Vertebrates Hair Mammary Glands Amniotic Egg Endothermy Four Limbs Cartilagenous Fish Hagfish, Lampreys Bony Fish Amphibians Mammals Birds Reptiles 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 Shrew Shrew-like Ancestor

Homininae : African Great Apes Major Primate Groups Family Hominidae Old World Monkeys Orangutan Chimp Human Tarsiiformes Gibbons Gorilla Lemurs New World Monkeys 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 Hasegawa et al. 1987 Orangutan Chimp Human Family Hominidae Old World Monkeys Orangutan Chimp Human Tarsiiformes Gibbons Gorilla Lemurs New World Monkeys 25 mya 12 mya 6 mya Hasegawa et al. 1987 5 mya 38 mya Estimated Divergence Times

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?

Candidate gene approach Microarray approach Approaches to Identify Genetic/Genomic Differences Between Chimps and Humans Candidate gene approach Microarray approach Nucleotide substitution approach 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 Recombination Mutation Selection Fixation 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.

Identified Human Accelerated Regions (HARs) 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)