Did Astronaut Scott Kelly Turn Into A Monkey?

In an incredible, first-of-its-kind experiment, NASA successfully mutated a human being into a rhesus monkey with minimal side effects.

Skeptical? You should be. However, several major news outlets did not exercise such caution. Many separate organizations reported that spending 340 days in space altered 7% of astronaut Scott Kelly’s genetic makeup, when compared to his Earth-dwelling identical twin Mark. This is especially striking considering that we share 98.8 percent of our DNA with chimpanzees. Is Kelly now less related to his twin than he is to a zoo animal? Fortunately for Kelly, these reports were shockingly false.

Scott Kelly and his twin, Mark. Which is the chimpanzee? (Photo credit: Wikimedia)

In 2015, Kelly embarked on a 340-day space mission, a record for American astronauts. Hoping to uncover how space affects human health, NASA awarded research grants to nine academic institutions with plans to study Kelly and his twin. Such an extraordinary space mission offered fertile ground for the experiments spanning biology, physiology, and psychology. In early 2017—nearly a year after Kelly’s return to Earth—NASA released preliminary findings that hinted at signs of biological stress and inflammation that Scott’s body accrued while in space. In January of 2018, the integrated team of researchers echoed the previous findings, and built upon them with post-flight data. The January press releases sat silently on the web for weeks with little attention from the media.

It wasn’t until some surprising headlines were published that the news began to spread like wildfire. The headlines were so surprising, in fact, that Scott Kelly himself expressed some shock. “What? My DNA changed by 7%!” tweeted Kelly. “Who knew? I just learned about it in this article. This could be good news! I no longer have to call [Mark] my identical twin brother anymore.”

Following the outbreak of false reports, NASA issued a revised public statement, prompting corrections from many news organizations.

As it turns out, Kelly did not return to Earth with different genes—the segments of DNA that make us who we are. What investigators in NASA’s Human Research Program did show, however, was that Kelly’s gene expression had changed during his year in space.

What’s the big difference? Were he to share just 93% of his DNA with his twin (and the rest of us Earth-dwellers), Kelly would be only as genetically similar to humans as monkeys are. In that extreme case of genetic mutation, or change, we could correctly say that Scott and Mark Kelly were no longer twins. But when gene expression changes, we make a different conclusion—thanks to the fascinating field of epigenetics.

Epigenetics is the study of how chemical changes to our DNA affect the expression of specific genes— which genes are turned on and by how much. Graycen Wheeler, a graduate student at the University of Colorado Boulder, studies these chemical changes and how they control our basic biology.

“One of the ways cells control gene expression is by changing the chemical markers that are attached [to] or around DNA,” said Wheeler in an email. “These markers act as little flags that say, ‘Make more of this gene!’ or, ‘We don’t really need so much of this one.’”

Markers on your DNA act as flags that change gene expression

Wheeler added that when cells change our epigenetic makeup, it doesn’t affect our hardwired DNA sequence—the actual letters of the code. Instead, our cells are responding to environmental triggers by changing how the code is read. Environmental triggers can range from the dramatic to mere common habits. For example, smoking can cause epigenetic changes that lead to cancer. In that case, your cell has placed a little flag on your DNA that says: “Lots more of this gene, please!”, which may eventually lead to tumor growth. Less dramatically, diet can also influence these DNA markers. “Diet affects your epigenetics because your body needs to express genes that allow it to best utilize the nutrients you give it,” said Wheeler.

Epigenetic flags can be a response to factors of your environment, like diet. (Image credit: The Ottawa Hospital Research Institute)

In the Twins Study, researchers found epigenetic modifications near hundreds of Kelly’s 20,000+ genes. Most of these changes were fleeting, though, as 93% returned to normal within days of Kelly landing back on Earth. NASA believes the remaining 7% of these epigenetic modifications are a result of space conditions. The stressors of space travel—low oxygen, high radiation, reduced gravity—likely caused the more persistent epigenetic modifications. But due to the large number of uncontrolled variables which affect gene expression such as diet, exercise, and sleep quality, the exact cause of the changes is challenging to pinpoint. Only time can tell how long these changes will persist.

In addition to misrepresenting changes to Kelly’s DNA, media outlets got the findings wrong in several other critical ways. For one, news organizations overstated the permanence of the modifications. Moreover, the amount of changes was made out to be significant, despite directly contradicting NASA’s statement that  “epigenetic changes detected in Kelly during spaceflight were well within the range of variability of his twin on Earth.”

The uniqueness of the study cannot be overstated, but reports should have acknowledged some important caveats. Adding to the confusion, NASA referred to the work as “the perfect nature versus nurture study.”

“This finding was super ripe for misinterpretation!” said Wheeler. “Even to someone who knows about epigenetics, the phrasing of most of the headlines reads as if the DNA sequence was changed rather than the epigenetics and the expression levels.”

Fake news is not restricted to the political arena. It also contributes to the spreading of bad science. NASA and the media could have been more clear—not only about what the findings mean, but also about what they don’t mean. This is especially true for a study with no shortage of interesting preliminary findings.

Possibly the most interesting preliminary result of this study concerns the length of Kelly’s telomeres, the protective caps at the end of DNA. Telomeres shrink as we experience stress and as we age, and this shrinkage may be related to a lot of health issues associated with old age. With the stressful conditions of space travel, researchers expected Kelly’s telomeres to shrink more rapidly. The team found, however, that some of his telomeres had actually extended during the mission. The telomeres shortened soon upon Kelly’s return, and then “stabilized to nearly preflight levels,” according to NASA. Nobody knows why space travel lengthens telomeres, but NASA suspects that Kelly’s “rigorous exercise regime and restricted caloric intake” contributed substantially. Exercise and caloric restriction were two key uncontrolled variables—meaning his twin was not on a similar regimen. Future work, and peer-review, will help us understand the significance of these results, as well as the epigenetic findings.

As is often the case, the reality of scientific results is less glamorous than the Facebook posts to which they lead. To be clear: there is no reason to discredit the NASA findings. Understanding the risks and biological limitations of space travel is a priority for NASA and its astronauts. The results of this groundbreaking experiment will be tremendously valuable for the Human Research Program, and so too will be the lessons of these misreports. After all, we can be grateful for a future with more healthy astronauts and fewer space monkeys.

By Max Levy