 Fossil evidence indicates that modern humans evolved in East Africa about 200,000 years ago  During most of there existence they survived by hunting and gathering  Agriculture started about 10,000 years ago  The development of agriculture gave rise to civilization.  the-story-of-all-of-us/videos/mankind-the- story-of-all-of-us-farming the-story-of-all-of-us/videos/mankind-the- story-of-all-of-us-farming

 Early agriculture was mostly subsistence farming  Subsistence farming – when the family produces just enough food to support the family unit (without excess intended for sale or trade)  Although this early farming method could deplete soil, it did not involved many of the environmentally detrimental techniques that are characteristic of modern farming.

 Agriculture by its very nature requires humans to manipulate the natural environment  Examples -plowing, tilling land -fertilizers -pesticides -monocultures -artificial selection -genetically modified organisms

 Pest – a troublesome, destructive, or annoying organism (this definition is from a human’s perspective of course)  Pests can cause many problems -can compete with humans for food (destroy crops) -can carry disease (example – malaria and yellow fever) -can have negative effects on native wildlife/environment -can cause damage to residential and commercial property

 Insects (can be killed by insecticides)  Fungi (can be killed by fungicides)  Mammals (can be killed by rodenticides and other poisons)  Nematodes (can be killed by nematicides)  Birds (can be killed by avicides)  Weeds (can be killed by herbicides)  Any organism that “interferes” with human activities can be considered a pest

 Introduced species – often become pests  Monocultures (growing a single kind of plant over a large area) encourages pest development -provide abundant food supply -often eliminate/reduce natural predators  Pesticides – often make the pest problem worst by making the targeted pest stronger and destroying natural predators

 Early pesticides – natural minerals or chemicals, were expensive and had limited success at controlling pests  Chlorinated hydrocarbons (including DDT) -discovered during WWI when insects were used to test chemicals (nerve gas) -became the most important group of insecticides

 Cheap and easy to use  Killed many different kinds of insects  Continued to kill insects long after they were applied (persistent)  DDT was the first widely used chlorinated hydrocarbon  DDT was banned in the U.S. in 1972 due to its adverse effects on the environment of-silent-spring/ of-silent-spring/

 Persistent vs biodegradable – persistent take a long time to break down in the environment while biodegradable pesticides break down more easily  Broad-spectrum vs. selective – broad-spectrum kill many different organisms including the target pest while selective kill the target organism *In North America only 1 out 8 insects is considered a pest!

 Pro – saved millions of lives and billions of dollars worth of crops, protect humans from disease and hunger  Con – can affect the natural ecosystem (often times in ways that we can not predict), can cause health problems, often make pests stronger (resistant)