Vertebrates Hagfish, Lampreys Cartilagenous Fish Bony Fish Amphibians Mammals Birds Reptiles Skull Backbone Paired Fins Jaws Bony Skeleton Swim Bladder Four Limbs Terrestrial Phase Amniotic Egg Endothermy Hair Mammary Glands
Vertebrates
Hagfish,Lampreys
CartilagenousFish Bony
Fish Amphibians MammalsBirdsReptiles
SkullBackbone Paired Fins
Jaws
Bony SkeletonSwim Bladder
Four LimbsTerrestrial Phase
Amniotic EggEndothermy
HairMammary Glands
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)
Tarsier
Macaque
Lemur
Primates : Humble Beginning
Primates
ShrewRabbit
Shrew-likeAncestor
Major Primate Groups
Lemurs
Tarsiiformes
New WorldMonkeys
Old WorldMonkeys
Gibbons
Orangutan
Gorilla
Chimp Human
Family Hominidae
Hominoidea : Apes and Humans
Hominidea : Great Apes and Humans
Homininae : African Great Apesand 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
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
What Features Are Associated With Primate Evolution?
Major Primate Groups
Lemurs
Tarsiiformes
New WorldMonkeys
Old WorldMonkeys
Gibbons
Orangutan
Gorilla
Chimp Human
Family Hominidae
25 mya
12 mya
6 mya
Hasegawa et al. 1987
5 mya
38 myaEstimated
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?
Approaches to Identify Genetic/Genomic Differences Between Chimps and Humans
1. Candidate gene approach
2. Microarray approach
3. Nucleotide substitution approach
4. Bioinformatic approach
Enard, W. et al. 2002. Molecular evolution of FOXP2, agene involved in speech and language. Nature 418, 869-872.
Candidate gene approach: FOXP2
- 2 non-conservative amino acid substitutions in humans-- flanking genomic DNA showed signs of a selective sweep
Signature of a Selective Sweep
Reduced polymorphismMore rare alleles
FavoredAllele
SelectionFixation
RecombinationMutation
• 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 motorsensoryfunctions and ultrasonic vocalizations.Shu et al. 2005. PNAS 102:9643.
FOXP2 plays a role in the development of brain regions that are important for communication
Pollard, KS et al. An RNA gene expressed during corticaldevelopment evolved rapidly in humans. Nature Aug. 2006
• 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.
Identified Human Accelerated Regions (HARs)
- 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)
Details of the Screening Process