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