Mile Markers in Deep Time A Brief History of Life and an Outline of Hominid Evolution

History of Life on Earth How did life originate? What were the first organisms? How has life changed through time (evolution)? Why do organisms become extinct? What causes mass extinctions? How do living systems recover after mass extinctions? What is our ancestry and our future?

Earliest Life: Prokaryotes Prokaryotes – cells with no nucleus Single cells Strings of cells Mats of cells - Stromatolites

Major Milestones Life begins – approximately 4.0 Ga First multicellular creatures – approx. 1.0 Ga

Major Milestones Abundant life with shells and hard parts – approx. 530 Ma

Major Milestones First and worst mass extinction – 245 Ma Dinosaurs and Early mammals appear after

Major Milestones Mass extinction: dinosaurs and others – 66.4 Ma Rise of mammals – 66.4 Ma to present First hominids – approx. 4.0 Ma

Hominid Evolution The interface of paleontology and archaeology

A family dynasty – the Leakeys Richard Leakey Mary Leakey Richard Leakey - son

Mary Leakey A lifetime of contributions including: Many “first discoveries” of skulls, etc. First hominid footprints

The Cradle of Humanity The East African Rift System Earthquakes and formation of rift as Africa splits Sinking of rift floor promoted accumulation of sediments Early hominids preserved in these sediments Recent erosion cuts through sediments to reveal fossils

Our earliest ancestor Hadar, East African Rift Australopithecus afarensis Famous Fossil: “Lucy” Age: About 4.0 Ma

“Lucy” Australopithecus afarensis An intelligent ape? Brain capacity was thought to have developed before upright walking Lucy’s knee clearly shows our ancestors walked upright BEFORE they developed larger brains

Footprints at Laetoli – A. afarensis More evidence for walking upright

Homo habilus Our own genus – circa 2.0 Ma

Australopithecus afarensis & Homo habilus

Hominid Time Line

The Hominid Time Line Accurate dating of fossils is critical Direct evolutionary relationships are still unclear New fossil discoveries prompt revisions all the time The burning questions: Who are we? What is our heritage? Where do we fit in the grand scheme of things?

Hobbits in Indonesia? Just Discovered: 10/04 Homo floresiensis Stood only 3.3 ft. tall! 55 pounds Brain size: grapefruit 18,000 to 13,000 BP