Human evolution

This section examines the evolution of the Homo sapiens by looking at how this modern species is classified. By observing what adaptations have been developed over time through the examination of the evolution of unsuccessful species that previously roamed the Earth provides us with information as to what structural features we have today enable us to live the way we do.  Homo sapiens are classified as mammals, primates, hominoids, hominids and hominins; below discusses the features of these classification groups.

Mammal features

  • three bones in middle ear
  • diaphragm separating chest cavity from abdomen
  • fur or hair on body surface
  • denature including incisors, canines, molars and premolars
  • mammary glands
  • lower jaw made from a single bone

Primates

Features

  • five digits that can grasp and curl
  • opposable thumbs and big toes
  • flat nails with touch receptors on many digits
  • large forward facing eyes
  • 3D colour vision
  • protective bone on eye socket
  • flexible skeletons, with the ability to rotate arms in shoulder sockets and allow extension
  • large brains
  • long gestation periods typically single offspring per pregnancy

Living primate groups

  • prosmians, including bush babies, tarsiers and lemurs
  • new world monkeys, including flat-nosed South American monkeys
  • old world monkeys, including downward-nosed African and Asian monkeys
  • apes, which are characterised by a broad chest and no tail

Hominoids, Hominids and Hominins

Hominoids include all apes, both greater and lesser apes (including gibbons, orangutans, gorillas, chimpanzees and humans).

Hominids include all great apes (including orangutans, gorillas, chimpanzees and humans).

Hominins are all bipedal species, including humans and their extinct ancestors.

Adaptations

Over time, lots of changes occurred as the species changed from being ape-like to being human.

Bipedal adaptations

  • curvature of the spine to better bear weight when standing
  • shorter and broadened (bowl shaped) pelvis
  • longer legs and shorter arms
  • position of the foreman magnum has moved to the centre of the skull rather than at the back
  • alignment of the big toe with the other toes

Skull adaptations

  • jaw more curved and parabolic rather than box-shaped
  • reduction of size in the front teeth
  • loss of bony ridges around the eyes
  • larger brain case size
  • flatter faces

Notable hominin species

Australopithecus afarensis

  • existed 4 to 3 million years ago
  • features:
    • small brain
    • prominent brow ridges
    • large jaw and canines
    • limb proportions were more similar to apes than modern humans

Australopithecus africanus

  • existed 3 to 2.1 mya
  • features:
    • distinctly human hands and teeth
    • limb proportions more similar to modern humans than apes

Homo habilis

  • existed 2.3 to 1.6 mya
  • features:
    • large brains
    • small teeth
    • limb proportions more similar to apes
    • used tools

Homo erectus

  • existed 1.8 million to  300 000 years ago.
  • first species to migrate out of Africa.
  • features:
    • large brains, with faces and skulls different to modern humans
    • skeleton similar to humans
    • advanced tool making skills

Homo neanderthalensis

  • existed 200 000 to 36 000 years ago
  • coexisted with Homo sapiens
  • features:
    • large brains
    • sloping foreheads, prominent brow ridges and large chins
    • heavily built
    • advanced social culture (renowned for burying the dead)

Homo sapiens

  • complex behavioural and communication patterns
  • S-shaped spine that allows for bipedalism and adds balance
  • foremen magnum at the skull base
  • arched feet for striding
  • less pronounced brow ridges
  • bowl shaped pelvis

See also