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Comment by i_am_jl | Hacker News Reader

Thanks for the confirmation that I wasn't in the grips of a fever dream.

I'm still having trouble wrapping my head around the existence of a study that incorporates fields as distant as anthropology and nuclear physics.

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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.

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.

It's actually a very common class of techniques. Carbon-14 dating relies on the ratios of carbon atoms, and is widely used for dating younger stuff. However, its relatively short half life means that for older stuff archeologists need to rely on other elements rarely found in organic materials like the uranium-lead decay path or in this case strontium.

Carbon dating is good up to 50kya, i.e. anything an archeologist is likely to be involved with. There's a separate issue dating things around 2500 BP called the Hallstatt plateau, but the slave trade this paper is looking at happened more recently than either of these (400 BP max). The problem is that carbon dating doesn't give you very good localization because it's generated by atmospheric sources. Strontium is almost exclusively of geological origin and the ratio varies a lot, so you can build a good map with it.

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