It is now believed that the largest contributing factor to the decline of the Indus Valley civilization was an outbreak of disease--since there were no treatments and the density of the civilization led the disease to spread very quickly.
It had it so they new if they were on someones territory
Instead of chasing after their prey, homo sapiens developed spears out of flint and rock to kill their prey. The discovery of fire also helped these homo sapiens cook their food, which helped them to avoid sickness as a result of food poisoning.
The United States didn't want to stay behind, so it increased funding for its own space program in order to be more productive and launch more satellites.<span />