The document summarizes evidence from the fossil record for the evolution of whales from terrestrial mammals. It describes how whales have been found to possess vestigial hind limbs and describes a series of transitional whale fossils from Pakicetus, Ambulocetus, and Rodhocetus that show whales evolving from four-legged land-dwelling creatures to fully aquatic mammals over tens of millions of years. It also notes how the number of whale species increased dramatically over the Eocene period, representing one of the clearest examples of macroevolution seen in the fossil record.

1. Evidence for Evolution: The Origin of Whales Ryan M Bebej University of Michigan February 10, 2008

2. Evidence for Evolution: The Origin of Whales What exactly is meant by evolution ? Where does evidence for evolution come from? What fossil evidence is there for the evolution of whales from land mammals?

8. Evidence for Evolution Anatomy Development Genetics Fossils

9. Beluga Humpback whale Orca Blue whale Order Cetacea

10. Whales are mammals… … but they are very different from terrestrial mammals!

11. 1859: Charles Darwin “ In North America the black bear was seen by Hearne swimming for hours with widely open mouth, thus catching, like a whale, insects in the water. Even in so extreme a case as this, if supply of insects were constant, and if better adapted competitors did not already exist in the country, I can see no difficulty in a race of bears being rendered, by natural selection, more and more aquatic in their structure and habits, with larger and larger mouths, till a creature was produced as monstrous as a whale.” - from The Origin of Species (ch.6) … was ridiculed and omitted much of this from the 2 nd edition

13. Hind limb vestiges Gray whale

14. 1945: George Gaylord Simpson “ Because of their perfected adaptation to a completely aquatic life, with all its attendant conditions of respiration, circulation, dentition, locomotion, etc., the cetaceans are on the whole the most peculiar and aberrant of mammals. Their place in the sequence of cohorts and orders [of mammalian classification] is open to question and is indeed quite impossible to determine in any purely objective way.” - from Classification of Mammals

22. Increasing Aquatic Ability Pakicetus 48 mya Ambulocetus 47.5 mya Rodhocetus 46.5 mya Dorudon 40 mya Time

23. Eocene Whales

24. Eocene Whales Number of Species 5 2 5 18 13 43 described species!

26. Questions?