Since at least the 2016 campaign, Donald Trump’s skin color has been a topic of conversation, but over the weekend, the New York Times quoted an anonymous senior White House official saying that the official position is: It’s the result of “good genes.” Here’s why that explanation makes no biological sense.
Human skin color is the result of a pigment called melanin that is made in special skin cells called melanocytes. The production of melanin is regulated by an enzyme that also affects a person’s eye color and hair color. Two main types of melanin can be made — the most common is the one that gives a person’s hair, skin, and areolas their hue, while the other one can tint hair, lips, and sexual organs reddish.
Variation in human skin color is comparatively recent in our evolutionary history. It likely dates back more than one million years, when our human ancestors began losing their body hair. Darker pigmented skin was important for preventing damage from UV-B rays in the sunny, tropical environment of Africa. Then, around 100,000 years ago, as humans began spreading around the world, skin color in some populations changed in response to the different climates. Populations in northern, less sunny climates underwent selective pressure because the sun-blocking melanin led to vitamin D deficiency, or rickets. Skin tone is therefore an evolutionary adaptation to the amount of sun in the environment. It likely took only a few thousand years for light or depigmented skin to develop, and it appears to have evolved more than once, with western European and eastern Asian populations being the most well-known examples.
Although skin color can change at the population level over a few dozen generations if the environment warrants it, the production of melanin is under fairly strict genetic control and doesn’t really vary over the course of a person’s life. Changes in the level or amount of pigment over time are not related to chronological aging, but rather reflect UV radiation exposure, also known as tanning. According to a paper by Nina Jablonski, a biological anthropologist at Penn State whose expertise is in the evolution of human skin color, at the scale of the human lifetime, the normal things that change skin color are UV exposure, tanning, and bleaching agents.
Trump’s skin color has not genetically changed over time, unless he has a disease that is known to affect skin color. Jaundice, which results from a variety of liver diseases, lends a yellowish tint to the skin and eyes. Argyria is when the skin turns blue because of too much silver in a person’s body. And hemochromatosis, a recessive hereditary disease, causes iron to build up in one’s organs and turn the skin a tanned or bronze color. It is a condition related to genes, but even Trump would be hard-pressed to suggest that a disease that can lead to impotence and heart failure is “good.”
Given that very condensed history of human skin color, what could Trump possibly mean when he says his skin color is the result of “good genes”? I asked two biological anthropologists for their explanations.
Jon Marks of UNC Charlotte told me that he thinks Trump is “speaking metaphorically. He’s saying, ‘I am a superior kind of being.'” This has to be the case, Marks says, because “scientists who work with genes don’t talk this way — the phrase is genetic nonsense. Genes are not good or bad — they’re pleiotropic, epistatic, and context-dependent.” In short, Marks suggests a quick Google Scholar search, which comes up with only two hits for “good genes” in the entirety of the American Journal of Human Genetics.
Patrick Clarkin, a biological anthropologist at the University of Massachusetts at Boston, pointed me to his blog, where he writes that Trump is a big believer in using “genes” to explain his success in life. Trump “has credited several of his ‘superior’ traits to his genes or some generic notion of heredity, a pattern I find interesting,” Clarkin says. The idea that organisms – humans included – are simply the result of their genes, with little to no influence from the environment, is known as genetic determinism. “I don’t know that Donald Trump believes everything in life is genetically determined,” Clarkin says, “but there are reasons to believe that he might think that way.”
Not only does the phrase “good genes” not make sense from a biological standpoint, it is problematic because “genes can easily become reductive and ideological,” Clarkin points out, leading the president of the United States to potentially use genes “to justify inequality and the status quo.” In fact, “eugenics” is literally the Greek for “good genes.”
In the end, there is no biological reason for Trump’s skin tone to change over the course of his adult life barring a disease like jaundice or hemochromatosis. The most likely explanation is either UV radiation or a tinted lotion. Trump’s constant callbacks to his “good genes,” though, probably reflect the erroneous belief that biology determines one’s status in life.
This article originally appeared on Forbes