Evolution has been described as "survival of the fittest" or the ability of a species to adapt to new environmental conditions over many generations. Any factors that influence survival or reproduction will determine which gene pools are carried by future organisms. Five factors that will influence human evolution are: 1) Our food supply, 2) Environmental pollution, 3) Medical technology, 4) Climate change and 5) Cultural memes.
1) Our food supply
Our modern diets contain many ingredients not found naturally, such as high-fructose corn syrup and hydrogenated fats. Our food supply is becoming less varied and more artificial. Our food chain depends on monoculture foods and genetically modified organisms (GMO) which we eat ourselves or which we feed to the animals that we consume as food. The lack of variety in our diet is likely to create dependencies which over many generations will cause some of our genes to become inactive just like the gene that once produced Vitamin C because genetic traits that do not provide an evolutionary advantage can be lost through mutations without affecting the ability to survive.
Large farming technology has become so efficient that individuals can no longer provide their own food. The days when a person could survive by hunting and gathering are long gone. Any disruption of the food supply chain by severe weather or a rare meteorite impact will result in many deaths.
Non-sustainable fishing practices will reduce the amount of fish that we consume. Consequently, the changes in our dietary polyunsaturated fatty acids (omega-3 and omega-6) will have an impact on the brain and eye development of the newborns. The effects will cascade into future generations causing inevitable genetic drifts. According to the Centers for Disease Control, the prevalence of Autism Spectrum Disorder (ASD) in the United States has increased from 6.7 to 11.3 per 1000 children from 2000 in 2008. Although the cause of ASD is not known, the steep upward trend casts suspicion on the synergistic effects of food additives with environmental toxins.
2) Environmental pollution
Today, we constantly breathe city air that is polluted with industrial exhaust and we drink water contaminated with chemicals and pharmaceutical products that are flushed into our sewers. Air pollution contributed to 1.2 million premature deaths in China in 2010.
Most of our modern society lives immersed in environmental toxins that include fertilizers, pesticides, nitrous oxides and fire retardants. Many of these substances are mutagens or carcinogens that cause changes to our DNA and which will subsequently affect our progeny. In 2006, some fish in the Potomac River in Washington, D.C. were reported to have developed both male and female sex organs due to pollution by compounds with hormonal activity. Millions of people drink this water every day. Humans may have already been affected by this type of contamination and we will probably see the effects within this generation.
The increase in pollution has been aggravated to a large degree by the greed of multinational corporations that exploit material resources and cheap labor in poor countries to create products for the people in rich nations. The leaders and politicians who are in a position to regulate non-sustainable exploitation of resources and the burning of fossil fuels are often corrupted by grants and favors from lobbyists representing the large corporations who argue that regulations will result in unemployment and economic austerity.
3) Medical technology
Modern medicine has extended the average human lifespan by many years through sanitation and immunization. Our medical practices have allowed procreation by individuals who previously might have died before giving birth or before being able to find a mate. Women with narrow hips who might have died in childbirth in earlier times can now pass their narrow hip genes to their daughters thus insuring that a new generation can only be born through the assistance of a surgical Cesarean section.
In vitro fertilization, birth control and abortion all affect the genetic traits that will survive or be suppressed. With our modern medicine, "survival of the fittest" has lost its meaning. Humans are changing their own destiny through unnatural selection. In India, the abortion of female fetuses has resulted in a great disparity in the ratio of males to females. According to the 2011 census, India has 37 million more men than women. Indian males now have trouble finding mates. In China, the policy of allowing one child per couple has stabilized the population and avoided a Malthusian crisis. Clearly, the use of medical practices to determine who lives and who dies is already affecting the future human genome.
Human evolution will also be affected by the medicines and drugs that we use. The indiscriminate use of antibiotics has allowed the emergence of MERSA and other antibiotic-resistant bacteria that will cause future pandemics which we will be unable to control. The widespread abuse of legal and illegal drugs like alcohol, tobacco, marijuana, cocaine and heroin will eventually give rise to a race of substandard humans that will be a burden on society. There is evidence that children of alcoholics inherit cognitive impairments.
4) Climate change
Today, we face a climate problem created by the greenhouse gases produced by our extensive use of fossil fuels: Global Warming. Some scientists have warned that by the year 2200, the atmospheric levels of carbon dioxide, methane, and nitrous oxide will be at the same levels associated with mass-extinction events in the Earth's past.
The melting of the Greenland and Antarctic ice sheets is already causing an increase in the level of the sea. Human populations in some low-lying areas, such as Bangladesh, will need to relocate as the level of the sea continues to rise.
Eventually, even the coast of the United States will be affected. It is estimated that by the year 2100 the sea level could rise by 1.5 meters (5 feet). It may be impossible to save cities like New Orleans which are already below sea level and only exist because they are protected by levees and pumping stations. A complete meltdown of the Greenland ice sheet would cause a sea level rise of 7 meters (23 feet), which would be enough to flood many important cities around the world including London, Miami and Los Angeles.
Global warming will also cause desertification and reduction of arable land. The rise in the sea level will trigger human migrations on an unprecedented scale and change the human genetic pool by forcing previously separated populations to mix or fight.
5) Cultural Memes
Memes are ideas that spread throughout human populations. Our brains provide the medium to harbor the memes. Many of these memes survive because they have practical value, but other memes preserve cultural traditions. Memes undergo evolution as they are adopted, modified or discarded.
The discovery that infectious diseases are caused by microorganisms changed the survival of humans. Memes like "wash your hands before eating" are deeply ingrained in our modern world. Memes modify our brain with pre-programmed opinions and actions. Many of these memes are adopted without conscious effort in childhood from our cultural surroundings. Our culture is encoded in memes. All memes, such as patriotism, anti-Semitism, racial superiority, capitalism, communism, creationism or Darwinism, are implanted in our brain through mental processes of logic, rationalization or indoctrination.
Memes for religious intolerance were the foundation of the Crusades and the Inquisition. It was permissible for Christians to kill Muslims for their religious beliefs. The Muslims responded with jihads. The memes for capitalism versus communism contributed to the wars in Korea and Vietnam. Memes for nationalism and xenophobia fueled the Cold War.
Memes are so important in human behavior that people often resort to violence if they cannot convince another person to share their beliefs. This is why genocides are often carried out during civil wars. Labels like "liberal" and "conservative" evoke memes that paralyze governments by disallowing moderation and compromise.
Evolution does not care whether the rational man with the bright ideas or the zealot with the gun survives. In the end, whoever remains alive will pass along his genes and ideology. All animals fight for territory and mates. Man is the only animal who kills others to make his ideology survive and eradicate opposing ideas and cultures. The 10 million deaths in the Soviet Gulags and the 6 million Jews killed in Nazi concentration camps are evidence of this. These exterminations from our grandparents' generation have been followed by more recent genocides during our own generation in Rwanda and Bosnia. All these killings affect the human gene pool. The meme for rational thought will not necessarily prevail in future humans.
If this assessment of the future of humanity seems pessimistic, just consider that since the invention of the long bow, which was designed to penetrate medieval armor, most new weapons have been used to kill people rather than for hunting. The six shooters of the American West, machine guns, automatic weapons like the AK-47, rocket propelled grenades, Napalm bombs and nuclear bombs are all examples of weapons developed to kill people. The fate of Homo sapiens is in our own hands.
Few humans could survive today by hunting and gathering. Communities depend on food that is transported long distances and requires preservation with chemicals, freezing or canning. The efficiency of modern farming has shifted the labor force toward factory work that produces consumer goods, but these industries rely on coal, petroleum and other fossil fuels that contaminate the air and water. Medical advances have increased our longevity. Information technology has made it possible to communicate instantly across the world. Humans have prospered across the globe, but deforestation, overhunting and pollution have caused the extinction of many species. If we continue destroying natural resources without thinking about the consequences, we will end up in artificial ecological niches that rely on biochemistry, electrical energy and communication systems. It is not hard to imagine that human survival will eventually require the creation of a man-made biosphere and that people will fight over what is left of a post-apocalyptic world of our own creation.