Re: Why is it necessary for human male to be bigger than human female?

I've decided to rephrase your question from WHY to WHAT, since I can't begin to answer for a culture's "Supreme Being."

What biological purposes are served by providing the male member of an animal species with a genetically determined larger body size than the female counterpart? If you examine the role of the male, particularly among primates, at least three physical bio-functions seem to me to favor a large, muscular, and strong male in a species.

1)Competition: The male is responsible for successfully selecting and keeping a choice of mate or mates;
2)Protection: The male is generally the major protector of the family unit and its family ("home") territory; and finally
3)Food Provision: While hunting and gathering food is ultimately shared, it is the male, certainly during the period of late pregnancy, birth and early nursing of the newborns, that must shoulder the major responsibility for locating, collecting and providing food for the enlarging family unit.

This is a very complex question, and I think you and your classmates can find some more size-related reasons to add to these three.

Good luck on your life-long learning.