Evolution

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Chapter 11 Evolution
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The Big Bang Theory

• 12-15 billion years ago all matter was compressed
  into a space the size of our sun
• Sudden instantaneous distribution of matter and
  energy throughout the known universe

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Archaean Eon and Earlier

• 4.6 bya Origin of Earth
• 4.6-3.8 bya
• Formation of Earths crust, atmosphere
• Chemical and molecular evolution
• First cells (anaerobic bacteria)

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Earth Forms

• About 4.6 and 4.5 billion years ago
• Minerals and ice orbiting the sun started
  clumping together
• Heavy metals moved to Earths interior, lighter
  ones floated to surface
• Produced outer crust and inner mantle

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First Atmosphere

• Hydrogen gas
• Nitrogen
• Carbon monoxide
• Carbon dioxide
• No gaseous oxygen

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Earth Is Just Right for Life

• Smaller in diameter reduced gravity, no
  atmosphere
• Closer to sun no water
• Farther from sun water as ice

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How Did Cells Originate?

• In the first 600 million years or so of Earth
  history, enzymes, ATP, and other crucial organic
  compounds probably assembled spontaneously.

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Possible Sequence
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RNA World

• DNA is genetic material nowbut what about the
  past?
• DNA-to-RNA-to-protein system is complex
• Could RNA have been first genetic material?
• RNA can assemble spontaneously
• If true, how the switch from
• RNA to DNA might have occurred
• remains a mystery.

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The First Cells

• Originated in Archaean Eon
• Were prokaryotic heterotrophs
• Secured energy through anaerobic pathways
• No oxygen present
• Relied on glycolysis and fermentation

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Proterozoic Eon

• Origin of photosynthetic bacteria
• Oxygen accumulates in atmosphere
• Origin of aerobic respiration

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Characteristics of Animals

• Multicelled heterotrophic eukaryotes
• Require O2 for respiration
• Sexual perhaps asexual reproduction
• Motile at some stage
• Develop from embryos

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Fig. 11-01
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Earliest Primates

• Primates evolved gt60 mya during the Paleocene
• First primates resemble tree shrews
• Long snouts
• Poor daytime vision

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Fossil Records

• Much of what we know today about evoultion has
  been obtained from the fossil record.
• Although some information seems clear cut, the
  overall picture remains gray as to the ultimate
  origin of human begins.
• Rem Theory of Evolution (not the Law).

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Fig. 11-02
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Hominoids

• Apes, humans, and extinct species of their
  lineages
• In biochemistry and body form, humans are closer
  to apes than to monkeys
• Hominids
• Subgroup that includes humans and extinct
  humanlike species

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From Primates to Humans

• Homologous structures related to one another
  through common ancestry.
• Analogous structures Similar fuction, but not
  related ancestrally.
• Uniquely human traits evolved through
  modification of traits that evolved earlier, in
  ancestral forms

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Trends in Lineage Leading to Humans

• Less reliance on smell, more on vision
• Skeletal changes to allow bipedalism
• Modifications of hand to allow refined hand
  movements
• Bow-shaped jaw and smaller teeth
• Longer lifespan and longer period of dependency

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Adaptations to anArboreal Lifestyle

• During the Eocene, certain primates became
  adapted to life in trees
• Better daytime vision (binocular)
• Shorter snout
• Larger brain
• Forward-directed eyes
• Capacity for grasping motions

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Fig. 11-05
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Darwinism at Its Best
Competition for finite resources led to the
development of many traits we see today.
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Fig. 11-04b
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Monkey see
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Fig. 11-07
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Fig. 11-09
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Australopiths

• Earliest known is A. anamensis
• A. afarensis and A. africanus arose next
• All three were slightly built (gracile)
• Species that arose later, A. boisei and A.
  robustus, had heavier builds
• Exact family tree is not known

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Humans Arise

• First member of the genus Homo is H. habilis
• Lived in woodlands during late Miocene

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Homo erectus

• Evolved in Africa
• Migrated into Europe and Asia about 1.5 million -
  2 million years ago
• Had a larger brain than H. habilis
• Was a creative toolmaker
• Built fires and used furs for clothing

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Homo sapiens

• Modern man evolved by 160,000 years ago
• Had smaller teeth and jaws than H. erectus
• Facial bones were smaller, skull was larger

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Where Did H. sapiens Arise?

• Two hypotheses
• Multiregional continuity model
• African emergence model
• Both attempt to address both biochemical and
  fossil evidence

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Multiregional Continuity Model

• Argues that H. erectus migrated to many locations
  by about 1 million years ago
• Geographically separated populations gave rise to
  phenotypically different races of H. sapiens in
  different locations
• Gene flow prevented races from becoming species

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African Emergence Model

• Argues that H. sapiens arose in sub-Saharan
  Africa
• H. sapiens migrated out of Africa and into
  regions where H. erectus had preceded them
• Only after leaving Africa did phenotypic
  differences between races arise

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Earliest Fossils Are African

• Africa appears to be the cradle of human
  evolution
• No human fossils older than 1.8 million years
  exist anywhere but Africa
• Homo erectus left Africa in waves from 2 million
  to 500,000 years ago

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Neanderthal Man?

• Neanderthals (H. neaderthalensis) are 200,000
  y.o.
• Germanys Neader Valley
• Culturally advanced?
• Stone tools
• Buried dead
• May have been supplanted by
• modern humans.

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Cro-Magnon

• Oldest fossils designated as H. sapiens.
• Fossils originated in France.
• 100,000 y.o.
• Stone tools, fire, accomplished hunters
• Art was present, language unknown.

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Fig. 11-14a
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Fig. 11-14b
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Fig. 11-14c