Human Evolution

  1. Introduction
    1. Much of this lecture is from Lucy: the Beginnings of Humankind by Donald Johanson and Maitland Edey.
    2. Another good text is: From Lucy to Language by Donald Johanson and Blake Edgar
  2. Most Controversial part of  evolutionary biology is the evolution of humans
    1. Evolution applies to humans - Darwin hinted at it in the Origin of  Species and later wrote a whole book on it

1.        If evolution works in other animals it certainly works in humans - what applies to moths applies to humans

2.        Scientific Controversy

a.        Each new fossil creates a revision of the story

b.       Not all of the information is now known by any means

3.        Causes of  human evolution

a.        Allopatric speciation

b.       Changes in climate and environment

  1. Trends in human evolution - start with tree-dwelling (arboreal) ancestor
    1. Hand and Arm

1.        Arm is undifferentiated - in contrast with most other mammals (for example the horse)

2.        The hand of primate has an opposable thumb - allows animal to grab branches in the trees

    1. Vision

1.        Color vision - tree dweller who eats fruit - need color vision to see fruit

a.        Contrast with dogs and cats - no color vision - they have better vision in dim light

b.       Steroscopic vision - both eyes directed forward

1.        Better able to judge distances in trees

    1. Care of  young

1.        Increases in primates

    1. Larger brain

1.        Coordinate arboreal existence

2.        Forces longer care of young in humans

3.        Learn how to behave in society

    1. Upright posture

1.        Uniquely human

2.        Plays a big role in human evolution

  1. Fossils and Human Evolution
    1. Starts with insectivores - like shrews - 200 million years ago

1.        Earliest mammals were insectivores

2.        Small - lived alongside dinosaurs

3.        Origin of whole mammalian stock

    1. Some insectivores were arboreal - tree shrews
    2. Dinosaurs disappeared - why? - we don't really know
    3. Prosimians - lemurs etc. - nocturnal

1.        Became common just after the loss of dinosaurs

2.        Lemurs still live on Madagascar

3.        54 to 38 million years ago

    1. Anthropoids branched off from prosimian line

1.        Monkeys and apes

    1. Miocene Apes

1.        During Miocene times there was a broad band of rainforest (jungle) from Zaire to Indonesia

2.        There was a high diversity of monkeys and apes in this forest

a.        We know them from fossils

3.        This forest was a paradise for monkeys and apes – for arboreal primates you need a big forest

4.        At the close of the Miocene the climate got drier

a.        The result is a contraction of the forest

b.       There is a long blank period in the fossil record from 10 to 3.5. million years ago

    1. The first discoveries of human-like creatures occurred in Ethiopia and northern Kenya

1.        Australopithecus afarensis

a. This is a small ape-like creature

     b. It has upright walking  like modern humans

1.        Known from skeleton

2.        Footprints

     c. Evolution of upright posture was a result of the spread of grassland - ground-dwelling ape

1.        Baboons develop a ground-dwelling habit at the same time

    d. Other apes remained in the forest - gibbons, gorilla, chimps and organ outang

    1. In Kenya and Southern Arica

1.        Homo habilis

a.        First tool maker - small pebble tools

b.       Probably a hunter

c.        Discovered by Louis Leakey

2.        Australopitehcus africanus and robustus - pebble tools also

a.        Plant eaters

b.       A. robustus probably ate roos and nuts - teeth adapted for chewing cellulosic material

c.        Both extinct around 1 million years ago

3.        Homo erectus

a.        Brain capacity bigger than Australopithecus but smaller than us

b.       Fossils all over Europe, Asia and Africa

c.        Hand axes

d.       Cooperative hunting

e.        Used fire in China - Choukoutien cave

f.         It is not known if  Homo erectus had language

4.        Homo sapiens - our species

a.        Earliest fossils about 250,000 years ago

b.       It is not clear how Homo sapiens replace Homo erecuts but it eventually happened worldwide

c.        Bigger brain capacity than any other homonid

d.       There is a big gap in the fossils to 80,000 years ago

1.        Neanderthal man - Homo neanderthalensis

a.        It is unclear exactly what this is - is it a variety of Homo sapiens or is it a new species?

b.       Common in Europe and SW Asia (middle East)

c.        Heavier skull and bigger brain than us

d.       Buried dead, wore clothes and made flake tools

e.        It is unknown whether  H. neanderthalensis had language

2.        Homo sapiens replaces H. neanderthalensis in Europe between 30,000 and 40,000 years ago

a.        Cro-Magnon man

b.       Had better tools than H. neanderthalensis

c.        Cave drawings - Altamira and Lescaux in the Pyrenees - the beginning of art

d.       These people had a spiritual life

3.        Some investigators suggest that H. neanderthalensis was an evolutionary adaptation to ice-age climates 

a.        Other suggest that H. neanderthalensis was a different species from us

b.       There is a suggestion that H. sapiens moved in on H. neanderthalensis and killed them off

4.        Shifting climates - allow the agricultural revolution

a.        Modern humans are the product of the last ice age

5.        H. sapiens colonized the world from  its origins in Africa

a.        We arrived in North America about 10,000 years ago

b.       We arrived in New Zealand and Hawaii about 2,000 years ago

i. Humans are a product of evolution just like any other animal