Smoke might not be so hot

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The good news about smoke and fire

We have previously mentioned the potential harmful effects of smoke-induced compounds formed during barbecuing or smoking of food. Now new findings point to a developmental edge for humans.

A genetic mutation may have helped modern humans adapt to smoke exposure from fires. This might have produced an evolutionary advantage over competitors like Neanderthals as modern humans are the only primates that carry this genetic mutation.

No fire without smoke

There is evidence that both humans and Neanderthals used fire. Our ancestors were likely using fire at least a million years ago, and maybe even two million years ago. Fire would have played an important role for cooking, protection and heating. Cooking with fire allowed our ancestors to incorporate a broader range of foods in the diets by softening roots and tubers and help increase the digestibility of other foods. Fire also provided warmth, and has long been used for landscape burning and as part of hunting and gathering.

But no fire without smoke (or is it the opposite?). And smoke-derived toxins like dioxins and polycyclic aromatic hydrocarbons can lead to respiratory infections and, for expectant mothers, exposure to these toxins can increase the chance of low birth weight and infant mortality. Even worse, they can increase the risk of cancer and lead to cell death at high concentrations.

Increased tolerance to smoke-induced toxins

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Exclusive mutation that protects humans (Illustration: MagneticHyena)

The mutation may have offered ancient humans a potentially increased tolerance to toxic materials produced by fires. Although you want your body to be able to detoxify the compounds, doing it too rapidly might overload the system and cause cell death. It is all about differences in the aryl hydrocarbon receptor that regulates the body’s response to smoke-derived toxins. The mutation in the receptor is located in the middle of the ligand-binding domain and is found in all present-day humans. Ligands are small molecules that attach to receptor proteins in certain areas in much the same way that keys fit into locks.

By inhaling smoke and eating charcoal-broiled meat Neanderthals were exposed to large amounts of smoke-derived toxins they metabolised too quickly, while humans would exhibit decreased toxicity because they metabolised these compounds more slowly. Thus, our tolerance allowed us to pick up other bad habits like smoking cigarettes.

But remember that the mutation is not giving us a free-out-of-jail card. Although we are at a great advantage compared to Neanderthals, having the mutation made a hundred-fold to as much as a thousand-fold difference, there is still quite a considerable risk remaining. So go easy with the barbecuing and don’t adopt the bad smoking habit.

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