Can someone tell me how some of us have jagged teeth (like shark incisors)?

Various shapes: Teeth can form in various shapes congenitally, but wear patterns can also cause the shapes to become jagged. An evaluation by a dentist or orthodontist can help you to know if the shape of your teeth has occurred from years of wear or a misaligned bite. If this is something you have had all your life, then it is just the natural shape. A dentist can shape them, if you are concerned with it.

Blame parents: Tooth size, shape, and position is genetically determined. Tooth shape can be altered by uneven wear, especially if teeth are malposed. Orthodontists can straighten your teeth. Family dentists can reshape your teeth. Seek consultations.

Mamelons: The bumps on your child's permanent teeth are normal. When your teeth meet, these get worn down.With time.

Normal but: It's normal in newly erupted adult teeth, the edges are sharp (called mamelons) they normally wear down in time, but sometimes in adult life , edges if teeth can ship from dental appliances etc. , or uses other than food like opening and cutting things with them causing them to be sharp . Also diet, smoking habits , occupational habits might determine the wear patterns.