The Human Story

THE HUMAN STORY

KEY WORDS AND TERMS USED IN THIS TOPIC

As you study this topic you should write the definitions for the following syllabus terms.

Term Definition mammal primate hominid hominin prosimians new and old world monkeys apes humans stereoscopic vision fossils karyotype analysis DNA hybridisation relative and absolute dating techniques mitochondrial DNA DNA sequencing the ‘Out of Africa’ model of human evolution the theory of Regional Continuity Australopithecus species Homo habilis Homo ergaster Homo erectus Homo heidelbergensis Homo neanderthalensis Homo sapiens polymorphism clinal gradation phenotype genetic engineering the Human Genome project cultural development THE HUMAN STORY

SUMMARY OF THIS TOPIC

Humans are mammals, and are classified at the Australopithecine species arose from a common order level as primates, at the family level as ancestor; probably either A. africanus or hominids, at the genus level as Homo and at the A.afarensis. species level as sapiens. Characteristics shared by The ‘Out of Africa’ theory proposes that modern primates include opposable first digits, eyes humans spread from Africa less than 10,000 years positioned towards the front of the head, nails ago, and are descended from an African Homo instead of claws and large brains. Primates have erectus. These modern humans replaced archaic been further divided into tree shrews, prosimians species that had previously moved out of Africa and anthropoids based upon brain size, thumb some 1.5 million years ago. Another theory, the opposability and vision. Recent technological theory of Regional Continuity, states that this advances, however, have led scientists to conclude recent migration out of Africa did not occur; that tree shrews are not actually primates, and have instead, Homo erectus moved out of Africa 1.5 led to the creation of two major sub-orders – the million years ago and evolved into modern humans Strepsirhines and the Haplorhines. Under this new in different countries. classification, humans are generally now grouped Humans have adapted to their environment by into a sub-family with gorillas and chimpanzees, expressing genes that are suitable to their whereas orangutans are grouped into another sub- particular surroundings. This results in a range of family. Much of this new knowledge has been human forms and is referred to as polymorphism. achieved through techniques such as karyotype The gradual change in human characteristics from analsysis, DNA hybridisation and the study of one region to another is known as clinal gradation. mitochondrial DNA. Human culture has developed from the group Fossil evidence has also helped in the hunting of Australopithecines up to 4 million years classification of humans and other primates. ago to the complex social structures, industry and Absolute dating techniques using radioactive agriculture of today. Differences in the behaviour isotopes, and relative dating techniques involving of humans and other primates reinforces the the comparison of fossils found in different rock concept that humans are better equipped to strata, are examples of methods used to establish develop culturally advanced societies, to the extent relationships between these organisms. that human populations are no longer controlled by Scientists who have contributed to our the environment. Studies such as the Human understanding of human evolution include the Genome Project have the potential to increase Leakey family, Donald Johansen, Robert Broom populations further by providing the knowledge and Raymond Dart. Although their theories differ and techniques to detect and cure genetic diseases in some areas, most of them have concluded that and to develop more effective drugs. members of the genus Homo and the THE HUMAN STORY MAJOR OBJECTIVES OF THIS TOPIC

As indicated in the HSC Biology syllabus, the - Australopithecus boisei major outcomes of this topic include the ability to: - Australopithecus africanus - Homo habilis  describe what is meant by the term, ‘species’ - Homo ergaster  explain why humans are classified as : - Homo erectus - Kingdom: Animal - Homo heidelbergensis - Phlyum: Chordate - Homo neanderthalensis - Class: Mammal - Homo sapiens - Order: Primate  compare the above species in terms of - Family: Hominid their : - Genus: Homo - body structure - Species: sapiens - cranial capacity  distinguish between the arbitrary - fossil ages and regional locations classification of humans as members of the - inferred culture family hominidae and the sub-family  discuss the contributions of the following homininae scientists to our knowledge of human  outline the major features of evolution: primates, and describe the differences and - The Leakey family similarities between prosimians, new and - Donald Johansen old world monkeys, apes and humans - Robert Broom  describe technological advances - Philip Tobias which have affected the classification of - Raymond Dart primates - Jane Goodall  outline how fossils form and  compare and contrast the ‘Out of Africa’ distinguish between relative and absolute theory of human evolution and the theory methods of dating fossils of Regional Continuity  outline reasons why fossil  outline the ways in which human diversity evidence alone is not enough to fully has come about interpret the past  define the terms ‘polymorphism’ and  describe how the following ‘clinal gradation’, giving examples of each methods can be used to compare different  outline the cultural changes that have primates: occurred in humans since they became - karyotype analysis organised hunters - DNA hybridisation  compare human culture with that of other - comparison of haemoglobins primates in terms of: - DNA sequencing - care of young - tracing mitochondrial DNA - length of juvenile stage  model DNA hybridisation and - development and size of social groups explain its use in establishing relationships - use of tools between organisms - communication systems  carry out an activity to model  describe how increased population karyotype analysis mobility, modern medicine and other  outline two different views of technology and genetic engineering may human evolution to include the following affect future human evolution species:  outline the purposes of the Human - Australopithecus ramidus Genome Project and discuss their - Australopithecus afarensis implications in terms of human evolution - Australopithecus robustus such hybrids are fertile themselves, and yet are not identical to either parent plant. Polyploid plants, which have more than one set of chromosomes, also pose a problem, because they are very similar 1) Humans have characteristics to their diploid ancestors yet cannot breed with them. that can be used to classify them with other organisms

Classification of humans and the THINK!!! Which of the following concept of species would have the most characteristics in common? a) Two orders of the same class The taxonomic levels used to classify organisms, b) Two phyla in the same kingdom from least specific to most specific are: kingdom, c) Two species in the same genus phylum, class, order, family, genus and species. A d) Two species in different orders species is generally defined as a group of organisms which share a common gene pool, and can interbreed successfully to produce fertile offspring. Each species is therefore reproductively  As a requirement of this topic, you need isolated from other species. Problems can be to identify the features of humans that encountered when determining whether organisms place them in each of their designated belong to the same species in the prokaryotes and taxonomic levels in some eukaryotes, as these organisms do not reproduce sexually. Other problems with this Table 7-1 , below , classifies human beings from definition of species occur in the production of least specific taxonomic level to the most specific. genetic hybrids such as triticale, which is the result of a cross between wheat and rye plants. Many

Category Taxonomic group Description Kingdom Animalia Heterotrophic, eucaryotic, multicellular organisms. Phylum Chordata Animals with a notochord and ( subphylum vertebrata) dorsal hollow nerve chord enclosed in a vertebral column.

Class Mammalia Skin covered with hair or fur, mammary glands, 4 chambered heart. Order Primates Fingers and flat nails, reduced sense of smell, opposable thumbs, usually stereoscopic vision. Family Hominidae Large brain, arms shorter than legs. Genus Homo Flat face, eyes forward, bipedal, colour vision. Species Sapiens Protruding chin, high forehead, thin covering of body hair, capable of speech and abstract thought. Table 7-1 The classification of humans Primate characteristics degree of binocular vision and degree of thumb opposability, another difference between the primitive primates and the more developed ones Humans belong to the mammalian order known as can be seen in gestation periods and the length of primates. Characteristics of primates include the life phases in each. The Lemur, for instance, has a possession of opposable first digits on the hands gestational period of only 18 weeks, compared to and feet (see fig. 7-1), eyes which are directed 34 weeks in chimpanzees and 40 weeks in man. towards the front of the skull, relatively large brains in comparison to body size, flat nails instead of claws and usually only two mammary glands. In addition, primates tend to produce few live young Primates at a time, and their gestation period is comparatively long in relation to other mammals. Many of these features were initially adaptations to an arboreal (tree) existence, as they provided the physical necessities for the movement from branch to branch by these animals. Early primates developed the habit of squatting, thus freeing the Tree shrews Prosimians Anthropoids (no longer hands for other, exploratory actions. Development tarsiers, regarded as of the forebrain occurred simultaneously with this lorises, primates by lemurs behaviour. In the higher primates, increased care some of the young and group behaviour also occur. taxonomists) Primates are usually placed into three groups; the most primitive of these being the tree shrews (some recent studies have in fact excluded tree shrews from this order). The prosimians, or ‘pre- monkeys’, possess more specialised primate features than the tree shrews- examples include Old world Apes Man greater opposability of the first digits, larger brains New world monkeys gorillas, and binocular vision. The most developed primate gibbons, monkeys baboons, group is the anthropoids, which includes orangutans spider macaques, monkeys, apes and man. Features of this group monkeys, mandrills, include even greater opposability of the thumb, a howler rhesus flatter face, a collarbone that gives the arm monkeys monkeys strength for swinging movements, an even larger brain case and stereoscopic, colour vision. Fig. 7-2 The main sub-orders of the primates. See later in this chapter for recent modifications to this classification.

Fig. 7-1 The foot of an orangutan, showing the opposable fifth digit which is an adaptation to its arboreal existence THINK!!! The skulls below belong to a tree shrew, a tarsier (a prosimian), and Fig. 7-2 shows the main sub-orders of the Dryopithecus, thought to be a common ancestor primates. Note that this classification has recently of apes and man. Can you identify each? Explain been modified (see later in this chapter), due to your answers. technological advances such as DNA hybridization techniques. One result of this is that tree shrews are no longer regarded as primates in many circles. Besides physical differences such as brain sizes, Table 7-2 The main primate groups

 As a requirement of this topic, you need to be able to discuss how technological advances have affected primate classification.

As mentioned above, traditional classifications of Table 7-2, below, describes the main primate the primate order divided these animals into three groups. main sub-orders; the tree shrews, prosimians ( lemurs, lorises, tarsiers) and the anthropoids Tree shrews Small, insectivorous, ( monkeys, apes and man).Further anatomical nocturnal. Eyes more research, fossil evidence and modern techniques towards the side of the such as DNA hybridisation , however, have head. resulted in many scientists now proposing a Prosimians Arboreal, mostly nocturnal; revised classification of these sub-orders. Firstly, all have some degree of tree shrews are no longer regarded as anatomically binocular vision and close enough to the other primates, and many opposable first digits. researchers have placed them into their own order, New world Arboreal, often using their Scandentia. Secondly, studies of the auditory monkeys tails as a fifth prehensile apparatus, dental arrangement and cranial blood limb. Flat-nosed. Larger supply of the tarsier have led many taxonomists to than prosimians, with place this animal in the same sub-order as the larger skulls and full original anthropoids. This new sub-order is now stereoscopic and colour often referred to as the Haplorhines, and those vision. primates remaining in the former prosimian sub- Old world monkeys Include both arboreal and order are now referred to as the Strepsirhines. terrestrial species. Use their Interestingly, another reason for re-grouping the tails for balancing rather tarsier is that, along with monkeys, apes and man, than hanging from trees. it has a dry nose whereas the Strepsirhines all have Noses point downwards. wet noses. Larger than prosimians, Within the Haplorhines/ anthropoids, humans were with larger skulls and originally placed separately in the family flatter faces. Full Hominidae and orangutans, gorillas and stereoscopic and colour chimpanzees were placed in the family Pongidae. vision. Recent evidence, both fossil and genetic, however, Apes Larger than monkeys, with has resulted in some taxonomists placing all these a larger brain case. primates into the family Hominidae, with the Relatively long arms and orangutans placed in a sub-family, the Ponginae, short legs. Bodies partially and humans, chimpanzees and gorillas in the sub- erect when on all fours. family Homininae. The gibbons, previously Tail absent. Well placed with the apes in the Pongidae, are now developed colour and often classified in their own family, the stereoscopic vision. Hylobatidae, because they are the only apes solely Humans Bipedal, brain three times confined to an arboreal existence. Other as large as that of the apes, classification systems place orangutans in the S- shaped spine, shorter family Pongidae and gorillas, chimpanzees and face than apes, well humans in the Hominidae. Reasons for placing developed colour and gorillas, chimpanzees and humans so closely stereoscopic vision, together include DNA hybridisation results, which greatest ability to have revealed that there is only a 1.2% difference manipulate things with the between human and chimp DNA and a 1.4% hand. difference between human and gorilla DNA. Some taxonomists believe that gorillas and chimps Fig. 7-3 shows a revised classification of primates, should be placed in this way with humans because based on these new findings. they share more than 97% of DNA with the human genome and have the capacity for limited language and simple cultures beyond family groupings.

ORDER ORDER Scandentia Primates (Tree shrews)

SUB-ORDER SUB-ORDER Strepsirhines Haplorhines (lemurs, lorises)

FAMILY FAMILY FAMILY FAMILY FAMILY Cercopithecidae Cebidae, Tarsiidae Hylobatidae Hominidae (Old world Callitrichidae (Tarsiers ) (Gibbons ) monkeys) (New world monkeys)

SUB-FAMILY SUB-FAMILY Ponginae Homininae (Orangutans ) (Humans, gorillas, chimpanzees)

Fig. 7-3 A revised classification of primates based on current technological advances

It can be seen from the above passage that (chimps and gorillas). classification is often quite an arbitrary process, with no absolutely correct system existing. Some 2) Fossil and other biological scientists, for instance, have further divided the sub-family Homininae into two tribes, the evidence assists in the Hominini, which includes humans and bipedal clarification of the relationships fossil groups, and the Panini, which includes gorillas and chimpanzees. The recent discovery of between humans and other a primitive, bipedal hominid, Kenyanthropus, by primates Maeve Leakey and her team led to its classification by the National Geographic as a member of the tribe, ‘Hominin’, because it was more similar on a The conditions under which fossils molecular level to humans and their bipedal are formed ancestors than it was to gorillas or chimpanzees. The National Geographic scientists believe that the A fossil is any trace of past life. A fossil could be term ‘hominin’ will eventually be universally the actual remains of an organism which has been adopted as people recognise the molecular preserved in ice, resins such as amber, or in poorly differences between humans and the ‘Panini’ oxygenated peat bogs. Fossils can also be moulds, in which the original organism leaves an from the hard parts of organisms, the geological impression, or casts, where a mould is later filled time scale only starts when the first of these types in with other materials. In other instances, the of organisms appeared on earth, which was about original organic material has been slowly replaced 590 million years ago. More primitive, soft bodied with inorganic minerals in a process known as organisms such as invertebrates and bacteria, are petrification. Fossilisation is a rare occurrence, as rarely present in the fossil record although the specific circumstances are necessary before it can earliest life forms, photosynthetic blue-green occur; firstly, the organism needs to have been algae, were thought to have existed over 3500 buried rapidly by sediment. This is more likely to million years ago. This is suggested by reddish occur with marine organisms, which are often layers of metal oxides in the rock strata, which buried rapidly by sediment moving into the sea indicate that oxygen released by this algae has from rivers. Secondly, decay of the organism must combined with the metal atoms in the rocks. be prevented or at least reduced, to allow time for The actual age of the earth has now been estimated fossilisation to occur. Since decay is caused by to be 4500 million years old. Methods used to microbes, the conditions in which this can occur determine this are known as absolute dating include low oxygen levels, acidity or low techniques, and include radioisotope dating, which temperatures. Thirdly, the organism must remain involves measuring how much of a particular undisturbed for a long period of time in order to radioactive element remains since it began form a fossil; sediment needs time to harden into decaying. This is then related to its half-life; the rock, and erosion or faulting of this rock must time taken for half of the original element to break occur before fossils can be uncovered. down into a new, more stable element. Rocks The most commonly preserved types of fossils are containing uranium are the most useful in the hard parts of organisms such as bones, teeth, estimating elapsed time because this element has a shells and plant pollen. Soft-bodied organisms half-life of 4500 million years. Rubidium (half life such as sponges and seaweeds are unlikely to be 49 billion years) and Potassium 40 (Half life 1.3 preserved as they usually decay before fossilisation billion years) are also used in absolute dating can occur. techniques. The half-life of carbon 14, on the other hand, is only 5730 years and thus only the relatively recent fossils (which ,being of organic Examples of organisms that have origin, usually contain traces of carbon) can be actually been found fully preserved include: dated using this method. Most fossils are therefore a) Insects such as mosquitoes preserved in dated by determining the age of the igneous rocks amber (fossilised tree resin) - the insect would that lie above and beneath them. Relative dating have been trapped immediately, and decay techniques can be used where these methods are would not occur in the resin, which would soon not possible; in these cases, fossils are compared to harden into amber. other fossils in the same sedimentary layer, or to b) Woolly mammoths fossilised in ice - the low ones in higher or lower rock strata in order to temperatures would prevent decay. determine their approximate age (see fig. 7-4). The c) ‘Bog men’ found in peat bogs - remains of presence of ‘indicator’ fossils such as pollen grains men preserved for several thousand years. that have been accurately dated in other rock Preservation occurs because of the low oxygen strata, may also be used in these circumstances. levels in the bog. Using the fossil record alone to interpret the past can often prove difficult, as fossils are rare, resulting in recurring ‘gaps’ in the geological record. In addition, there is hardly any record of Geological time and dating the lower plant and animal life forms because they techniques contained no hard parts. Moreover, dating techniques may differ, and may produce The geological time scale is a relative scale that inconsistent results or be open to different does not depend upon modern dating techniques. It interpretations. uses the idea that in sedimentary rocks the oldest rocks are lower than the higher rock layers and Z thus the relative ages of different fossils can be compared. Because almost all fossils are relics Y X pygmy chimpanzee

chimpanzee

gorilla

orangutan Fig 7-4 Relative dating techniques can be used to date rock layer X by comparing its indicator fossils with those in other layers of known age. From the gibbon diagram, it can be seen that it is the same age as layers Y and Z. Fig. 7-5 Phylogenetic tree based on DNA hybridisation in the primates Radioactive dating techniques are Recent DNA hybridization studies of species of usually used on igneous rocks only. This is the protozoan Trypanosoma from different African because sedimentary rocks are composed of the countries have found that some species were not as weathered remains of older rocks, and closely related as previously thought. Similar metamorphic rocks are made from older rocks studies have also found that the giant panda is that have been transformed by heat and pressure. more closely related to bears than raccoons, which An accurate idea of the age of the rock when the is contrary to previous views. fossil formed would therefore be difficult to Similarities between blood proteins determine. (haemoglobins) have also been found between man and the apes. When agglutination methods (which involve mixing the blood of the two species and Biochemical relationships among assessing the amount of antibody formation) are primates used, gorillas, chimps and humans have been found to be equally related. When, however, the sequence of amino acids in the haemoglobin Evidence from recent biochemical studies has molecules of each are compared, chimpanzees and revealed similarities between different primate humans are found to be identical, with gorillas species, therefore throwing light on possible past having two amino acid differences. relationships. Karyotype analysis involves DNA sequencing, in which the DNA of different comparing the chromosomes of different species. primates is replicated and compared, has also From these studies, it has been found, for example, shown similar relationships among the higher that almost 99% of the genetic material of humans primates. The study of mitochondrial DNA, and apes is identical. Indeed, 13 of the which has a high rate of mutation, can be used to chromosome pairs in humans and chimpanzees are determine the amount of time different races of identical. people have been geographically separated from DNA-DNA hybridisation involves cutting and each other, and has led scientists to conclude that separating the double strands of DNA from each Homo sapiens evolved from hominid ancestors in species studied. One of the strands is radioactively Africa up to 250,000 years ago. labelled, and then is allowed to anneal with the other strand. The more similar the DNA, the more  As a requirement of this topic, you need the pieces will join together to form a hybrid to be able to model DNA-DNA double strand; this is indicated by the amount of hybridisation radioactive base pairs from the first strand that stick to the second. Results of these DNA The main steps involved in this process are shown hybridisation techniques have revealed that below, and are illustrated in fig.7-6: humans and chimpanzees bear the closest genetic resemblance to each other (see fig. 7-5). DNA strands of the two different species to be studied are cut into smaller sections using A karyotype shows the number and type of ultrasound techniques. chromosomes in a particular species. Humans have ↓ 23 pairs of chromosomes, whereas apes have 24. The double strands of each section are separated Chromosomes 6, 13, 19, 21, 22 and X are identical into single strands by heating. In humans this is in humans, chimpanzees, orangutans and gorillas. approximately 86ºC. The bases on a strand of one The steps below show the process involved in the species are radioactively labelled. preparation of a human karyotype for analysis. ↓ The two strands anneal when brought together in A blood sample is taken from the organism whose areas where base pairs match up. karyotype is to be examined. ↓ ↓ The degree of similarity is indicated by the number The blood is centrifuged, with red cells settling to of radioactive bases in the labelled strand that are the bottom, and white cells floating to the top. The joined to the other strand, and by the temperature red cells are discarded. required to break them apart. The more similar the ↓ strands are, the higher is this temperature. The remaining white blood cells are grown for several days in culture media. ↓ The white blood cells (mainly lymphocytes) are treated with colchicines to stop cell division at metaphase. ↓ A drop of the lymphocyte suspension is mounted on a microscope slide, dried and fixed with alcohol i) chimpanzee and a stain that causes banding to appear on each DNA chromosome. ↓ The stained chromosomes are viewed under the microscope and photographed. A typical spread of ii) human DNA chromosomes is shown in fig. 7-7. ↓ Individual chromosomes are cut out and arranged in homologous pairs of similar size, shape and banding, and each pair is placed in order of diminishing size.

iii) strands cut into smaller sections and separated. One strand is radioactively labelled

iv) degree of similarity is indicated by the number of radioactive bases from the labelled strand that join the other strand

Fig. 7-6 DNA hybridisation

 As a requirement of this topic, you are expected to process information from secondary sources to model karyotype analysis. used to study the relationships of human populations throughout the world. Studies of polymorphisms (differences in the DNA sequence due to mutations) over the last fifteen years have been used to compare evolutionary differences between species. Here, mitochondrial DNA has been shown to be more effective in resolving differences between closely related individuals than nuclear DNA because more substitution mutations are usually present. The area of mitochondrial DNA often used in this technique is known as the ‘D-loop’, which comprises about 7% of the molecule and which undergoes the highest mutation rate. Some researchers, however, are finding that analysis of the whole mitochondrial DNA molecule is more accurate. Most of these polymorphic studies have concluded that the human race had its origins in Africa about 250,000 years ago and subsequently colonised the rest of the world. This differs from Fig. 7-7 A set of human chromosomes ready for the previous theory of Regional Continuity, which rearrangement into homologous pairs. A similar suggested that modern humans evolved from photograph could be used to prepare a human archaic forms such as Homo erectus concurrently karyotype in the classroom. in different regions of the world.

The importance of mitochondrial DNA in tracing human evolution

Mitochondrial DNA is unique, in that it can only THINK!!! The eye disease known as arise from the division of pre-existing Leber’s Optic Neuropathy, appears to be sex- mitochondria and has a slightly different base linked because it only seems to be passed on sequence to the DNA in the rest of the cell. Recent from women to their children. However, it does studies have also found that mitochondrial not seem to follow typical Mendelian ratios. Use inheritance is maternal. In addition, mitochondrial the above passage to explain this. DNA has a higher rate of substitution mutations 3) Debate continues on the than nuclear DNA, and it does not undergo recombination during meiosis. relationships between hominid All of the above features have made mitochondrial species DNA useful in tracing human evolution. Firstly, the fact that this DNA is only inherited from the mother and does not undergo recombination Scientists who have contributed to enables it to be used to trace direct genetic our understanding of human lineages. In Argentina, for example, the search for relatives of people who went missing during the evolution long term military dictatorship there was aided by mitochondrial DNA comparisons. It was found Scientists have used fossil evidence to establish the that in many cases it was too difficult to locate all evolutionary history of humans. Although their four grandparents of a particular child; this was theories differ in some areas, most of them have needed for a definitive match to the DNA sequence concluded that members of the genus Homo and of the child. Instead, a systematic study of the the Australopithecine species arose from a mitochondrial DNA of the grandmothers was used common ancestor; probably either A. africanus or and proved successful in many cases. On a larger A.afarensis. Over the last 4 million years, fossils scale, this feature of mitochondrial DNA has been show that cranial capacity has increased from around 400ml in the early Australopithecines to 1350ml in humans; teeth have become less specialised and more adapted to an omnivorous diet; stance has become more erect; tools have become more sophisticated and culture has become more advanced. Table 7-3 outlines some of the main contributions made by scientists to our understanding of human evolution.

Mary Discovered remains of Proconsul in Leakey 1948, Australopithecus robustus in Tanzania in 1959, A. boisei in 1959, Homo habilis in 1961 and footprints of the bipedal A.afarensis in 1976.This last find surprised scientists, because the Australopithecines didn’t seem to have large enough brains to correspond with a bipedal existence. Louis Discovered Homo habilis with his Leakey wife in 1961. Maeve Discovered Australopithecus Leakey anamensis, a bipedal hominid. Donald Discovered Australopithecus Johansen afarensis (‘Lucy’) in Ethiopia in 1974. Robert Found remains of an Broom Australopithecine in South Africa and fossil evidence of its upright posture. Raymond Discovered Australopithecus Dart africanus in South Africa in 1924. Philip Discovered a fossil of Homo habilis Tobias with the Leakeys in 1961.

Table 7-3 Scientists involved in human evolution Human evolutionary relationships  As a requirement of this topic, you need to analyse and evaluate the evidence for Table 7-4, below, describes the main hominid two different models of human groups as inferred from fossil evidence. evolution

Australopithecus 4.4 Teeth intermediate The evolutionary tree shown in fig. 7-8 shows one ramidus million between humans and view of man’s ancestry over the last 4 million years ago apes; earliest tool years. In this diagram, Australopithecus afarensis makers. is shown to be a common ancestor of the Homo Australopithecus 4 Remains found in groups and A. africanus, A. boisei and A. robustus. anamensis million 1995; thought by some years ago to be the same as A. Supporters of this theory include Don Johansen afarensis. and Tim White, and to some extent, Richard Australopithecus 3.9-2.9 Cranial capacity 380- Leakey. In another model, some scientists, afarensis million 450 ml; some were including Colin Groves, believe A.africanus to be years ago hunters. Remains found the common ancestor of these two groups, and do in Ethiopia referred to not believe A.ramidus is an ancestor of the as ‘Lucy’. hominids at all. The evolutionary model proposed Australopithecus 3-1.6 Slightly bigger brain by Bernard Wood is similar to that of Johansen africanus million capacity than A. and Leakey, but proposes that A.africanus is a years ago afarensis. Larger teeth direct ancestor of the Homo groups and that Homo than humans, erectus is not a direct ancestor of Homo sapiens. vegetarian. There is some doubt as to whether Homo ergaster Australopithecus 2.8-1.2 Cranial capacity 550 robustus million ml, crest on the top of is a separate species, with many scientists years ago the skull, discovered by proposing that it is just another form of Homo Mary Leakey in 1959. erectus. The remains of A .animensis were found Australopithecus 2.8-1.2 Cranial capacity 550 in 1955, but there is a belief that this hominid may boisei million ml; vegetarian, large be the same species as A.afarensis. An additional years ago molar teeth. point of controversy involves whether or not Homo habilis 2.3-1.5 Worked with stone Homo habilis, discovered by Richard Leakey in million tools; cranial capacity 1962, is a distinct species or merely a member of years ago 700 ml. the Australopithecus africanus species. Homo erectus 2-1.5 Hunter-gatherers; brain million capacity 850-1000 ml; years ago around 1.5 metres tall. Homo ergaster 1.8-1.6 Cranial capacity 880 Donald Johansen’s discovery of million ml; thought by some to ‘Lucy’and other Australopithecines in Ethiopia, years ago be the same species as and the Leakey’s discovery of other members of Homo erectus. this genus in Laetoli, brought scientists to the Homo 800,000- Also known as Archaic realisation that bipedal stance evolved before an heidelbergensis 100,000 Homo sapiens;cranial increase in cranial capacity occurred. Evidence years ago capacity 1300 ml. Homo 230,000 Slightly larger brain for this can be seen in the shape of their pelvis, neanderthalensis years ago than modern humans; which is very similar to that of humans, and also buried their dead and in the footprints found fossilised in volcanic ash used sophisticated by Mary Leakey in 1976.In addition, the spine of tools. Australopithecines was S-shaped, allowing them Homo sapiens 125,000 Cranial capacity 1350 to be balanced when upright, and their feet were years ago ml; early humans were similar to those of humans, with a non-opposable called Cro-magnons. big toe to take the weight of the body. Like Introduced paintings modern hominids, the hole where the spinal cord and sculptures; more is attached to the skull (the foramen magnum) refined tool making. also pointed downwards, which encouraged an upright stance. Table 7-4 Evolution of the main hominid groups 230,000 years Homo 125,000 years neanderthalensis Homo sapiens

2.8-1.2 million years A. boisei 800,000-100,000 years H. heidelbergensis

2-1.5 million years 2.8-1.2 million years H. erectus 1.8-1.6 million years A.robustus H.ergaster

3-1.6 million years Fig. A.africanus 2.3-1.5 million years _ 7-8 H.habilis One view of

3.9-2.9 million years A.afarensis

4 million years A.animensis

4.4 million years A. ramidus

man’s ancestry over the last 4 million years. Supporters of similar models to this include Leakey, Johansen and White. To construct the Bernard Wood model mentioned above, omit,A.anamensis and A. ramidus, place A.africanus below Homo habilis and place Homo erectus in a separate branch at the top, next to Homo sapiens and Homo neanderthalensis..

 As a requirement of this topic, you need similarities and differences of any two to provide an overview of the species used in tracing human evolutionary relationships.

Australopithecines and human H. neanderthalensis Homo sapiens evolution

Studies of Australopithecine fossils have led many Fig. 7-9 b) Evolutionary tree in which A.afarensis scientists to believe that A.afarensis and alone is the common ancestor of the robust group A.africanus were the common ancestors of both and the Homo species. the Homo species and the more recent Australopithecines (see fig. 7-9 a). Reasons for this include the fact that A.afarensis and A.africanus The relationship between Homo were smaller (about 1.3 m tall) and slighter than sapiens and Neanderthal man A.robustus and A. boisei. The former species are said to belong to the ‘gracile’ Australopithecines, Neanderthal man (230,000-34,000 years ago) and with the later belonging to the ‘robust’ modern day Homo sapiens (100,000 years ago to Australopithecines. Indeed, fossils of the robust the present) were once thought to belong to the group appeared more recently to those of the same species, but recent DNA comparisons gracile group, and studies of their dentition reveal suggest that they belonged to separate gene pools. they were vegetarian, as opposed to A.afarensis, Instead, Homo sapiens (known during this period which had a generalised diet. It is now almost as Cro-magnon man) is believed to have co-existed universally agreed upon that the robust group were with Homo neanderthalensis for some 50,000 an evolutionary ‘dead end’ that eventually became years, perhaps eventually killing off this species or extinct. The fact that A. africanus was also competing more successfully with them for food vegetarian and slightly larger than A.afarensis has and shelter. For whatever reason, Neanderthals thrown some doubt on its place in the evolutionary disappeared from the fossil record some 34,000 tree (see fig. 7-9 b), but it was clearly a good deal years ago. smaller in stature than the robust species. Although Neanderthal man had a larger cranial All Australopithecines had a jaw more similar in capacity than Cro-magnon man (about 1500 ml as shape to that of humans, an average brain size of opposed to about 1350 ml), fossil evidence 480 ml (the size of the gracile forms was 400-600 suggests that the latter species was more ml,with the robust forms having the larger cranial intelligent. Examples of this include finds of more capacity of 550 ml), and a vertebral column and sophisticated weapons, tools and artwork than their limbs suited to a bipedal gait. The robust Neanderthal counterparts. Realistic cave paintings Australopithecines were about 140 cm tall and found in western Spain and southern France are weighed up to 80 kg as opposed to about 35 kg in examples of this, along with the remains of stone the gracile forms. tools with smaller, flatter and narrower blades. Hence, although Neanderthals had developed a A. robustus culture in which their dead were buried formally, A. A. A. boisei tools were fashioned and clothes were made from afarensis africanus animal skins, it was not as refined as that of the Homo erectus Cro-magnons. Physically, Neanderthals were more heavily built than Cro-magnon man, with heavier brow ridges, a H. neanderthalensis Homo sapiens lower forehead and more protruding face. Some of the scientists who believe they belonged to the same species as Homo sapiens have explained the Fig. 7-9 a) Evolutionary tree in which both gracile disappearance of these features from the fossil Australopithecines are ancestors of the robust record by suggesting the Neanderthals interbred group and the Homo species with Cro-magnon man, but remains of intermediate forms have not been found. A. A. A.robustus afarensis africanus A. boisei Homo erectus Models of human migration and scientific circles. If Wolpoff’s theory is correct, we evolution would expect the amount of genetic variation within each racial group to be similar, as they have all been evolving together. i) The ‘Out of Africa’ model for human evolution modern modern modern European African Asian This theory proposes (fig. 7-10 a) that the human race had its origins in Africa about 1.5 million years ago and subsequently colonised the rest of the world. These modern humans, who are Y believed to have spread from Africa less than archaic archaic archaic 10,000 years ago, eventually replaced other European African Asian descendants of Homo erectus (such as Neanderthal man) which had already moved out from Africa. The archaic populations probably died out because they could not compete successfully with the modern forms for food and shelter. Evidence for European African Asian this idea includes studies of mitochondrial DNA H. erectus H. erectus H.erectus from the arm bone of Neanderthal remains, which suggests Neanderthals were a different species to X the Homo sapiens species living concurrently in the same area. In addition, studies of modern human mitochondrial DNA made by Allan Wilson Fig. 7-10 a) The ‘Out of Africa’ theory of human and his team have indicated that all humans can be evolution. X represents the initial migration of traced back to a single female, ‘Eve’, who lived in homo erectus 1.5 million years ago. Y represents Africa around 200,000 years ago. Because the ‘Out the migration of modern Homo sapiens from of Africa’ theory implies that modern humans have Africa 10,000 years ago. been living in Africa longer than in any other country, we should expect the amount of genetic variation within African groups to be very high modern modern modern compared to other groups around the world. European African Asian ii) The theory of Regional Continuity (Multi- Regional hypothesis)

This theory (fig. 7-10 b) agrees that modern archaic archaic archaic humans evolved from the African Homo erectus, European African Asian which appeared on earth around 1.5 million years ago. However, proponents of the theory, such as Milford Wolpoff, believe that there was no second migration from Africa about 10,000 years ago. Instead, modern humans evolved from Homo European African Asian erectus in different parts of the world, with genetic H erectus H.erectus H. erectus. exchange occurring between different regional groups. Fossil evidence does indeed suggest that Homo erectus moved out of Africa around 1 X million years ago, but this is not inconsistent with the ‘Out of Africa’ model. Wolpoff and others, Fig. 7-10 b) The theory of Regional Continuity. X however, also believe that mitochondrial DNA represents the single migration of H.erectus 1.5 studies can be used to support their theory, and million years ago. they have suggested that the physical traits of modern Australians (aboriginals) suggest they evolved from a Homo erectus population in Java. This latter theory has not been accepted in many Cultural development and human The theory of Regional Continuity evolution proposes that gene flow existed between different populations of early Homo species. This may have ensured that all the populations of Culture can be broadly defined as an accumulation the Homo species remained in the same gene of experiences that are passed on from generation pool and evolved simultaneously. to generation through the use of language or symbols. Cultural evolution can occur much more rapidly than biological evolution, and fossil evidence has shown that it accelerated quickly Polymorphism and clinal gradation with the onset of group hunting. This phenomenon, which required organisation and communication Polymorphism is defined as the occurrence of a among group members, probably began with range of forms due to the expression of different Homo erectus some 1.5 million years ago. As with genes within a population. The different blood their Australopithecine ancestors of up to 4 million types of humans are an example of this; the four years ago, Homo erectus were hunter-gatherers, blood types are determined by three alleles, A, B made tools from stone and constructed shelters. and AB. Polymorphism can also be seen in the Unlike the Australopithecines, however, their tools different amounts of melanin in people’s skin. were more sophisticated and they introduced the These levels are determined by two pairs of genes; use of fire. Homo neanderthalensis further people with white skins have the genotype aabb developed this culture 200,000 years ago to and people with dark skins have the dominant include burying their dead, hunting herds of large genotype AABB. The distribution of many human mammals, wearing clothes and necklaces and genes has resulted from the adaptation to different storing food in summer for use in winter. The geographic areas and isolation. This explains why development of rituals in Neanderthals, and art in there is a high frequency of the gene for sickle cell Cro-magnon man (who appeared around 125,000 anaemia in some African populations; possession years ago), are further indications of increased of the heterozygous form of the disease results in communication among group members and the resistance to malaria, and genetic isolation over improvement of intellect and imagination. time has resulted in more people displaying this Other cultural advances over the last 40,000 years adaptation. have included the production of stone sculptures Clinal gradation refers to the gradual change in from 30.000 years ago, the development of human characteristics from one region to another. agriculture, permanent settlements and language, The result of these gradual genetic changes is that more complex social structures within groups and there are no distinct ‘races’ of people, as there are the creation of more sophisticated tools, pottery always areas where genetic intermingling takes and equipment. As the culture of Homo sapiens place between different populations. The gradual became more complicated, learning took longer, decrease in skin pigmentation as one moves away with the result that infancy and childhood became from the equator is an example of a clinal more prolonged. gradation. With more travel and racial intermingling, clinal gradations may eventually  As a requirement of this topic, you need become less obvious among humans. to compare humans with other primates in terms of care of young, length of juvenile stage, social groups, use of tools and communication systems. The evolutionary significance of these differences should be assessed.

THINK!!! Outline the two i) Care of young - In the prosimians, a less mechanisms mentioned in the passage that have advanced primate group, parental care of the led to polymorphism among humans. young only lasts for a brief period; in lemurs, for instance, the infants are completely independent after 6 months. In most new world monkeys, such as the spider monkey, the mothers carry the young around with them for a slightly longer period. Interestingly, this role is taken over by the fathers in marmosets. Orangutan and gorilla young are iii) Social groups, use of tools and completely weaned after 2.5 to 3 years, but communication systems – These aspects of chimpanzees remain with their mothers for up to 7 primate behaviour are described in Table 7-6 , years. Human young remain dependent on their below. The ability of higher primate groups to parents for the longest period; this can be up to 16 learn new skills and pass them on to others in their years. group is an example of their capacity for culture. A Japanese study of rhesus monkeys, for instance, ii) Length of juvenile stage – Table 7-5 shows the found that they could develop learned behaviours time taken to reach sexual maturity for six such as potato washing, wheat washing and different primates. It can be seen that, in general, swimming, and pass these skills on to other the larger the brain capacity of the primate, the members of their species. Gorillas and longer is its juvenile stage. This is directly related chimpanzees are also capable of learning from to the ability of the more evolved primates to experience. spend a longer period of time learning life skills In conclusion, the more evolved the primate, the before they reach adulthood. longer the young are cared for, and the more developed is its communication, social Primate Length of juvenile organisation and use of tools. stage lemur 1.5 – 2 years macaque 4-5 years Jane Goodall (1934- ) worked with gibbon 6 years chimpanzees and observed that they not only orangutan 7-10 years used tools, but also made them. This helped to gorilla 7-8 years discard the theory that humans were the only chimpanzee 8-9 years primate capable of making tools. Her research in man 10-15 years Tanzania was in fact funded by Louis Leakey. Other examples of her findings included the use Table 7-5 The length of the juvenile stage in of empty kerosene cans by a chimp called Mike different primates to intimidate larger males, and the transfer of toolmaking knowledge from one tribe to another.

Primate Behaviour and social organisation Table 7- lemur Live together in groups of 6-10; females dominate and 6 – defend the group. Territories are marked out with urine and Primate territorial calls are also made. spider monkey Move in bands. Females protect and care for the young; males protect the group, sometimes throwing sticks or joining together to intimidate predators. gorilla Live in groups of between 18-24 members, usually with twice as many females as males. Each group has a large mature male as the leader. Various vocalisations are used to communicate. orangutan Males are usually solitary, with females being accompanied by one or more young. Vocal calls are used to communicate. Males develop large, fleshy facial discs. chimpanzee Live in groups of between 15 to 120; a male dominance hierarchy exists. Strong bonds occur between siblings and mothers. Facial expressions and a wide range of vocal sounds are used in communication. man Has developed language as a form of vocal communication, along with gestures and facial expressions. Lives in family units or tribes. behaviour and social organisation Current and future trends in human population numbers in the last 10,000 evolution years and to discuss the potential impact of modern technologies on future human populations. The following are examples of ways in which modern technology and other developments have Homo sapiens appeared on the earth around affected our own evolution. 125,000 years ago. For millions of years, human populations remained low because their simple i) Increased population mobility - With increased hunter-gatherer lifestyles could not offer protection movement of individuals throughout the world , against starvation, sickness and predation. Weaker more interbreeding between traditionally individuals did not survive, and human numbers recognised ‘races’ is occurring, with the result that were therefore kept in check. With the polymorphism among humans is becoming less development of farming around 10,000 years ago, obvious. Physical features that were once perhaps however, populations increased as more food the result of environmental selection pressures, became available. With less time needed to find such as dark skin pigmentation in Africans and this food, individuals could pursue other activities, short, stocky physique in the inhabitants of colder resulting in the development of better tools, areas, are no longer as geographically determined buildings, farming equipment and utensils. as they once were. Recorded history began around this time, due to the creation of permanent written records which ii) Modern medicine - Advancements in medicine could be passed on. A further boost to human such as immunisation, screening tests, more numbers came with the onset of the industrial effective drugs, surgical techniques and public revolution around 300 years ago. During this awareness campaigns, have helped to prolong the period, machines were developed that could lives of people who would otherwise have died. increase food production and make other aspects This is an example of humans being able to control of life easier. In the last century, advances in their environment to the extent that they are no technology, agriculture, public health and modern longer susceptible to the natural selection pressures medicine have resulted in the reduction of death experienced by other animals. A result of this is rates and better health, resulting in a virtual that harmful genes, which would otherwise have population explosion. Fig. 7-11 shows how human been ‘bred out’, may stay within populations. populations have changed over the last 30,000 Increased life spans and lowered mortality rates, years. while being desirable, may also place pressures on 6000 welfare systems. iii) Genetic engineering - The development of Pop. genetically modified plants and animals has the x 106 potential to ease the world’s food problems through increased production and will therefore increase populations by reducing global starvation.

The potential to cure diseases such as Cystic 3000 fibrosis using gene replacement therapy may also affect our evolution by allowing individuals to survive who may otherwise have died; further advances in this technology may in fact result in the complete removal of harmful genes from the human species. Adverse results could include the genes for pesticide and disease resistance 500 spreading to weeds and animal pests, thereby reducing agricultural productivity. 0

 As a requirement of this topic, you need to account for changes in human

costing in excess of 6 billion dollars. The number of genes in the human genome is roughly 100,000, technological and 3 billion nucleotide pairs are involved. Despite revolution these seemingly impossible numbers, a draft human genome map was completed in 2000, and the sequencing of chromosomes 22, 21, 20 and 14 industrial has been completed. revolution Benefits arising from the human genome project include a better understanding of human evolutionary relationships and the ability to detect, development of and even cure, up to 4000 genetic disorders. farming Hundreds of tests have now been developed to screen people for mutations associated with genetic disorders such as muscular dystrophy, sickle cell anaemia, cystic fibrosis and Huntington’s disease. In addition, tests have recently been developed to detect mutations for breast, ovarian and colon cancers. Knowledge of 30,000 25,000 20,000 15,000 10,000 5,000 0 an individual’s risk levels for these diseases can years ago aid in their prevention – those at a higher risk of Fig. 7-10 Human population changes over the last breast cancer, for instance, will have the option of 30,000 years. undergoing more regular mammograms. A knowledge of the genes causing hereditary diseases also means that a whole new range of drugs can now be developed which target these Adverse effects a population diseases at the molecular level. increase can have on communities include: i) A shortage of resources (food, water, fuel etc. ) Useful websites to refer to in this may result; ii) Pollution levels could increase topic enormously, adversely affecting our health; iii) Clearing of forests for agricultural purposes i) Introduction of the sub-tribes ‘Panini’ and could result in increased soil erosion and the ‘Hominini’: destruction of the habitats of native animals. news.nationalgeographic.com/news/2001/ Animal and plant species could become 12/1204_hominin_id.html extinct.Three ways in which humans are attempting to amend this by controlling their ii) Primate classification: own numbers are the use of birth control, http://www.geocities.com/RainForest/Canopy/322 education and an increase in the standard of 0/primates101.html living. iii) Human mitochondrial DNA:  Another requirement of this topic is http://biocrs.biomed.brown.edu/Books/Essays/Mit that you are expected to outline the ochondrial DNA.html purpose of the Human Genome and Project and briefly discuss its http://www.actionbioscience.org/evolution/ingman implications. .html

A genome is defined as the full set of genetic iv) Australopithecines: information on an organism’s chromosomes. The www.oneonta.edu/academics/anthro/links/aust.htm main purposes of the Human Genome Project are a) to map all the genes in the human genome; b) to v) Jane Goodall: deduce the DNA sequence of each gene and c) to http://www.webster.edu/woolflm/janegoodall.html identify disease- causing genes. This undertaking involves scientists from all over the world and is REVIEW QUESTIONS 5. Which of the following would be the most likely to be preserved as fossils? a) sponges and seaweeds a) MULTIPLE CHOICE b) plant pollen and bacteria c) bones and shells 1. Which of the following lists the taxonomic d) teeth and internal organs levels from the least specific to the most specific? 6. The most accurate method of determining the age of the earth would be: a) phylum, order, genus, family, kingdom, a) comparing fossils in one layer of rock with species, class those in another b) kingdom, order, species, family, genus, b) radioisotope dating using carbon 14 class, phylum c) radioisotope dating using radioactive c) kingdom, phylum, class, order, family, uranium genus, species d) using ‘indicator’ fossils such as pollen d) species, genus, family, order, class, grains phylum, kingdom 7. DNA hybridization involves: 2. The features that place humans in the family a) determining the degree to which the DNA Hominidae include: from one organism anneals with the DNA a) mammary glands, 4 chambered heart from another organism b) arms shorter than legs, large brain b) comparing the amino acid sequences in the c) speech, protruding chin DNA of two different organisms d) opposable thumbs, stereoscopic vision c) tracing the inheritance of mitochondrial DNA within a species 3. Which of the following primates possesses a d) determining the similarities in blood prehensile tail? proteins between two species a) an orangutan b) a lemur 8. According to the models proposed by most c) a baboon researchers, the hominid most likely to be a d) a spider monkey common ancestor of humans and the Australopithecines is: 4. Which of the following primates have now a) Homo erectus been placed into the sub-family Homininae by b) Homo neanderthalensis many scientists? c) Australopithecus afarensis a) humans, gorillas, chimpanzees d) Australopithecus robustus b) humans, chimpanzees, gibbons, gorillas c) new world monkeys, humans , gorillas 9. The ‘Out of Africa’ model of human evolution d) humans, orangutans, gorillas, chimpanzees proposes that: a) the human race evolved from Homo erectus in Africa about 1.5 million years ago , but modern humans spread from Homo heidelbergensis, Homo Africa less than 10,000 years ago neanderthalensis, Homo sapiens. b) the human race evolved simultaneously b) Give reasons why scientists have different from Homo erectus in different parts of the views about the evolutionary relationships world you have illustrated in your diagrams. c) the human race evolved from Homo neanderthalensis in Africa about 1.5 14. a) Define the term ‘polymorphism’ million years ago, but modern humans b) Describe two examples of polymorphism spread from Africa less than 10,000 years in humans and explain how they may be ago the result of environmental selection d) the human race evolved simultaneously processes. from Homo neanderthalensis in different parts of the world 15. Briefly describe the effects the following may have on human evolution: 10. Of the primate groups listed below, the one a) increased population mobility with the longest juvenile stage would be: b) modern medicine a) lemurs c) genetic engineering b) chimpanzees c) gibbons 16. Discuss the contribution of two of the d) macaques following people to our knowledge of human evolution: The Leakey family, Donald Johansen, Robert Broom, Raymond Dart, Philip Tobias, Jane Goodall b) SHORT ANSWER AND 17. a) What are the main purposes of the LONGER RESPONSE Human Genome Project? b) Discuss some of the effects our increased QUESTIONS knowledge of the human genome will have on society. 11. Briefly describe the features that classify humans as: 18. Give an example of a) Class mammalia a) an absolute dating technique used to b) Order primates determine the age of fossils c) Family hominidae b) a relative dating technique used to d) Tribe hominini determine the age of fossils

12. Outline some of the relationships that have 19. Describe one way recent technological been established between different primates advances have changed opinions about the using: classification of primate groups, giving a a) DNA-DNA hybridization specific example of a primate that has been b) karyotype analysis re-classified by some taxonomists. c) DNA sequencing d) comparison of haemoglobins 20. a) What is a fossil? e) comparison of mitochondrial DNA b) Outline the conditions needed before fossils are able to form. 13. a) Draw diagrams to illustrate two alternative evolutionary trees that include some or all of the following hominids: Australopithecus ramidus, ANSWERS Australopithecus afarensis, Australopithecus robustus, a) MULTIPLE CHOICE Australopithecus boisei, Australopithecus africanus, Homo habilis, Homo erectus, 1. c) 2. b); speech and a protruding chin are more more chromosome pair than humans. characteristic of the actual species, Homo These similarities have encouraged sapiens taxonomists to group them all into the Hominidae. 3. d); prehensile tails are a characteristic of new c) DNA sequencing: This has also shown world monkeys similar relationships among the higher primates. 4. a); orangutans have been placed in the sub- d) Comparison of haemoglobins: When the family, Ponginae sequence of amino acids in haemoglobin molecules is compared, chimps and 5. c); hard parts of organisms are the most likely humans have been found to be identical, to be preserved with gorillas having two amino acid differences. 6. c); carbon 14 does not have a long enough e) Comparison of mitochondrial DNA: This half-life to date the oldest rocks on earth, has led scientists to conclude that Homo whereas radioactive uranium does ; the sapiens evolved from hominid ancestors in other alternatives are relative, not absolute, Africa up to 250,000 years ago. dating techniques

8. c); the Homo species mentioned are too recent, and A. robustus is believed to represent an evolutionary dead-end. 13. a) i) (similar to the models of Johansen, White 9. a); alternative b) represents the Theory of and Leakey) Regional Continuity Homo neanderthalensis Homo sapiens 10. b); a longer juvenile stage corresponds with a more evolved organism, and chimpanzees are regarded as the most evolved of the primates mentioned A. boisei H. heidelbergensis b) SHORT ANSWER AND LONGER RESPONSE H. A. erectus robustus QUESTIONS

H.habilis 11. a) Skin covered with hair or fur, mammary A.africanus glands, 4 chambered heart. b) Fingers and flat nails, reduced sense of A.afarensis smell, opposable thumbs, usually stereoscopic vision. c) Large brain, arms shorter than legs. A. d) Bipedal; the ability to walk upright on two ramidus feet. ii) ( similar to the Bernard Wood model)

12. a) DNA hybridisation: This has resulted in the placement of gorillas, chimpanzees and humans into the sub-family Homininae. b) Karyotype analysis: These studies have revealed that humans, chimpanzees, orangutans and gorillas have 6 identical chromosomes, and that apes have only one Homo 15. a) This may result in polymorphism among neanderthalensis Homo sapiens humans , such as skin colouring, becoming less obvious. b) The introduction and widespread use of H. A. immunisation, screening tests, more erectus boisei effective drugs etc., have increased human life spans and overall health, but may result in detrimental genes remaining in the gene pool. c) Genetically modified plants and animals A. that are disease resistant and have higher robustus yields will be beneficial to world A.africanus populations because they will reduce the food shortage. Gene therapy has the potential to cure genetic diseases and remove harmful genes from the population. Genetically modified organisms could adversely affect the A.afarensis ecosystem if released into the wild, resulting in the possible extinction of some species. b) Reasons for different views include the differing interpretations of fossil remains; 16. i) The Leakey family: Mary Leakey some scientists, for instance, believe that discovered Australopithecus robustus in Homo ergaster and Homo erectus are the 1959, footprints of the bipedal same species, and that Australopithecus Australopithecus afarensis in1976, and animensis and Australopithecus afarensis are Homo habilis with her husband Richard the same species. Other differences in in 1961.Maeve Leakey discovered opinion include the positions of A. afarensis Australopithecus anamensis in 1995 and and A. africanus in the evolutionary tree: Kenyanthropus platyops in 2001. some believe that A. africanus, being ii) Donald Johansen: Discovered intermediate in anatomy between the robust Australopithecus afarensis in Ethiopia in and the gracile Australopithecines, was a 1974. common ancestor of both the robust group and the Homo groups. Others, however, believe that A. afarensis was the common 17. a) i) To map all the genes in the human ancestor. Scientists may also have different genome; ii) to deduce the DNA sequence views about the importance of certain of each gene and iii) to identify disease- anatomical features in determining causing genes. relationships. b) Scientists will have the ability to detect, and even cure, up to 4000 genetic 14. a) The occurrence of a range of forms due disorders. In addition, a knowledge of the to the expression of different genes genes causing hereditary diseases means within a population. that a whole new range of drugs can now b) i) Skin colour- the amount of melanin in be developed which target the molecular the skin tends to decrease the further one basis of these diseases. Ethical issues that moves away from the equator, may arise could involve the prospect of suggesting that it is an adaptation to the discrimination based on an individual’s amount of sunlight in a particular area. genome. ii) Blood types- there is a higher than average accumulation of the sickle-cell 18. a) Radioisotope dating is an absolute dating anaemia gene in certain African technique; this involves measuring how populations because in the heterozygous much of a particular radioactive element form it confers resistance to malaria. remains since it began decaying. b) An example of a relative dating technique is where fossils are compared to other fossils in the same sedimentary layer, or to ones in higher or lower rock strata in order to determine their approximate age.

19. Further anatomical research, fossil evidence and modern techniques such as DNA hybridisation, have resulted in many scientists re-classifying some primates. Examples include the tree shrews, which are no longer regarded as anatomically close enough to the other primates and have been placed in their own order, Scandentia. Also, studies of the tarsier have resulted in it being re-classified with the original anthropoids in the new sub- order, Haplorhines. Fossil and genetic evidence has now placed humans, gorillas, chimpanzees and orangutans in the family Hominidae.

20. a) Any trace of past life. b) i) The organism needs to have been buried rapidly by sediment; ii) Decay must be prevented, so conditions of low oxygen, low temperature or acidity are needed; iii) The organism must remain undisturbed for a long period of time.