Human evolution
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Human Evolution. Characteristics: Eyes in front of the face Opposable thumb Well developed brain Omnivorous. D: Eukarya K: Animalia P: Chordata C: Mammalia O: Primate. Primate Classification. The Geological Time Scale. Humans. Chimpanzees.

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Human Evolution

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Human Evolution


Eyes in front of the face

Opposable thumb

Well developed brain


D: Eukarya

K: Animalia

P: Chordata

C: Mammalia

O: Primate

Primate Classification

The Geological Time Scale



  • Fossil Patterns were used to create 5 Major Categories of Time (Eras):

    • Archaean

    • Proterozoic

    • Paleozoic

    • Mezozoic

    • Cenozoic

Types of Evolution

New species from heritable changes through time (linear)

New species from speciation events (branching)





Which pattern did human evolution follow?

Aside: Hypothesis Driven Science

  • How do you test hypotheses on the past?

    • Experimentation is not possible

  • Need to come up with hypotheses that can be tested by observations


  • Fossils

  • Biogeography

  • Comparative Morphology

  • Comparative Development

  • Comparative Biochemistry

The preserved remains or traces of organisms from the past

Found in sedimentary rock layers created by water deposition

Dated and used to determine Earth’s biological past

Over time, fossils found in stratified soil layers show consistent patterns in the diversity of living organisms


On November 30, 1974 Donald Johanson and Tom Gray discovered a remarkablycomplete hominid fossil in Hadar, Ethiopia. This fossil became known as ‘Lucy’ and was later determined (by radiometric dating) to be 3.2 million years old. This isone of the most compelling missing link fossils ever found.

Lucy was not human—clearly a different species,which was named Australopithecus afarensis—but shewas clearly hominid and very different from chimps.

Outstanding and mysterious question: what has happened to our speciessince the divergence from the lineage leading to chimpanzees?

What Makes A Hominid? - Bipedalism

  • Primary feature distinguishing hominids from other hominoids is walking erect on two legs – erect bipedalism

Why did bipedalism become the primary adaptation of hominids?

1.Carrying behavior

2. Heat stress - facilitates heat loss through convection by exposing body to air currents, only humans have sweat glands that produce moisture to cool body

3. Most energy efficient way to travel long distances

4. Allows for better vision in open environments & defensive action against predators by freeing hands to throw objects

The impressionsin the ash suggestthat weight was shifted during walkinglike a modern bipedalhuman rather than like a modernchimpanzee.

Footprints in volcanic ashat Laetoli (3.7 million years old)



Was Lucy bipedal?

Other evidence for bipedalism.

Chimp pelvis

Lucy pelvis

Angle that the femurmakes with kneealso is important, and different in bipeds thanin chimps.

This arrangement moreefficient for bipedalism.

Variation within and between species

Homo sapiens

Australopithecus afarensis

How much “normal” variation can there be within a species?

Normal % Variation

Standard Curve (Bell-shaped)


1 sd=66%

2 sd=95%


Lab Hints

“R” program for statistics is on CU Learn website

After completing one set of skull measurements, I will give you a handout with the rest

Measure facial projection with zygomatic arches parallel to the floor (skull tilt affects the measurement)

Lab report due next week

There will also be a quiz next week.

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