Smoking and evolution
The genes of resistance to cigarette toxins and carcinogens turned out to be very ancient
Polina Gershberg, Naked Science
The genes that provide people with resistance to harmful fuel combustion products and harmful substances of cigarette smoke may be the same genes that helped our distant ancestors cope with ancient toxins. An article about this is published in The Quarterly Review of Biology (Trumble, Finch, The Exposome in Human Evolution: From Dust to Diesel).
"We suggest that adaptation to ancient pathogens and toxins in the air may, in some cases, protect us today from new harmful factors such as cigarette smoke and car exhaust," write the authors of the article, Ben Trumble from Arizona State University and Caleb Finch from the University of Southern California. They conducted a detailed study of the human exposome – the interaction of genes and environmental factors that humans have encountered throughout their evolution. Each new environmental factor represented a unique threat to Homo sapiens and was eliminated with the help of various genes associated with immunity.
So, when sub-Saharan Africa turned from a forest into a savanna, the human ancestors living there regularly inhaled mineral dust and aerosol particles from the feces of herd animals. With the opening of the fire, the immune system had to cope with the effects of toxins from burning wood and charred meat. Later, when hunting and gathering gave way to agriculture, people were attacked by allergens and toxins produced by pets and poor sanitary conditions in residential premises.
Scientists have found that some genes provide evolutionary advantages over long periods of evolution and under changing conditions. For example, ancient people became resistant to campfire smoke and burnt food substances thanks to the AHR gene, which encodes aromatic carbohydrate receptors. "AHR plays an important role in the detoxifying response to modern household smoke," the researchers write. "We suggest that genetic adaptation to ancient airborne toxins may play an important role in mitigating the effects of modern exposures, including being an important factor in the longevity of some older smokers."
The main factors that influenced the human exposome during the history of its development (from top to bottom): dust/minerals, wood combustion products, industrial oil / coal, exhaust gases, cigarettes, heavy metals, ozone, charred meat, sugar, obesity, fecal particles, infectious epidemics / © Trumble, Finch, The Quarterly Review of Biology, 2019 Gorenje
Many other genes important for neutralizing toxins eventually lost their advantages or became too dependent on external conditions. This happened to the APOE gene, which encodes a substance important for lipid and cholesterol metabolism – apolipoprotein A. The most ancient isoform of this protein, which our ancestors had, provided high survival in an environment with an increased frequency of infectious diseases. But it also negatively affects the aging of the arteries and brain, leads to the development of Alzheimer's disease and is directly related to a reduction in life expectancy.
Newer isoforms do not have such an adverse effect on blood vessels, but also do not contribute to adaptation to infections. The ancient variant of APOE is still circulating in the human population and may regain its significance if global warming contributes to epidemics.
Understanding the significance of such genetic adaptations is the key to solving future health problems. Researchers are confident that studying these mechanisms will help to find out how human health and life expectancy will change in the conditions of global warming.
Portal "Eternal youth" http://vechnayamolodost.ru