2. Examine the arm bones of the two skeletons. Was Grandmother right- or left-handed? How about Grandfather?

He looks ambidextrous but he may also be right handed due to the slight more bone on his right arm.

Explanation:

Its a little hard to tell, my guess is that he was ambidextrous, but his right arm does look slightly more dominant so really it may be his right arm.

i think its the first one