Introduction to Evolution

Darwin’s Theory of Evolution Evolution, or change over time, is the theory of the process by which modern organisms have descended from ancient organisms. A scientific theory is a well-supported explanation of phenomena that have occurred in the natural world.

Evolution Myth Top 3 1. Humans Evolved From Monkeys –Humans and monkeys had a common ancestor about 50 million years ago. Nowhere, except in the most illiterate anti-evolution literature, will you find a claim that humans evolved from monkeys.

2. It’s Only A Theory –“Theory” does not mean “hypothesis” or “guess” “Theory” means an organized set of related ideas. If you have a set of previously disconnected observations, and you come up with a possible explanation, you have an organized set of related ideas - a theory. A theory that hasn't been confirmed is a hypothesis. People commonly but incorrectly talk as if theories and hypotheses are the same thing.

3. If Nobody Saw It, We Can’t Be Sure It Happened –If you find your house trashed and your TV and stereo missing, will you hesitate to call the police because nobody saw it happen? Would you want the judge to dismiss the case just because you only had forensic evidence, but no witnesses?

Fossils Fossils are the remains of organisms that have turned to rock. They provide a picture of organisms that live long ago. Fossils are used as evidence for evolution. –Pictures of extinct creatures that humans create are inference.

Inference based on Fossil Evidence Evidence Inference

So, how do you date a fossil? What ways do scientists have of telling how old a fossil is?

Stratigraphy Study of the position of rock layers or strata in sedimentary rock. The higher or more shallow layers are younger and the lower or deeper layers are older. The location of the fossil within the layers indicates fossil age.

Stratigraphy

Radioactive Isotopes Radioactive elements like uranium- 236, potassium-40 and carbon-14 have known decay rates (or half-life) The amount of radioactive decay is measured, and an approximate age for the fossil is determined.

Ardi 4 million y.o.

Homologous Structures The limbs from very different animals which have very different functions, but very similar structures. Can be anything from forelimbs, to hindlimbs, to eyes and other organs. Indicates ancestral relationships between very different animals.

Homologous Structures

More Homologous Structures

Primate Homology

Pentadactyl Limb

Bird Homology

Vestigial Structures Structures or organs that are functional in some species, but seemingly useless in others. It is basically believed that the more advanced animals have evolved past the organ, but have not lost it yet. Indicates ancestors.

Vestigial Structures

More Vestigial

Whale Evolution

Embryology The embryos (the prebirth, prehatching stage of vertebrae life) are compared. Resemblances are noted. The further along in pregnancy the embryos look similar, the more closely related the organisms are.

Embryology

Comparitive Embryology

Biochemistry Compare the information encoded within the DNA. The more similar the DNA strands are, the more closely related the organisms are. The likelihood of developing identical sequences of DNA without being related is highly unlikely.

Biochemistry (DNA)

Skull and Bone Comparisons The skulls and bones of hominids are compared and contrasted to determine evolutionary trends through time.

HUMANS DO NOT COME FROM MONKEYS!!

Skull Comparisons