N 1961, President John F. Kennedy and his advisers decided to invade Cuba with 1400 CIA-trained Cuban exiles. When the invaders were easily captured and soon linked to the U. S. government, Kennedy wondered in hindsight, "How could we have been so stupid?" This is an example of:
Groupthinknormative social influenceGeneralized anxiety

The answer is Groupthink.

Explanation:

Groupthink can be defined as a psychological phenomenon that usually takes place inside a specific group of people. In this group, there is a desire to achieve harmony or conformity, but that desire produces an irrational result concerning decision-making.

There is another aspect that usually takes place in a group and this is called cohesiveness. This aspect can produce that the different members who belong to a group have a tendency to agree at all costs, and this produces that the group reduces conflict, as well as an achievement of consensus decision without the existence of critical evaluation.      

early settlements on the subcontinent. both the indus and the ganges rivers carried rich silt from the mountains to the plains. when the rivers flooded, the silt spread over the plains and made the soil in the river valleys fertile for farming.

the answer to your question is,

old stone age.

-mabel < 3