1 wheeeee ! 2 what are we doing today? whale fossil hunt whale ankle comparisons whale dna...
TRANSCRIPT
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What are we Doing Today?
•Whale fossil hunt•Whale ankle comparisons•Whale DNA comparisons•WHALE EVOLUTION
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But Where Did They Come From?
ONE OF DARWIN’S IDEAS…
… 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.Charles Darwin, The Origin of Species, 1859 (first edition), Chapter 6: Difficulties on Theory
Darwin was wrong about the BEAR (he removed this idea in later editions), but spot-on with the process –
NATURAL SELECTION.
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But WHALES SWIM;they DON’T WALK ON
LAND !
So - Where DID Whales Come From?
What would the earliest whales look
like?
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The Earliest MODERN WHALES…
65mya
NOW
MIOCENE
23 mya
Only go back toabout 23 mya…the beginning of the MIOCENE…
Great swimmers…
but NO WALKING
LEGS !
5 mya
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HOWEVER !
65mya
NOW
MIOCENE
23 mya
We DO have some whale-like fossils, with strange teeth,
from the EOCENE !
5 mya
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But… Where’s the Eocene?NOW
4.5bya
65mya
NOW
55 mya
34 mya
EOCENE
Miocene:Earliest modern whales
23 mya
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OK! So, where shall we look
forEocene Fossils?
The Tethys Sea
India Moved North…
…Squished into Asia…
Mountains of Pakistan
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Let’s Hunt Whale Fossils…
• Work in pairs• Open Your Eocene Timeline• Remove whale strips from plastic
bag• Listen for descriptions and timing• Place whale strip on timeline• Wait for next “discovery”
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Early Whale Teeth…
in a 4-legged mammal?
a Mesonychid - called Pachyaena
~ 55 mya… with tiny
hooves!
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Early Whale Teeth
Pakicetus - an early whale ~50 mya
1983 - Gingerich - Pakistan
WITH LEGS !
In Pakistan……and hooves, too!
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Eocene Epoch Timeline Dorudon 36 mya (39-36 my) 1936
Pachyaena 55 mya (58-34 mya) 1955
Pakicetus 50 mya (1983 - Pakistan)
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Eocene Epoch Timeline Dorudon 36 mya (39-36 my) 1936
Pachyaena 55 mya (58-34 mya) 1955
Pakicetus 50 mya (1983 - Pakistan)
Basilosaurus 37 mya (39-36 mya) 1990
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Early Whale Teeth
Rodhocetus - an early whale
~46 mya
early 1994 - Gingerich - Pakistan
And tiny hooves, too !
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Eocene Epoch Timeline Dorudon 36 mya (39-36 my) 1936
Pachyaena 55 mya (58-34 mya) 1955
Pakicetus 50 mya (1983 - Pakistan)
Basilosaurus 37 mya (39-36 mya) 1990
Rodhocetus 46 mya (early 1994 - Pakistan)
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Eocene Epoch Timeline Dorudon 36 mya (39-36 my) 1936
Pachyaena 55 mya (58-34 mya) 1955
Pakicetus 50 mya (1983 - Pakistan)
Basilosaurus 37 mya (39-36 mya) 1990
Rodhocetus 46 mya (early 1994 - Pakistan)
Transitional form? Predict What? (draw) Where?
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Early Whale Teeth… in Pakistan
Ambulocetus - the “walking whale”
~48 mya
late 1994 Thewissen
With tiny hooves, too !
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Eocene Epoch TimelineDorudon 36 mya (39-36 my) 1936
Pachyaena 55 mya (58-34 mya) 1955
Pakicetus 50 mya (1983 - Pakistan)
Basilosaurus 37 mya (39-36 mya) 1990
Rodhocetus 46 mya (early 1994 - Pakistan)
Ambulocetus 48 mya (late 1994 - Pakistan)
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But Mesonychids are EXTINCT!
•Perissodactyls (odd-toed)
•Artiodactyls (even-toed)
Maybe Hooved Mammals?:
= Ungulates: Two Orders:
SO, Who are the Closest Living Relatives of
Whales?
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Whale Ankles?
MesonychidPrim.Perissodactyl
Prim. Artiodactyl
Pakicetus
Pig
Compare ankle bones…
one big ridge
two small ridges
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DNA DifferencesFewer than five differences…
• 2 porpoise & sperm whale• 3 porpoise & right whale• 3 sperm whale & right whale• 3 sperm whale & hippo• 3 porpoise & hippo• 3 right whale & hippo• 3 giraffe & deer• 3 giraffe & cow• 4 cow & deer
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DNA DifferencesSeven differences…
• 7 pigs and peccaries
DNA DifferencesRemaining species…
Higher numbers - more distantly related
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Whale Evolution Recap• Fossil teeth link whales to the 4-
legged mesonychids of the Paleo-Eocene
• Tiny hooves on mesonychids and early whale toes tie whales to the ungulates
• Ankle bones of early whales point to artiodactyl ungulates as the closest relatives of whales
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Whale Evolution Recap
• DNA confirms the artiodactyl connection and points to hippos as the closest cousins of whales
• Consilience: these multiple independent lines of evidence strengthen, narrow and confirm the hypothesized close relationship between whales and artiodactyls