So according to Wikipedia they can tell the ages from the bones which makes sense due to things like cranial seams sealing up as we get to 30. What I don't get is how the hell do they know they were engaging in sex work or drugs? Skeletons don't show marks of sex slavery or prostitution... you'd need to ID an individual for that information as well as drug use. Missing teeth doesn't always mean drugs, could be purposely removed or malnutrition etc.
Edit: Even the source on the Wikipedia page has nothing to support that statement of sex work/drug use. The article used for citation refers to a woman who was "identified" by police only to be informed by the family the identified individual was incorrect. The person passed away years before due to a health issue. There is a dead link in that article referencing the 11 bodies.
I'm not convinced this wasn't the work of a serial killer.