There’s much that still puzzles scientists about Neanderthals, despite all the advances we’ve made in sequencing their genomes and reconstructing how they might have lived. One of those mysteries is the high level of an isotope called nitrogen-15 in their remains.
To understand the mystery, first you have to understand about isotopes. Isotopes are slightly different versions of the same element. To be nitrogen, an atom needs to contain seven protons, but it doesn’t matter how many neutrons it has. Nitrogen-14 (seven neutrons) is much more common than nitrogen-15 (eight neutrons). Plants, for example, are low in nitrogen-15, which tends to accumulate as you go up the food chain — so a mammal that eats a lot of plants has a small accumulation of nitrogen-15, and the animal that eats a lot of that small mammal over its lifetime accumulates even more nitrogen-15. In the end, an apex predator which eats solely meat has comparatively large amounts of nitrogen-15 in its remains.
Since you are what you eat (very literally), that can tell us something about Neanderthal diets. To scientists’ surprise, nitrogen-15 levels in Neanderthal remains are comparable to the remains of exclusively carnivorous animals, suggesting a life spent always hunting for the next McDeer or Kentucky Fried Mammoth. On the other hand, tooth scrapings and other evidence suggest that Neanderthals ate a not insignificant amount of vegetation as well.
A scientist, Kimberly Foecke, has stepped into the breach (of course), with a theory: could rotting meat contain more nitrogen-15, proportionately, and lead to a false conclusion that the diet was heavier in meat than it actually was? To test this, she’s been buying steaks (from organically raised animals, trying to keep the conditions as close to “natural” as possible) and letting them rot. (I know, I know — waste of a good steak. Especially with the way my dad cooks a steak. Nom.)
What are the results? Turns out that as meat rots, the proportion of nitrogen-14 to nitrogen-15 changes due to microbial activity — the microbes break down nitrogen-14 faster than nitrogen-15, leaving more of it in the meat. This fits with a theory that Neanderthals might kill large animals like mammoths and hang round for a while slowly consuming the meat from the corpse, over the course of several days. That would certainly give the meat time to rot, and thus affect the amount of nitrogen-15 consumed by the Neanderthals!
It’s not the whole answer, because Kimberly Foecke also wants to test out how different kinds of food preparation affect nitrogen-15. Could cooking concentrate it somehow? There’s plenty more to learn, and it sounds like it involves a lot of steak.
When there’s rotten meat in my home, it’s usually because I’ve capriciously eaten something else instead of the planned meal. Maybe now I claim it for science instead!
Nope. Wife looks unimpressed.