[JasonCEC]

For anyone looking into this, the field is (usually) called "organic geo-chemistry" and/or "paleo-isotope ecology"; the two fields are interwoven to get results like these, or the diet of early mammals. It's generally a collaboration between anthropologist and paleontologist.

[AlotOfReading]

The term "isotopic analysis" is a bit more specific to what's going on here. There are dedicated labs specializing in it that will do samples for (relatively) cheap, especially for the fancier methods. Paleontologists aren't necessarily any more skilled here than anthropologists/archaeologists. Those three are fairly similar roles with a lot of skill overlap that doesn't necessarily include analytical/nuclear chemistry stuff. The labs tend to be staffed by specialists from non-historical departments at the institution they're associated with in my experience.