In 1-2 sentences, explain why people will do less of an activity when the marginal costs are greater than the marginal benefits.

People will do less of an activity when the marginal costs are greater than the marginal activities simply because it isn't worth it. We want to get the most out of our actions.

When the marginal costs, or, in other words to make it simpler, the cons are greater than the marginal benefits, or pros, it's a waste of time.

We need to have more pros than cons, in order to make activities worthwhile. In this scenario, there must be a change in the strategy and the processes, to either reduce marginal costs or increase marginal benefits.

darwinism is survival of the fittest there for social darwinism is the survival of the wealthiest

i would say it is the roman empire europe after the norman conquest.