An experiment is designed to test what color of light will activate a photoelectric cell the best. the photocell is set in a circuit that "clicks" in response to current. the faster the current, the more clicks per minute. in this experiment, the number of clicks in one minute is recorded for each color of light shining on the photocell. to change the color of light, a different color of cellophane is placed over the same flashlight and the flashlight is then located a specific distance from the photocell.

in the above experiment, which factor is the independent variable?

1. the number of clicks
2. the color of the light
3. the original source of the light
4. the photocell

Humans are believed to have evolved in coastal regions in east africa. the region had an abundant supply of fish for early humanoids to eat. when scientists analyze the fads gene they see an interesting pattern. people whose families have lived in this area of east africa for generation show a high level of diversity in alleles for the fads gene. conversely, people whose families had migrated inland a moderate distance from sources of fish showed a much lower diversity for fads gene alleles. additionally, the fads alleles found in people whose family has lived inland for generation are almost all gene alleles which produce fads proteins with a high level of function and activity. how do anthropologists explain this?