That is simply not true. Someone with an IQ of 80 will not be able to get a PHD, period. On the reverse, someone with an IQ of 180 could get a PHD in their sleep. I didn’t get a PHD but did get a MBA @ a Top 10 program. There were people in the program that barely did any effort and zipped right through and others that did 40-50 hours/wk outside of class to pass.
You are playing in the margins there. Very few people have an IQ of 80 or 180.
The point is, no DNA test is going to tell you if a hard working person with a 100 IQ will be more successful than a lazy person with a 115 IQ. Similarly, no test will tell whether a sober person with a 110 IQ will be more successful than a drunk with a 125 IQ.