Vestigial because they don't use it but it's still there
Physical anthropologist John Hawks and colleagues suggest that evolution is speeding up as population sizes are being continued to mushroom and new mutations which are endorsed.
Human population increased rapidly. The increase began those days of upper Paleolithic which is documented by archaeological evidence.
Acid rain is caused by a chemical reaction that begins when compounds like sulfur dioxide and nitrogen oxides are released into the air. Hope this helps
