Why does a person need protein in their diet?

The body needs protein to build and repair tissues to make hormones, enzymes, body chemicals e.t.c.

The body also uses protein as a building block of blood , bones, skin , muscles, cartilage e.t.c.

Explanation:

genetic variation will increase because of a new habitat and food source.

explanation:

they had the law tat factories that produces smoke cannot be built near residential buildings.

building of proper sewage system was done to ensure that the waste is carried away from the humans so that they do not get diseases from it.

also they built water systems to provide water in those areas which are drought prone.