Marine biologists have long thought that variation in the shell color of aquatic snails evolved as a protective camouflage against birds and other predators.
Curious Fact
Why do aquatic snails have variation in the color of their shell?
Traditional Explanation
It helps camouflage them, so birds and other predators can't find and eat them.
Evidence for Traditional Explanation
Brown shells are more common where the seafloor is dark, and white shells are more common where the seafloor is light.
New Explanation
The amount of heat absorbed leads to physiological stress that can affect the color of the shell.
Evaluate
There isn't yet evidence for the new theory, but we're told certain predictions the theory makes. Since high waves refract the incoming light, less heat is absorbed at the seafloor, which leads to brown shells. Where water is calm, more incoming light makes it to the seafloor, which leads to whiter shells.
Goal
We need evidence that makes it more plausible that heat absorption is the causal difference-maker for brown vs. white shells, not camouflage.
The most typical causal strengthener has a No Cause, No Effect form. Since the new theory predicts that variations in heat absorption causes variations in shell color, we could see an answer like .
The predictions mentioned in the final sentence connect heat absorption to the Sun's rays, but the theory isn't specifically about the Sun, so we may see an answer that uses some other mechanism that relates to heat, to show that shell color varies with exposure to this heat.