Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Adaptation to High Population Density and Air Travel
Humans evolved to live in small family groups. The first cities were settled 3000 to 4000 B.C., but significant numbers of people moved to live in large cities only over the last several centuries. Air travel is an even more recent development and became available in the last 100 years. Bats, however, have evolved to deal with these challenges over the course of 60–70 million years.
