My father had an ear pit and he passed that on to me and my sister (2 of 6 children). Having had 6 childres myself, I have passed this on to only one of my children... my youngest. I don't know the cause of these, except that they seem to be hereditary.
I've lived my life with this and do not know of any health issues related to them. I've actually been the healthiest and strongest of my fathers children. And until recently, I have never had a problem with hearing loss (but this is most likely due to age).
Aside from occasional curiosity on the part of others, and the need for particular hygene relative to them (ear pits) I've lived my life without paying any partictular attention to them.
These are more like a skin pore to me than a type of cavity, but like a skin pore (or tiny cavity) should be maintained clean like any pore or cavity, ie ears, nose, belly button as they tend to acumulate "stuff".
Other than this, I don't know that there is anything to worry about. It makes those of us that have them rather unique as it puts us in a rare and interesting catagory.
That's a really good question! I don't know, off hand, the genetics behind ear pits. Since they are harmless things, there may not have been much reason for anyone to do any studies on this. There are some anomalies of ear canal development that have been well-described, but these should not be confused with simple ear pits.