I can hardly call it "new", since any available sources seem to be about 4-5 years old, but I can't recall anyone ever bringing this up here before, so I figured why not.
Since the dawn of psychology, the general theory surrounding paraphilias was the brain sort of classically conditioning itself to associate something with sexual arousal, so the presense of a fetish would be like a pavlovian reaction.
But some new(ish) research posits that it might actually be tied to disturbed lateralization in the brain.
If you don't know what lateralization is, basically, we have two hemispheres of our brain that, in theory, perform the same functions, but certain circumstances in our prenatal environment lead us to lateralize certain brain functions, or delegate most of the work to one hemisphere or the other. For example, most people lateralize their language functions to the left hemisphere of their brain (90-95% of right handed people, 61-73% of left handed people). But sometimes, those circumstances in our prenatal environment will lead to a disturbed lateralization. A disturbance is a tiny error that causes the brain to involve one of the hemispheres more than it should. So, for people with the language functions lateralized to the left hemisphere of their brain, normally the right hemisphere barely registers any activity; but with a disturbed lateralization, it involves the right hemisphere more than it's supposed to. This doesn't sound like it should be a problem, except the function is already lateralized to the dominant left hemisphere and the underdeveloped right hemisphere has no idea what the fuck it's doing, so some wires get crossed, and in the case of language functions, we get stuttering, dyslexia, aphasia, and other language disorders.
So. Some researchers hypothesize that that's what paraphilias are; our brain's attempt to make sense out of the normal sexual functions of our brain with a dash of who the fuck knows what else from the non-dominant half.
To test this, there was a study conducted in 2008 that involved 200 heterosexual men (to further their hypothesis, the ratio of paraphilias in men vs. women is about 20:1, roughly the same ratio as other disturbed lateralization disorders). The study examined their sexual fantasies with the WSFQ (Wilson Sex Fantasy Questionnaire) and neurodevelopmental markers like sibling sex composition, handedness, parent's age at birth, 2D:4D finger length ratios, and asymmetry of finger lengths and wrist widths.
The results showed that higher levels of paraphilia had a strong correlation with having greater numbers of older brothers, higher right-hand 2D:4D, and higher tendency of left handedness.
So, in conclusion, the study suggests that the root of paraphilias lies in developmental instability and maternal immunity, which means (in these males anyway) that excessive exposure to estrogen led to small abnormalities in the development of their brain.
I can say that I'm a straight male, right handed, with one older brother, no younger siblings, high 2D:4D ratio in both hands, and whose parents were in their early 40s when I was conceived. I used to have a stuttering problem when I was younger but have since gotten over, and I have ADHD and OCD (yes, at the same time. It's like there's a party in my frontal lobe). I would say that my paraphilia-level is high, to the extent that I have a much more difficult time getting off if there is nothing present to appeal to my fetishes.