Which is a direct impact of the movement to ban DDT?

How do i can change this sentence : a modern physician in a small town not only is proficient in general medicine but surgery as well. to parallel structure?

The greatest gift the sumerians gave the world was the invention of writing. the sumerians were a wealthy people. they needed some way to keep track of what they owned. they began drawing pictures. they used a reed as a pen. they drew on soft pieces of clay. the soft clay was then dried in the sun. the tablet became a permanent record. later, the sumerian drawings changed into wedge-shaped symbols. this kind of writing is called cuneiform. by putting symbols together, the sumerians could write entire sentences.

Which sentence best summarizes this excerpt from book 21 of the odyssey?