Should a list of employees be sorted alphabetically by first name?

Imagine a list or grid of employees, assuming the non-technical user hasn't clicked any column headers yet, do you think they would expect the employees to be sorted by first name or last name or the order they were added to the system, i.e. oldest employee first, newest last.

In addition if they added a new employee should that appear at the end or slotted in alphabetically?

Many thanks