Question

If there was only two people on this world first why do we have so many last names

Answer 1

Yes,well, families and families make other families and then from there they can make different last names. Adam and eve had a family, and then from there, as thing's came down to our days, last name's started to change.

Hope this helps.
~Jurgen

Answer 2

In the early years of the Middle Ages, most people in Europe lived in small farming villages. Everyone knew his neighbors, and there was little need for last names. But as the population expanded and the towns grew, a need arose to find ways to differentiate between two people who shared the same first name.