1. Darwin’s Theory of Evolution
1. Like organisms beget like organisms
2. Few organism in natural environment actually survive
3. In a population there are variations among individuals
4. Some variations are more “favorable” than others for
that given environment
5. Given time, small accumulated changes can lead to
differentiate groups of organisms from one another

2. Artificial Selection: Domestication
Domestication: Growing a plant and consciously or
unconsciously causing it to change genetically from its
wild ancestor to better benefit humans
Human domestication of plants began in the Fertile
Crescent (modern day Middle East) about 10,000 years ago
Domestication almost certainly began as an accidental or
unconscious act

3. What Plants Do
Since plants are relatively immobile, they must have developed
ways to spread their offspring out as far as possible so that they
could have as many viable offspring as possible
Plant seeds are, therefore, quite crafty. They can be transported
by wind, water, explosive power or by hitching a ride on animals.
Berries are a particular vehicle for this travel as they entice birds
with their sweet fruit and bitter seeds to ingest them without
destroying them

4. Where did Humans start domesticating plants?

5. The Fertile Crescent

6. Why was the fertile crescent a great area to domesticate plants?
Has a Mediterranean climate
(mild wet winters, long,hot dry summers)
Plants adapted to these conditions
annuals: seeds remain dormant during summer rapid growth in spring
energy put into producing large seeds
Large number highly productive of wild plants
Few changes were needed to be made to the plants
Easy to domesticate
Many of the plants were hermaphroditic
pollinate themselves, don’t lose traits
some cross pollination helped create new hybrids

7. Early domestication: a hypothetical situation
When picking berries in the hot sun amongst the mosquitos,
Achmel, a hunter-gatherer from modern Iran, chooses the ones
that are biggest, sweetest and most visible.
The berry seeds pass through Achmel and begin growing new
bushes at the latrine that have generally large, sweet, visible
berries.

8. What were humans looking for in a plant?
Humans naturally selected large, sweet seeds to eat.
Fleshy or seedless fruits, oily seeds, and long fibers.
Olives for oil, hemp, and flax for fibers.

9. Some Example Domesticates
Peas: Selected for non-exploding pods
Wheat/Barley: Selected for non-exploding husks
Almonds: Selected for lack of Cyanide… good idea
Cotton: Selected for fiber or, more recently, oil
The Mustard Plant...

10. The mustard family
Selected mustard plant for the bulbous root

11. The mustard family
Or selected for the leafy section

12. The mustard family
Or selected for the buds

13. The mustard family
The flower and stalk

14. The mustard family
Or selected just for the size of individual side buds

16. Waves of Domestication
10,000 Years ago:
Barley/Wheat, Peas
4,000 Years ago
Olives, figs, dates, pomegranites, grapes, corn
More recent
Apples, pears, plums, cherries, strawberries
Why these different times?

17. Genetics and Acorns
Why were some crops domesticated before others, and some
still haven’t been? --- it’s all about the genes
A quick review of Punett Squares
Polygenic and Pleiotropic
So why not acorns?
10 year growth
squirrels
Bitterness is Polygenic in acorns

18. Why is it hard to domesticate some plants
Why is it hard to domesticate some plants? More than one gene controls a trait, like bitterness in Oak acorns Slow growth Competition from other organisms in selecting traits Reproduction was not self-pollinating Plant did not have many initial desirable traits to start with

19. What plant domestication tell us about Natural selection?
It acts as a model to show how natural selection works.
Most plants produce offspring that are like them
There is variation in plant populations (mutations)
Plants are adapted for their environment (fertile crescent)
Over time Humans have been able to create new varieties of plants using artificial selection
Traits are controlled by genes