I do not think this is particularly something to worry
about, especially if you have had it for a long time without any significant changes. On the other hand, if you are worried about it it would not be a bad idea to show it to your dentist
or your primary care doctor
and see what they think. The fact that your father, who is a dentist, is not worried about it is also a good sign!
The most likely possibility is that you have spots of pigment in the tongue. These are caused by collections of pigmented cells called melanocytes, and they are really quite similar to moles and freckles that occur on the skin.
Just like moles and freckles, these spots on the tongue are usually benign. There is a slight chance always that they can be a site for the growth of a serious type of cancer, called melanoma. Therefore they always bear watching. If they start to grow rapidly or if they develop an irregular border or raised appearance of if they change in colors, then these are signs that are more concerning and that should prompt you to go see your doctor for advice and evaluation.