Buzz
While some sociologists argue that race is purely a social construct, geneticists suggest that certain racial traits can be traced back to their genetic origins. Often, there is confusion in discussions: racial traits are real, yet they might not always align with our social definitions of race. The debate continues, with many of the distinct features and adaptations of humans still unexplained.
10. Epicanthic Folds
An epicanthic fold is a fold of skin on the upper eyelid that covers the inner corner of the eye, typically found in people of East Asian heritage. The traditional explanation suggests it evolved in tropical climates to shield from UV rays or in cold Arctic areas for warmth. However, this doesn’t clarify how it developed and persisted in Asian populations from regions that were neither tropical nor Arctic.
Some suggest that the epicanthic fold evolved as a way for steppe-dwelling peoples to shield their eyes from dust or as a protection in regions where sunlight reflects off bright surfaces. It may also be linked to minimal brow ridges in certain populations, as these ridges help guard the eyes. Since the presence of epicanthic folds doesn’t seem to have had a major impact on the lives of those who possess them, others argue that it was simply a neutral adaptation that was passed down, possibly amplified by sexual selection.
Epicanthic folds are also present in Native Americans, the Khoisan of southern Africa, Polynesians, and even some Europeans, particularly the Irish, as exemplified by President John F. Kennedy. This trait is also found in infants of all racial backgrounds, and its persistence may be connected to certain developmental disorders like Down’s syndrome. Consequently, in the early 20th century, children affected by such conditions were referred to as 'Mongoloid.'
9. Red Hair
Red hair is a recessive genetic characteristic caused by a mutation in the melanocortin 1 receptor (MC1R), predominantly found in Germans and the Celtic populations of Scotland and Ireland. It is also observed among Udmurts and Tajiks in Central Asia.
In order for the red hair mutation to be expressed, it must be inherited from both parents, meaning there are many more carriers of the red hair gene than actual red-haired individuals. Additionally, there are multiple variations of the MC1R mutation, leading to different shades of red hair, as well as combinations with other hues, giving rise to colors like strawberry blonde and auburn.
Human skin pigmentation is determined by two types of melanin: eumelanin, which gives a brown or black color and is responsible for dark hair and skin, and pheomelanin, which carries a pink or red tint and is found in the lips, nipples, and genital areas. Higher levels of pheomelanin relative to eumelanin result in pale skin, red hair, and freckles. The evolutionary benefit of this trait was to enable individuals in northern regions and cloudy climates to absorb more vitamin D. However, the downside is that redheads are more prone to sunburn, skin cancer, and thermal pain, and they also need higher doses of anesthetics in medical settings.
Red hair genes first appeared in modern humans about 40,000 to 50,000 years ago. A similar mutation was also found in Neanderthals, producing red hair and pale skin. This trait is thought to have emerged in our Neanderthal relatives as an adaptation to better synthesize vitamin D, the same reason it developed in our species.
8. White Skin
Pale skin, particularly among Europeans, is a genetic rarity. The skin color gene SLC24A5 exists in two forms: dark (D) and light (L). Each person inherits one version of the gene from each parent. Those with the DD variety tend to have very dark skin, those with the LL variety are typically very pale, and those with the DL combination fall somewhere in between. This helps explain why children can inherit skin tones that are darker or lighter than their parents, as well as why one of the Aylmer twins has dark skin and dark hair while the other has pale skin and red hair.
Scientists once thought that ancient European populations evolved pale skin after migrating from Africa about 40,000 years ago as a way to better absorb vitamin D in northern latitudes, where sunlight is less intense than in the tropics. The theory proposed that early dark-skinned Europeans suffered from vitamin D deficiency, weakening their bones, while individuals with lighter skin had an advantage in those environments. However, genetic research has revealed a more complicated story.
Though humans began migrating into Europe around 30,000 to 40,000 years ago, recent studies indicate that Europeans were likely dark-skinned until around 8,000 years ago, or possibly even later. Genetic analysis of 8,000-year-old skeletons in Spain revealed that one individual had the genetic markers for blue eyes, but lacked markers for light skin, and was genetically closer to modern northern Europeans than to southern Europeans.
The new hypothesis suggests that Neolithic farmers developed lighter skin as a way to absorb more vitamin D from sunlight, but this change occurred only after adopting agriculture and a cereal-heavy diet that was deficient in the vitamin. Early European hunter-gatherers would have been tall, dark-skinned, and occasionally blue-eyed, in stark contrast to the shorter, paler farmers who later dominated the continent.
7. Blue Eyes
Recent studies suggest that all blue-eyed people share a common ancestor. Initially, everyone had brown eyes, with the difference between brown and green eyes explained by varying melanin levels in the iris. The OCA2 gene, responsible for melanin production in skin, hair, and eyes, underwent a mutation around 6,000 to 10,000 years ago. This mutation didn’t completely halt melanin production, but it did reduce it in the iris, resulting in blue eyes.
The amount of melanin in blue eyes is consistent with only slight variation, indicating that blue eyes can be traced to a single evolutionary ancestor. While the genes responsible for brown eyes vary greatly, studies on blue-eyed individuals from diverse locations such as Jordan, Denmark, and Turkey show a consistent mutation in the OCA2 gene, which is linked to the appearance of blue eyes.
From a biological perspective, blue eyes are considered a neutral mutation. They don’t affect an individual’s survival and are simply a product of genetic mixing. Initially, the appearance of blue eyes was thought to be a byproduct of the development of pale skin, but this theory doesn’t account for the existence of blue-eyed, dark-skinned Europeans.
It seems more plausible that blue eyes spread across Europe due to sexual selection. The theory posits that blue-eyed individuals were considered more attractive, which helped them find mates more easily and pass on their genes. While this theory cannot be definitively proven, it remains a reasonable explanation. Perhaps every blue-eyed person today owes something to a single Neolithic Casanova with striking blue eyes.
1. Dark skin was likely the natural skin tone of early humans, while lighter skin developed later as an adaptation to the European and East Asian environments. Additionally, dark skin might have provided a protective evolutionary advantage against skin cancer when early humans began to lose their body hair.
3. When our earliest ancestors transitioned to a lifestyle of hunting and gathering on the open plains, they lost most of their body hair, likely to help them stay cool. Beneath this hair, their skin would have been pale, similar to modern chimpanzees. However, between 1.2 to 1.8 million years ago, Homo sapiens developed dark skin as a defense against harsh UV rays.
4. Early hominids likely had dark skin, and the development of lighter skin in specific regions like Europe and East Asia was likely an adaptation to the local environment. It’s also possible that dark skin provided a survival advantage by guarding against skin cancer, especially as early humans lost their body hair.
5. As our human ancestors evolved, particularly between 1.2 and 1.8 million years ago, the shift from pale to dark skin was a significant adaptation, helping to shield them from intense UV radiation while they adapted to the open plains where they lived.
1. Researchers suggest that dark skin might have evolved as a protective measure against painful sunburns, to improve vision (as low pigment levels are linked to vision issues), to shield sweat glands from the Sun, and to maintain the body's folic acid levels, which are essential for neural development and can be damaged by UV rays. Additionally, dark skin could offer protection against fungal infections in humid climates.
2. Both Darwin and evolutionary biologist Jared Diamond proposed that the development of dark skin could have been driven by sexual selection pressures. However, the research on albinos indicates that the reality for the pale protohumans hunting in the wild may have been far more perilous, making the theory of dark skin evolving to protect against skin cancer a serious possibility once again.
3. Asian Flush
1. When alcohol is consumed, enzymes in the liver called 'alcohol dehydrogenases' (ADHs) break down the alcohol into acetaldehyde, an organic compound. This acetaldehyde is further converted into acetic acid by another enzyme. In 50% of Asians and 5% of Europeans, mutations in these enzymes accelerate alcohol metabolism up to 100 times faster. This leads to a rapid buildup of acetaldehyde, causing the capillaries in the face to dilate, which turns the face red. It may also result in nausea and headaches.
2. Geneticist Kenneth Kidd from Yale University proposed that the ADH1B*47His mutation, which causes this effect, may have been selected through natural selection. A team from the Kunming Institute of Zoology studied 2,275 people from 38 ethnic groups across China and discovered that nearly 99% of people in southeastern China carried this mutation. This finding seemed to align with areas of early rice cultivation, leading the team to suggest a direct connection. Another gene allele, ALDH2*2, with similar effects, is also present in the region.
3. The mutation may have originated with the Baiyue people of southeastern China as a response to the development of potent, rice-based alcoholic drinks. Those with the mutation causing the 'Asian Flush' were less prone to alcoholism and more likely to thrive in society. Essentially, the flush acted as nature's way of saying 'Maybe you’ve had enough,' while those who didn’t flush were more likely to be too hungover to go to work or reproduce.
4. Some researchers remain skeptical, pointing to similar allergic reactions occurring in European and Indian populations. They also question the timing of the mutation's emergence and the rise of rice agriculture, as the dates don't entirely align. Nevertheless, these mutations appear to have influenced the development of certain Asian societies, as individuals with either of these genes are statistically less likely to succumb to alcoholism.
5. Pygmy Stature
3. The Batwa and Baka people, who live in the Central African rain forest, are notably shorter in height compared to their neighbors and are often referred to as pygmies. Other groups exhibiting pygmy stature are found in the Andaman Islands, Malaysia, Thailand, Indonesia, the Philippines, Papua New Guinea, Brazil, and Bolivia. This short stature is believed to have evolved independently multiple times throughout human history as an evolutionary advantage.
4. Scientists hypothesize that the short stature of pygmies may have developed as an adaptation to living in a rain forest environment. While rain forests host intricate ecosystems, they often lack abundant food sources for humans. Some theories suggest that the pygmies' short size was due to limited nourishment. Smaller bodies may have conserved calories more efficiently, and taller individuals found it harder to navigate dense vegetation, while the humidity of rain forests posed challenges for larger bodies trying to sweat and cool down.
5. Recent studies indicate that pygmy stature is likely a genetic adaptation to the environment, rather than simply a result of inadequate nourishment. Evidence supporting this theory of convergent evolution was found through a genomic study of the Batwa and Baka people, comparing their genomes with those of nearby populations.
1. The pygmy traits related to stature and growth hormone in each group appear to have distinct genetic origins, with both being adaptive mutations beneficial to the pygmy populations. There are ongoing plans to extend these genetic studies to pygmy groups in Southeast Asia to further explore the concept of convergent evolution as an adaptation to environmental pressures across different continents.
2. Ashkenazi IQ
5. It has long been observed that Ashkenazi Jews tend to perform better on standardized IQ tests, typically scoring 12–15 percent higher than the average score of 100. In 2005, evolutionary anthropologist Henry Harpending of the University of Utah, along with controversial independent scholar Gregory Cochran, published a paper in The Journal of Biosocial Science proposing that this advantage among Ashkenazim may have a genetic foundation.
1. The paper argued that genetic lysosomal storage diseases, such as Tay-Sachs, Gaucher's disease, Niemann-Pick disease, and Mucolipidosis type IV, which are disproportionately found in Jewish populations, might paradoxically enhance overall intelligence. If an individual inherits two copies of the gene for these diseases, they manifest as debilitating disorders. However, possessing only one copy of such a gene is thought to promote neuronal growth, accelerate brain cell interconnections, and possibly encourage neuron proliferation in DNA repair genes.
2. Needless to say, this thesis sparked controversy. Harpending and Cochran's paper, though referenced, lacked proper footnotes and was criticized for lacking scientific rigor. Some critics feared the findings due to the historical association of Jewish 'cunning' with European anti-Semitism. Cochran, however, believes that history played a significant role in shaping these results. The forced isolation of Jews in ghettos and specific industries during the Middle Ages imposed intense evolutionary pressures, leading to the development of an adaptation with complex outcomes. This could be viewed as a form of 'unwilling and unconscious eugenics.'
3. Many social scientists remain skeptical. Some suggest a more straightforward genetic explanation: Jews were historically pushed into intellectually demanding professions in trade and finance, causing those with lower IQs to drift away from the religion and culture through conversion. Others propose that the history of persecution acted as a survival-of-the-fittest mechanism, where the wealthiest and most intellectually capable Ashkenazim were the best positioned to survive pogroms and massacres.
4. Other scholars argue for cultural explanations. The religious mandate to study the Torah is thought to have raised literacy rates among Ashkenazi Jewish males to the highest levels worldwide. Cultural practices like bilingualism, chess, music, and high expectations may have also contributed. These explanations are particularly compelling to many, as they avoid the taint of anti-Semitism and present potentially 'accessible behaviors to improve intelligence' across all human populations.
5. Sickle-Cell Anemia
3. Sickle-cell anemia is a hereditary blood disorder that causes red blood cells to take on an abnormal crescent or sickle shape. When a person inherits the sickle cell gene from both parents, the disease manifests, leading to health complications and a reduced life expectancy.
4. While mutations typically result in rare conditions, sickle-cell anemia is widespread, found in regions like North America, Southern Italy, Northern Greece, Southern Turkey, the Middle East, Saudi Arabia, Central India’s Eastern Province, and most prevalently in equatorial Africa. Studies of the mutation’s haplotypes suggest the mutation has emerged independently four times: three times in West and Central Africa and once in India.
5. Sickle-cell anemia is particularly common in areas where malaria is widespread. The sickle-shaped red blood cells can help destroy malaria parasites by trapping them against the cell walls. While researchers have long been intrigued by how sickle cells offer protection against malaria, earlier studies proposed that something in the hemoglobin of sickle cells interferes with the Plasmodium parasite. However, recent research by scientists at the Instituto Gulbenkian de Ciencia (IGC) in Portugal has questioned these findings.
1. Studies on mice have indicated that sickle hemoglobin doesn't prevent the parasite from infecting blood cells, but instead helps the host become more tolerant to the parasite. Sickle cells produce an enzyme called heme oxygenase-1 (HO-1), which in turn generates carbon monoxide. This substance has been shown to protect the host from the parasite without disrupting its life cycle.
2. Miguel Soares, the leader of the research team, explained their findings in a press release: 'Due to its protective effect against malaria, the sickle mutation may have been naturally selected in sub-Saharan Africa, where malaria is widespread and one of the leading causes of death. Likewise, other clinically silent mutations may have been favored by evolution because of their ability to provide a survival advantage against Plasmodium infection.'
3. Lactose Tolerance
5. In infancy, most humans can digest milk easily thanks to the enzyme lactase, which breaks down lactose, a sugar found in milk. However, for most people throughout history and even today, lactase activity diminishes as they reach adulthood, causing lactose intolerance. Today, approximately 35 percent of the human population is lactose tolerant, including individuals of Northern and Central European descent, as well as some people from African and Middle Eastern backgrounds. The spread of lactose tolerance has remained somewhat mysterious.
Around 8,000 years ago, people living in what is now Turkey began to experience mutations near the gene responsible for producing the lactase enzyme. This allowed them to consume milk safely in adulthood. This adaptation spread rapidly throughout Europe, the Middle East, and India, stopping only at the Himalayas. Similar adaptations emerged independently in other regions of the world.
Milk is highly nutritious, providing calcium, micronutrients, proteins, and carbohydrates. However, the exact reason why humans developed an adaptation to drink milk remains unclear. Our ancestors had already discovered that turning milk into cheese or yogurt would break down the lactose, making it digestible, although this process also reduced its caloric content by 20 to 50 percent.
There are many theories as to why milk drinking became so beneficial that it spread rapidly. Some suggest that milk provided essential nutrients missing from many early domesticated crops. MIT geneticist Pardis Sabeti believes milk helped women build fat stores, thereby increasing fertility. It may also have served as a safer water source or acted as a supplement when crops failed.
Anthropologist Henry Harpending proposes that the caloric benefits of milk consumption may have helped populations survive famines more effectively and expand their territories, leading to the growth of civilizations. The rise of lactose tolerance is considered evidence that humans are still evolving. Today, varying levels of lactose tolerance exist in about 90 percent of the global population, with low tolerance or intolerance being most common among African, Asian, and Mediterranean populations.
