Because people can learn from other people, in both in failures and in successes. The founding fathers of the United States took after the Roman republic in modeling after there government. This is why the United States Congress is structured in the same manner as the Roman Congress. Versus the rectangular or roundtable types of congresses that are seen in European countries.
They also took after the Romans on the idea of a republic being comprised of people elected to represent them. These people are also meant to be changed out on a regular basis. And that the public was in control of who was calling the shots on their behalf.
The invention of the microscope, contributed to the discovery and accelerated research of microscopic, single cell and multi-cell organisms that are found all around our planet, this also led to our better understanding of pathogens such as germs, viruses, bacteria, fungi, parasites, and much more. <span />