Oversimplified strongly held views about males and females refer to

Gender stereotypes

the tasks and activities that a culture assigns to each sex

Estúpido vas a la escuela y no te olvides de tomarte una cerveza.

The changes to agriculture in the united states since 1900 is that increased mechanization has increased food production, thereby increasing the need for labor. there has been an increased need for higher speeds of food production due the fact that the population in the united states continues to rise.