A zoologist is investigating a population of squirrels whose coat color is controlled by a single gene whose two alleles (B1 & B2) are codominant. B1B1 individuals are black, B1B2 individuals are brown, and B2B2 are tan. She surveys the population and finds 145 black squirrels, 221 brown squirrels, and 43 tan squirrels. Is this population in HWE? If not, what might explain this pattern?