Achievement Standard 90713: Describe trends in human evolution

This is the AS and links to past papers. When I have time to put some notes up I will move this to a separate page as I have done with other standards.
Copy of this page with links to Wikipedia articles
Describe/Explain/Discuss trends in human evolution

1 Trends refers to progressive change over a period of time in relation to:
  • human biological evolution
  • human cultural evolution
  • patterns of dispersal of hominins. The term hominins refers to living and fossil species belonging to the human lineage. This is a subgroup of hominids which includes both humans and the great apes.

2 Trends in human biological evolution begin with early bipedal hominins and may require comparison with living hominids (apes). Trends are limited to:
  • skeletal changes linked to bipedalism
  • changes in skull and endocranial features
  • changes in the manipulative ability of the hand.

3 Trends in human cultural evolution will be limited to evidence relating to:
  • use of tools (stone, wood, bone), fire, shelter, clothing, abstract thought (communication, language, art), food-gathering, and domestication of plants and animals.

4 Interpretations on the origins and trends of human evolution will be based on current evidence and may change as a result of recent developments.
5 Evidence relating to human evolution must be scientific evidence which is widely accepted and presented in peer-reviewed scientific journals.
6 Terms
  • Describe requires the student to define, use annotated diagrams, give characteristics of, or an account of.
  • Explain requires the student to provide a reason as to how or why something occurs.
  • Discuss requires the student to show understanding by linking biological ideas related to the trends in human evolution. It may involve students in justifying, relating, evaluating, comparing and contrasting, and analysing.

Links to past papers
2007 Exam paper marking
2006 Exam paper marking
2005 Exam paper marking
2004 Exam paper marking


Human Biological evolution


Introduction

Humans are mammals. We belong to the mammal group called primates. The primates are placental mammals (marsupials and monotremes are a more primitive group without a placenta). They first evolved about 100 million years ago in the Cretaceous. The most primitive primates resemble modern bushbabies or tarsiers. The most primitive primates are called prosimians and include lemurs.
All primitive primates are aboreal and have adaptations for this including binocular vision and prehensile hands, feet and, occasionally, tails.
  • Binocular vision: eyes with overlapping visual field; provides depth perception for accurate jumping to trees or catching prey
  • Prehensile means grasping, a common adaptation in climbing animals
The next group of primates to appear were the simians, or monkeys. A group of these managed to migrate to South America and became the “new world” monkeys; the other ones are known as old world monkeys.

Apes
What we call 'apes' are a biological classification known as a 'superfamily, Hominoidea. They include gibbons and some other tail-less primates. However, the group that concerns us is the family Hominidae, or great apes, which includes chimpanzees, gorillas, orangutans and humans among living species.
Apes and monkeyes

Bipedalism

This means walking on two legs.

Reason for bipedal gait:

  • More energy efficient for moving over the ground (as forest cover became discontinuous)
  • Can carry things – arms no longer needed for support, so free to hold things while walking. Hands freed for other tasks.
  • Able to see further over the grass – spot predators, possible food sources e.g. vultures (indicating carcasses for scavenging)

How it might have evolved:

  • Possibly started from walking along branches
  • Became an advantage as forest cover lost (rise of Himalayas, drying out)

Physical changes associated with bipedal gait:

  • Spine – straighten
  • Point of attachment of spine to skull (foramen magnum) moves to allow head to balance on the spine when erect
  • Hips flatten to become weight bearing – have to hold up the torso
  • ‘foot thumb’ moves to front of foot to prevent injury and improve balance and gait
  • legs develop ability to 'lock' straight - stand without undue muscular effort (walking upright with bent legs very difficult)

Bipedal gait was probably also important for two other aspects of hominin development towards H. sapiens.:
  • freeing up the arms and hands eventually led to the extension of the rudimentary tool-use of early apes (still used by chimps) to the use of modified tools - for example, hand axes. However, it was not until later that they started carrying the tools around with them
  • the modifications to the chest muscles once knuckle walking ceased to be common allowed for more breath control, which led eventually to speech
  • the first bipedal hominin was probably Australopithecus afarensis. They were probably stilll partly aboreal. The first tool users were probably Homo habilis.

Grasping ability

The ability to grasp originally developed in primates to facilitate climbing. Monkeys and chimps have opposable thumbs on both hands and feet. The branch-grasping ability is described as prehensile. Some monkeys also have a prehensile tail which can act as a 5th limb.
Something that evolves for one purpose can be used for another. For example, feathers probably developed for insulation and display before they were used for flight. Primates began to use their grasping fingers for other purposes:
• Grooming: picking lice etc. out of fur. This in turn evolved into a means of reinforcing social bonds.
• Picking things up: some apes (e.g. chimps) eat some meat. They can carry their kill back to the others. Eventually, they started to use primitive tools e.g. stalks of grass to pick termites out of wood, or wads of leaves to soak water up where they can’t reach with their mouth.
When bipedalism developed, the opposable thumb on the legs became a liability. It would have been easily damaged during bipedal walking. However, it developed into a specialized organ to improve balance and walking.