Air pollution is not just a matter of age. Now it can shape the evolution of human society.
Toxic air is still harmful to billions of people every day and every hour. We continually breathe in harmful emissions from vehicles, coal-burning plants, refineries, and natural gas. In addition, more than a billion people inject toxins into their lungs from cigarettes.
92% of the world's population lives in areas with 'fine dust' - very small particles of particles that have a harmful effect on human body tissue. Air pollution and tobacco each year also causes 20 million deaths for teenagers.
Australia is still overcoming the consequences of a historic wildfire.(Photo: The New York Times).
The toxins in the air harm people in many ways. In addition to being a powerful factor in lung cancer and heart disease, researchers also found a link from these toxins to disorders like diabetes or Alzheimer's.
'How can air pollution cause these diseases?' , scientists question. They are also bewildered about people's resilience.
Many researchers think the answer may lie in the distant evolution of humanity, millions of years ago, before the first cigarette was burned, before the first car smoke was emitted from the lips. school.
Biologist Benjamin Trumble of Arizona State University and Professor Caleb Finch, University of Southern California, said : Our ancestors have also struggled with air pollution.
Scientists think that humanity evolved on the basis of combating pollutants. To this day, even though it may have been restricted, these types of adaptations are still helping our bodies fight the effects of secondhand smoke or air pollution. However, these evolutionary legacies can also be a burden. Some genetic adaptation may have increased our vulnerability to air pollution-related diseases.
Africa 7 million years ago gradually became arid. The Sahara emerges to the north, and the grasslands extend to the east and south of the black continent.
The ancestors of chimpanzees and gorillas are still in the forest, but our ancient relatives have adapted to the new environment. The body frame is enhanced and slimmer, this evolution makes the body suitable for walking or long distance running.
Dr. Finch and Dr. Trumble believe that the 'first humans on Earth ' faced a challenge that was barely mentioned: Air.
Periodically, the prairies once experienced major dust storms from the Sahara. Our distant ancestors are therefore at risk of breathing in these siliceous sand particles, damaging the lungs.
'As the dust density increases, we are more likely to notice lung problems , ' says Dr. Finch. The evidence is clearer today that Greek researchers discovered that when the winds coming from the Sahara blew into their country, hospitals were receiving more respiratory illnesses.
2014 was recorded as the hottest year in history.(Photo: Nasa).
Dust is not the only danger. The breathing process of the ancient humans may also be stimulated by pollen and particulate matter from the feces of giant grazing herds on the prairies.
The two doctors said that scientists should consider whether these new challenges will change our biology, through natural selection. For example, are those less adversely affected by cigarette smoke inheriting genetic variants that protect ancient ancestors from fires?
One way to answer these questions is to study the genes that have evolved, ever since our ancestors left life around the jungle to explore the wider world.
One of them is MARCO , genee specifies blueprint for the production of a molecular structure used by immune cells in our lungs. Cells use this structure to remove both bacteria and particles, including silicon dust.
The human version of the MARCO genee is distinctly different from other apes. The denaturation happened at least half a million years ago (Neanderthals - a sub-species of modern humans also carry variants)."Breathing the dusty air has driven the evolution of MARCO into the bodies of ancient apes , " said Dr. Trumble.
Smoke has created new evolutionary pressure. Human liver enzymes have gradually become stronger to break down toxins that enter the bloodstream through respiration.
Besides the MARCO gene, Gary Perdew - molecular toxicologist at Pennsylvania State University - and his colleagues found evidence of evolution to combat the harmful effects of secondhand smoke in another gene: AHR.
This gene creates a protein found in cells in the intestines, lungs and skin. When toxins enter the body and become entangled in proteins, the cells release enzymes that break down toxins. However, this gene in humans has a weaker response to the toxin than in other species, probably because in the decomposition of toxins there are debris that can damage the tissues.
Not only modern people, our ancestors must also learn to adapt to environmental pollution.(Photo: The New York Times).
In the days when humanity did not use fire, the human body did not need to use much to AHR. Therefore, in theory, humans still tolerate the damage that proteins cause during the detoxification process. However, since the invention of the fire, we inhaled more dust, which led to a higher demand for AHR protein, so the health threats therefore increased.
Dr. Perdew believes that humans evolved with a weaker AHR response as a way to find compromises, to minimize the damage of air pollutants without causing too many side effects. But this adaptation is never perfect, the fact that thousands of people still die from poison gas. However, the purpose of evolution is not to possess perfect condition.
We entered the Industrial Revolution era from two centuries ago. Besides clean water, improved medical drugs, other innovations also significantly reduce deaths from infectious diseases, and life expectancy soars. Even so, we humans have been exposed to toxins in the air more and more.
The Industrial Revolution exploded with the use of a lot of fuel from coal, cars became popular, power plants and refineries appeared more and more, tobacco companies scaled up. Industrial production. Today, 6.5 trillion cigarettes are sold each year.
Over hundreds of thousands of years, our bodies have been trained to react on the defense of bad actors from the outside. In particular, the body can strongly express this mechanism through inflammation. The frequency of manifestations of infection in the human body is increasing.
Many studies now show that chronic inflammation shows an important link between air toxins and disease. For example, chronic encephalitis can reduce the ability to remove faulty proteins. And when these proteins accumulate, they can lead to dementia.
Pathogens can be indirectly introduced into the body through contaminated particles. Specifically, when it enters the nose, they can contact the nerve endings and cause more severe inflammation.
' Some genetic variations that have arisen in the past in response to smog can produce certain useful adaptations today. For example, some smokers still live long, 'said Dr. Finch.
Scientists study other genes and discover a lot of the opposite, for example: A variant that used to be useful in the body gradually became harmful in an era of increased air pollution.
Over hundreds of thousands of years, our bodies have been trained to react on the defense of bad actors from the outside.(Photo: The New York Times).
ApoE4 is one of them. This variant was first brought to light by scientists who discovered the possibility that they greatly increased the risk of developing Alzheimer's disease. Recently, researchers also discovered that ApoE4 increases the risk of dementia when people are exposed to polluted air.
However, these studies are gradually restricted in industrialized countries. When scientists conducted research elsewhere, such as poor agricultural areas in Ghana, or indigenous peoples of the forests of Bolivia, they also found that ApoE4 had many different effects.
In these areas, infectious diseases are a major cause of many deaths, especially among children. The researchers found that in such places, the ApoE4 variant increased the proportion of adult or married survivors.
Natural selection has supported ApoE4 for hundreds of thousands of years because this variation increases the survivability of individual species. Even so, ApoE4 and many genes may have had harmful side effects we didn't detect until modern times - periods of air pollution.