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.
Thus, the odds of an 18-year-old with little Army experience being accepted into the 75th Ranger Regiment are slim to none. In the same vein, a 40-year-old applicant whose best athletic days have passed him by is just as likely to be passed over.Getty Images/Getty Images News/Getty Images. Officer Age Requirements.he Rangers do not put an age limit on officers looking to join the regiment. However, they must be ranked between first lieutenant and major (O-2 to O-4). This means newly commissioned officers are not eligible to join, while officers ranked O-5 and above are no longer able to apply.