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Neanderthal diets: follow-up

After last week’s post on the question of Neanderthal diets (in which it is suggested that they ate a diet heavy in meat, including meat which had been rotting for some days), anthropologyglobal asked an excellent question I have some potential answers for:

What about the odour? How did they have anything so odorous?

First of all, I suspect that when you’re hungry, refrigeration is only possible via using the environment, and your sensibilities aren’t trained by a life of going to the store for your next meal, you’re less picky about the smell of your meat as long as it isn’t going to make you sick. You’re also likely to have a greater tolerance for meat that could make you sick if it’s what you and your parents have always eaten. You could have inherited or generated through exposure a tolerance to toxins produced by the bacteria, and would most likely have a gut fauna adapted to eating that kind of fare. We must consider both environmental and developmental causes — maybe in this case, if you’re used to it, it just isn’t that bad (and modern humans could develop a taste for it too).

We do have one sad testament in recent history that humans can stand to eat rotten meat when they have to: in August 2019, the BBC reported that Venezuelan families were buying rotten meat because it’s all there was. The country is in crisis with shortages, power outages and high inflation. So that’s what it takes to convince a modern human to eat rotten meat — and while people were getting sick from it, it was also helping some people survive.

Secondly, Neanderthal DNA shows that while they are relatives of Homo sapiens, they’re very different as well. In terms of potential genetic ability to cope with ingesting rotting food, let’s consider their immune systems. There’s been at least a couple of studies into immune response based on the amount of Neanderthal DNA influence. Responses are very different between the immune systems of people of African origin and those of European descent, when the activities of macrophages and monocytes from each lineage are compared in a controlled experiment. These experiments are based on the immune cells of modern humans only, just to be clear — those whose near ancestors did interbreed with Neanderthals, and those whose ancestors wouldn’t have come into contact with Neanderthals.

(This is flawed on an individual level, of course, because there are a lot of people who have both African and European heritage recently and directly, and a lot of us would have no idea of our heritage from just a few generations ago. But in a representative sample, it seems to have been enough to make a significant difference.)

The differences in Neanderthal genomes can also account for differences in the sense of smell, of course! Just to begin with, on the highest level, we know that the human olfactory bulb is around 12% larger than the Neanderthal one, and the size of the olfactory bulb is linked to ability to process and discriminate between different smells. Maybe rotting meat just didn’t smell as bad to them!

Well, we know that there’s a particular gene in humans (OR7D4) that maps pretty directly onto how humans smell androstenone (think mating boar). Even in modern humans that has a lot of variation (some can smell it and think it smells like urine; others find it smells sweet; yet others can’t smell it at all). Granted, in this particular case, it turns out Neanderthals (based on the genome sample we’ve reconstructed, anyway) could smell it and their experience correlates with the worst-case “it smells bad” group. Nonetheless, it’s a demonstration of how your genes can directly influence your sense of smell, and maybe there’s a gene somewhere which Neanderthals carried and we do not, making rotting meat smell less offensive.

All in all, it’s difficult to come to a solid conclusion about how Neanderthals coped with the smell of rotting meat, but hopefully I’ve given some ideas about how they might have been different to modern humans!

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