Creation And Evolution Session 3Presentation Transcript
Evidence for Evolution: The Origin of Whales Ryan M Bebej University of Michigan February 10, 2008
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?
What is evolution?
“ In biology, nothing makes sense except in the light of evolution.”
“ No educated person any longer questions the validity of the so-called theory of evolution, which we now know to be a simple fact.”
Evolutionism : a naturalistic worldview that uses evolutionary biology to support the claim that there is no God & that there is no purpose to human existence
This is philosophical & not scientific, yet it has become thoroughly entangled with the scientific components of evolution…
What is evolution?
Evolution as mechanism : the process that renders change in lineages through time (natural selection, genetic drift, mutation)
Evolution as history : the fact that life has changed through time
Common descent : all forms of life are linked in a family tree & share common ancestry
This provides a robust rationale for explaining many aspects of embryology, comparative anatomy, biogeography, paleontology, etc.
What is evolution?
“Evolution is both a fact and a theory. It is a fact that evolutionary change took place. And evolution is also a theory that seeks to explain the detailed mechanism behind that change.”
- Kenneth R. Miller, Brown University
Author of Finding Darwin’s God:
A Scientist's Search for Common
Ground Between God and Evolution
Evidence for Evolution Anatomy Development Genetics Fossils
Beluga Humpback whale Orca Blue whale Order Cetacea
Whales are mammals… … but they are very different from terrestrial mammals!
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
1936: Remington Kellogg
Seminal “Review of the Archaeoceti”
North American & Egyptian whales
All clearly fully aquatic
Zygorhiza kochii Basilosaurus cetoides 50 cm 50 cm
Hind limb vestiges Gray whale
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
1981: Pakicetus inachus
Pakistan (48 Mya)
Fluvial sediments bordering remnants of the Tethys Sea
Dentition like previously known cetaceans
Dense auditory bullae with sigmoid process on tympanic & other ear features that are only seen in whales !
Eocene Whales Number of Species 5 2 5 18 13 43 described species!
Within the scientific community, while the precise mechanisms for it are debated, evolutionary change is generally assumed
Evidence for the evolution of life & common descent comes from a variety of sub-disciplines & is constantly accumulating
In just the past 30 years, a group of mammals whose origin was thought to be “quite impossible to determine in any purely objective way” (Simpson, 1945) has become one of the most convincing & complete examples of macroevolution & evolutionary radiations in the fossil record.