I'm not a biologist or anything but I think it's pretty obvious that person's health/hormonal balance would have a huge effect on a person's mood, endurance and outlook on life. Your mood determines...
The proper way of saying "Human to Human" is Human to Human. EX. Can a worm pass from Human to Human? No.
Biology is extensively used in medicine; a technology used to help people be healthier.
Normality exists in societal and scientific expectations. However I believe that existence constitutes normality. -clm
well human biology is a type of study of science you do all about the human body.