What are some of the biological features that humans have developed that the early mammals did not possess?

In a relatively small iguana population the allelic frequency is tracked for three generations. webbing is a recessive allele; no webbing is the dominant allele. during one very rainy spring and summer, a flood washes all the iguana without webbed feet out to sea. by the fall, and three generations later, you have the gene pool seen here.

What are some things that limit population growth?

What environmental cues and landmarks do the geese use to determine the timing and direction of their migration over the mountains? how do they find their way?