Our traditional understanding of human twins would not allow for what Mark Kelly recently released via a tweet about his living twin: “I used to have an identical twin brother.”
The twin he is referring to, Scott Kelly, spent a full year on the International Space Station, and upon his return to earth, his gene expression, known as the epigenome, had changed substantially. So while the twins still look alike, the way their core DNA expresses itself has changed.
That Scott’s epigenome would be altered by his unusual experience is not particularly surprising; that’s what the epigenome is meant to do. It may have similarly altered if he had gone scuba diving every day for a year. The more interesting part has to do with the why of the change. As Cheryl Walker, Ph.D., director of the Center for Precision Environmental Health at Baylor College of Medicine, puts it, “we don’t know whether those changes in the epigenome are good and are helping the human body adapt to space, or whether they are reflecting an adverse effect of space.”
Did you get that? We don’t know if the changes rendered in Scott Kelly’s coding is devolution or evolution. Or, to paraphrase Shakespeare: “Dysfunction or Adaptation; that is the question.”
What if it’s evolution and what we see in Scott Kelly is the leading edge of what humans will do when thrust in to space permanently? What if we’re that adaptable, and further, what if adaption is the core protocol of life? What if everything is adaptive behavior?
Throughout the natural world, there are incredible examples of the crazy adaptability of living things. Survivors can adapt, or they won’t be survivors for long. Apples, for example, are heterozygous, which means that if you plant the seed from a given apple, the tree that grows will not produce the same apple. The apple tree rolls the dice with each generation in the hopes to produce enough hardy varieties that can adapt to whatever environment the tree might encounter. Humans hold the apple constant by grafting the limbs of the pleasing varieties on to other trees so we can keep producing the ones we want, but the seeds are programmed to reshuffle characteristics with each generation, and if some of those adaptations are failures, so be it.
Humans are also marvels of adaptation, which is why we’ve pushed our presence to every corner of the globe. For example, Eskimos can live in the cold on a diet of mostly animal blubber, and the natives of the Amazon can live in perpetual heat on a diet of plants and roots. These humans have the same DNA, but adapted to wildly different applications. Each human starts with ½ of the DNA of each parent, but there is variety; non-identical twins from the same parents will be different.
Like the apples, humans roll the dice with each generation.
These adaptations are biological, hard wired AND moving at two speeds. There is the adaptation driven by natural selection; so, over time, some humans develop greater height, or more body hair, or different color skin (the genome, or “hardware) and there is the adaptation that Scott Kelly experienced where his body began to adjust to the current environment (these are adaptations of the epigenome, or “software”).
Epigenomics is a fairly young science, and it is the study of the more rapid changes to DNA. Each cell carries the entire DNA sequence inside itself, but it is the epigenome that tells the liver cells to do what liver cells do. Since a cell might have to adapt to a variety of quickly changing conditions, the epigenome is positioned to react quickly, often in ways we wouldn’t want. The epigenome allows for survival if some food group is suddenly unavailable, but it also allows for smoking to affect your grandkids, even if you die before they are born and their parents didn’t smoke at all.
It all seems like a sort of natural genius, but then the implications sink in. If epigenetics is as logical as natural selection, then it does not make mistakes. This would mean there is no dysfunction, and very little cultural adaptation separate from biology, and all human adaptation is born of the body. If nature doesn’t make mistakes, then there are no pathologies, no problems outside of what we define, just the relentless adaptation of humans to circumstances and the biological imperative to continually roll the dice so that someone is adapted enough to survive. Such a view would be both a confirmation and a departure from the prevailing views of human behavior. It would be beyond nature v nurture.
Here are a few possible examples:
Perhaps the human life span is an adaptation. It has been observed that mammals typically live to be six times the age to maturity, so for humans, that’s about 120 years. But, perhaps that is an adaptive feature, separate from the human potential to live. Maybe our genes determined that after 120 year, life would not be worth living, or they picked up a signal from the earth that 120 years was enough and space needed to be made for the next generations. 120 years is enough time to get a complete outcome from a given set of DNA instructions and it’s time to move on to the next set of experiments.
Much ink has been spilt over the nature of sexual attraction and gender identity. But, what if it’s all adaptive, and same-sex attraction is not just inborn, but malleable and socially necessary? Yes, we are born with a gender chromosome, and there are only two choices, but the expression is different. Sexual behavior changes over time and perhaps it’s not just a reflection of changing cultural norms. Think how sodomy gave way to homosexuality which gave way to the all-purpose and all-encompassing “gay.” What if these were adaptations to first, a society where men with power horded all the females and later, a society so safe that men with feminine characteristics would be more successful?
The birth cycle is a hot bed of adaptive behavior. We’ve clearly manufactured a problem called “teen pregnancy.” The imperative of biology states that young females are meant to be pregnant; their bodies are peaking in terms of fertility, and the boys of the same age are driven mad with desire to help them. And yet, it has been reported that testosterone levels in young men are falling as we push baby making out to the edges of female possibility. Perhaps this is adaptation in action, with a dose of help from accumulated fat that comes with higher consumption of refined sugar. What if abortion is adaptive; the female knows that the first baby would prevent the formation of a later baby and therefore, must be eliminated? Perhaps infertility is nature’s way of saying “I’m out of time” or “I won’t live long enough to see this baby through.” The decision never to have a child could be similarly rooted.
What if depression is not a chemical imbalance but a natural and logical reaction to a living condition that is arid and lonely? The same would hold true of suicide; what if, under certain circumstances, it makes perfect sense? Death could be what is needed if some biological imperative in the body has figured out that the dice roll didn’t work out and the person intuitively knows that they are flawed and should be discontinued. It is said that miscarriages are the body’s way of turning off when something is wrong, perhaps suicide is the same thing.
What if autism is adaptive; some people need to be able to relentlessly focus on one thing to the exclusion of all other things? They used to be weirdos, but we applied a disease model to them, and they became maladaptive. Perhaps they are not.
It is received wisdom that gang activity is adaptive to the decline of male involvement with sons, and so the gang becomes a substitute family and the older gang members substitute mentors. The forming and separating of social tribes is common for everyone and criminal gangs are simply another adaptive behavior. Maybe gangs are absolutely nature in action, and adapted to service markets not addressed by the dominant gangs.
One could carry on with the behaviors we’ve defined as pathologies or crimes; homelessness, abuse, rape, infanticide… Might these behaviors have a natural, epigenetic origin?
The long process of selecting and rewarding certain behaviors and isolating and punishing certain behaviors is an adaptive process with winners and losers, and no perfect endpoint. As the role epigenetics plays in our life is further explored, our definition of universal goods will change with it. We’ll adapt, like it or not. Humans always think, at the time, that they knew the universal good. Perhaps we should not be so sure because we don’t know what adaptation is right around the corner.