Notes on Human Origins by Rob DeSalle

Evolution is changes in the species (the individual)

species are differentiated by two characteristics: can they inbreed? and how different is their structure?

5 ways for evolution to occur (the first two are the most common with some debate about which of the first two is most common)

1. Adaptation

2. Genetic Drift

3. Mutation

4. migration

5. altered mating pattterns (mating across species for example)

Problems with evoluitonary adaption explanations

1. Very hard to test (if I say the reason that humans stood up is to display their genitalia, how would I test that). Or in the case of the Righteous mind, if I say we developed a "hive" mentality because group behavior is "better", that is both circular and untestable

2. How do we know when it's adaption and when its drift?  The only way to narrow it down is if there are bottleneck events that can be connected showing that a specific genetic change was emphasized with a decrease in population because with smaller populations we don't get an equal distribution of the genes.

3. Adaption does not always work for survival of the organism in which the gene adapted. So to say that we "adapted" for group behavior because it made us live longer we are making an erroneous correlation into an explanation (if there is even a correlation). A trait may be destructive but may be necessary to another trait that is beneficial. For example, we could say group behavior is destructive but it is necessary in order to have resistance to disease (because we pass around our immunities among each other).

4. Traits are often there and we don't know why--we only hypothesize without seeing the whole picture that may have led to that trait

5. exadaptations can occur.  That is the trait is present for a while without being used for what it is currently used for and then something happens that triggers its use.

Homonids have been around for 7 million years (marked by the shift to bipedalism), and the genus homo for 2 million

Why go bipedal?  the most promising explanation is the belief that it decreased solar ray exposure and increased the ability to cool off, vital considerations given that overheating can destroy the brain and ultiamtely kill

Tools seem to have been developed about 2.5 million years ago

Hominids left Africa around 1.8million years ago

Entered Europe between 800,000-1 million years ago

Neanderthals showeed up about 200,000 years ago in Europe and continguous Asia

Homo Sapians arrived 40,000 years ago (Cro Magnon man) in Europe and appear to be at least partially if not largely responsible fro the demise of Homo Neaderthal. It is believed they came out of Africa with their beginning ancestral divergence appearing to date back 160,000 years. Initially behavior was similar to other hominids but 75, 000 years ago more modern behavior began to occur including the first symbolic behavior. All other Hominid species began to disappear around the same time across the world--about 40,000 years ago, suggesting that something in Homo Sapian out competed other hominids.

Mitochondrial DNA shows that homo sapians did not share MDNA with Neanderthals (no in breeding) and that all MDNA for homo sapians originated in Africa