Natural SelectionNatural Selection

Or, how did we get here….Or, how did we get here….

Natural SelectionNatural Selection

The Theory of Natural Selection is so simple that anyone can misunderstand it…. (Anonymous)

Charles Darwin (1809-1882) saw three problems in need of a solution. Darwin was not the only one to see these problems BTW

Other ‘Naturalists’ were struggling with the same issues

The Theory of Natural Selection is so simple that anyone can misunderstand it…. (Anonymous)

Charles Darwin (1809-1882) saw three problems in need of a solution. Darwin was not the only one to see these problems BTW

Other ‘Naturalists’ were struggling with the same issues

Problem the FirstProblem the First

There is change over time in the flora and fauna of the Earth What we would commonly call ‘evolution’ today

The fossil record showed this to be pretty clear, even to people in the mid 1800s

This was not controversial in Darwin’s time, and is not now.

There is change over time in the flora and fauna of the Earth What we would commonly call ‘evolution’ today

The fossil record showed this to be pretty clear, even to people in the mid 1800s

This was not controversial in Darwin’s time, and is not now.

The Second ProblemThe Second Problem

There is a taxonomic relationship among living things People were big into classifying stuff

It was pretty obvious that there was a relationship between different species Different birds, different grasses, different cats etc

There is a taxonomic relationship among living things People were big into classifying stuff

It was pretty obvious that there was a relationship between different species Different birds, different grasses, different cats etc

The Third ProblemThe Third Problem

Adaptation Different kinds of teeth for different animals, say carnivore ripping teeth and herbivore grinding teeth

Different tissues within species Heart vs. eye etc.

Adaptation Different kinds of teeth for different animals, say carnivore ripping teeth and herbivore grinding teeth

Different tissues within species Heart vs. eye etc.

The Solution!The Solution!

Natural Selection provides a mechanistic account of how these things occurred and shows how they are intimately related.

It is one of those ‘oh man is that ever easy, why didn’t I think of that?’ type things.

Natural Selection provides a mechanistic account of how these things occurred and shows how they are intimately related.

It is one of those ‘oh man is that ever easy, why didn’t I think of that?’ type things.

How’s it work?How’s it work?

There is competition among living things More are born or hatched or whatever, than survive and reproduce

Reproduction occurs with variation This variation is heritable Remember, there was NO genetics back then, Chuck knew, he just knew….

Realized that is wasn’t ‘blending’

There is competition among living things More are born or hatched or whatever, than survive and reproduce

Reproduction occurs with variation This variation is heritable Remember, there was NO genetics back then, Chuck knew, he just knew….

Realized that is wasn’t ‘blending’

How’s it Work?How’s it Work?

Selection Determines which individuals enter the adult breeding population This selection is done by the environment

Those which are best suited reproduce

They pass these well suited characteristics on to their young

Selection Determines which individuals enter the adult breeding population This selection is done by the environment

Those which are best suited reproduce

They pass these well suited characteristics on to their young

How’s it Work?How’s it Work?

REPRODUCTION is the key, not merely survival

If you survive to be 128 but have no kids, you are not doing as well as I am

I have reproduced… Assuming the traits that made me successful will help them then I amore fit NOW than the 127 year old guy

REPRODUCTION is the key, not merely survival

If you survive to be 128 but have no kids, you are not doing as well as I am

I have reproduced… Assuming the traits that made me successful will help them then I amore fit NOW than the 127 year old guy

This lecture keeps evolving…..This lecture keeps evolving….. Survival of the Fittest (which Chucky D NEVER said) means those who have the most offspring that reproduce

So, the answer to the trilogy of problems is:

‘Descent with modification from a common ancestor, NOT random modification, but, modification shaped by natural selection’

Survival of the Fittest (which Chucky D NEVER said) means those who have the most offspring that reproduce

So, the answer to the trilogy of problems is:

‘Descent with modification from a common ancestor, NOT random modification, but, modification shaped by natural selection’

Different types of selectionDifferent types of selection Directional Selection

What most of us think about when we think about selection

An extreme value is selected for

Human brain size is a nice example

Directional Selection

What most of us think about when we think about selection

An extreme value is selected for

Human brain size is a nice example

Different kinds of selectionDifferent kinds of selection Stabilizing or Normalizing selection

The middle is selected for

Many examples here Symmetry Two eyes

Stabilizing or Normalizing selection

The middle is selected for

Many examples here Symmetry Two eyes

Different kinds of selectionDifferent kinds of selection Disruptive selection

Extremes are selected for

Might be where the two sexes come from

Trait was probably gamete sized

Two ‘mating types’

Disruptive selection

Extremes are selected for

Might be where the two sexes come from

Trait was probably gamete sized

Two ‘mating types’

Other Evolutionary TheoriesOther Evolutionary Theories Lamarckism

Inheritance of acquired characteristics E.g., giraffes really wanted leaves, so they stretched their necks and…..

Sounds crazy, but a lot of people think this way

‘We will all have giant heads and tiny bodies someday’

‘Cave swelling fish don’t use their eyes so they disappear’

‘We don’t use our appendix so it is disappearing’

Lamarckism Inheritance of acquired characteristics E.g., giraffes really wanted leaves, so they stretched their necks and…..

Sounds crazy, but a lot of people think this way

‘We will all have giant heads and tiny bodies someday’

‘Cave swelling fish don’t use their eyes so they disappear’

‘We don’t use our appendix so it is disappearing’

Silly incorrect evolutionary theories and ideas

Silly incorrect evolutionary theories and ideas Orthogenesis

There is some plan to evolution. NO WRONG INCORRECT, THANKS FOR PLAYING

The idea of an ‘evolutionary ladder’ fits in here

It is wrong too……

Orthogenesis There is some plan to evolution. NO WRONG INCORRECT, THANKS FOR PLAYING

The idea of an ‘evolutionary ladder’ fits in here

It is wrong too……

Still another silly ideaStill another silly idea Intelligent Design Just Creationism with a fancy name

God does not belong in a science class, any more than experiments belong in church

NOT A SCIENTIFIC THEORY

Intelligent Design Just Creationism with a fancy name

God does not belong in a science class, any more than experiments belong in church

NOT A SCIENTIFIC THEORY