Commentary: A More Perfect Astronaut
With new techniques in genetic experimentation, can biologists make hardier space dwellers?
- By Kenneth S. Kosik
- Air & Space magazine, July 2001
(Page 2 of 2)
In addition to physical traits, social relationships among animals can have a genetic component. Some male mice, for example, tend to be deadbeat dads, with little interest in caring for their young. Researchers recently have shown that if you take from a prairie vole a gene for something called the arginine vasopressin receptor and transfer it into a mouse, you can produce male mice that, like the voles, stick more closely by their offspring. A simple genetic change leads to a profoundly altered behavior. Could such knowledge be useful for humans, many of whom have trouble spending long periods in isolation, whether in Antarctica or on a three-year trip to Mars?
The bad news for experimentalists is that evolutionary change, even in fast-reproducing species, takes time. How can we study long-term adaptation to space without waiting decades? The answer lies in understanding the deep and profound basis of the evolution. First and foremost, evolution is based on genetic diversity. In humans, the actual DNA sequences, or strings of letters we call the genetic code, differ slightly from individual to individual. These small differences are thought to contribute to, among other things, variations in susceptibility to illnesses such as Alzheimer’s disease, diabetes, and cancer. This is true for other species as well. If 100 rats are placed on the space station, minor differences in their genomes may contribute (along with many other factors, from cage design to nutrition) to their reproductive success. The space station will, for the first time, allow us to watch living organisms adapt to space over generations, and to see which ones do better and which do worse.
Which organisms will make the best test subjects? To watch evolution in action, we need species with short reproductive periods, such as yeast. It also will be useful to study creatures whose genome is known. The list of species whose genome has already been crudely mapped include the fruit fly, a small worm called Caenorhabditis elegans, the wild mustard weed, numerous single-cell organisms, human beings, and soon the mouse and zebra fish. And because sequencing the entire genome of any organism is no longer a formidable task, we shouldn’t limit ourselves to the few species most often studied by biologists. For NASA’s purposes, it might make sense to sequence other organisms that hold the potential of becoming well adapted to space. For example, certain fish create an electric field around them, which they use to detect the presence of intruders. Knowing whether a visitor has entered the field requires a memory of what was previously in the field. And locating the disturbance caused by the intruder requires a set of coordinates related to the orientation of the creature’s body. Will this mechanism work just as well when gravitational orientation is lost? Experiments to test questions like this could yield profound insights into how weightlessness affects both the genetic and physiological bases of spatial learning and memory.
The ability of engineers to build vehicles and space stations that can safely house humans and other species in Earth orbit, or on a voyage to Mars, opens a new biological niche into which life can radiate. With advanced techniques in genetic research arriving at the same time that a sophisticated laboratory is being assembled in Earth orbit, the tools are finally in hand to explore this subject in earnest. The collected genomes of all species, with their staggering diversity, plus the much larger set of synthetic genomes certain to be created from this raw material, hold the potential to create life-forms capable of surviving, even thriving, in the hostile environment of space. The scientific and ethical implications of this will affect not only future astronauts, but the destiny of life on Earth.
Kenneth Kosik is a Professor of Neurology and Neuroscience at the Harvard Medical School, and a senior neurologist at Brigham and Women's Hospital in Boston. He was a principal investigator for the STS-90 Neurolab space shuttle mission in 1998.