Evolution

“Of course, long before you mature, most of you will be eaten.”

“The picture’s pretty bleak,

gentlemen. The earth’s climate is

changing, the mammals are

taking over, and we all have brains

the size of a walnut.”

“Now this end is called

the thagomizer, after the late

Thag Simmons.”

“Evolution’s been good to you, Sid.”

Top Ten Myths About Evolution

1. Humans Evolved From Monkeys

• Humans and great apes had a common ancestor about 5 million years ago

• Humans and monkeys had a common ancestor about 50 million years ago

2. It’s Only A Theory“Theory” does not mean “hypothesis” or

“guess”• Music Theory• Stress Theory• Quantum Theory• Number Theory“Theory” means an organized set of related

ideas.

3. If Nobody Saw It, We Can’t Be Sure It Happened

• If you find your room trashed and your TV and stereo missing, will you hesitate to call the police because nobody saw it happen?

4. Science Can’t Say Anything About Origins

• Maybe not. But once the origin happens, everything after that is history. And historical evidence is preserved in the physical record.

5. Obsolete Concepts

“Survival of the Fittest”• “The winner of the Super Bowl is the team

with the most points.”• What does “fittest” mean?

6.There Are No Intermediate Fossil Forms

7. Evolution Is Not Testable• Darwin suggested birds had evolved from

reptiles in 1859; Archaeopteryx was discovered in 1862.

• Piltdown Man– Famous Early Fossil Man Hoax– Controversial from the start because it

didn’t match evolutionary expectations.

8. Evolution Means Humans are Just Animals

• Are you a vegetable or mineral?• Humans have hair and nurse young just like all

other mammals• Traits like nurturing, cooperation and

monogamy are often favored by evolution because they enhance survival of species

9. Evolution is Just Random

• Is the following number sequence random: 592653589793238462643383279?

• It not only looks random: it is random. • But lacking in meaning? No. These are the

digits of pi beginning with the fourth decimal place.

• Random does not mean “meaningless”

The Scientific Meaning of Random

• Something cannot be predicted with better accuracy than that predicted by statistics.

• The phenomenon is its own simplest description

Randomness and Evolution

• Biological systems are far too complex to describe or predict mathematically

• We have incomplete information• Significant events like climate change or

asteroid impact are unpredictable.

10. Complexity Cannot Arise Naturally

The Second Law of Thermodynamics is often paraphrased as:

• ”Things always go from bad to worse”• ”Disorder in the Universe is always increasing"

The Second Law of Thermodynamics

• The Second Law is about entropy• Entropy = (Heat Absorbed)/Temperature• Entropy can decrease locally if it increases

elsewhere• Intuitive notions of “disorder” are of no

relevance whatsoever

Chemical Reactions are not Random

Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl

Na Cl Na

Cl Na Cl Na Cl Na Cl Na Cl Na Cl

Channeled Scablands, Washington

Scabland Terrain, Oregon

The Geologic Record• Physical evidence records mostly small-

scale, gradual processes• Fossils show a gradual increase in

complexity with time• Fossil forms intermediate between major

groups are well documented• Over most of its history, life on Earth was

simple

Were the Dinosaurs Failures?

• Human History = 5000 years• Dinosaurs = 150,000,000 years• Dinosaurs had:

– 30,000 years for every year of human history– 80 years for every day– 8 hours for every second

Prebiotic Evolution

• The basic molecules of organic chemistry are easily made

• The first self-replicating molecule was almost certainly not DNA

• DNA assembles from simpler materials all the time

DNA• Deoxyribonucleic acid• Total length of human DNA in a single cell is

about a meter• A human body contains about 20 trillion

cells• The total length of DNA in a human body is

thus 20 trillion meters, or twenty billion kilometers, the circumference of the orbit of Pluto.

Plants and Animals

• CO2 + H2O + Energy = Sugars, Starches, etc. + O2 (toxic waste). O2 is actually toxic (even to us!)

• 6CO2 + 6H2O C6H12O6 +(glucose) + 6O2

• Idea: Take the sugars and starches (from somebody else) combine it with the waste O2, and get energy

Amazing Events in Life History

• “Invention of Sex” - Who Needs It?• We are a team - Mitochondria• The Great Freeze 900-600 m.y. ago• Mass Extinctions

– Dinosaurs = 4th worst– Permian extinction (220 m.y. ago) took out 90% of

all species

Selection• Deliberate selection for desirable traits by

humans (only since ca. 1700)• Unsystematic selection for desirable traits

by humans (domesticated animals and plants)

• Unconscious and unintentional selection by humans (self-domestication of animals)

• Natural selection with no human intervention at all

Lessons from Selection• Artificial selection has produced organisms

radically different from their natural state• Natural selection has resulted in dramatic

changes in natural populations with and without human intervention

• Microorganisms and viruses change with dazzling speed (mutation of flu viruses, resistance to antibiotics, move to new hosts)

This Descended from Wolves?

Evolution By Natural Selection• Charles Darwin and Alfred Russell Wallace,

1859• Organisms are adapted to their

environments• Individuals vary• More organisms are born than can possibly

survive• Variations best suited to the environment

tend to survive and be passed on.

Mutations• Change in DNA code• “If you fix it often enough, you’ll break it”• Most organisms already adapted• Chance of random beneficial change small• Many mutations are neutral• Radical changes usually harmful• Mutations may be useful if the rules change

Radiation

• If no competitors or predators, otherwise harmful variations may flourish– Example: loss of flight or sight

• After mass extinctions• Spread into unoccupied habitats• Rapid proliferation of variations

Convergent Evolution

• Unrelated organisms may develop similar features

• Often dictated by physical constraints• Shark, tuna, dolphin, seal, squid, penguin,

ichthyosaur• Deer, pronghorn, impala• Albatross, pterosaur

Exaptation

• Modification of existing structure to serve new function

• Fin – paw – wing – hand• Scale – feather• There are no half-formed organisms

What Good is Half an Eye?

What Does a Bug See?

What Does a Bug See?

What Good Is Half An Eye?

• A “partially-developed” eye can be very useful• Selection will favor:

– More Receptors (Sharper Image)– Wider Angular Spread (Better direction

discrimination)– Better Image Processing

What Good is Half a Wing?

Powered Flight• Insects• Birds• Bats• Pterosaurs?

Gliders• Squirrels• Lemurs• Marsupials• Fish• Frogs• Snakes• Lizards

Physics of Gliding

• Terminal Velocity• Air Resistance = Gravitational Acceleration

– 200 km/hr for a human– 20 km/hr for a mouse

• Gliders are All Small• Can Survive Fall• Selection favors duration and control

Two Bumblebee Myths

Theoretically, bumblebees should not be able to fly.

• Bumblebees can’t glide well. Neither can many aircraft

A bumblebee can carry more than its own weight, something no airplane can do.

• C-5A empty 238,000 lb., maximum takeoff weight 840,000 lb.

Classification of Dogs and Humans• Kingdom Animalia• Phylum Chordata• Class Mammalia• Order Carnivora (Dogs) Primates

(Humans)• Family Canidae Hominidae• Genus Canis Homo• Species familiaris sapiens

Strigiphilus garylarsoni

“Actually, I considered this an extreme honor. Besides, I knew no one was going to write and ask to name a new species of swan after me. You have to grab these opportunities when they come along.”

Below Species

• Ideally, species is a genetic group capable of breeding

• Subspecies• Race

– As used for humans, has little scientific meaning

• Population

The Five Kingdom System• Animals• Plants• Protista (one-celled organisms)• Fungi• Bacteria*• Ediacaran Fossils? (ca. 700 m.y. ago)

What’s Bigger Than a Kingdom?• Bacteria differ from all other kingdoms in

lacking a cell nucleus• We need a bigger box• Superkingdoms or Domains

– Monera (Bacteria)– Archaea– Eukarya (have cell nucleus)

• Need electron microscopes and molecular biology to see differences