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.
In order to become an attorney, a person must obtain a Juris Doctor degree from an accredited law school, although this requirement may vary in some states. Attendance at law school usually entails three years of full-time study, or four years of study in evening classes, where available.