniques Development of speech and language MAJOR PHASES IN HOMINID EVOLUTION Humans and their fossil ancestors between the common ancestor and modern humans are classified as hominids The three main genera (phases) of human evolution are: Ardipithecus Australopithecus Homo

5 Section B Practice Questions Question 1 (Taken from DBE Feb-March 2013 Paper 1) Professor Lee Berger and his colleagues studied the fossils they found in a cave at the Cradle of Humankind. The skeletons from the cave are ranked amongst the most complete finds to date. The adult female, Australopithecus sediba, was remarkably well preserved and some of the following characteristics were identified: Images showing the structure of the skull and bones of the palm of A sediba

6 1.1. Write down THREE characteristics from the list above that also apply to the Homo species. (3) 1.2. State TWO advantages of A. sediba being bipedal. (2) 1.3. Professor Berger called Australopithecus sediba a transitional fossil. Using the information in the list above, explain why he called A. sediba a species in transition. (2) Question 2 (Taken from KZN Prelim Paper ) The diagrams below show the skull capacity of extinct hominid species and the time they occurred 2.1. Draw a bar graph to compare the skull capacity of the above hominid species (6) 2.2. What trend can be observed from the graph above? (3) 2.3. Describe TWO visible differences between A. Afarensis and H. Sapiens. (4) 2.4. List FOUR characteristics that humans share with other primates. (4) 2.5. Homo sapiens are considered to be the most developed species. Although Homo neantherthalensis has a brain capacity of 1 500cc Homo neantherthalensis is extinct but Homo sapiens are still in existence. Explain how this is possible. (3)

7 Question 3 (Taken from DBE Exemplar Paper ) Diagrams A and B below illustrate the skulls of Homo sapiens and Homo erectus. The diagrams are drawn to scale Which of the diagrams (A or B) represents the following: a. Homo sapiens b. Homo erectus (2) 3. 2 Tabulate TWO visible differences between the skulls in diagrams A and B that represent changes in the structure that characterises human evolution. (5) Question 4 (Taken from DBE Nov Paper ) Study the diagrams below of the upper jaw, skull and the foot of two organisms A and B. The diagrams are NOT drawn to scale With regard to the drawings above: a. Tabulate TWO visible differences between the upper jaws of organisms A and B (5) b. Name ONE visible difference between the feet of organisms A and B. (2) 4. 2 Which organism (A or B) is more likely to be bipedal? (1) 4. 3 Give a reason for your answer to question 4.2. (2)

8 Question 5 (Taken from DBE Feb-Mar Paper ) The diagram below represents a cladogram (phylogenetic tree) showing primate evolution. The letters, A to E, indicate the characteristics which are shared by the different species of primates which follow the letter. The point where various species of primates differ from each other is indicated by the branching-off/split into new species Which LETTER represents a common characteristic of all primates? (1) 5.2. List THREE structural characteristics represented by the LETTER named in QUESTION (3) 5.3. Which organism is most similar to the chimpanzee? (1) 5.4. Name any TWO structural characteristics of the skull that make the organism named in QUESTION 5.3 different from the chimpanzee. (2) 5.5. Write down the names of the organisms that display the characteristic C but not characteristics D and E. (2) Question 6 (Taken from DBE Nov Paper ) Describe the structural changes to the skull that characterise the evolution of modern humans from their ape-like ancestors, and explain the significance of these changes. (20)

9 Section C: Solutions Question Projecting nose Smaller canines Bipedal 1.2. They had a wider view to spot danger They could carry offspring /food/tools Large surface area for thermoregulation 1.3. Have characteristics of both Homo species and Australopithecus species Question The younger the skull, the larger he skull capacity OR The older the skull, the smaller the skull capacity

10 Enlarged and more complex brain relative to body size Reduced snout with reduced sense of smell Eyes in front of skull- stereoscopic vision Eyes have cones Two hands five digits Mobile opposable thumbs Digits with flat nails Long, slender limbs that rotate freely at shoulders and hips Sexual dimorphism male and female clearly distinguished Have molars and premolars with rounded cusps 2.5. Did not have a language therefore could not communicate unlike Homo sapiens that had a lanugauge and could comminicate Homo sapiens had the ability to inhabit different environments to suit their needs unlike Homo neanderthalensis who could not and therefore became extinct Question a. B b. A 3.2 Diagram A Smaller brain capacity Brow ridge pronounced Lower jaw had a poorly developed chin Diagram B Larger brain capacity Brow ridge not as pronounced Lower jaw has a much better developed chin

11 Question b Differences in Feet In A the big toe is close to the other 4 smaller toes /faces forward In B the big toe is apart/opposable from the other 4 smaller toes /points outwards OR In A the heel bone is relatively larger and in B it is relatively smaller OR In A the bones in the foot are straight and in B they are curved OR In A phalanges are relatively shorter and in B they are relatively longer 4.2 A 4.3 Foramen magnum more towards the centre of the skull in A/ more forward OR In B the foramen magnum more towards the back of the skull Question A 5.2. Opposable thumbs with power and precision grip Bare fingertips with nails Long arms Freely rotating arms Eyes in front Stereoscopic vision Eyes with cones Large brain size compared to body mass Two mammary glands Sexual dimorphism Olfactory brain centre reduced

12 5.3. Humans 5.4. Shift in the position of foramen magnum to a forward position Gently curved jaws Flat face Well developed chin Not prognathus Forehead less sloping No pronounced brow ridges Smaller canines Spaces between teeth bigger Larger brain size 5.5. Rhesus monkey Gibbon Question 6

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