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Vertebrates Cartilagenous Bony Hagfish, Fish Fish Amphibians Lampreys Reptiles Birds Mammals Hair Mammary Glands Amniotic Egg Endothermy Four Limbs Terrestrial Phase Bony Skeleton Swim Bladder Skull Backbone Paired Fins Jaws Mammals • Hair, mammary glands • Most advanced nervous system • Learning important to survival • Warm blooded • Humans are mammals Humans are primate mammals • Class Mammalia – Order Primates • Prosimians (e.g. lemurs) • Tarsiers • Anthropoids (e.g. monkeys, hominoids) Lemur Tarsier Macaque Primates : Humble Beginning Rabbit Primates Shrew Shrew-like Ancestor Major Primate Groups Family Hominidae Tarsiiformes Lemurs Old World Monkeys New World Monkeys Orangutan Gibbons Chimp Human Gorilla Homininae : African Great Apes and Humans Hominidea : Great Apes and Humans Hominoidea : Apes and Humans What Features Are Associated With Primate Evolution? I. Sensory Adaptations – Protected, forward looking eyes with stereoscopic vision – Improved sight : more detail even in low light – Reduction of olfactory structures What Features Are Associated With Primate Evolution? II. Adaptations for tree-climbing and insectivory – – – – Freely moving limbs and digits Long mobile digits capable of grasping Retention of tail as organ of balance Evolution of upright body posture and extensive head rotation – Increased body size – Evolution of nervous system to give precise and rapid control of movement Major Primate Groups Family Hominidae Tarsiiformes Lemurs Old World Monkeys New World Monkeys Orangutan Gibbons Chimp Human Gorilla 5 mya 6 mya 12 mya 25 mya 38 mya Estimated Divergence Times Hasegawa et al. 1987 What Traits Do Humans and Apes Share? •Larger Brain •Absence of a tail •More erect posture •Greater flexibility of hips, ankles, wrist, thumb •DNA sequence similarity Gorilla Chimpanzee Human Horai et al (1995) Proc. Nat Acad Sci. 92:532-536. Mito DNA (complete sequences) Kim and Takenaka (1996) A. J. Phys. Anth. 100:301-309 Y-chromosome DNA Ruvolo (1997) Mol Biol Evol 10:1115-1135. Examined 14 different DNA data sets Satta et al (2000) Mol. Phyl. Evol 14:259-275. Autosomal DNA (45 genes, 47,000 bp of DNA) Paabo (2003) Nature 421:409-412. Review of human and chimp/ape genomes. Common Ancestor of Chimp/Human • Knuckle-walker? • Broad-fruit based diet • May have hunted • May have used tools • May have had complex social relationships: (e.g.warfare, cannabalism, sharing, teaching, compassion) Our Understanding of Human Evolution is Primarily Based on Fossils Can genes help explain our evolution? - What type of changes (regulatory or structural mutations?) - How many genes are involved? Approaches to Identify Genetic/Genomic Differences Between Chimps and Humans 1. Candidate gene approach 2. Microarray approach 3. Nucleotide substitution approach 4. Bioinformatic approach Candidate gene approach: FOXP2 - 2 non-conservative amino acid substitutions in humans -- flanking genomic DNA showed signs of a selective sweep Enard, W. et al. 2002. Molecular evolution of FOXP2, a gene involved in speech and language. Nature 418, 869-872. Signature of a Selective Sweep Selection Fixation Recombination Mutation Favored Allele Reduced polymorphism More rare alleles FOXP2 plays a role in the development of brain regions that are important for communication • FOXP2 is expressed highly in zebra finches during the vocal learning period of development. Haesler et al. 2004. J. Neurosci 24:3164. • FOXP2 knock-out mice have altered motorsensory functions and ultrasonic vocalizations. Shu et al. 2005. PNAS 102:9643. Pollard, KS et al. An RNA gene expressed during cortical development evolved rapidly in humans. Nature Aug. 2006 Identified Human Accelerated Regions (HARs) • Scanned the 2/3 portion of the genome that is non-coding • Many of the identified regions are associated with transcription factors and neurodevelopment genes. • The most dramatically changed element (HAR1) is a novel RNA gene expressed during human cortical development. Details of the Screening Process - Search chimpanzee genome sequence against rat and mouse genome sequences. (96% identity > 100 bp) - 35,000 regions identified - Searched these regions in all other available amniote genomes searching for regions with significant changes in human. - 49 regions identified with a statistically significant rate increase in humans (96% in non-coding regions, 24% next to a neurodevelopmental gene)