A person who holds to the philosophy of evolutionism.
What’s evolutionism?
It is an attempt to put scientists who believe that the theory of evolution is a useful theory on the same level as people who believe in creationism.
Science is not philosophy. There is no way to equate a scientific theory with a philosophy.
Creationism is neither a scientific theory nor a philosophy; it is a religious belief.
Creationism may in fact be true, but there is no way to prove it scientifically, and there is no way to argue for it philosophically.
Philosophers can argue for the existence of God, and that God created the universe, but there is no way to argue philosophically that God created the world as we know it about ~6000 years ago.
Likewise there is no way to prove scientifically that the Earth was created ~6000 years ago.
The paper you site is an excellent contribution to the scientific discourse. It will either be found to be incorrect, or it will help to improve the methods that scientists use to show if/when natural selection occurs.
The scientists' reluctance to question natural selection outright is an understandably conservative conclusion from their results. What they discovered did not disprove natural selection, in merely brought into doubt conclusions made by other scientists.
This is the way that science should be done.