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HBIO2 > Evolution
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Study of Hominids

  • Members of the family Hominidae
  • Key changes during evolution
    • Bipedalism
    • Increased brain size

Hominid Chronology

  • Australopithecus - 5 million yrs ago
  • Homo habilis - 2 million yrs ago
  • Homo erectus - 1.5 million yrs ago
  • Homo neanderthalensis - 400 000 yrs ago
  • Homo sapiens (modern human) - 200 000 yrs ago

Australopithecus

  • Fossils found in Africa only
  • Small brain (low cranial capacity)
  • Bipedalism
    • Footprints were found in fossils (volcanic ash)
    • Foramen magnum positioned more forward than in apes
    • Pelvic bone was shorter and broader than in apes
  • Ape-like above waist, human-like below waist (long arms compared to legs)

Homo habilis

  • Brain size was slightly larger than Australopithecus (600cm³)
  • Oldowan Tradition
    • Method used to make choppers (Homo habilis means "handy man")
    • Rock was hit against another which resulted in a sharp-edged flake
    • Allowed them to cut foods
    • Gained proteins from meat but still ate fruits and plants
  • Had opposable thumbs that allowed power and precision grips

Homo erectus

  • Travelled from Africa to Asia and Europe
  • Physical appearance
    • Large cranial capacity - almost 2x of Australopithecus (1000cm³)
    • Thick bones and strong muscles for powerful movement
  • Acheulian Tradition
    • New method used to make hand-axes
    • Allowed the production of a variety of larger tools
  • Culture
    • Home base for social interaction
    • Control of fire
    • Prolonged childhood → prolonged learning → developed simple language

Homo neanderthalensis

  • ?Not ancestors of modern humans
  • ?Became extinct due to competition with modern human
  • Physical appearance
    • Brain was larger than modern human (1450cm³) because of muscle attachments
    • Stronger muscles and larger-boned skeleton than modern human
    • Short stature and compact body conserved heat during ice age
  • Mousterian Tradition
    • Method used to make flake tools
      • Flakes were broken off from a stone core
      • Followed by refinement
      • Edges were sharpened by pressure-flaking (can be re-sharpened over time → tools last longer)
    • Other tools made: scrapers (remove waste from animal hides), notched flakes, pointed tools (spears)
    • Combined with other materials to allow a wide range of use
  • Culture
    • Build shelters (with wood, animal skin, mammoth bones)
    • Had a religion (graves)
    • Body paintings
    • Fire allowed to cook frozen meat, warm homes during ice age

Homo sapiens (modern human)

  • Physical appearance
    • Globe-shaped braincase - smaller than Neanderthals (1350cm³)
    • Flat face below the front of the braincase
    • Small brow-ridges
    • Chin
    • Lighter bones and less muscle bulk
  • Cro-Magnon tradition
    • Method used to make blade flake tools
    • This was done by indirect percussion and pressure flaking
    • Tools were used to make other tools
  • Cro-Magnon hunting
    • Spear-hunting to kill from distance
    • Harpoons-hunting to kill fish
    • Built traps
    • Language allowed group hunting
  • Culture
    • Women remained at home with children
    • Cave paintings, made sculptures, decorated tools
    • Had a religion
    • Made cloth

Evidence of diet

  • Apes ate hard food, which was tough and fibrous
    • Thick enamel
    • Microwear (large numbers of small microscopic scratches)
    • Large jaws and bony crests on skull (strong jaws with powerful muscles)
  • Canine teeth
    • NOT evidence for diet
    • Smaller teeth allowed side-to-side movements of the jaw required for chewing
    • But large canine teeth showed aggression

Cultural evolution and physical change

  • Early stone tools
    • More efficient and less physical lifestyle
    • Caused changes in skeleton (smaller and thinner bones)
  • Control of fire
    • Evidence from burned fossils (animal bones)
    • Light allowed activity at night (extends days)
    • Offered protection as animals avoid fire
    • Cooking of food → digestion requires less energy
    • Heat homes

Hunter-gather way

  • Main food source was from hunting with little or no agriculture
  • Moved on once food ran out in their area and build a new home base
  • Food was shared
    • Women and children gathered food near home (plants, fruits, nuts, mushrooms, edible roots, ...)
    • Men were hunting animals and fish in small groups

Social groups

  • The larger the brain capacity, the more energy is required
  • Meat contains most energy
  • Human female
    • Had to rely on her male partner to gather enough food
    • In return, she entered a pair-bond throughout the reproductive cycle (different in apes)
    • Both parents cared for the newborn (↑survival)
    • Care of both parents increased survival of newborn
  • Male apes
    • Not involved in the care of their offspring
    • Did not provide food for female apes

Ramapithecus

  • Features similar to humans
    • Small canines (side-to-die movement required for chewing)
    • V-shaped jaw
    • Large teeth and thick enamels (hard food)
  • Early conclusion
    • Ramapithecus and humans share common features
    • Both must have split away from gorillas and chimps a very long time ago
  • Conflicting evidence
    • Immunological studies showed
      • Humans and gorillas are very similar
      • Ramapithecus and gorillas are very different
    • Only humans must have split from gorillas and at a much earlier time
  • New conclusion
    • Small canines must have been from a female
    • Jaw was reconstructed by using bones from different specimens
    • Thick enamel is related to diet and not evidence for common ancestors
  • It was found that Ramapithecus was actually a female of the species Sivapithecus
    • Male and female had a large size difference
    • Evolved after orang-utan line split from gorilla and chimp line