Nature Institute Perspectives #5
Where does a frog come from? The answer seems obvious. It comes from a tadpole. But does it?
Surely, without the tadpole the frog does not develop. But just as surely, nowhere do we find the frog in the tadpole. The frog comes into existence only as the tadpole disappears. We need to be keenly aware of what we mean, and what we don’t mean, when we say, “A frog develops out of a tadpole”—or a tadpole out of an embryo, or an embryo out of a fertilized egg, or an adult human being out of a child.
As we will see, when we give careful attention to what is actually happening when a new phase of life develops out of a previous stage, there are large implications for our overall understanding of developmental processes. New and exciting questions arise about how we conceive of development— including that trans-species developmental process we call evolution. -(From the Introduction)