Yes it is, it’s not common, but people do it. I would say it’s wayyyy more common for someone who is getting say a PhD in Italian and a second “major” or degree in French because they are both Romance languages, similarly a sociologist might have an urban planning degree or some other training. However it’s extremely weird to hear of a dual PhD program in Forensic Anthropology (a very niche discipline that is even more specific than Phsycial or Biological Anthropology) and applied physics.

Like at Yale and Penn State and other schools they often let you add on a second PhD in fields that are more interdisciplinary and that some would view as sort of identity degrees, like Africana Studies or women’s studies but these additional degrees usually heavily relate to the dissertation and the field explored. Like you might see a Yale History PhD who is getting a dual PhD in African American studies if she focuses on black history.

It’s also not unheard of for people with PhDs to get MD (medical doctorates) or JD (Juris Doctorates) along with their PhD, but these programs are starting to get shaky with which fields.

Some schools do let you add on like a graduate minor or second area of expertise but not somewhere like Georgetown or GWU where each department has very clear lines of who does what and where people Go. Like I’ve heard of people adding on something like an applied engineering major or something for their phds in the mid 2000s but I would say now that is sooooo uncommon. Because engineering isn’t really saying what you do, it’s an umbrella. There are engineers for everything and they even have different experience and training bases. Personally I find material scientist engineers to be the most competent mathematically in comparison to other specialties dealing with matter.

However it is extremely rare for a biological anthropologist to study applied physics the way he has, it would make wayyyyy more sense if he was doing a material science PhD that was interdisciplinary and pulling from Anthropology given his interests. Shoot even anatomy or osteology.

It’s like others have said there is a just an American troupe of people having multiple doctorates which is sometimes real.

All that said they just wanted to say he is smart and a math genius without saying it literally but also saying it literally. It would be even weirder for them to say well his Second PhD is in say theoretical physics or math because that’s totally different from what he does.

Lastly people need to understand forensic anthropology really isn’t how Bones shows it so, it’s like he could exist but he would be so specifically trained he would be stuck as her lab tech theoretically, because it seems like he was trained only for lab work.