If we could see your choices, it would better help us to help you.
Explanation:
But, if you are referring to the most widely accepted theory:
Anthropogenic (man-made) Global Warming, or AGW. The theory states that man-made greenhouse gases, primarily carbon dioxide (CO2 ), are the predominant cause for the global warming that has occurred during the past 50 years.
<span>(decreased variation in tail feather color because no form of the trait is advantageous) Due to the fact that the tail color is no longer a necessity, so it will eventually stop being needed and variation will decrease.</span>
