Applied Science Unit. Lecture 2. Human Evolution

Human Evolution - Historical Perspective (50 years ago)

Human Evolution - Historical Developments

  • Piltdown Man

    • Discovery: 1912 in England

    • Significance: Initially thought to be the missing link; featured large brain with ape-like jaw/teeth

    • Composition: Composite of orangutan jaw and modern human skull; lacked proper articulation which would have revealed it as a fake

    • Implications: Combination of modern ape and human material buried with actual ancient fossils, misleading the understanding of human evolution

The Beginning of Human Evolution

  • Timeframe: Approximately 10 million years ago in Africa

  • Climatic changes: Transition from undifferentiated tropical forests to a mixture of woodland and savanna, causing evolutionary pressures

Evolutionary Pathways

  • Most Recent Common Ancestor (MRCA)

    • Timeframe: Approximately 7 million years ago (mya)

    • Closest living relative: Chimpanzees

    • Geographical significance: Most human species have been named from Africa, aligning with Charles Darwin's predictions about the origin of the genus Homo and species H. sapiens

Evolutionary Split of Primates

  • Timeline: Sometime around 7 mybp, distinct evolutionary paths emerged for East African primates versus Central and West African primates

  • Environmental context: West Africa was primarily wooded while East Africa had more open environments, likely leading to bipedalism in East African primates

  • Theories on Bipedalism Emergence:

    • Carrying offspring?

    • Tool-making development?

    • Thermoregulation advantages?

    • Aquatic foraging behavior?

    • Predator avoidance strategies?

    • Enhanced locomotor efficiency?

Earliest Hominins: Pre-Australopiths

  • Sahelanthropus tchadensis

    • Known as Toumai, which means "hope of life" in Goran

    • Discovery: 2002 by Michel Brunet, single skull, jaw fragments, and several teeth found in Chad

    • Dating: Approximately 6.5 mybp

    • Morphological trait: Forward-positioned foramen magnum, indicating bipedalism

  • Orrorin tugenensis

    • Meaning: "original man" in local Tugen language

    • Discovery: February 2001 by French researcher Brigitte Senut, involving a few teeth and limb bone fragments in Tugen Hills, Kenya

    • Dating: Approximately 6 mybp

    • Morphological trait: Valgus angle of femur suggests bipedalism

  • Ardipithecus kadabba

    • Discovery: Found in Middle Awash region of Ethiopia

    • Dating: Approximately 5.5 mybp

    • Evidence: Morphological features indicating bipedalism

  • Ardipithecus ramidus (Ardi)

    • Dating: Between 5-4.4 mybp

    • Habitat: Forest-dwelling; characteristics indicating ability to be bipedal but also adapted for tree-climbing

    • Evidence: Based on pelvis bones showing adaptations for climbing

Earliest Hominins: Australopiths

  • Australopithecus anamensis

    • Discovery: First uncovered in 1995, Northern Kenya

    • Dating: Between 4.2 and 3.9 mybp

    • Ancestry: Likely descendant from a knuckle-walking ancestor

  • Australopithecus afarensis (Lucy)

    • Discovery: Mid-1970s by Donald Johanson

    • Dating: Approximately 3.3 mybp

    • Notable finds: "Lucy’s child" discovered in Dikika, Ethiopia, estimated to be around 3 years of age

    • Morphological traits: Unquestionably bipedal with some adaptations for climbing; stature approximately 3-4 feet tall, significant sexual dimorphism