Evolutionary Timetable

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Evolutionary Timetable

• From the beginning A quick history

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• Although anthropologists study hominids (in
  particular Homo sapiens), we must still examine
  within the context of time and evolution
• change through time.
• The human species as we know it has inhabited the
  Earth for only 2 million years, about 0.04 of
  the Earths history and 0.01 of the estimated
  history of the universe.

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• Big bang
• Was it really a bang?
• Age of the universe is thought to be around 13-19
  billion years old
• For our purposes we will say 15 billion.
• We can measure the age of the universe by
  examining the red shift.
• Current evidence suggests that the universe began
  in a single location (called singularity).

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• This speck began to expand and event called the
  Big Bang.
• Not necessarily an explosion but more like a
  balloon rapidly expanding.
• Within 3 minutes after the beginning of the Big
  Bang protons and neutrons formed and joined to
  make atomic nuclei.
• It took another 100,000 years for electrons to
  join the nuclei for form atoms.

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• By 12 bya galaxies had begun to form as gravity
  pulled matter together.
• About 5 bya the universe (as we know it) was 2/3
  present.
• 4.3 bya our solar system was formed. Earth came
  500 million years later.
• By 3.8 bya life was established.
• We know this indirectly from fossils found in
  Greenland, southern Africa, and Australia.
• About 2 bya complex single-celled organisms
  containing nuclei and organelles evolved.

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• 1.7 bya multicellular organisms first appear
• Bacteria and fungi are dating to about 1.2 bya
• About 543 mya, in the Cambrian period, complex
  multicellular organisms burst on the scene.
• This event is so sudden that it is called the
  Cambrian Explosion.
• In 5 million years all major body plans of
  multucellular animals had evolved, including
  ancestors for vertebrates.
• By 425 mya fish had evolved and plants and
  animals began to colonize the land.
• Insects appear 400 mya
• Reptiles appear 350 mya
• Mammals 256 mya

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Geological Eras

• Paleozoic
• The first vertebrates appeared 500 m.m.y.a.
• Mesozoic
• Reptiles were dominant land vertebrates.
• Placental mammals appeared 70 m.Y.A.
• Cenozoic
• Divided into two periods Tertiary and Quaternary
  and 7 epochs Paleocene, Eocene, Oligocene,
  Miocene, Pliocene, Pleistocene and Holocene.

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Geological Time Scale
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Geological Time Scale
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Drifting Continents and Mass Extinctions The
Pace of Change

• During this time, life was not the only thing
  evolving on earth.
• The earth itself was evolving as the continents
  changed shape and positions
• This is known as continental drift, which
  operates through the process of plate tectonics.
• The earth is divided into 16 plates.

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Continental Drift

• The drift of the plates across the surface of the
  earth has been going on over millions of years,
  which still changes the outward appearance of the
  earth.
• When you look at the map of the world, you see
  how well the east coast of North and South
  America fits into the west coast of Europe and
  Africa.
• Over millions of years these continents have
  slowly drifted apart.

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• By the time of the dinosaurs and early mammals,
  all the continents had drifted together to form a
  huge supercontinent we call Pangea, which
  literally means all lands.
• Around 200 mya, Pangea began to break apart.
• The resulting landmasses were the ancestors of
  our present day continents.
• They have drifted over the globe
• As they drifted the created numerous
  environmental zones causing some species to
  become extinct while allowing others to flourish.

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• About 65 million years ago the dinosaurs were the
  dominant form of land animals.
• Then one day, an asteroid, thought to measure 6
  miles in diameter crashed through the earths
  atmosphere and into the crust where the north
  coast of the Mexican Yucatan is now.
• The impact made a crater 200 miles in diameter.
• The blast of the asteroid was like a nuclear
  bomb.
• The environmental change was disastrous.
• Dinosaurs became extinct, along with every other
  species of land animals weighing more than 55
  pounds.
• Cretaceous/Tertiary (K/T) extinction
• Mammals adaptive radiation was rapid and
  happened with in about 20 million years.
• By this time all of the major types of mammals we
  know today appeared.

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