Another reason for the extinction of Neanderthals?
Neanderthals did not tolerate smoke from bonfires well
Kirill Stasevich, "Science and Life"
As you know, in the genus Homo, in addition to Homo sapiens sapiens, there were other species – for example, Denisovans and Neanderthals (Homo neanderthalensis), about which we hear most often. However, only a reasonable person received an evolutionary advantage.
Biologists and anthropologists have several assumptions about why this happened, and usually such hypotheses concern Neanderthals, starting with the fact that they disappeared due to climatic troubles, and ending with the hypothesis about the assimilation of Neanderthals, which is indicated, in particular, by Neanderthal genetic traces in our genome.
Another version is put forward in their article in Molecular Biology and Evolution (Hubbard et al., Divergent Ah receptor ligand selectivity during hominin evolution) by researchers from the University of Pennsylvania – in their opinion, Neanderthals disappeared because they could not tolerate smoke from fire (Matt Swayne, Where there's smoke and a mutation there may be an evolutionary edge for humans). During gorenje wood (as well as coal, petroleum products, tobacco, food) polycyclic aromatic hydrocarbons are formed (these include, for example, benzpyrene and naphthalene). The body tries to get rid of them with a set of enzymes that oxidize all sorts of foreign substances.
The problem is that when such hydrocarbons are disposed of as an intermediate, extremely aggressive and therefore extremely dangerous molecules are obtained – epoxides, quinones and others. Epoxides, in particular, attach to DNA, and as a result, problems arise with DNA replication – when a new DNA chain is synthesized on an old template, and with transcription – when RNA is synthesized on DNA for subsequent assembly of a protein molecule. Enzyme machines running on modified DNA make mistakes, that is, mutations, because of which the cell can either simply die or become malignant.
It all starts with the fact that the polycyclic hydrocarbon that got into the body, say, along with the smoke from the fire, sits on a special cellular receptor, which is called the aromatic hydrocarbon receptor. Sensing a foreign molecule, he transmits a signal to the cell to increase the production of enzymes that break down such hydrocarbons. Obviously, it is necessary to get rid of them, but here a paradox arises: if the enzymes work very actively, they will flood the cell with toxic products of oxidation of hydrocarbon molecules, and the cell will only get worse. It turns out that the cleaning enzymes should work slowly, slowly.
What does Neanderthals have to do with it? When Troy D. Hubbard and his colleagues compared the hydrocarbon receptor gene in Neanderthals, modern humans and monkeys, it turned out that in one place the gene variant in H. sapiens differs from other variants. In Neanderthals, the gene sequence (and, accordingly, the structure of the receptor protein) was such that this receptor worked 150-1000 times more efficiently than in humans. That is, when "smoky" molecules appeared, Neanderthal cells were literally filled to the brim with oxidizing enzymes that produced a huge amount of toxic metabolic products from hydrocarbons.
It should be remembered here that fire was used by both a reasonable person and a Neanderthal man, and the advantages of fire were obvious: it was possible to cook food on it so that it was better and easier to digest and, consequently, gave more energy, and it was possible to bask around it, which was especially useful in northern latitudes.
Fire definitely simplified life, but it had a side effect in the form of smoke. Neanderthals turned out to be too sensitive to smoke, but a reasonable person was lucky with a mutation in the receptor.
Now we encounter aromatic polycyclic hydrocarbons much more often than in prehistoric times. These substances, as it was said, arise from the combustion of petroleum products and coal, they can be found in smoked and fried, we inhale them with tobacco smoke – and you can imagine what would happen to Neanderthals if they were in the modern world.
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23.08.2016