Darwin’s Daring Kitcher: “Believing Where We Cannot Prove” Pages

Darwinian History 1. Describe an ancestral population of organisms. 2. Trace modifications of the population through the subsequent generations, showing how characteristics were selected, inherited, and become prevalent.

Many Purposes Can describe why a trait exists Can describe relationships between organisms Can account for similarities and differences among species Can explain organisms’ locations Can try to explain extinctions Can be used in many broad classes of biological phenomena

Evolutionary Theory in Action: Madagascar Island inhabited by a peculiar group of mammals, most of which are endemic tenrecs: small, insectivorous mammals : features mark them as primitive : have specialized characteristics similar to other animals that do not inhabit this island (convergent evolution) Why are they found here and nowhere else?

Evolutionary Story In the late Mesozoic or early Cenozoic period, primitive mammals rafted across the Mozambique channel to Madagascar. Channel widened, preventing more advanced mammals from crossing. The tenrecs were protected. Without competition, they have maintained the simple body plan and exploited unoccupied niches.

Claims Subject to Independent Check: Madagascar 1. Madagascar drifted away from Africa’s east coast. Can check using geological criteria for the movement of land masses (criteria independent of biology)

2. Tenrecs could have rafted across the Mozambique channel, but that the present channel is a barrier to more advanced mammals. Test by looking to see if the animals in question can disperse across channels of appropriate size.

3. Specialized methods of defense are advantageous against predators on Madagascar. Study animal interactions to see if certain defenses are effective against local predators.

4. Tenrecs are related. Studies of minute features of tenrec anatomy should reveal common features; should have similar protein structure.

Darwin’s theory can be compared to Newton’s Physics. Unified theory whose problem-solving strategies are used in many different areas. Problem solutions can be independently checked. Open new questions. History of surmounting apparent obstacles.