Electronic/World Wide Web>Internet Article:  Sadedin, Suzanne (Nov 7, 2016), Why do women have periods? What is the evolutionary benefit or purpose of having periods? Why can’t women just get pregnant without the menstrual cycle?, Retrieved on 2018-03-20

Source Material [www.quora.com]

Periodicals>Journal Article:  Leach, Helen M. (June 2003), Human Domestication Reconsidered, Current Anthropology, Volume 44, Number 3, Retrieved on 2015-11-12