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9.8 Option- The Human Story: 3. The hominid debate

Syllabus reference (October 2002 version)
3. Debate continues on the relationships between hominid species	Students 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 compare the above species, including comparisons of: body structure cranial capacity fossil ages and regional locations cranial capacity inferred culture outline and examine the evidence for the pattern of human migration based on: the ‘Out of Africa’ model the theory of regional continuity (multi-regional hypothesis	Students: gather, process, present and analyse information to provide an overview of the similarities and differences of any two species used 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 human evolution: the Leakey family Johanson Broom Tobias Dart Goodall gather and process information from secondary sources to analyse and evaluate the evidence for two different models of human evolution

Extract from Biology Stage 6 Syllabus (Amended October 2002). © Board of Studies, NSW
[Edit:16 June 09]

Prior learning: Recall statements in HSC module 9.3 (subsection 1).
Science Stages 4–5 syllabus: Outcome 5.8 (content 5.8.3 a, b).

Background information:
Hominids (using the more traditional definition of the term- see 9.8.1)are animals that walk upright on two feet (bipedal) and have characteristics that are more human than ape-like. Today there is only one living hominid, Homo sapiens. In the past however, there were several species of hominids often living in close proximity to each other.

gather, process, present and analyse information to provide an overview of the similarities and differences of any two species used in tracing evolutionary relationships

• Gather information taking care to collect data efficiently. You will find that different sources have different points of view. This is true especially with the age of fossil finds and the size of the cranial capacity. The books listed below and webpages are a good starting point. The Australian Museum has a collection of exhibits on this subject. Some useful links are:
  Hominid timeline Washington State University, USA.
  Prominent hominid fossils Talkorigins.
  The evolution of man Hooper Virtual Paleontological Museum. Canada.
  Human evolution link pages Indiana University, USA.
  
  Choose resources that are suitable for the investigation such as recent publications, popular press articles and the Internet.
• Process the information by looking for patterns. Write a summary of the two species chosen and in your summary comment on the similarities and differences between the two species
   
• Analyse the information once you have presented it in a table. You will find contradictions in the information from different sources. Comment on this. Two species that could be chosen are Homo neanderthalensis and Homo sapiens.
  
  These two species overlapped each other in the time scale. In some locations they were thought to live in adjacent caves. Much controversy arises from the disappearance of the Neanderthals. Were they driven to extinction by Homo sapiens or did they interbreed? The table below summarises the similarities and differences between the two species.
  
  

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

• Johanson’s theory is that Australopithecus afarensis is the ancestor of the Australopithecines and the genus Homo. The other Australopithecines and Paranthropus species do not lead directly to humans.

  

• Richard Leakey’s theory is that the Australopithecines and the Homo line are both separate and have a different ancestor that is yet to be discovered. This common ancestor would be further back in time.

  

• Tattersall’s theory is that there has not been a simple transformation of one species into the next but rather a complex meandering with many extinctions that were dead ends.

  Tattersall’s theory UNESCO.

compare the above species including comparisons of:

• body structure
  
• cranial capacity
  
• fossil ages and regional locations
  
• inferred culture
  

• Ardipithecus ramidus (also known as Australopithecus ramidus) lived in eastern Africa and the Awash Valley of Ethiopia 4.4 mya (millions of years ago). The brain size is unknown but it is thought to be close to the divergence of the African apes and humans. A small body more human than apelike. Possibly bipedal approximately 122 cm tall. The culture of the animal is unknown but it has not been found with tools. It lived on the open savannah and looking over tall grasses is thought by some to show the start of bipedalism.
   
• Australopithecus afarensis (the southern ape of Afar). The overall head shape is like an apes but with human-like thick enamel on the teeth. The dental arch is neither the U-shaped arch of apes or the parabolic shape of humans. These small intermediate hominids had a small brain but an upright posture and bipedal gait. The spine was S-shaped and the foramen magnum pointed downwards. The teeth were small and unspecialised. They ranged from 1.0 metre to 1.5 metres in height. They were sexually dimorphic with the males larger than the females. Cranial capacity was 375 to 550 cc. The were found 3 to 4 mya at Laetoli in Tanzania and Hadar in Ethiopia as well as two sites in South Africa, Sterkfontein and Makapansgat. Two famous examples of this species are ‘Lucy’ discovered by Johanson and the Laetoli footprints discovered by Mary Leakey. They were not known to use tools and lived in small groups.
   
• Paranthropus robustus (also known as Australopithecus robustus) had a larger brain and a heavier body than the previous species. They also had a large crest on the skull for the attachment of the muscles that controlled the heavy jaws. Thought to be a herbivore. The body height was 1.7 metres. The face was long flat and broad. The cranial capacity was between 450 and 550 cc. Found in southern Africa around 1-3 million years ago. They lived in groups.
   
• Paranthropus boisei (also known as Australopithecus boisei) a large robust vegetarian from East Africa originally called Zinjanthropus by Louis Leakey. Occupied Olduvai Gorge at the same time as Homo habilis. A shortened but heavily buttressed face with enormously developed chewing muscles attached to a sagittal crest. Walked upright with foramen magnum more towards the centre of the skull than Australopithecus. The legs were short and the arms were long. The cranial capacity was between 500-545 cc. The fossil age is between 1.75 to 1.4 million years ago in Kooba Fori (Kenya), Olduvai Gorge (Tanzania) and eastern Ethiopia. It was originally thought to be a toolmaker but later the tools were attributed to Homo habilis.
   
• Australopithecus africanus (the southern ape of Africa) This was one of the early hominin species from Africa to be named. Raymond Dart who named this species in 1924 from a fossil he called the ‘Taung child’. Another famous example was ‘Mrs Ples’. The species lived in southern and East Africa 3.2-2.5 million years ago. The cranial capacity was 420 to 490 cc. The build was small and they were thought to live in groups.
   
• Homo habilis was the first toolmaker. The name means 'handy man' and it is considered to be the first human. The height was 1.3 m and the animal weighed about 40 kg. The males were larger than the females. They had a rounder head with smaller molars than the previous species. They had no chin and a sloping forehead. The cranial capacity was between 500-800 cc. Their fossils have been found at Lake Turkana in East Africa, Koobi Fora (Kenya) and at Oldowan Gorge. They made and used simple tools named Oldowan technology which consisted of simple choppers. They built shelters and cooperated in groups.
   
• Homo ergaster (Turkana boy) was originally known as African Homo erectus. It was first discovered at Olduvai Gorge by Louis and Mary Leakey. Their son Richard discovered many fossils on the shores of Lake Turkana. Homo ergaster had a projecting brow ridge and the beginnings of a projecting nose. The cranium was rounded with a modern body structure but a brain still half the size of modern humans (848 - 908 cc). These hominids lived 1.7 million years ago. They made stone tools called Acheulian industry. Large flakes of stone were made into hand axes for cutting and chopping.
   
• Homo erectus was one of the first early humans to leave Africa. Their fossils are found as far away as China (Peking man) and Indonesia (Java man). They stood upright and were large brained (900 -1200 cc). They had a stocky body, a sloping forehead and large brow ridges. They lived from 1.7 million years ago until 250 000 years ago starting in East Africa and moving out in the first wave of human migration. Their stone tools were Acheulian style. They lived in caves and used fire They probably used wooden and bamboo tools as well but these have not been preserved.
   
• Homo heidelbergensis (also known as archaic Homo sapiens). They were large brained hominids that may have evolved into Neanderthals. The cranial capacity is between 1100 and 1300 cc. Fossils have been found in Europe and western Asia 500 000 years ago. They were also in Africa 600 000 years ago. They used tools and may be the inventors of the prepared core stone tools, which were more sophisticated than the previous species.
   
• Homo neanderthalensis lived at the same time as early Homo sapiens. They were a tall strongly built group with more musculature than modern humans. They had a smaller forehead with a large eyebrow ridge and more prominent jaw with little or no chin. Their cranial size was on average larger than modern humans (1400-1750 cc). They lived in Europe and western Asia. Their tool culture is known as Mousterian and was very complex including scrapers, stone knives and projectile points. They used tools crafted from bone and were hunter-gatherers. They were socially organised and dug traps, buried their dead, wore jewelery and decorated clothes. They hunted large animals such as mammoths and bears, indicating social organisation. They died out 30 000 years ago and there is some controversy about whether early Homo sapiens interbred with them or caused their extinction.
   
• Homo sapiens are the only hominins living today. The early types were called Cro magnon. Homo sapiens have a well-developed chin, no eyebrow ridges, a long narrow skull but with a wide face. The cranial capacity is between 1350 - 1500 cc. The foramen magnum is centred, the legs are longer than the arms, teeth are small and unspecialised. Fossils are found in East Africa and then throughout the rest of the world. The culture is sophisticated with many tools and examples of art. The social structure is complex.
   
  The table below summarises this information:
   
  

  Hominid	Body structure	Cranial capacity (cc)	Fossil age and locations	Inferred culture
  Ardipithecus ramidus	ape-like body	unknown	Eastern Africa and Ethiopia 4.5 to 4.4 million years ago	unknown
  Australopithecus afarensis	bipedal upright posture, S-shaped spine, foramen magnum is centred under the skull	420-490	Eastern Africa 4 to 3 million years ago.	unknown
  Paranthropus robustus	height 1.75m. Bony crest on skull, robust	450-550	Southern Africa 3 to 1 million years ago.	unknown
  Paranthropus boisei	robust, short but heavily built, sagittal crest, short legs, long arms	500-545	East Africa 1.75 to 1.4 million years ago.	possible stone tool user
  Australopithecus africanus	Slender built	420 to 490	Southern and East Africa 3.2 to 2.5 million years ago	lived in groups
  Homo habilis	rounder head and smaller molars	500-800	Africa 2.2 to 1.6 million years ago	Oldowan tools, shelters.
  Homo ergaster	projecting brow ridge, long limbs, tall	848-908	Africa 1.7 to 1.4 million years ago.	Acheulian tools. fire-users
  Home erectus	stocky, less protruding face	900-1200	Africa, Asia, Europe, 1.7 million to 250 000 years ago	Acheulian tool technology
  Homo heidelbergensis	slender build, double arched brow ridge, slight mid-face projection	1100-1300	Europe, western Asia 500 000–125 000 years ago	Acheulian tools
  Homo neanderthalensis	1.6 m tall, smaller forehead, large eyebrow ridge, little or no chin	1400-1750	Europe, western Asia 200 000–30 000 years ago	Mousterian tools, burial rituals, built shelters from animal skins
  Homo sapiens	well developed chin	1350-1500	All over the world 130 000 to present day.	complicated tools and social structure

 

process secondary information and use available evidence to assess the contribution of one of the following to our increased understanding of human evolution:

• the Leakey family
  
• Johanson
  
• Broom
  
• Tobias
  
• Dart
  
• Goodall

• You only have to choose one of the above scientists. Some suggested webpages are given to start you on your research.
  
  Louis Leakey Lucid Interactive
  Mary Leakey Talk Origins
  Richard Leakey Talk Origins
  Leakey family Time Magazine, includes audio of Richard Leakey.
  The Leakey Foundation
  All of the anthropologists Minnesota University
   
• Process the information by assessing the reliability of the information by considering information from different sources.
   
• Use the available evidence to show progression of ideas.

The Leakey family is summarised below as a model.

The Leakey family
No other family has had such an influence on a field of scientific study as the Leakey family. Louis his second wife Mary, their son Richard and Richard’s second wife Maeve have all made outstanding contributions to the study of the evolution of humans. More recently the next generation in the form of Louise Leakey (the daughter of Richard and Maeve) has begun to work in the field of anthropology. The Leakey family finds include Proconsul, Australopithecus boisei, Homo habilis, Homo erectus, Australopithecus anamensis and Australopithecus aethiopicus.

The table below summarises their contribution.

Year	Event
1933	Louis and Mary meet.
1959	Mary finds Zinjanthropus (Australopithecus boisei)
1964	Louis finds the tool-maker, Homo habilis
1972	Richard finds a 1.8 million year old Homo habilis skull
1978	Mary announces Laetoli footprints (Austraopithecus afarensis)
1984	Kamoya Kimeu, a member of Richard’s team finds Turkana boy (Homo ergaster)
1985	Richard discovers Black skull (Australopithecus [or Paranthropus] aethiopicus)at Lake Turkana with Alan Walker
1989	Richard enters wildlife conservation
1995	Maeve Leakey announces new species Australopithecus anamensis
1999	Maeve Leakey discovers a new genus Kenyanthropus platyops

Louis Leakey was also known for encouraging the research into primates by Jane Goodall, Dian Fossey and Birute Galika and in changing the view that hominids evolved in Asia.

gather and process information from secondary sources to analyse and evaluate the evidence for two different models of human evolution

• Gather information from a range of resources including popular scientific journals and the Internet. Some starting points are given below. Look for two alternative models of human evolution.

Books:
Lewin, R. (1993.) The Origin of Modern Humans. Scientific American LIBRARY NY
Parker, S. (1992.) The Dawn of Man. New Burlington Books. London.
Jones, Steve, R.D. Martin and David Pilbeam. (1992.) The Cambridge Encyclopaedia of Human Evolution. New York. Cambridge University Press.
Tattersall, Ian. (1993.) The Human Odyssey. Prentice-Hall.
Tattersall, Ian. (1995.) The Last Neanderthal. MacMillan. USA

Webpages:
Tattersall’s theory UNESCO
What makes us human? Smithsonian Institute

• When you have enough information process it by organising the information from the two models in such a way that they can be compared. You might have two columns with each model as headings and aspects to compare on the left hand side.

• Analyse the information in the table and any other information you have. Weigh up the strengths and weaknesses of each of the models. Are more gaps necessarily a bad thing?
   
• In your opinion is one model more credible than the other? Give reasons for your decision.
   
• Analyse and evaluate alternative models and look for contradictions such as different naming systems between the different models. Older models of evolution had a straight line of evolution between extinct apes and modern humans. The evidence from fossils is that there were many dead ends and extinctions in hominid evolution. At various times in the past there were more than one species living in an area at the same time. This means that there could not have been a straight line of evolution. When evaluating the evidence for different models of hominid evolution make sure that the information is recent and takes into account the latest finds.
   
• Use a search engine such as Google using search terms such as hominid + evolution. You could also search hominin as some web sites use this term. (See The Human Story, 1 for an explanation of the differences between hominid and hominin.)

outline and examine the evidence for the pattern of human migration based on

• the ‘Out of Africa’ model
  
• the theory of regional continuity (multi-regional hypothesis)

• Anthropologists agree that human origins came from Africa. The oldest hominid fossils are found there. Homo erectus spread throughout the world travelling through Europe and into Asia.
   
• The ‘Out of Africa’ model proposes a more recent African origin of modern humans who replaced the existing Neanderthals and other archaic species of hominins. This was the second time that hominins had migrated from Africa and this time they were the modern species Homo sapiens.
   
• The ‘Out of Africa’ theory is a replacement theory where one species was replaced by the modern humans coming out of Africa. This means that any racial differences must have occurred at a later time. The evidence for this theory comes from the fossil and genetic evidence.
   
• The fossil evidence is stronger for the ‘Out of Africa’ model than for the regional continuity theory. The oldest fossil of Homo sapiens has been found in Africa. In Africa there are transitional fossils between pre- modern (archaic) and modern types. This suggests that humans evolved in Africa.
   
• The genetic evidence for the ‘Out of Africa’ model first came from the University of California in Berkeley in the 1980’s. By mapping the mitochondrial DNA (mtDNA) and then comparing the results from different groups of humans throughout the world it is possible to work out the relationships between the groups. The small number of genes in the mitochondria makes it easier to map than the entire nuclear genome. Over time mutations occur causing changes to the sequence of the DNA. The more similar the mtDNA the closer the relationship between the groups. If the mutations that occur are regular, then a ‘molecular clock’ can been used to work out when groups last shared a common ancestor. Mitochondria have a maternal pattern of inheritance. This is because at fertilisation the egg cell (ovum) provides the mitochondria. If a mother has no female offspring then that line of descent would disappear. Over time and by chance, the lineage can be traced back to one woman. This has been tracked back to a hypothetical woman who lived in Africa and is known as ’Mitochondrial Eve.’
   
• More genetic evidence comes from tracing the genetic diversity of populations. The populations in Africa have the greatest genetic diversity. This requires a longer time to occur and supports the ‘Out of Africa’ model.
   
• The regional continuity theory states that there was local evolution in different regions from Homo erectus to Homo sapiens. This occurred simultaneously many times all over the world and in each region. Interbreeding occurred between the regions to maintain an interbreeding species but not enough to eliminate regional differences. Each regional group of Homo erectus developed into that region's Homo sapiens. Modern Chinese developed from the group of Homo erectus living in China.
   
• Evidence for this comes from the Zhoukoudian caves near Beijing and from locations in Java and in Australia. In northern Asia features of modern human skulls including face shape, cheekbones and shovel-shaped incisors can be traced back to the Peking man specimens from China. The fossils from Java can be arranged in a sequence with no evidence of African migration. Early Australian fossil hominids show that there were several migrations of humans into Australia. These occurred when the sea level was lower than today forming land bridges. Some of the Australian fossils show similarities to the fossils from China (Lake Mungo fossils) and others are more similar to the fossils from Indonesia (Kow swamp fossils). This is still controversial.
   
• Comparison of the evidence for each model: For ‘Out of Africa’ to be correct then anatomically modern humans should appear in Africa earlier than elsewhere, transitional fossils from archaic humans to modern humans should only occur in Africa, and there should be no regional continuity of features from ancient to modern humans outside of Africa. For the regional continuity theory to be supported then modern humans will appear throughout the world at the same time, transitional fossils should be found everywhere. Continuity of anatomy from ancient to modern forms should be clear.

An interesting website with documentaries is The Institute of Human Origins . You can click on different topics such as Evidence, Anatomy, Lineages and Culture. You will need macromedia Flash to view the documentaries.

You can also get very valuable information from The Talk.Origins Archive , maintained by Jim Foley, USA.