Overview of La Rinconada, Peru.
Evolution may be the ultimate last defense against invasion by other humans. The debilitating effects of altitude sickness seems to have prevented people native to low-lying areas from moving into high altitude regions, such as the Himalayas, according to recent research published in the journal Applied Geography. That study mapped how Tibetan villages continued up to a approximately 17,000 feet (5,200 meters) above sea level, but Han Chinese villages stopped at only 8,900 feet (2,700 meters).
On the other side of the planet, people who settled the Andes mountains evolved their own mechanisms to deal with high altitudes, according to a study published in the Proceedings of the National Academy of Science. Another study documented that descendants of Spanish colonists lack those adaptations and their offspring tend to be smaller than native Andeans.
Yet another ethnic group in the Ethiopian highlands evolved a third biological form of altitude tolerance. A collaboration of American and Ethiopian scientists suggested in Genome Biology that the Tibetans, Andeans and Ethiopians independently developed altitude adaptations in similar portions of their DNA, a phenomenon known as convergent evolution.
Sultan Kosen, the World's Tallest Living Man, is measured by Hollywood Guinness World Records Museum owner Tej Sundher on May 14, 2013 in Hollywood, California. Sultan Kosen of Turkey is 8 feet, 3 inches tall.
Living in the security of higher altitudes also has drawbacks. In both the Andes and Himalayas, children and adolescents tend to grow slower and reach shorter adult heights than lowlanders. However, anthropologists note that people living at high altitudes also tend to be poorer and more malnourished than lowland peoples, which could account for that difference in height and growth along with genetics and the effects of low oxygen.
Whatever the reason for shorter stature in people from high altitudes, vertically-challenged males may face a tougher time in the dating game. A study of British men found that taller gents had more reproductive success than smaller blokes. However, biology seemed to put a cap on the height advantage. Extremely tall men suffered from more health problems and a higher rate of childlessness.
A young woman in a bikini measuring her hips at a beach.
Finding jeans that fit an adolescent may be influenced by where that teen's genes originated. Young people from closer to the poles had wider hip width measurements than youths from closer to the equator, observed a study published in the American Journal of Physical Anthropology. People from closer to the poles were also generally taller and heavier-set than tropical peoples.
The study's authors suggested that the regional variations in body shape may be an example of Bergmann's and Allen's rules. These biological rules hold that animals living in colder environments will evolve relatively larger, with shorter limbs and less surface area compared to their volume. Both of these adaptations reduce the loss of heat to the environment and increase chances of survival in the frigid north.
A woman with different colors on her face.
In the days before vitamin D fortified milk, peoples' main source for the vitamin was the sun. Humans can create vitamin D if they get enough sunlight, but a deficiency in the nutrient results in weak bones, a condition known as rickets in children.
However, for ancient northern Europeans, long, dark winters would have made it difficult to get enough sunlight and vitamin D. Since sunbathing during sub-zero Scandinavian winters would have been a frostbite risk, natives of the north may have evolved paler skin in order to get enough vitamin D. Light skin blocks less of the ultraviolet radiation needed to make vitamin D. Therefore, lighter-skinned people may have had healthier children who carried more of their pale genes on to the next generation.
On the other hand, heavy exposure to the sun's ultraviolet light may destroy folate, a nutrient essential for healthy development of babies, wrote Penn State anthropologists in PNAS. Since humans lack a protective fur coat and clothing could result in overheating, people closer to the tropics may have needed darker skin to act as a natural sunblock.
People who eat large amounts of fish can overcome the need for vitamin D from the sun, since fish provide the nutrient. Hence, the Inuit can survive with little sun exposure in the Arctic, according to the Smithsonian Institute.
Surma boys in Ethiopia drinking fresh milk.
Eating fish may help the Inuit get around biological challenges, but other groups evolved to gain a survival advantage at meal times even in harsh environments. Adults who can continue processing lactose after childhood have the advantage of being able to survive on the milk of livestock that can forage on landscapes, which would otherwise provide no sustenance to humans.
Like a permanent milk mustache, biologists found a shared genetic signature that marks many Europeans and Indians as descendants from a common milk-drinking ancestor within the last 7,500 years. That research was published in Molecular Biology and Evolution.
Chinese workers start the annual Shaoxing wine-making for the lunar calendar winter solstice at a Shaoxing winery. Shaoxing wine is one of the most famous varieties of Huangjiu, or traditional Chinese fermented rice wine, and been in production since the imperial days, and large quantities are stored in the classic Shaoxing wine containers over long periods of time.
Different ethnic groups process alcohol using different variations of an enzyme, known as alcohol dehydrogenase. For example, East Asians have a variant that breaks alcohol down into another chemical, acetaldehyde, faster than other groups. A study published in BioMed Central Evolutionary Biology found evidence that the gene responsible for this may have evolved along with the domestication of rice. The gene is common in Han Chinese, but rare in Tibetans. Variations in the gene suggest that it emerged 10,000 to 7,000 years ago.
A normal red blood cell (left); a sickle cell (right).
A 1954 paper published in the British Medical Journal on sickle-cell anemia documented one of the first discovered examples of how disease shaped human evolution. The mutation that causes sickle cell anemia was most common in populations that had historically lived in areas of Africa where malaria was common.
If an individual inherits only one copy of the sickle cell gene they end up with a mixture of crescent-shaped cells and regular circular cells. That mixture of cells grants them greatly increased resistance to malaria, one of the greatest killers of humans in history. In West Africa where malaria and humans have co-existed for thousands of years, up to 25 percent of the population carries the sickle cell trait.
A corpulent man leaving a pool.
People may have suffered more frequent episodes of famine on the savannah than forest dwelling ape ancestors. The human propensity to build up and maintain fat reserves may have come in response to the need to keep our big brains supplied with energy when there was food shortage. Evolving to store extra energy in our love-handles may have allowed humans to keep their greatest survival tool, their brain, functioning even in a famine. The book “Fat Detection: Taste, Texture, and Post Ingestive Effects” detailed how humans' fat-rich diet differs from our ape cousins and explains the brainy reasons behind that difference.