In addition to founder effects, the new population is often a very small population and so shows increased sensitivity to genetic drift, an increase in inbreeding, and relatively low genetic variation.
The short answer for how long does it take to become a lawyer is that in the United States it takes a minimum of three years. In order to practice law anywhere in the western world, one must pass an examination in the geographic jurisdiction that the proposed lawyer wants to practice law.
To become a lawyer in Germany, you have to study law at university for four or five years. Then you have to pass the First State Examination (Erstes Staatsexamen) in Law, which is administered by the ministry of justice of the respective state; the university administers only a little part of the examination.