Indohyus Ambulocetus “Walking Whale” How did Ambulocetus make its living? Typical mammalian ear bones Bottle-nosed dolphin Tursiops truncatus Thick, shell- like auditory bullae Detached auditory bullae Involucrum Characteristics of Auditory Bullae in Mammals 1) All mammals except those listed below: Auditory bullae fused used with skull Relatively thin No involucrum 2) Indohyus: Fused used with skull Slightly thickened Slight involucrum 3) Ambulocetus: Fused used with skull Thick Involucrum 4) Modern whales and dolphins (Cetaceans): Auditory bullae detached (except in some baleen whales) Thick, shell-like Involucrum Basilosaurids (Dorudon) Basilosaurids (Dorudon) Right Whale F Plan of bones in the forelimbs of all vertebrates are essentially the same A one-month old embryo What kind of creature is this? Gill arches Later in development will be covered with hair Fore Limb Tail Hind Limb The same embryo 8 months later Vestigial Traits are Common Vestigial trait is a structure found in greatly reduced, often nonfunctional, form that is homologous to function structures found in other species Example: Hair and gill arches in developing dolphins Example: Long tail and gill arches in humans Example: Pelvic girdle structures in cetaceans Vestigial Traits are Common Vestigial trait is a structure found in greatly reduced, often nonfunctional, form that is homologous to function structures found in other species Example: Dewclaws in terrestrial vertebrates (e.g., hoofed mammals) Vestigial Traits are Common Vestigial trait is a structure found in greatly reduced, often nonfunctional, form that is homologous to function structures found in other species Example: 5th digits in developing birds, both upper and lower limbs Traits usually have patterns that match a time sequence Example: It appears that the pelvic girdle is becoming more rudimentary over time, auditory bullae are getting thicker Time sequence patterns II Example: It appears that horses have been losing toes over time Law of Succession Fossil species similar to later fossils or living species tend to be found in the same geographic region Summary of Observations 1) Unique traits often cluster in groups of organisms --Mesonychus, Indohyus and Ambulocetus had hooves --Indohyus, Ambulocetus, Basilosaurus and modern cetaceans (whales and dolphins) have thick auditory bullae with an involucrum 2) Body parts with wildly different functions have the same basic plan Example: Vertebrate pectoral girdle (arm and shoulder) 3) Vestigial traits are common… 3) but still follow the same body plan as functional versions Example: Basilosaurus and modern whales have highly reduced hind limb structures with a pelvis, femur, tibia, fibula, tarsals, metatarsals and phalanges (in embryo even if missing in the adult) Summary of Observations 4) Embryos often develop traits not found in the adult but are found in other species -- In fish, gills develop from embryonic gill arches. Mammals do not have gills; however, all mammalian embryos develop gill arches. -- as embryos, birds develop 5th digits even though adult birds only have 3 (upper limb) or 4 (lower limb) digits 5) More derived traits are found in younger fossil forms -- Pelvic girdle in whales appears to become increasingly vestigial over time -- Horses feet appear to lose digits over time (yet as embryos develop 5) 6) Related fossils found in same parts of the world; modern species tend to be found where their fossils are -- Wombats and fossil marsupials in Australia -- Armadillos and glyptodonts in South America Descent with modification If this explanation E.g., we expect to find fossils older than Ambulocetus that are morphologically “between” Ambulocetus and Indohyus… is correct, then we should see transitional fossils …and fossils “between” Ambulocetus and Basilosaurus; similar to but more recent than Ambulocetus and more aquatic-adapted. If this explanation is correct, then we should see transitional fossils …and we do A transitional form between Indohyus and Ambulocetus Ambulocetus can walk on land--full sacrum Georgiacetus cannot--hips Another would dislocate and every nerve transitional fossil and blood between vessel to legs Ambulocetus and would be Dorudon severed Georgiacetus vogtlensis Another newly described (2009) transitional fossil leading to whales and dolphins Maiacetus inuus For others, see Berkeley evolution website Maiacetus inuus Transitional form are astonishingly common Example: Mammals Reptiles to mammals Therapsids Mammal-like reptiles, or reptile like mammals? Synapsids Mammal-like reptiles Definite feathers Caudipteryx (A small theropod dinosaur) 170-ish MYA Another dromaeosaur Microraptor gui 125 MYA The relationship between dinosaurs and birds Transitional fossils between fish and amphibians If descent with modification is correct, then we genetic relationships should match fossil relationships Example: Cytochrome c gene comparison among minke whales, sperm whales, orcas, harbor porpoise, pygmy sperm whale, bowhead whale and deer Comparison of Ribosomal Genes A more complete comparison (most of the genome) Genetically, cetaceans are astonishingly similar to hoofed mammals, especially hippopotamuses Pre-genetics understanding of the relationships between hoofed mammals and cetaceans Order: Artiodactyla Order: Cetacea What the genes tell us Order: Cetartiodactyla Cytidine Monophospho-N- Acetylneuraminic Acid Hydroxylase (CMAH) In humans called CMAH-∆92 because of 92-base deletion mutation CMAH-∆92 is a pseudogene, or broken copy of a functional gene in other species What happens when CMAH is broken? From: Kavaler et al. (2011) FASEB 25:1887-1893. Normal (wild type) and Cmah knockout Cmas-/- (engineered to have the Cmah-∆92 mution) fed normal control diet (NCD) and high fat diets (HFD) Morbid obesity and diabetes mellitus Type 2 are far more common in humans than any other primate, even with equal caloric intake Descent with modification has explanatory power Chimps have CMAH (functional) Humans have broken CMAH-∆92 (nonfunctional) P. reichenowi does not infect CMAH explains why P. humans because we inherited a reichenowi causes malaria in broken copy from an ancestor chimps but not humans Plasmodium reichenowi If Descent With Modification were true, how can complex traits evolve? If Descent With Modification were true, how can complex traits evolve? The same genes control analogous structures in variously complex light-sensing organs If Descent With Modification were true, how can complex traits evolve? Variations of F-type and V-type ATPase motors are found in all organisms; usually associated with energy metabolism Complex motors can evolve from simpler parts; each simpler part is found in other organisms performing a function, often unrelated to energy metabolism Complex motors can evolve from simpler parts; each simpler part is found in other organisms performing a function, often unrelated to energy metabolism For example, the same motor, built of the same proteins from the same genes as the F-type motor, spun backwards and attached to a protein filament, is the bacterial flagellum Descent with modification has explanatory power A dolphin captured in the Sea of Japan a few years ago Not a normal dolphin! Descent with modification has explanatory power Why does this dolphin have hind flippers? --Dolphins have a genetic program for hind limbs inherited from ancestor --An inherited mutation in a controller gene normally turns the program off early in development --This dolphin has another mutation in that controller gene that turned it back on This is an example of an atavistic trait.