People cannot devote themselves to the study of natural processes unless they have leisure, and people have leisure when resources are plentiful, not when resources are scarce.
Conclusion
Agriculture did not begin under conditions of drought and hunger (it began when resources were plentiful)
Evidence
Agriculture required the active study of natural processes in order to make complex discoveries about how various plants reproduced and grew to maturity. Devoting yourself to the study of natural processes requires leisure, and leisure requires plentiful resources.
Evaluate
Around 50% of all Main Conclusion questions involve a conclusion that is a rebuttal to someone else's thinking. Knowing this tendency helps us to find the conclusion here. "Although anthropologists claim X ... " is our signifier that the author is probably trying to rebut their claim.
If we follow that hint, we see that she definitely is doing just that. They have claimed that agriculture began under conditions of drought and hunger, and our author lays out a case that agriculture, based on what it requires, would have to have began during a time of plentiful resources.
Goal
Find an answer that sounds like .