Evolution

The Evidence

‘Evolution’ stands for several theses:

• Mutability of species (i.e. species change over time)– (observed/confirmed)

• Natural selection – (observed/confirmed)• Community of descent (i.e. all life forms share a

common evolutionary history ; all forms are related by descent)

– Including humans and chimpanzees; humans and fish; humans and turnips; humans and bacteria

– (inference; but based on diverse and compelling evidence)– (indirectly observed/indirectly confirmed)

Evidence for evolution1. Fossil Record2. Vestigial Structures3. Skeletal Homologies4. Embryological Homologies5. Cellular Homologies6. Genetic Homologies7. Imperfect Design (Dysteleology)8. Observed instances of origin of new species

Fossil record

Archaeopteryx, dinosaur-bird transition

Fossil record

Tiktaalik rosae, fish-land vertebrate transition found Canadian Artic 2004

Vestigial structures

Vermiform appendix

Vestigial structures

Hand bones

Skeletal homologies

Embryological homologies

Haeckel 1874

Embryological homologies

Richardson et al 1997

Cellular homologies

Genetic homologies1. All living things use same genetic code: DNA,

RNA2. All living things employ same 20 amino acids to

form proteins3. All living things use only right-handed molecules4. Homologous proteins and genes found in

organisms as widely different as humans, fruitflies, tulips, brewers yeast, and bacteria

Genetic homologies

Human-chimp 98% overlap

Same base-pair errors occur in human & chimpanzee pseudo-genes: Coincidence?

Missing Human Chromosome Pair

If humans and other apes evolved from a common ancestor why do we have only 23 chromosome pairs to chimps’ 24?

Tinkering

Dysteleology (poor design)

Dysteleology (poor design)

Dysteleology (poor design)

Dysteleology (‘tinkering’)

Dysteleology (‘tinkering’)

• Eukaryotic cells (like ours) a symbiotic merger of several previously independent prokaryote bacteria

• Mitochondria (animals)• Chloroplasts (plants)• Centrioles, nucleus too?

Poster child of tinkering

Symbiotic merger of at least 4 separate organisms; 5 counting mitochondria

Have we ever observed the origin of any new species?

• First, what do we mean by a species?• Morphological species concept: based on

observable body shape, size, markings etc.• Reproductive species concept: two organisms

are of the same species if they can successfully produce fertile offspring

Origin of new species observed

Polyploidy = chromosome # increase (genome doubling etc.; common in plants; but also seen in amphibians, fish)

Origin of new animal species observed

• Fruitflies• Mosquitoes• Cichlid fishes• Amoeba-bacteria

symbiont