4 Diversity of Whales Today Mysticetes (baleen whales):
5 Diversity of Whales Today Odontocetes (toothed whales):
6 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 TheoryDarwin was wrong about the BEAR (he removed this idea in later editions), but spot-on with the process – NATURAL SELECTION.
7 Here’s a Peek into the Past… So, Where DID Whales Come From?Here’s a Peek into the Past…
8 Moving in…Notice that the earliest MAMMALS… were TERRESTRIAL - with LEGS !
9 But WHALES SWIM; they DON’T WALK ON LAND ! So - Where DID Whales Come From?What would the earliest whales look like?
10 The Earliest MODERN WHALES… NOWOnly go back to about 23 mya… the beginning of the MIOCENE…5 myaMIOCENE23 myaGreat swimmers… but NO WALKING LEGS !65mya
11 HOWEVER ! from the EOCENE ! We DO have some whale-like fossils, with strange teeth,NOW5 myaMIOCENE23 myafrom the EOCENE !65mya
12 But… Where’s the Eocene? NOWNOWMiocene: Earliest modern whales23 mya34 myaEOCENE55 mya4.5bya65mya
13 OK! So, where shall we look for Eocene Fossils? 38Mountains of PakistanThe Tethys Sea55India Moved North……Squished into Asia…
14 Where shall we look?PakistanLots of exposed marine Eocene rocks in the Pakistan mountains
15 Let’s Hunt Whale Fossils… Work in pairsOpen Your Eocene TimelineRemove whale strips from plastic bagListen for descriptions and timingPlace whale strip on timelineWait for next “discovery”
32 But Mesonychids are EXTINCT! SO, Who are the Closest Living Relatives of Whales?Maybe Hooved Mammals?: = Ungulates: Two Orders:33-38: Hooved animals and ANKLE evidencePerissodactyls (odd-toed)Artiodactyls (even-toed)
36 Ungulate Foot Bones…FOSSIL HORSEFOSSIL PIGHeel BoneAnkle Bone
37 Whale Ankles? Compare ankle bones… Pig Pakicetus Mesonychid two small ridgesMesonychidPrim. ArtiodactylPrim.PerissodactylAnkles Compared (with arrows showing…)one big ridge
38 Whale Phylogeny, 2001 Philip Gingerich Early whale ankles indicate close relationship with artiodactyls (even-toed ungulates)Mesonychid ankles indicate they are closer to perissodactyls (odd-toed ungulates)
39 But WHICH Artiodactyls? Will DNA Tell Us?40-48: DNA analysis indicates hippos are the most closely related living animals to whales.Let’s Compare DNA…
40 DNA Analysis Compare segments of beta-casein gene
41 DNA Analysis Compare segments of beta-casein gene
49 Whale Evolution RecapFossil teeth link whales to the 4-legged mesonychids of the Paleo-EoceneTiny hooves on mesonychids and early whale toes tie whales to the ungulatesAnkle bones of early whales point to artiodactyl ungulates as the closest relatives of whales
50 Whale Evolution RecapDNA confirms the artiodactyl connection and points to hippos as the closest cousins of whalesConsilience: these multiple independent lines of evidence strengthen, narrow and confirm the hypothesized close relationship between whales and artiodactyls