1. Journal Entry #4 – Earth’s History and Radiometric Dating

3. Anchorage to Homer (or a brief history of the Earth) 226 Miles 4.6 Billion years

4. Mile 54 – 3.5 billion years ago First prokaryotic cells (Between girdwood and portage)

5. Mile 128 – 2 billion years ago Eukaryotic cells Free oxygen in the atmosphere (Seward-Homer split) SewardHomer

6. Mile 176 – 1 billion years ago Multi-cellular organisms (Kasilof)

7. Mile 196 – 600 million years ago First animals (Ninilchik)

8. Mile 202 – 500 million years ago Diversification of animals (Cambrian explosion) First land plants

9. Mile 207 – 400 million years ago First insects First amphibians (Happy Valley)

10. Mile 214 – 250 million years ago Dinosaurs! First mammals Anchor Point

11. Mile 223 – 65 million years ago End of the dinosaurs Earliest primates (Just outside of Homer)

12. Mile 225 – 20 million years ago Diversification and spread of primates

13. 500 yds to go! – 6 million years ago Earliest hominids

14. Sometime around 5-7 million years ago… Orrorin tugenensis (Kenya)Laetoli, Tanzania

15. 500 ft! – 2 million years ago Beginnings of our genus Homo Earliest stone tools

16. ~ 2.5 - 2 MA…appearance of our genus, Homo (Africa) “Turkana Boy” – WT 15000 ER – 3733 (Kenya) ER – 1470 (Kenya) Oldowan Stone Tools

17. 50 feet from end of Homer Spit – 200,000 years ago Earliest anatomically modern humans