Do you know why your skin color is black or white? what are their benefits?

introduction

Two individuals from diverse regions of the world coincidentally cross paths. They discover they have numerous common hobbies and interests, even sharing a preference for the same types of food. However, what truly astonishes them is their striking physical resemblance - so much so that one could mistake them for twins if they hadn't been brought up on separate continents by entirely different families. Despite their uncanny likeness, they are not biologically related.

Tales of doppelgangers,

individuals who bear a remarkable resemblance to others, have been prevalent throughout history. Yet, such occurrences are becoming increasingly frequent. This can be attributed to the fact that, genetically speaking, the human population possesses more similarities than disparities. As the global population expands, the likelihood of encountering a lookalike also increases due to potential overlaps in our DNA.

Population genetics, as my doppelganger mentioned, is a branch of biology that focuses on studying the genetic composition of populations. These populations consist of organisms of the same species residing in the same location and timeframe, capable of producing fertile offspring with one another. Determining the boundaries of populations is not always straightforward, whether we're discussing pineapples, porcupines, or people. If organisms of the same species are confined to an island for numerous generations without any migration or new individuals joining, it's relatively simple to define a population. However, when organisms traverse diverse habitats or entire continents, utilizing various modes of transportation and engaging in unrestricted reproduction, the lines between populations become blurred. Population genetics aids scientists in quantifying changes within these indistinct entities known as populations. By employing statistical methods, they can construct models that forecast the frequency of alleles, which are different versions of genes responsible for traits such as flower color. These models can predict the likelihood of certain visible characteristics appearing more or less frequently. Personally, I am inclined towards an abundance of red flowers, as I am a hopeless romantic. Additionally, these models enable biologists to compare genetic similarities and differences, unveiling the relationships between organisms. For instance, consider the platypuses inhabiting a vast region. It is possible that the platypuses in the Southern section of the river exhibit greater genetic similarity to each other than to those in the Northern section.

This could suggest there are lots of smaller populations that don’t interbreed very much. Or, say there aren’t any clear subgroups within this large population. Instead, there’s a gradual continuum of genetic variation throughout. This could suggest a large, well- connected population of platypuses getting it on for generations. From genetic sequencing in a lab to detailed observations in nature, data can be statistically analyzed to understand populations. Different approaches emphasize different parts of the picture. Methods seeking connections can illuminate how even different species like chimps, humans, and mushrooms are genetically related. Methods seeking differences can highlight small nuances between populations. With these methods, biologists can measure genetic diversity or, the genetic differences among individuals. The more genetic variation in a population’s gene pool the easier it is for that population to adapt and survive whatever the environment throws their way. It’s like the difference between having a wrench and an entire toolbox. Smaller populations tend to have less genetic diversity, which means fewer tools to fix stuff when it breaks. And this means individuals are more similar to each other.

For instance, take the cheetah of today. The loss of their natural habitat and various other factors have significantly reduced their population and genetic diversity in recent years. This lack of diversity makes them more susceptible to diseases, and their offspring have a lower chance of surviving into adulthood. You see, a virus or even a cancer can exploit a specific weakness in the cheetah's immune system. In a population with very similar genetic makeup, a single disease can decimate a large number of individuals. On the other hand, a population with greater genetic diversity can have a range of immune strengths, making it less likely for a single illness to cause widespread devastation. Different categories of living organisms tend to exhibit varying levels of genetic diversity. In plants, animals, and fungi, genetic variation above 5% is considered high. However, the split gill mushroom surpasses all known eukaryotes with diversity levels of up to 20%. Prokaryotes, such as bacteria, are hyperdiverse because they do not rely on sexual reproduction. They acquire diversity through a completely different mechanism, which we will discuss in a future episode. Among organisms with a backbone, the average genetic diversity is only 0.25%. Humans, in particular, fall below this average, with genetic diversity hovering around 0.1%. This may explain the existence of numerous look-alikes among us. So, you might be inclined to think that these hyperdiverse mushrooms have a better chance of surviving the challenges life throws at them compared to us. And that's a valid thought. I, for one, applaud the fungi that may out-adapt us all. However, there's another important lesson here that we must not overlook: you and I share a lot in common. In fact, 99.9% of our genes are identical. All humans, regardless of their location, are remarkably similar genetically.

Furthermore, it is worth noting that in the case of humans, there is a greater occurrence of genetic variation within populations rather than between them. Surprisingly, you may share more genetic similarities with an individual from a different continent than with someone residing in your own town, even if society perceives the local person as the same race as you and the distant individual as a different race. However, there is one exception to this pattern. There is a specific trait where the majority of variation does exist between populations rather than within them. Nevertheless, it is important to acknowledge that this particular trait only accounts for a minuscule portion of our DNA. Unfortunately, throughout history, this trait has been wrongly utilized to classify individuals and to rationalize inequality and suffering.

throughout the course of human evolution, mankind has been confronted with the challenge of harnessing the benefits of ultraviolet rays emitted by the Sun, while simultaneously avoiding their detrimental effects. When the skin is exposed to an adequate amount of UV light, it produces vitamin D, which is essential for the development of strong bones. However, excessive exposure to UV light can destroy folate, a crucial vitamin necessary for nucleic acid synthesis. Consequently, regardless of our geographical location, we have always strived to find the perfect balance of UV light. It is important to note that the intensity of UV rays varies across different regions of the Earth. Areas closer to the equator receive a higher concentration of UV rays, while those closer to the poles receive a lower amount. In regions with more sunlight, having darker skin is advantageous as it contains higher levels of melanin, a substance that absorbs the majority of UV light. This darker skin tone allows for the protection of valuable folate while still enabling the production of vitamin D. Conversely, individuals living in sun-deprived areas near the poles require lighter skin with less melanin in order to allow more UV light to penetrate the skin and produce vitamin D. However, this increased exposure to UV light also heightens the risk of sunburn. As humans migrated and settled in different parts of the world, our skin color gradually adapted to the availability of sunlight in those regions. This has resulted in a diverse spectrum of skin tones, with no distinct boundaries between shades. Rather than being evidence of our differences, this continuum of skin color serves as a testament to our shared need for sunlight and our remarkable ability to adapt.

Alright, so characteristics such as skin color or eye color exist on a spectrum. Therefore, we utilize the term clines, which refers to gradients of change on a continuum, to describe and represent genetic diversity. These clines can correspond with your ancestry, reflecting the genetic history and origin of your ancestors. As demonstrated by the skin color spectrum, the environment in which your ancestors originated can influence the traits you inherit. Additionally, it is possible to uncover clues about your ancestry by examining patterns in your DNA. However, these patterns are not defined by distinct dividing lines. In fact, there is no single trait or gene that reliably distinguishes between what we refer to as different "races." This is because race is a social construct, an idea that has been created and agreed upon by society, rather than a biological category. Race is a means by which we categorize people based on traits that we have arbitrarily chosen to emphasize, such as the amount of pigment in someone's skin or the texture and color of their hair. Unfortunately, when we view individuals through the lens of race, it often leads us to make incorrect assumptions about their ancestry or country of origin. This is because racial categories have placed excessive emphasis on a few visible features, like skin color, which do not have clearly defined boundaries. For example, someone with ancestors from China and Ireland undoubtedly has DNA from both sides of their family. However, due to societal emphasis on certain visible traits, this person may be labeled as "racially Asian," thereby erasing a part of their ancestry without providing any meaningful information about their biology. As biologists continue to expand their knowledge of human variation and genetics, it has become evident that "race" is not a genuine biological attribute. Nonetheless, it has played a significant role in shaping history and has even influenced the field of biology.

In the United States, individuals of different racial backgrounds, such as people of color, have been subjected to prejudice and inequalities. These biases and disparities, whether consciously acknowledged or not, have a significant impact on their lives, identities, and experiences. This concept of race can be likened to money. Just like money, race has a tangible effect on one's access to resources and opportunities, as well as how they are treated by others. However, both money and race are also abstract ideas that we have collectively agreed upon to hold meaning. There is no inherent reason why a piece of paper or a metal coin should be exchanged for necessities like shelter or food. Similarly, there is no genetic marker in our DNA that makes categories like "Black" or "white" biologically significant. Nevertheless, these social and political constructs have real consequences, shaping the opportunities, resources, and treatment that individuals encounter. People of color in the United States disproportionately face poverty, exposure to pollutants, and limited access to medical care, which in turn impacts their health. Unfortunately, these health disparities are often wrongly attributed to genetic differences. These patterns of inequality can be observed in almost every country, although the perception of race may vary across different cultures. However, it is possible to address and combat race-based inequality. It is disheartening to continually reiterate this point, but it is necessary. Traits such as skin color or hair texture may appear as significant differences that divide us, but this perception is a result of the power and reinforcement we have given to these characteristics over generations. Population genetics reveals that there is much more that unites us in our DNA than what sets us apart. Whether we are discussing animals like platypuses or human beings, there is no clear-cut boundary that separates distinct populations. By studying genetic similarities and differences, population genetics helps us understand how living organisms have evolved and continue to evolve.