Gill Sans Bold. Biology HSC Course Stage 6. The human story. Part 3: The hominin debate

Transcription

1 Gill Sans Bold Biology HSC Course Stage 6 The human story Part 3: The hominin debate IncorporatingOctober2002 AMENDMENTS

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3 Gill Sans Bold Contents Introduction...3 The hominins...5 The Australopithecines...12 The genus Homo...20 The Leakey family...37 Louis Leakey...37 Mary Leakey...40 Richard Leakey...41 Alternative models of human evolution...43 Different theories...45 Summary...51 Suggested answers...53 Exercises Part Additional resources...61 The Human story...62 Part 3: The hominin debate 1

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5 Gill Sans Bold Introduction Continuing the human story you will be looking at human evolution and the debate about human evolution. Humans developed from primates or ape like ancestors. The first fossil skull found was in the Neander Valley in Germany in This strange skull was at first thought to belong to a man suffering a disease such as rickets. It took a while before scientists would accept that you could have a creature showing both ape and man like features. This skull was Homo neanderthalensis and since then there have been many fossils discovered fuelling the debate on human evolution. In this part you will have the opportunity to learn to: examine at least two alternative views of human evolutionary relationships using the same fossil evidence including: Ardipithecus ramidus (Australopithecus ramidus) Australopithecus afarensis Paranthropus robustus (Australopithecus robustus) Paranthropus boisei (Australopithecus boisei) Australopithecus africanus Homo habilis Homo ergaster Homo erectus Homo heidelbergensis Homo neanderthalensis Homo sapiens Part 3: The hominin debate 3

6 compare these hominid groups, including comparisons of: body structure cranial capacity fossil ages and regional locations inferred culture In this part you will have the opportunity to: gather process, present and analyse information to provide an overview of the similarities and differences of the named hominid species and discuss the role of any two species in tracing evolutionary relationships process secondary information and use available evidence to assess the contribution of one of the following to our increased understanding of hominid evolution: the Leakey family Johanson Broom Tobias Dart Goodall gather and process information from secondary sources to analyse and evaluate the evidence for the alternative models of human evolution Extract from Biology Stage 6 Syllabus Board of Studies NSW, originally issued 1999 modified November The most up to date version can be found on the Board's website at 4 The human story

7 Gill Sans Bold The first hominins can be defined as an animal that walked upright and had characteristics that were more human than ape like. There is only one living hominin Homo sapiens but this was not always the case. There is evidence to believe that early hominins lived at the same time and in some cases in the same area. The hominin story begins four million years ago. There were four major evolutionary phases during the development of the hominins. Australopithecus stage and the occurrence of bipedalism (four million years ago). Evolution of the genus Homo with a large brain and the ability to make durable tools (2.5 million years ago). Migration of Homo erectus out of Africa (two million years ago). Homo sapiens stage ( years ago). Before looking at the hominins in more detail, it is important to know some of the features of hominins. An important part of the definition of a hominin is bipedalism. Recall from an earlier part of this module the meaning of the term bipedalism. Check your answer. The anatomical structures that support bipedalism are: position of the foramen magnum centrally located under the skull S shape spine rather than the C shape of apes Part 3: The hominin debate 5

8 non opposable toe straight finger bones the femur sloping inwards. If a fossil has these features then this is evidence for an advanced hominin. As well as the features that support bipedalism (walking on two feet), there are some other features that anthropologists look for. These are the increase in brain capacity (apes are less than 400 cc), a parabolic jaw rather than the rectangular jaw of apes, no eyebrow ridges and the presence of a chin. The foreman magnum in humans is located centrally under the skull. Femur sloping inwards is an indication of bipedalism. 6 The human story

9 Gill Sans Bold The human spine is S shaped rather than C shaped ape spine. Increased brain capacity from 400 cc in apes to 1500 cc in humans. Part 3: The hominin debate 7 Human feet have an arch and a non opposable big toe.

10 The human jaw is parabolic compared to the rectangular shape of the ape jaw. Complete the table below to show the features that anthropologists look for in fossil hominins. Anatomical feature Ape like (primitive) Human like (advanced) foramen magnum shape of spine big toe shape of finger bones slope of the femur eyebrow ridges chin jaw shape (dental arcade) brain capacity Check your answers. You are going to read about the following species that illustrate the development of the hominins. Below is a table to summarise the information that is given. Fill in the table as you read through the information. The first one is done for you. Ardipithecus ramidus Australopithecus afarensis Australopithecus africanus Paranthropus robustus Paranthropus boisei 8 The human story

11 Gill Sans Bold Homo habilis Homo ergaster Homo erectus Homo heidelbergensis Homo neanderthalensis Homo sapiens minin Body structure Cranial capacity (cc) Fossil age and locations Inferred culture pithecus ramidus ape like body unknown but less than 420 cc Eastern Africa and Ethiopia 4.4 million years ago unknown ralopithecus afarensis ralopithecus africanus anthropus robustus anthropus boisei Part 3: The hominin debate 9

12 mo habilis mo ergaster mo erectus mo heidelbergensis mo neanderthalensis mo sapiens 0 The human story

13 Gill Sans Bold The map below shows the location of important hominin sites throughout Africa. As you read through the information, locate the sites mentioned on the map. Olduvai Gorge Hadar Omo East Turkana (Koobi Fora) km Sterkfontein Kromdraai 500 miles Swartkrans The Australopithecines A general description of an Australopithecus is an animal 1.2 to 1.5 m tall, which stood upright and walked bipedally with a cranial capacity of 450 to 650 cc. The cranial capacity is the internal capacity of the skull case. To get an idea of the size of this hominin s brain fill a container with 400 ml of water. This is similar in size to an Australopithecus brain. Now fill a container with 1550 ml this is approximately the size of your brain. The foot of Australopithecus had a human appearance but the fingers were not as nimble as ours. The spine was S shaped and the foramen magnum pointed down both evidence for a bipedal gait. Australopithecus was an ape like human. Australopithecines are split into the gracile form and the robust form. The gracile form was smaller and had thinner bones while the robust form had thicker bones and much larger teeth. There were different species of Australopithecus living at the same time. There was a light bodied meat eating species called Australopithecus africanus living at the same time as Australopithecus afarensis and a heavier herbivorous species called Australopithecus aethiopicus. Two other species called Australopithecus boisei and Australopithecus robustus lived more Part 3: The hominin debate 11

14 recently and at the same time as the first Homo species. The robust australopithecines are sometimes put into the separate genus Paranthropus. As you read about these groups you will see different naming systems in nearly every resource that you read. This is an indication of the arbitrary nature of classification systems. If you look at the table below you will see two classification systems for Australopithecus. One genus Australopithecus Two genera Australopithecus and Paranthropus gracile A. afarensis A. afarensis A. africanus A. africanus robust A. robustus P. robustus A. boisei P. boisei Australopithecus may or may not have been ancestral to modern humans but they were around for at least three million years so they were a very successful group of animals. Ardipithecus ramidus Ardipithecus ramidus (also known as Australopithecus ramidus) lived in woodlands in eastern Africa, and the Awash Valley in Ethiopia 4.4 mya (million years ago). It is characterised by having thinner tooth enamel and to show more primitive features relative to other Australopithecines. The brain size is unknown. It is thought to be close to the divergence of the African apes from the hominins. Don t forget to fill in the table as you read through the information. Body structure A small body, more ape like than hominin. Possibly bipedal or semi bipedal approximately 122 cm tall. The teeth are intermediate between extinct apes and Australopithecus afarensis. Cranial capacity The cranial capacity is unknown because not enough pieces of the skull have been found. It is assumed to be smaller than Australopithecus afarensis. Fossil age and locations Eastern Africa and the Awash Valley, Aramis in Ethiopia 4.5 to 4.4 mya (millions of years ago). 2 The human story

15 Gill Sans Bold Inferred culture The culture of the animal is unknown but it has not been found in conjunction with tools. It is suggested that this hominin lived in a woodland environment but was bipedal which goes against the general idea that bipedalism evolved in an open savannah. Some classification systems do not put this species in Australopithecus. Australopithecus afarensis Australopithecus afarensis (the southern ape of Afar) is humanlike in that it has small canines and thick enamel on the teeth. The shape of the teeth row shows neither the U shaped (rectangular) arch of apes nor the parabolic arch of humans. The overall head shape is like an ape with a small brain but with strong adaptations for bipedal walking although with slightly curved feet and hands which suggests that they climbed in trees as well. Fossil jaw from Australopithecus afarensis. The jaw is more rectangular than parabolic. (Photograph: Dr. Mark Leney hominid.webjump.) This was named after the Afar region in Ethiopia where the first fossil was found three to four million years ago. These creatures were intermediate between apes and modern humans; they had a small brain but an upright posture and bipedal gait. They did not use fire or tools. Key sites for this species include Laetoli in Tanzania and Hadar in Ethiopia and two sites in South Africa, Sterkfontein and Makapansgat. Australopithecus is not found outside of Africa. Part 3: The hominin debate 13

16 Body structure This hominin was bipedal with an upright posture. The spine was S shaped and the foramen magnum pointed downwards. The teeth are small and unspecialised. They were 1.0 m to 1.5 m tall and weighed 28 kg (30 to 40 kg). They were sexually dimorphic with the males larger than the females. The build was light with some ape like features, for example the shape of the thorax, long arms relative to legs and curved finger bones. This suggests that they spent some time in the trees. They also had a low flat forehead, projecting face and prominent eyebrow ridges. Cranial capacity Cranial capacity was between cc. Fossil age and locations The fossil age is three to four million years. It was found in eastern Africa. The most famous example of this species is Lucy who was discovered by Donald Johanson and Tom Gray in Lucy is thought to be 3.2 million years old. She was unusual because nearly half of the skeleton was preserved. She was called Lucy because the Beatles song Lucy in the sky with diamonds was popular at the time. Since the discovery of Lucy at least thirteen individuals of this species had been found in the area and are collectively known as the first family. Another important fossil are the Laetoli footprints discovered by Paul Abell and Mary Leakey in This amazing fossil shows that at least two bipedal hominins walked through this area more than three million years ago. These footprints were preserved because of a volcanic eruption which left a fine layer of ash. The ash layer was then rained on making a type of cement. The footprints were set in the mixture and then covered by another layer of ash and further layers of volcanic material. The footprints lay beneath the surface for millions of years until they were exposed by weathering and erosion. Remarkably they were discovered by Mary Leakey s team before they weathered away completely. Inferred culture Not known to have used tools. Lived in small foraging social groups. Australopithecus africanus Raymond Dart, an anatomist named the first Australopithecus, in It was found in South Africa leading to the name Australopithecus that means southern ape. This specimen was the skull of a child and is called The Taung baby. It belongs to the species Australopithecus africanus (southern ape of Africa). 4 The human story

17 Gill Sans Bold The Taung baby Australopithecus africanus. (Photograph: Mark Leney hominid webjump) Robert Broom discovered adults of the same species in the 1930s and since then many specimens have been found extending north into east Africa. Australopithecus has an ape like appearance. Body structure Small light build with relatively long arms and more human features such as a high forehead and less prominent eyebrow ridges. Reduced sexual dimorphism. Cranial capacity cc Fossil ages and regional locations Southern Africa extending into East Africa about 2 3 mya. Inferred culture Lived in groups. Paranthropus robustus Paranthropus robustus (also known as Australopithecus robustus) had a larger brain size with a heavy body and obvious crest on the head for the attachment of large jaw muscles. It is not a direct ancestor for modern humans. It was a heavy bodied and heavy jawed herbivore. This hominin is more massively built than Australopithecus afarensis or Australopithecus africanus, with a flatter face. Part 3: The hominin debate 15

18 Skull of Australopithecus robustus. Body structure The body had a height of 1.75 m and weighed 60 kg. The bony crest on skull, called the sagittal crest, was the attachment point for the large chewing muscles. The face was long, flat and broad. The body was robust. They had very thick jaws, small incisors and canines and very large molars. The pre molars were like molars giving a large chewing surface for the vegetarian diet. Cranial capacity The cranial capacity was between cc. Fossil age and locations Found in southern Africa (Kromdraai) and Swartkrans around 3 1 million years ago. One skull of this species was found with puncture marks in the skull that fit the teeth of a leopard. It was thought that this fossil was a leopard s meal but fell into a sinkhole below the leopard s feeding tree and became fossilised in the cave deposits. Inferred culture Lived in groups. This species arose as the climate became drier and the environment changed into more open woodland. Paranthropus boisei Paranthropus boisei is also known as Australopithecus boisei. This is a hyper robust form from East Africa originally called Zinjanthropus boisei by Louis Leakey (nicknamed Zinj or Nutcracker man ). Lived at the same time as Homo habilis in Olduvai Gorge. 6 The human story

19 Gill Sans Bold Paranthropus boisei showing the sagittal crest and large molars. Body structure Thought to be a robust Australopithecus. A shortened but heavily buttressed face, tiny front teeth and large cheek teeth and enormously developed chewing muscles attached to a sagittal crest. Walked upright with a foramen magnum further forward than Australopithecus. Short legs and long arms. Cranial capacity The cranial capacity was between cc. Fossil age and locations The fossil age is between 1.75 to 1.4 million years ago. Many fossils at Kooba Fora (Kenya). Olduvai Gorge (Tanzania) and eastern Ethiopia. Similar to Australopithecus robustus but found in eastern Africa. Inferred culture A large robust vegetarian. Possible stone tool user. This species was at first thought by the Leakey family to be the tool user who belonged to the tools found in Olduvai Gorge but these were later attributed to Homo habilis who lived at the same time. The Australopithecines were more ape like than human and so are not placed in the same genus as humans. Do Exercise 3.1 now. The genus Homo Australopithecus were found in Africa at the same time as the first of the true humans, Homo habilis. The Homo genus contains large brained bipedal animals that use tools. Part 3: The hominin debate 17

20 This next stage of hominin evolution moves out of Africa. The first member of the genus Homo was discovered in Java by Eugene Dubois in It had characteristics between Australopithecus and modern humans and was called Java man. The next discovery was in China and was given the name Peking man. These have both been put into the same species, Homo erectus ( upright man ). Homo erectus was found throughout Europe years ago. In Spain, a particularly large group of Homo erectus has been named Homo heidelbergensis. Homo erectus then evolved into archaic Homo sapiens and may be the ancestors of Homo neanderthalensis. Homo erectus has been found in many locations including southern and central Europe and east Africa. The species of the genus Homo that you will be studying are: Homo habilis Homo ergaster Homo erectus Homo heidelbergensis Homo neanderthalensis Homo sapiens. Homo habilis By two million years ago the genus Homo was around in the form of Homo habilis. This was the first toolmaker. The skull of Homo habilis. Homo habilis was discovered by the Leakeys in Olduvai Gorge during the 1960s and 70s. Homo habilis means handy man. This name was given because of their simple pebble tools found with the hominin fossils. This is the first true human. Body structure The body had a height 1.3 m and weighed 40 kg with a larger brain size than Australopithecus. The males are larger than females. They had a rounder head with smaller molars and less projecting jaws. They had large molars, no chin and a sloping forehead. 8 The human story

21 Gill Sans Bold Cranial capacity The cranial capacity was between cc. Jaw of Homo habilis. Compare the shape of this jaw to the shape of the Australopithecus afarensis jaw. (Photograph: Dr. Mark Leney hominid.webjump ) Fossil age and locations Found on the shores of Lake Turkana, East Africa, 2.2 million to 1.6 million years ago. Also found at Koobi Fora in northern Kenya and Olduvai Gorge. Inferred culture They made and used simple stone tools called Oldowan technology, built shelters, and cooperated in groups. They ate a mixed diet of plants and animals. Use the map of Africa to locate these sites. Olduvai Gorge, Lake Turkana, Koobi Fora, Swartkrans, Kondraii, Sterkfontein. Simple pebble chopper, part of the Oldowan technology. Part 3: The hominin debate 19

22 Homo ergaster (Turkana boy) Known as African Homo erectus or early Homo erectus. Specimens were originally given the name Homo erectus but the name Homo ergaster is being used more and more for the African finds. The first discoveries of this species were made by Louis and Mary Leakey at Olduvai Gorge. Richard Leakey (their son) and his team discovered many finds on the shores of Lake Turkana. The most spectacular find was Nariokotome (or Turkana) Boy. Body structure Homo ergaster had a projecting brow ridge, a short face and the beginnings of a projecting nose. The cranium was rounded with essentially modern body structure with moderately large faced skulls that had brains twice the size of modern apes but still half the size of modern humans. Turkana boy died as an adolescent but would have reached a height of six feet with long slender limbs. There was a different in brain case construction from the Asian Homo erectus. Cranial capacity Cranial capacity was between cc. Fossil age and locations This fossil was is dated at 1.7 million years ago. It was found in northern Kenya (Koobi Fora), to the east of Lake Turkana, Ethiopia, Eritrea. Homo ergaster was the first hominin to move out of Africa. This species is known as Homo erectus in China and Indonesia. Inferred culture Homo ergaster made stone tools called Acheulian industry. Large flakes were made into hand axes which were very versatile for cutting, and chopping. These tools were more complex than the simple pebble tools of Homo habilis. 20 The human story

23 Gill Sans Bold Home erectus Homo erectus (Peking man) skull cap. Notice the heavy eyebrow ridge. (Photograph: Dr. Mark Leney hominid webjump) The skull of Homo erectus ( years ago.) Famous examples of Homo erectus are Java man and Peking man have been found that existed 1.7 million to years ago. Eugene Dubois discovered the first of these fossils in 1890 and called it the missing link between apes and man. The fossils from China were lost during the chaos of the last world war ( ) but good casts remain of the skulls. Homo erectus is the earliest trace of humans outside of Africa. The earliest are in Africa at 1.7 million years of age. Homo erectus stood upright and was a large brained hominin. Its cranial capacity overlaps with some modern humans. Body structure Homo erectus had a stocky skeleton; the skull had a sloping forehead and large brow ridge. The face was not as flat as modern humans but was less protruding than Homo habilis. Long, low skull vaults with sharp angles at the back and protruding eyebrow ridges. Part 3: The hominin debate 21

24 Cranial capacity The cranial capacity is cc which is about 70% of modern humans but falls within the range of modern humans. Homo erectus (Peking man) frontal view. (Photograph: Dr. Mark Leney hominid.webjump) Fossil age and locations Lived 1.7 million to to years ago. Lived in East Africa for a million years and spread out of Africa to Asia. Inferred culture Homo erectus had a stone tool technology of scraping, chopping, cutting, piercing and pounding tools. This type of tool is called Acheulian. More of a scavenger than a true hunter, Homo erectus lived on fruits, nuts, berries, small animals and larger animals killed by other predators. They lived in caves and used fire. The flake tools were manufactured from local rock including chert and flint. It is suspected that they also used wooden and bamboo tools which have not survived to the present day. 22 The human story

25 Gill Sans Bold Tools of Homo erectus. Homo heidelbergensis Specimens that were previously called archaic Homo sapiens have been placed in this group. They were large brained hominins that may have developed into Homo neanderthalensis years ago. Skull of Homo heidelbergensis. Part 3: The hominin debate 23

26 Views of Homo heidelbergensis skull. (Photograph: Javier Trueba/Madrid Scientific Films) Body structure Sometimes called a large Homo erectus with a bigger brain capacity. Cranial capacity The cranial capacity is between 1100 and 1300 cc. Fossil age and locations Homo heidelbergensis lived in Europe and western Asia to years ago. They were in Africa years ago. Inferred culture Homo heidelbergensis was a stone tool user. They may have invented the prepared core stone tools. 24 The human story

27 Gill Sans Bold Homo neanderthalensis Homo neanderthalensis. (Photograph: Dr. Mark Leney hominid.webjump) Neanderthals lived at the same time as early Homo sapiens (Cro Magnon). Skull of Homo neanderthalensis (Neanderthal man) years ago. Body structure Neanderthals were 1.6 m tall. They had a smaller forehead, with a large eyebrow ridge and more prominent jaw, little or no chin, and a large nose. There was a distinctive swelling at the rear of the skull with a big area for the attachment of the neck muscles. Their bodies were strong and muscular. Neanderthals were stronger and more robust than modern humans but generally shorter with a broad rib cage. The forearms and lower legs were relatively short and the lower limb bones were heavily built with broad fingertips. They lived through the European ice ages and were adapted to cold conditions. Part 3: The hominin debate 25

28 Cranial capacity They had a rounded cranium, sloping forehead, thick brow ridges and an underdeveloped chin. Cranial capacity 1500 cc ( cc). On average, larger than the modern population. Fossil age and locations Lived in Europe and western Asia during the ice age, to years ago. Inferred culture Their culture was called Mousterian and their tools consisted of scrapers, stone knives, and projectile points for spears and arrows. Tools crafted from bone were also used. They were wandering hunter/gatherers. They dug traps and had a high degree of social organisation. They had burial rituals and built shelters from animal skins, wore clothes and jewellery. They had a complex social organisation that allowed them to hunt large animals such as woolly mammoth, bears and bison. They lived in the cold conditions of the last ice age. Lived in caves and used fire. Specimens have been found that were partially blind, one armed and crippled. This indicates that there was a complex social system that looked after the weaker members of the group. Tools of Homo neanderthalensis (Mousterian technology). The group died out years ago. There is some controversy about whether Cro Magnon killed or interbred with the neanderthals. Some recent fossils show intermediate characteristics between the two while the results from DNA examination shows no interbreeding between the species. 26 The human story

29 Gill Sans Bold Homo sapiens Cro Magnon skull. (Photograph: Dr. Mark Leney hominid.webjump) The earliest types of this modern species are called archaic Homo sapiens. Archaic Homo sapiens is a classification that contains fossils that do not fit easily into existing groups. These hominins were not quite Homo sapiens but they possessed many modern features. Cro Magnon is the same species as present day humans and is structurally identical to humans. Their hunting skills surpassed the Neanderthals. They killed dangerous species like woolly mammoths, sabre toothed tigers and giant ox. They may have contributed to the extinction of these species. Cro Magnon left behind artworks on the walls of caves. Skull of Cro Magnon. Body structure Well developed chin, no eyebrow ridges, high forehead, skull long and narrow but the face was wide. Structural identical with modern humans. Part 3: The hominin debate 27

30 Cro Magnon skull showing the position of the foramen magnum and the parabolic shaped dental arch. (Photograph: Dr.Mark Leney hominid.webjump) Cranial capacity Cranial capacity was between cc. Fossil age and locations years ago in Omo in East Africa. Cro Magnon man moved into Europe. Fossils found all over the world. Inferred culture Cro Magnon had a sophisticated culture with complicated tools. They constructed lean tos and huts with stone foundations. They buried their dead with ritual, made cave paintings, and made bone and ivory tools. Their art is found in the famous caves of Lascaux in France and Altimira in Spain. 28 The human story

31 Gill Sans Bold Cro Magnon cave art. Further development included the domestication of animals, agriculture, wooden weapons, city dwelling, and eventually leading up to today's technology. Cro Magnon blade tools. Make sure you have finished filling in the table and check your answers. Summary of hominin evolution There are a number of trends from early Australopithecus to present day humans. These are increasing brain size increasing body size Part 3: The hominin debate 29

32 increasing use and sophistication of tools decrease in tooth size decrease in skeletal robustness. There is much debate on the shape of the hominid family tree. The robust australopithecines are not ancestral to humans but are on a separate branch. It is possible that Homo habilis is a descendant of Australopithecus afarensis but it is still a matter for debate. It is thought that Homo habilis became Home erectus but there is still debate about the evolution of and relationship between Homo sapiens, Neanderthal and other archaic sapiens. You will be looking at the different classification schemes later in this part. Use the following table to graph the cranial capacity for each of the hominins listed. 30 The human story

33 Gill Sans Bold Hominin Cranial capacity range (cc) Ardipithecus ramidus Unknown but less than 420 Australopithecus afarensis Australopithecus africanus Paranthropus robustus Paranthropus boisei Homo habilis Homo ergaster Homo erectus Homo heidelbergensis Homo neanderthalensis Homo sapiens Graph the time span of each of the hominids using a different colour for each. Hominid Time span (years) Part 3: The hominin debate 31

34 Ardipithecus ramidus 4.4 million Australopithecus afarensis 4 to 3 million Australopithecus africanus 3 to 2 million Paranthropus robustus 3 to 1 million Paranthropus boisei 1.75 to 1.4 million Homo habilis 2 to 1.6 million Homo ergaster 1.7 million Homo erectus 1.7 million to Homo heidelbergensis to Homo neanderthalensis to Homo sapiens to present day You need to learn the names of all the hominins that have just been mentioned. Take some time now to learn the names and the similarities and differences between the different fossils. Do Exercise 3.2 now. 32 The human story

35 Gill Sans Bold The Leakey family In the last section the names of Louis, Mary and Richard Leakey occurred as the first to find species of hominins. The Leakey family has been foremost amongst anthropologists. No other family has so dominated a field of research as the Leakey family. Their combined research has added much to the knowledge of hominin evolution. The three most famous members of this family are: Louis Leakey Mary Leakey Richard Leakey. Louis Leakey ( ) Louis Leakey was described as brilliant, passionate, energetic, eccentric and occasionally erratic. He was born outside of Nairobi in His parents were English missionaries to the Kikuyu tribe. Louis grew up playing with the tribe; he spoke the language fluently and was initiated into the tribe. At the age of 13 he found some stone tools and he was determined to study in this area. When he attended University in England a rugby accident gave him epilepsy and headaches and stopped his studies but he still managed an expedition to Africa. He returned to his studies in 1925 with brilliant passes in anthropology and archaeology. He married Frida Avern in His studies led him to believe that man developed in Africa rather than Asia as was popularly thought at the time. In 1930 he was awarded a PhD. In 1933 he started an affair with Mary Nicol despite the fact that he had a pregnant wife and one child. This scandal plus his work with the geologist Percy Boswell, who ridiculed his aging of his Olduvai finds, destroyed his chance of an academic career. In 1936 he married Mary Nicol. During World War II Louis worked in intelligence as a spy. After the war he took a poorly paid job as curator of the Coryndon Museum (now Kenya National Museum). In 1947 he organised the first Pan African Congress of Pre history and restored his reputation as an important scientist. He and his wife Mary excavated Olduvai Gorge in Tanganyika (now Tanzania). In 1959 Mary discovered a hominin skull that they called Zinjanthropus boisei. This outstanding find brought them celebrity and grants came pouring in. The National Geographic Magazine took Part 3: The hominin debate 33

36 an interest in their work and from that time on wrote many articles about their discoveries and provided funds for them to continue their work. With this funding they were able to widen their excavations and found many more hominin fossils including the toolmaker that they had been looking for, Homo habilis. While Mary stayed behind continuing the excavations Louis spent more time travelling the world and raising funds for the digs. He was also interested in other projects and it was his influence that started some major projects into primate behaviour. The most famous examples of these were Jane Goodall s work on chimpanzees, Dian Fossey s gorilla work and Birute Galikas studies of orangutans. He was also involved in the search for ancient civilisations. He travelled constantly speaking to groups of people and raising money for the work that Mary was doing in Olduvai Gorge. He developed medical problems and collapsed and died in England in 1972 aged 69. A few days before his death his son Richard showed him his latest fossil find which supported Louis s theory that the hominins had been around for a long period of time and were not descended directly from the Australopithecines. Louis Leakey is remembered for his study of Olduvai Gorge and the hominin fossils within it. He successfully put forward the idea that East Africa was an important area for the evolution of the hominins and that the evolution of humans was slower than previously thought. Most fossil finds are open to different interpretations due to the lack of actual remains. Often only a few pieces of a fossil are found. The nature of fossilisation is such that it is mainly the teeth and the skull bones that remain to be found. Therefore a whole species may be based on just a few pieces of bones. This is true for the first remains of Homo habilis found at Olduvai Gorge by Louis Leakey. At the same time that Paranthropus boisei lived in Olduvai Gorge there lived another fossil hominin. The Leakeys were finding many tools in their diggings and they wanted to find the toolmaker. At first they thought it was Paranthropus boisei but then they started finding small pieces of bone that belonged to another species. When they announced in Nature magazine that they had found the toolmaker and it belonged in the same genus as modern humans there was a public outcry. Experts disagreed with the reconstruction of the find and the reasons for placing the fossil in the genus Homo. It was said that Homo habilis was not significantly different from Australopithecus africanus. The fossil evidence was originally a few fossil bits and pieces a lower jaw, parts of a brain case and some body bones. Added to these parts of another brain case and a pair of upper and lower jaws. This was described at the time as a jumble of fossils. Up to this point it was thought that only one species of hominin lived at any one time and that this species evolved directly into the next hominin. The evidence from Olduvai Gorge was that there were more than one species living at the same time. This was the first time it was suggested that there were two species of hominins living at the same time and the same place. It meant that not every hominin was on a direct line to modern humans. Another problem was placing the fossil into an already existing genus with only a few pieces of bone as evidence. A criterion for inclusion in the genus Homo is a brain size of cc. When announcing the discovery the Leakey team suggested that a brain size of more than 600 cc was sufficient for inclusion in the genus Homo. Their first specimen had a brain size of 680 cc, walked upright and used tools with a precision grip. Tool use as a criterion for inclusion in Homo also caused debate. Species are usually defined by anatomical features not by behaviour. Leakey wanted to use tool use as a definitive part of the genus, Homo. 34 The human story

37 Gill Sans Bold Amongst taxonomists there are two main groups called the splitters and the lumpers. As the name suggests splitters want to put each new find into a new group of its own while lumpers want to place each new find into an already existing group. The new species Homo habilis was greeted by these two groups with two different points of view. The lumpers wanted it placed with either Australopithecus or Homo erectus. The splitters wanted it placed into a species of its own. Louis Leakey was known as a splitter and had already named fossils as different species that had been discarded by the scientific community. The main difference between Homo habilis and Australopithecus africanus was the tool making and a slightly bigger brain although the teeth were similar. He popularised the search for hominins bringing many new scientists into this field of study with his unique style and enthusiasm. He furthered the research into primate behaviour by setting up the studies of Jane Goodell, Dian Fossey and Birute Galika. His enthusiasm was infectious. He traveled the world raising funds and lecturing while Mary stayed behind and carried out the research. Mary Leakey ( ) Mary was born Mary Nicol in Her father was a landscape artist and she spent much of her childhood in Europe. When she was 13 her father died and she was shattered. She moved back to England where she had trouble settling down. She was expelled from two schools and was known as a rebellious girl. She became interested in archaeology and worked as a scientific illustrator. She met Louis Leakey in 1933 and started an affair with him soon after. On his next expedition to Africa she arranged to meet him on one of the digs. Louis s wife divorced him and Mary and Louis were married in She returned to Kenya with Louis and worked on many excavations in the following decades. Her first fossil find was of an extinct primate Proconsul. In 1959 she found Zinjanthropus boisei (now Australopithecus boisei). From the mid 1960s she lived at Olduvai Gorge often by herself. She grew apart from Louis partly because of his womanising and partly because he was working on so many projects. For twenty five years she worked at Olduvai Gorge with Louis only making occasional visits. In 1974 she excavated near Laetoli and in 1978 her team discovered a footprint track left by two bipedal hominins. The footprints gave a glimpse into the life of Australopithecus afarensis 3.2 million years ago. In 1983 she retired from active fieldwork. She died in Although she never achieved any academic degrees her work was recognised as outstanding and she is known as a better scientist than her husband because of her perseverance and meticulous care. She set new standards in the study of pre history with her rigorous approach. She was intensely focussed and diligent. Her major discoveries were the early ape Proconsul, the skull of Australopithecus boisei and the Laetoli footprints. Part 3: The hominin debate 35

38 Richard Leakey (1944 ) Richard was the second son of Louis and Mary Leakey. At an early age he decided not to follow in the footsteps of his parents and he dropped out of high school. He started a safari business and learnt how to fly. In 1964 he led an expedition to an area that he had observed from the air. He realised that fossil hunting was in his blood. In 1966 he married another fossil hunter, Margaret Cropper who had worked with the Leakey family. In 1968 he was appointed director of the National Museum of Kenya. He started looking for fossils in the Lake Rudolf area (now Lake Turkana). The expedition was a success and many fossils were found including Homo habilis and Homo erectus. In 1969 his wife had a daughter and later that year they divorced. The following year he married Maeve Epps, a zoologist. In 1969 he was diagnosed with terminal kidney disease. His younger brother Philip donated one of his kidneys to save his brother. Richard nearly died at this stage but recovered after eight months of near death illness. In 1984 Richard s team discovered the most impressive fossil, Turkana boy, this fossil is nearly a complete skeleton of Home ergaster. The following year another major find was made the first skull of a new species Australopithecus aethiopicus. From 1989 to 1994 Richard took up the fight against elephant and rhino poachers. In 1997 he was elected in the Kenyan parliament. In 1993 he had a crash in his plane. At the time he was campaigning against poachers and there is some suspicion that the malfunction of his plane was an attempt to silence him. He was badly injured in the accident and had both legs amputated below the knees. His wife, Maeve, continues the family tradition. In 1995 she described a new species Australopithecus anamensis and in 2001 she announced another species Kenyathropus platyops. The tradition of the Leakey name lives on. 36 The human story

39 Gill Sans Bold The table below outlines the events of the Leakey family history. Year Event 1933 Louis and Mary meet Richard is born in Kenya 1959 Mary finds Zinjanthropus (Australopithecus boisei) 1964 Louis finds Homo habilis the tool maker 1972 Richard finds 1.8 million year old skull and Louis dies a few days later 1978 Mary reveals Laetoli footprints (Australopithecus afarensis) 1984 Turkana boy (Homo ergaster) is found, Mary retires 1985 Black skull at Lake Turkana (Australopithecus aethiopicus) 1989 Richard enters wildlife conservation 1993 Richard loses both legs in a plane crash 1995 Maeve Leakey announces new species Australopithecus anamensis 1996 Mary dies at Maeve Leakey announces new species Kenyathropus platyops There are many sites that deal with the Leakey family. Access them through Use your local library, CD ROMs or the Internet to assess the contribution of the Leakey family to our increased knowledge of hominin evolution. Do Exercise 3.3 now Part 3: The hominin debate 37

40 Alternative models of human evolution As each new fossil hominin is discovered, the debate on the evolution of humans is rekindled. Depending on which classification system you use and whether you are a lumper or a splitter, there are between eight and eighteen species amongst the fossil hominins. The evidence is open to different interpretations. As new evidence is found researchers can refine or change their ideas on human evolution. Below is a table of alternative names that show the same fossil with different names. Australopithecus ramidus Australopithecus robustus Australopithecus boisei Ardipithecus ramidus Paranthropus robustus Zinzanthropus boisei Paranthropus boisei Paranthropus aethiopicus Homo habilis Homo erectus Archaic Homo sapiens Homo sapiens neanderthalensis Homo sapiens sapiens Homo rudolfensis Homo ergaster Homo heidelbergensis Homo neanderthalensis Homo sapiens Table of alternative names. Some anthropologists believe that all of the hominins may have been on a direct line or there may have been branches that led to extinction. Others think that there were two or three parallel lines of evolution with only one leading directly to modern humans. Some of the scientists want them to group together the fossil hominins others want each new find to be a separate species. Below is a collection of family trees for hominins. These are arranged chronologically and show the changes that have occurred as each new fossil was discovered. 38 The human story

41 Gill Sans Bold recent Homo sapiens Homo sapiens Homo sapiens Homo sapiens Homo sapiens yrs yrs upper Pleistocene yrs yrs middle Pleistocene yrs yrs lower Pleistocene 1.8 million yrs 2 million yrs Pliocene 5 million yrs Miocene 22 million yrs Homo neanderthal Homo erectus Homo habilis Homo erectus Homo neanderthal Homo erectus Australopithecus Australopithecus Homo habilis Australopithecus Homo habilis Australopithecus Ramapithecus Ramapithecus Ramapithecus Homo neanderthal Homo erectus Homo erectus Homo habilis?1420 Ramapithecus Le Gros Clark Napier Brace Louis Leakey Richard Leakey Different family trees devised for hominins. Australopithecus Often the fossils found in different layers in the same area will have a variety of form, sizes and shapes. There is sexual dimorphism between the sexes of the same species. This leads to different interpretations. There is some general agreement about the evolutionary progression from a species of Australopithecus to Homo habilis to Homo erectus. In this progression brains become larger, faces shortened, the teeth become smaller and bipedal walking increased. Below are three views about the relationship of Australopithecus and its evolution into the genus Homo Homo P. boisei P. robustus Homo P. boisei P. robustus Homo P. boisei P. robustus Millions of years ago (a) A. afarensis A. africanus A. africanus (b) A. afarensis a) Australopithecus afarensis is the common ancestor of two lineages, one that leads to the Homo habilis branch and the other to the rest of Australopithecus and Paranthropus. b) Australopithecus afarensis was the ancestor of Australopithecus africanus which then gave rise to the Homo line and the rest of the Australopithecines Part 3: The hominin debate 39? A. africanus? (c) A. afarensis

42 c) A common ancestor gave rise to Australopithecus afarensis and Australopithecus africanus. The Australopithecus afarensis line evolved into the genus Paranthropus while an intermediate ancestor Australopithecus afarensis and Australopithecus africanus became the genus Homo. Different theories On a broader view there are several different theories on the shape of the hominin tree. Below are three diagrams of well known anthropologists view of the hominin family tree. 40 The human story

43 Gill Sans Bold Johanson s theory Australopithecus afarensis is the ancestor of Australopithecines and the genus Homo. The other Australopithecus and Paranthropus fossils do not lead directly to modern man. Part 3: The hominin debate 41

44 Leakey's theory Richard Leakey's theory is that the Australopithecines and Homo have a different ancestor. In Leakey's view the missing link is still to be found and is further back in time. 42 The human story

45 Gill Sans Bold Tattersall s theory The emergence of Homo sapiens has not been a single transformation of one species into another but a meandering path with extinctions that led nowhere. The robust australopithecines were a separate branch as was Homo erectus and Homo neanderthalensis. Part 3: The hominin debate 43

46 There is a collection of cut out cards in the Additional resources. Each card is one of the species that you have to include in your study of hominins. Cut these out and them use them to form alternative theories of hominin evolution such as Johanson, Tattersall and Leakey shown in the information above. When you have finished making the trees keep these cards as a handy study item for revision. Do Exercise 3.5. You have come to the end of this part of the module. In the next part you will look at the migrations of hominins from their African origins to their present distribution, worldwide. 44 The human story

47 Gill Sans Bold Part 3: The hominin debate 45

48 Summary Evolution of hominins There has been biological evolution in the hominin line over the last five million years from Australopithecus to modern Homo sapiens. This change has included: Increased size and shape of the skull and cerebral cortex with the size of the brain going from 400 to 1600 cc. Skeletal structures have changed to allow bipedal gait and leaving the hands free to manipulate tools. The larger brain allowed the development of speech and cognitive awareness. Changes in the facial shape allowed the development of speech. Bipedal locomotion allowed the hands to be free to manipulate tools. If you were given a skull and asked to determine whether it was more human or ape like here are some features to look for. Human like features small canines, uniform teeth shortened jaw line and face no massive eyebrow ridges a nasal bridge larger brain capacity foramen magnum under the skull erect head S shaped spine, narrow pelvis locking knee joints Ape like features large canine teeth receding chin prominent eyebrow ridge small brain capacity 46 The human story foramen magnum towards the rear of the skull

49 Gill Sans Bold C shaped spine Leakey family Louis, Mary and Richard Leakey have been outstanding contributors to the study of hominins. Their finds include: Proconsul, Australopithecus boisei, Homo habilis, Homo erectus Australopithecus aethiopicus. Kenyathropus platyops Louis Leakey was also instrumental in encouraging the research into primates and in changing the view that hominins evolved in Asia. Part 3: The hominin debate 47

50 Suggested answers What is a hominin? A definition of bipedalism is walking on two feet. Quadrapedalism is walking on four feet. Anatomical feature Ape like (primitive) Human like (advanced) foramen magnum located towards the rear of the skull centrally located under the skull shape of spine C shaped S shaped big toe opposable non opposable shape of finger bones curved straight slope of the femur straight sloping inwards eyebrow ridges present reduced chin absent present jaw shape rectangular parabolic brain capacity less than 400 cc greater than 400 cc Hominin Body structure Cranial capacity (cc) Fossil age and locations Inferred culture Ardipithecus ramidus ape like body unknown eastern Africa and unknown Ethiopia 4.5 to 4.4 million years ago 48 The human story Australopithecus afarensis unknown bipedal upright t eastern Africa 4 to 3 illi

51 Gill Sans Bold posture, S shaped spine, foramen magnum pointing down 3 million years ago. Australopithecus africanus bipedal, upright, slight build Southern Africa 3 2mya Lived in groups Paranthropus robustus height 1.75m. Bony crest on skull, robust southern Africa 3 to 1 million years ago. unknown Paranthropus boisei robust, short but heavily built, sagittal crest, short legs, long arms east Africa 1.75 to 1.4 million years ago. possible stone tool user Homo habilis rounder head and smaller molars Africa 2.2 to 1.6 million years ago Oldowan tools, shelters. Homo ergaster projecting brow ridge, long limbs, tall Africa 1.7 to 1.4 million years ago. Acheulian tools. fire users Home erectus stocky, less protruding face Africa, Asia, Europe, 1.7 million to years ago Acheulian tool technology Homo heidelbergensis large Homo erectus Europe, western Asia years ago Acheulian tools Homo neanderthalensis 1.6 m tall, smaller forehead, large eyebrow ridge, little or no chin Europe, western Asia years ago Mousterian tools, burial rituals, built shelters from animal skins Homo sapiens well developed chin All over the world to present complicated tools and social structure Part 3: The hominin debate 49

52 Exercises Part 3 Exercises 3.1 to 3.4 Name: Exercise 3.1: Australopithecus a) Name two members of the Australopithecus genus. b) What is the difference between gracile and robust body structures and give an example of each type. c) What are the cranial capacities for? Ardipithecus ramidus, Australopithecus afarensis and Paranthropus robustus. d) Some Australopithcines have been placed in the separate genus Paranthropus. Why? Exercise 3.2: The genus Homo a) Brain capacity is used in the classification of hominin fossils. What is the difference between the brain capacity of Homo habilis and Homo sapiens? b) Name five members of the genus Homo and give the cranial capacity of each. 50 The human story

53 Gill Sans Bold c) Bipedalism is thought to have reduced the surface area for heat to strike the human body and increase the surface area for cooling breezes. Name another advantage of bipedalism. d) What features of a fossil would you look for to indicate that it was bipedal? e) From your graph how has the cranial capacity of fossil skulls changed? Part 3: The hominin debate 51

54 Exercise 3.3: The Leakey family a) The Leakey family is famous for the work they have done on early hominins. What contribution to the understanding of human evolution is attributed to this family? b) Name three early hominins and name the people who discovered them. 52 The human story

55 Gill Sans Bold Exercise 3.4: Alternative models of human evolution a) Different anthropologists have different views of the shape of the hominin tree. In the space below draw two different hominin family trees. State the anthropologist that put forward the theory and express your opinion on which is the most likely from the available evidence. Part 3: The hominin debate 53

56 b) Below are two different interpretations of hominin family trees. Why is it possible to draw different conclusions from the same evidence? c) Discuss the role of any two hominins in tracing evolutionary relationships. 54 The human story

57 Gill Sans Bold Part 3: The hominin debate 55

58 Additional resources Australian hominin fossils People first arrived in Australia by sea to years ago. The fossil remains that have been found show great differences and unexpected dating. The earliest remains were found at Lake Mungo in NSW and are dated at years old. The most famous skeleton of this group belongs to a skeleton known as Mungo man. This is the skeleton of a tall man. Red ochre is present in the grave suggesting the idea that the site is a ritual burial. Some researchers sat that the bones of Mungo man are gracile and share features with fossils from China. Another type of fossil hominin comes from Kow swamp in Victoria. These fossils are robust and share features with fossils found in Indonesia. They have large heads with thick bones with prominent brow ridges and flat foreheads. It is possible that there was more than one migration into Australia and the present population is a result of the interbreeding between these two populations. 56 The human story

59 Gill Sans Bold This article comes from the magazine New Scientist. This is a respectable scientific magazine. Each article has been peer reviewed and is a good source of secondary material. The human story Ann and Patrick Fullick Humans could justifiably be called the most successful of all living organisms. We have colonised every continent, and our technology, cultures, communication skills and use of world resources make us appear very different from the rest of the animal world. Yet we have a remarkable biological similarity to our nearest living relatives, the chimpanzees. No one knows for certain when our lines diverged the evidence is hard to find and difficult to interpret, so models of human evolution are constantly disputed and altered. In 1859, Charles Darwin s book On the Origin of Species made the idea of ape ancestry a compelling scientific hypothesis. Since then, many hundreds of fossils and many tens of thousands of stone tools have been found to prove that Darwin s theory applies to humans. The prehistoric evidence as well as comparisons between living humans and other animals, and the study of human culture tell us more each day about the path we trod between the African forest and modern life. Humans are mammals, just like horses, mice and dolphins. More precisely, we are primates, a group of mammals that first appeared more than 60 million years ago and which includes the lemurs, monkeys and apes. Primates are especially good at surviving in the trees. Climbing and running through branches requires dexterity, good eyesight and excellent judgment a fall from a tree can be fatal, and food trees and insects must be discovered, remembered, gathered and caught. Primates are well endowed with brains. They can manipulate food items with their hands. They generally give birth to only one offspring at a time, and consequently have good maternal care, which ensures a good chance that at least a couple of the low number of offspring survive to reproductive age. The primates are long lived by comparison with other mammals of similar size. Chimpanzees regularly reach their forties in captivity, while the much bigger horse is old in it s twenties. Part 3: The hominin debate 57

60 Ardipithecus ramidus Australopithecus afarensis Unknown tructure: some ape like features al capacity: unknown ons: Eastern Africa, Ethiopia. 4.4 to 4.5 mya e: Lived in groups. Body structure: Gracile, some ape like features Cranial capacity: cc Locations: Eastern Africa, Ethiopia. Age: 3 to 4 mya Culture: Possibly made and used tools. Australopithecus africanus Paranthropus robustus tructure: Small gracile type, al capacity: cc ons: Southern Africa. 2 to 3 mya e: Lived in groups. Body structure: robust, sagittal crest. Cranial capacity: cc Locations: Southern Africa Age: 1 to 4 mya Culture: Lived in groups 58 The human story

61 Gill Sans Bold Paranthropus boisei Homo habilis dy structure: Hyper robust anial capacity: cc ations: Eastern Africa e: mya ture: Possibly made and used tools. Body structure: Gracile Cranial capacity: cc Locations: Eastern and southern Africa Age: 2 to 1.6 mya Culture: Oldowan tool technology. Homo ergaster Homo erectus dy structure: Gracile anial capacity: cc ations: Africa e: 1.7 to 1.4 mya ture: Acheulian tools technology. Body structure: Stocky with a large brow ridge. Cranial capacity: cc Locations: Africa, Europe and Asia Zhoukoudian Cave, China Age: 1.7 million to 250,000 years ago Culture: Acheulian tool technology. Part 3: The hominin debate 59

62 Homo heidelbergensis Homo neanderthalensis dy structure: Large bodied. anial capacity: cc cations: Europe and western Asia e: 700,000 to 125,000 years ago. lture: Made and used tools. Body structure: Very strongly built, strong muscular body Cranial capacity: cc Locations: Europe and western Asia Age: 100,000 to 35,000 years ago. Culture: Mousterian tool technology. Buried dead. Homo sapiens dy structure: Modern human structure anial capacity: cc cations: World wide e: 130,000 to present lture: Art, burial practices, advanced tool king Cut out cards forming family tree. 60 The human story