A meteorite comes into the Earth's atmosphere. It is big enough to not be completely vaporized by the heat but small enough to avoid detection from any satellites. It lands without much fanfare. However, the meteorite has an unusual property that could have been man-made. While humans and invertebrates remain unaffected, what ever animal is within one mile of the meteorite permanently becomes an anthropomorphic version of itself.
They gain human level intelligence but not knowledge. They have basic human characteristics (bipedal, hands with opposable thumbs, etc.) but still keep a lot of their animal characteristics. Their senses will go up to human level unless they are already above it (ex. dogs will get better eyesight but keep above human smelling).
Fish would breath both air and water. Birds (and bats) would develop hands on their wings. Mammary glands would still be exclusive to mammals.
As established, anything without a vertebrate would not be effected. So insects, mollusks, worms and the like would remain normal.
While humans would not change one way or another, there is still a chance that someone saw the meteorite fall and would be interested to see where it had landed...
Anyway, the story begins...