Final answer:
Challenges to Tutt's hypothesis about industrial melanism in moths have arisen due to observations that other factors, beyond bird predation, may influence moth color changes, particularly as environmental conditions have improved with cleaner factory emissions.
Step-by-step explanation:
Recent observations have challenged Tutt's hypothesis that industrial melanism in moths is caused solely by selective predation by birds. Instead, it has been suggested that other factors may also play a role in the changing colors of moths. During the Industrial Revolution, soot and other wastes darkened tree trunks, making darker moths less visible to predators and thus more likely to survive.
This led to an increase in the darker colored peppered moths in polluted areas. However, as air quality has improved and factories release less soot, tree bark has lightened, and the lighter colored moths are becoming more common again. This fluctuation in moth populations supports the idea that the environment heavily influences evolutionary pressure and that adaptive traits in organisms can change as their habitat does.