Transcript Whale Evolution

WHEEEEE !
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What are we Doing Today?
• Whale fossil hunt
• Whale ankle comparisons
• Whale DNA comparisons
• WHALE EVOLUTION
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Becoming Whales
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Diversity of Whales Today
Mysticetes (baleen whales):
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Diversity of Whales Today
Odontocetes (toothed whales):
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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.6
So, Where DID Whales Come From?
Here’s a Peek into the Past…
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Moving in…
Notice that the earliest MAMMALS…
were TERRESTRIAL - with LEGS !
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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…
Only go back to
about 23 mya…
the beginning of
the MIOCENE…
Great
swimmers… but
NO WALKING
LEGS !
NOW
5 mya
MIOCENE
23 mya
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65mya
HOWEVER !
We DO have some
whale-like fossils,
with strange teeth,
NOW
5 mya
MIOCENE
23 mya
from the
EOCENE !
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65mya
NOW
But… Where’s the
Eocene?
NOW
Miocene:
Earliest
modern
whales
23 mya
34 mya
EOCENE
55 mya
4.5bya
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65mya
OK! So, where
shall we look for
Eocene Fossils?
Mountains of Pakistan
The Tethys Sea
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India Moved North…
…Squished into Asia…
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Where shall we look?
Pakistan
Lots of exposed
marine Eocene
rocks in the
Pakistan mountains
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Let’s Hunt Whale Fossils…
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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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Eocene Epoch Timeline
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Early Whale Teeth
in Dorudon
1936
~ 36 mya
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Eocene Epoch Timeline
Dorudon 36 mya (39-36 my) 1936
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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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Eocene Epoch Timeline
Dorudon 36 mya (39-36 my) 1936
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Pachyaena 55 mya (58-34 mya) 1955
Early Whale Teeth
WITH LEGS !
…and hooves,
too! In Pakistan…
Pakicetus - an early whale
~50 mya
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1983 - Gingerich - Pakistan
Eocene Epoch Timeline
Dorudon 36 mya (39-36 my) 1936
Pakicetus 50 mya (1983 - Pakistan)
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Pachyaena 55 mya (58-34 mya) 1955
Early whale teeth in…
Basilosaurus
~37mya
and
LEGS,
too…
1990 Gingerich - Egypt
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Eocene Epoch Timeline
Dorudon 36 mya (39-36 my) 1936
Basilosaurus 37 mya (39-36 mya) 1990
Pakicetus 50 mya (1983 - Pakistan)
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Pachyaena 55 mya (58-34 mya) 1955
Early Whale Teeth
Rodhocetus - an early whale
And tiny hooves, too !
early 1994 - Gingerich - Pakistan
~46 mya
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Eocene Epoch Timeline
Dorudon 36 mya (39-36 my) 1936
Basilosaurus 37 mya (39-36 mya) 1990
Rodhocetus 46 mya (early 1994 - Pakistan)
Pakicetus 50 mya (1983 - Pakistan)
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Pachyaena 55 mya (58-34 mya) 1955
Eocene Epoch Timeline
Dorudon 36 mya (39-36 my) 1936
Basilosaurus 37 mya (39-36 mya) 1990
Rodhocetus 46 mya (early 1994 - Pakistan)
Transitional form?
Predict What? (draw) Where?
Pakicetus 50 mya (1983 - Pakistan)
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Pachyaena 55 mya (58-34 mya) 1955
Early Whale Teeth… in Pakistan
With tiny hooves, too !
Ambulocetus - the “walking whale”
late 1994 Thewissen
~48 mya
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Eocene Epoch Timeline
Dorudon 36 mya (39-36 my) 1936
Basilosaurus 37 mya (39-36 mya) 1990
Rodhocetus 46 mya (early 1994 - Pakistan)
Ambulocetus 48 mya (late 1994 - Pakistan)
Pakicetus 50 mya (1983 - Pakistan)
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Pachyaena 55 mya (58-34 mya) 1955
Ambulocetus
Carl Buell
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Whale Phylogeny, 1994
Hans Thewissen
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But Mesonychids are
EXTINCT!
SO, Who are the Closest Living
Relatives of Whales?
Maybe Hooved Mammals?:
= Ungulates: Two Orders:
• Perissodactyls (odd-toed)
• Artiodactyls (even-toed)
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Perissodactyls
Odd-Toed Ungulates
Horses & Zebras
Rhinos & Tapirs
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Artiodactyls
Even-Toed Ungulates
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Leg Anatomy…
Heel Bone
Ankle Bone
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Ungulate Foot Bones…
FOSSIL HORSE
FOSSIL PIG
Heel Bone
Ankle Bone
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Whale Ankles?
Pig
Compare ankle bones…
Pakicetus
two small ridges
Mesonychid
Prim. Artiodactyl
Prim.Perissodactyl
one big ridge
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Whale Phylogeny, 2001
Philip Gingerich
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But WHICH Artiodactyls?
Will DNA Tell Us?
Let’s Compare DNA…
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DNA Analysis
Compare segments of beta-casein gene
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DNA Analysis
Compare segments of beta-casein gene
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DNA Differences
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DNA Differences
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DNA Differences
Fewer than five differences…
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porpoise & sperm whale
porpoise & right whale
sperm whale & right whale
sperm whale & hippo
porpoise & hippo
right whale & hippo
giraffe & deer
giraffe & cow
cow & deer
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DNA Differences
Seven differences…
• 7 pigs and peccaries
DNA Differences
Remaining species…
Higher numbers - more distantly related
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Phylogenetic Tree - WHALES
Based on DNA Differences
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Provisional Phylogeny - Cetartiodactyls
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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
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Whale’s Closest Cousin: Hippos
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FAREWHALE!
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Have a Whale of a Time!
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FINI