In 1905, Levene was appointed as head of the biochemical laboratory at the Rockefeller Institute of Medical Research. He spent the rest of his career at this institute, and it was there that he identified the components of DNA.
It also takes anywhere from 18 to 24 months to get promoted to O-2 following entry to the Army, so the effective minimum age to join the Rangers for officers is around 23 to 24 years old. Officers can then continue to apply until they are promoted to O-5.
The average age of the American soldier in Vietnam was nineteen. As the months of the war became years, the public became impatient. Only a small percentage of Americans believed their government was evil or sympathized with the Viet Cong. But many began to feel it was time to cut losses.