In today’s modern era tattoos are so common, it is hard to find an adult without some kind of ink marking. Many refer it to as the mark of the slave, I believe this is a more personal reference in the current time that biblical rule has installed. But it is best not to argue especially when dealing with other members of your own. It is highly suggested that most of our ancestors were never tattooed and the arguments can be made with references to Tacitcus (if I remember correctly). Plus, other findings in the ancient world, the ice maiden is a good example.
This being said I will give my opinions on tattooing and how they may have been applied in the past. It is well known that many other cultures had various methods of tattooing particular the Chinese and Maori. Arguments could also be made in the stone age as many weapons were forged and harden in the fire that would leave marks on the body deep in the skin. Many in the neo culture discredit any tattooing and well straight out tell you that are ancestors were not tattooed. But just like most that think polygamy is a good idea without thinking of today’s consequences or little thought of.
I will use the example of polygamy as I will explain this down below.
Just like higher lords and kings would often take multiple wives and concubines, many stood at the risk of assassination by a political adversary. This ensured that their bloodlines in the political spectrum existed. Such may have been true with skin marking for tribal or possible warrior bands and other forms of divine association. This being said I believe kings had the funding to possible import the trade to be done, well the individuals associated may have actually used a dye to mark their skin. Dye itself was used in clothing and other products that were produced with the labor of peoples. It would make sense they may eventually use this practice to mark their loyalties to nobility or others.
The Picts and Celts were said to have painted themselves this way so I think its safe to say that the dye process was a thing. As for the actual tattooing much has been speculated that the trade routes into the silk road were used by our forebears. Some practices from the east may have been adopted such as the methods of scaring or much like or similar to the Maori. I am also sure that I am missing someone else along the way on the continent that practiced such.