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Transcript
WHEEEEE !
1
What are we Doing Today?
• Whale fossil hunt
• Whale ankle comparisons
• Whale DNA comparisons
• WHALE EVOLUTION
2
Becoming Whales
3
Diversity of Whales Today
Mysticetes (baleen whales):
4
Diversity of Whales Today
Odontocetes (toothed whales):
5
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…
7
Moving in…
Notice that the earliest MAMMALS…
were TERRESTRIAL - with LEGS !
8
But WHALES SWIM;
they DON’T WALK ON LAND !
So - Where DID Whales
Come From?
What would the earliest
whales look like?
9
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
10
65mya
HOWEVER !
We DO have some
whale-like fossils,
with strange teeth,
NOW
5 mya
MIOCENE
23 mya
from the
EOCENE !
11
65mya
NOW
But… Where’s the
Eocene?
NOW
Miocene:
Earliest
modern
whales
23 mya
34 mya
EOCENE
55 mya
4.5bya
12
65mya
OK! So, where
shall we look for
Eocene Fossils?
Mountains of Pakistan
The Tethys Sea
38
55
India Moved North…
…Squished into Asia…
13
Where shall we look?
Pakistan
Lots of exposed
marine Eocene
rocks in the
Pakistan mountains
14
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”
15
Eocene Epoch Timeline
16
Early Whale Teeth
in Dorudon
1936
~ 36 mya
17
Eocene Epoch Timeline
Dorudon 36 mya (39-36 my) 1936
18
Early Whale Teeth…
in a 4-legged
mammal?
a Mesonychid called Pachyaena
~ 55 mya
… with tiny hooves!
19
Eocene Epoch Timeline
Dorudon 36 mya (39-36 my) 1936
20
Pachyaena 55 mya (58-34 mya) 1955
Early Whale Teeth
WITH LEGS !
…and hooves,
too! In Pakistan…
Pakicetus - an early whale
~50 mya
21
1983 - Gingerich - Pakistan
Eocene Epoch Timeline
Dorudon 36 mya (39-36 my) 1936
Pakicetus 50 mya (1983 - Pakistan)
22
Pachyaena 55 mya (58-34 mya) 1955
Early whale teeth in…
Basilosaurus
~37mya
and
LEGS,
too…
1990 Gingerich - Egypt
23
Eocene Epoch Timeline
Dorudon 36 mya (39-36 my) 1936
Basilosaurus 37 mya (39-36 mya) 1990
Pakicetus 50 mya (1983 - Pakistan)
24
Pachyaena 55 mya (58-34 mya) 1955
Early Whale Teeth
Rodhocetus - an early whale
And tiny hooves, too !
early 1994 - Gingerich - Pakistan
~46 mya
25
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)
26
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)
27
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
28
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)
29
Pachyaena 55 mya (58-34 mya) 1955
Ambulocetus
Carl Buell
30
Whale Phylogeny, 1994
Hans Thewissen
31
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)
32
Perissodactyls
Odd-Toed Ungulates
Horses & Zebras
Rhinos & Tapirs
33
Artiodactyls
Even-Toed Ungulates
34
Leg Anatomy…
Heel Bone
Ankle Bone
35
Ungulate Foot Bones…
FOSSIL HORSE
FOSSIL PIG
Heel Bone
Ankle Bone
36
Whale Ankles?
Pig
Compare ankle bones…
Pakicetus
two small ridges
Mesonychid
Prim. Artiodactyl
Prim.Perissodactyl
one big ridge
37
Whale Phylogeny, 2001
Philip Gingerich
38
But WHICH Artiodactyls?
Will DNA Tell Us?
Let’s Compare DNA…
39
DNA Analysis
Compare segments of beta-casein gene
40
DNA Analysis
Compare segments of beta-casein gene
41
DNA Differences
42
DNA Differences
43
Questions
• If the porpoise and the sperm whale were
removed from our chart which mammal is
the closest relative to the right whale?
Explain your answer.
• Which animal is least like the right whale?
Use evidence to support your answer.
• Are hippos or right whales more closely
related to sperm whales? Explain!
44
1. Why do you think I’m showing this cartoon here?
2. What story does the cartoon suggest happened?
3. In what two important ways does this cartoon
conflict with the actual records of evolution?
45
DNA Differences
Fewer than five differences…
•
•
•
•
•
•
•
•
•
2
3
3
3
3
3
3
3
4
porpoise & sperm whale
porpoise & right whale
sperm whale & right whale
sperm whale & hippo
porpoise & hippo
right whale & hippo
giraffe & deer
giraffe & cow
cow & deer
46
DNA Differences
Seven differences…
• 7 pigs and peccaries
DNA Differences
Remaining species…
Higher numbers - more distantly related
47
Phylogenetic Tree - WHALES
Based on DNA Differences
48
Provisional Phylogeny - Cetartiodactyls
49
50
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
51
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
52
Whale’s Closest Cousin: Hippos
53
54
FAREWHALE!
55
Have a Whale of a Time!
56
FINI