Everyone born has genes. They come from your two parents and you cannot change them.
You carry two copies of everything, one from each parent. Each parent passes on one of their two, at random.
So you carry recessives you cannot see, and so does everyone else. Two carriers can have a child who shows it.
Use an Analysis scroll. It writes you a book listing what you show and what you carry.
Nothing else tells you. You cannot tell by looking at someone.
Two related parents are more likely to match up the same recessive, so bad traits surface.
It also costs the child hearts. Unrelated parents give 23. Full siblings give 17.
Births can throw a new trait that neither parent had. It is uncommon.
Inbreeding makes it much more likely. That is the one thing inbreeding is good for.
calm_aura, dragongaze, elderlung, green_thumb, moonblessed, skullboundsinew,
sleeplessgait, wardenmarrow
barren_blood, brittle, food_allergy, picky_palate, sterile_strain, the_shakes, unease
Size, speed and hunger do not switch on or off. You land somewhere between your parents.
Size runs from about 1.5 blocks to about 2.5 blocks. A tall enough player will not fit through a 2-block gap.
Three traits only founders start with: calm_aura, green_thumb, moonblessed. They are inherited
normally after that, and they are never rolled as mutations.
Capturing a mob's soul can put its blood into your line. See Souls.