Biologically speaking, the radiation-damage problem is complex and daunting to solve through genetic or proteomic tinkering. Cancer is just one of many bleak radiation risks. Others include increased neuronal senescence, affecting neurodegenerative disorders and dementia (remember, neurons generally are not replaceable). Senescence can occur in progenitor cell lines as well posing a threat to connective tissue, bone, and immune-cell maintenance. Fortunately, the body is rife with DNA repair mechanisms and proteins designed to soak up radiation and other damage (sometimes called heat shock proteins). Conveniently enough, these are more robust or more numerous in other organisms. The water bear, a tiny arthropod form the phylum Tardigrada, is famously resistant to radiation (and many other environmental hazards). Scientists have already proven that its protective proteins and DNA repair mechanisms can protect human DNA (in petri dishes) from the ravages of radiation.
To sleep, perchance to dream
Cryonic storage, along with other forms of suspended animation, has captured the imaginations of science fiction authors and the wallets of wealthy, death-fearing individuals since scientific inquiry began to burgeon in the 1950s. Unfortunately, true cryonics has proven moribund. Simply put, freezing the body turns water to ice—crystalline and sharp—which does unkind things to cellular structures. Moreover, beyond the simplest of simple multicellular organisms—namely, the ubiquitous and nearly indestructible water bear—there has never been an inkling of success at bringing an animal to a complete molecular halt and then simply restarting it. On the other hand, slowing metabolism is successfully used clinically already, albeit in the rather limited and coarse fashion of using ice baths to induce hypothermia. This has led to an increase in viability and time to intervention in situations such as sepsis or cardiac arrest in which the body’s cells are rapidly dying. These periods are measured in minutes to hours, not decades to centuries; however, imagine if they could be extended to such long periods (see Kevin J. Anderson’s story “Time Flies”).
This leads to the tantalizing and perhaps more plausible possibility of hibernation, a strategy used successfully by several vertebrates—whether lungfish surviving the dry, hot summers or bears dealing with nutrient-poor winters in arctic and subarctic climes (see Les Johnson’s story “Nanny”). Hibernation is a logical target for research for a number of reasons:
1. Mammals already do it, meaning there is an inherent biological feasibility either through gene editing, protein/hormone administration, or both.
2. Hibernation has clear endogenous (hormone and blood protein) triggers for induction and exit.
3. Hibernation dramatically slows metabolic processes including energy requirements and cellular turnover, which in turn delays metabolic waste accumulation and cell damage.
Moreover, studies of animals that facultatively hibernate (meaning that they do if the winter is cold or food scarce) reveal that hibernation correlates with longer lifespan in addition to reduced caloric intake. Bear hibernation is particularly fascinating, as it occurs without loss of lean mass or brain density, in addition to a total lack of production of urine or feces, in a fairly long-lived animal.
Hibernation could reduce caloric needs by up to ninety percent based on animal models and produce up to a ninety-percent lengthening of lifespan at the theoretical high end. Simply stated, a month of lifespan is earned for every year in hibernation. Ten individuals in hibernation would strain life-support systems about as much as one individual awake and active. If every individual spent one year as crew and nine in hibernation during the journey to Alpha Centauri, that 150-year journey suddenly becomes a fifteen-year journey, which is far more doable within a single crew’s lifespan.
Nutrition, Waste, and Green Living
Colony ships and colonies will need to provide renewable foodstuffs to meet nutritional needs without the requirement to carry masses of stored food. Aquaponics have long been theorized to be important in interstellar travel and early planetary colonization, and with good reason: They handle both food production and waste conversion. Modern aquaponic systems involve bacteria, fish, and plants in a mutualistic system where fish provide nutrition to plants in the form of urea, bacteria break down solid waste into inorganic sediment, and plant roots feed the fish, with the leaves, fruits and a certain percentage of fish available for harvest.
Anthroponics takes this one step further, processing human urine into urea as well. Human manure is suitable as a soil fertilizer with one major drawback: It is up to fifty percent bacteria by dry mass. Sterilization processes exist, but as anyone who’s read about E. coli outbreaks from lettuce or organic produce can attest, they are not perfect.
Meeting on-board nutritional needs of colony-ship residents will be a key logistical challenge. Even now nutritional guidelines are constantly being modified and the relative importance of various micronutrients continues to be discussed. The role of carbohydrates and fats in health and disease (what’s good, what’s bad, and how much) continues to be hotly debated. In the recent past, vitamin D was thought a low-yield as a supplementation target and omega-3s continue to prove ever more crucial to an increasing number of physiologic processes. Additionally, we continue to learn more about trace metals as both poisons and piconutrients.
Precious Metals
One rarely explored issue, the depletion of pico- and micronutrients on long interstellar voyages, is a particular area of concern. These include such metals as copper and zinc that are more often thought of as ingredients in brass than important cofactors for the functioning of enzymes. Though we require mere micrograms of these nutrients per day, deficiencies can lead to fatal disease. A well-developed aquaponics system could address this by storage of dry minerals, chelation with amino acids to improve solubility, and dilution into the aquaponics system. Many seaweeds, including commonly eaten varieties such as porphyra, chlorella, and spirulina, concentrate important minerals including iodine, zinc, gold, and copper efficiently, and would be easily accommodated by a sufficiently sized aquaponics system.
Lead Poisoning and Acid Air
A final concern regarding waste and nutrition is heavy metal poisoning. Ships will be composed of many metals with toxic potential, and plastics, coolants, fuels, and other synthetic fluids will inevitably off-gas volatile organic compounds. The latter was important enough to NASA in their quest for long-term journeys that they investigated plants’ abilities to absorb and neutralize these organic compounds, the results now seen in any garden store with multiple common and hardy houseplants proudly marketed as air-purifying.
Heavy-metal toxicity is a more difficult problem, but one that has a technical solution. Because heavy metals will likely be constantly introduced into the biome, a constantly filtering system will be important. Complex mammals and most plants have systems to deal with this known as sequestration. However, the modern technological world full of metal and alloys contains concentrations well beyond the body’s capacity to cope; simply walling off toxic metals within the body can wreak havoc as the metals continue to accumulate. The effects of lead toxicity on the brain are well known from the poisoning of children by lead-based paints prior to the paint ban a few decades ago; likewise, aluminum toxicity plays a known role in dialysis dementia and has been implicated as a risk factor in several cancers and neurodegenerative diseases.
The tendency of shipboard-grown plants to accumulate metals will likely exacerbate the problem. Genetic engineering, nanotechnology, and simple physical chemistry offer potential for solutions. Multiple bacteria, simple multicellular organisms, and plant species have an alternate strategy for dealing with heavy metals: protein channels known as efflux pumps, which simply dump the toxic substances back out of the cell. These genes may prove good targets for integration into humans and would likely to continue to benefit us once we colonize. Another strategy involves engineering sacrificial plants that preferentially sequester toxic heavy metals from the aquaponic system, which can then be disposed of. Nanotechnology designed to sca
venge toxic metals from our bodies, rendering them non-bioavailable, is an alternate strategy. Organic compounds known as chelators bind to metals rendering them inert and destined for elimination in urine or feces. Such compounds already exist and are effective in cases like lead poisoning. Materials science innovations may also play a role with surfaces that preferentially bind toxic metals suited for submersion in aquaponics systems.
Vitamins
The hominid lineage stands in an odd spot, born of committed frugivore primate, and now functionally obligate omnivores, and as a result we have an odd array of nutritional dependence compared to other animals. Many substances we call vitamins or micronutrients are things other animals produce independently. Vitamin C, for instance, is made endogenously by most mammals. Its production enzyme was lost somewhere in early primates without consequence because it was unnecessary to animals that got so much of it from their diet. Vitamin K, on the other hand, important for blood clotting, skin, and neurologic function, is something most mammals with carnivorous diets make endogenously, given their low leafy green intake.
The genes and proteins that make many, if not most, of our vitamins are found in other animals, often mammals, or in the bacteria that line their guts. Any of these would provide profitable avenues of manipulation of genetics, ones that would continue to pay dividends as we colonize new worlds.
Fitness
Maintaining fitness on board is incontrovertibly important and has been a concern of NASA and other space agencies since the 1960s, when they first noted that rapid deconditioning of astronauts in microgravity can occur in a matter of days. Since then, a variety of exercise equipment and conditioning regimens have been developed and continue to be refined. While some health concerns associated with zero gravity would be obviated under the gravity associated with thrust, others would remain, particularly the need to maintain cardiovascular and muscular health on board an undoubtedly crowded ship.
Prior to industrialization, physical fitness was closely linked to participation in tasks and sports, meaning a certain level of skill was required for maintaining fitness. Whether throwing a ball, executing a well-timed jump, or the complex coordination of movements of wrestling, dance, or gymnastics, the integration of the body, brain, and skill cannot be overlooked. For thousands of years, sports have been instrumental in fitness and should likely continue on our colony ships, which would necessitate one or more areas large and empty enough for group participation. This might initially seem an extravagant luxury, but its justification is clear.
Infectious Disease
Hygiene and sterility can only go so far in preventing the spread of disease on board a ship. This is because many pathogens—especially bacteria—are considered normal flora, meaning they’re regular hitchhikers on our body. Some we simply couldn’t live without (like probiotics). Others we simply can’t be rid of. The potential for pathogenesis, then, is one we will always carry, and, with a small population using a closed system for waste and nutrition, infection is more an inevitability than a risk.
Aggressive infection control will thus be paramount and will likely require quarantine spaces with self-contained life-support systems. Normal and pathogenic flora quickly adapt to traditional antibiotics, the former often “helpfully” transferring those genes to new pathogens. Molecular techniques already play a role with rapid drug development tailored to antigens (identifying structures on pathogens’ surfaces) and vat-grown monoclonal antibodies to specific microbes and the toxins they produce. Immune-boosting drugs are likewise being developed. These development cycles are currently on the order of months to years, but the ability to do so “on the go” and in close to real time as new pathogens present themselves may be the difference between life or death for the crew of our starships.
Novel technology may shine in this realm. While there are certainly places for nonpathologic bacteria to live in our bodies, there are certain areas where no bacteria should be, such as blood, brain, lungs, and kidneys. Artificial cells or nanomachines with a zero-tolerance policy for bacteria that restrict themselves to these tissues could limit the pathogenicity of any bacterium.
Reproduction and Child Rearing
Shipboard reproduction is likely to be a functional or obligate necessity given the lengths of our journey to the stars. Beyond simple pragmatics there are specific concerns of any child born on board a ship of limited size and population. Next, how are the children selected? Will crew be free to procreate on their own (see Kacey Ezell and Philip Wohlrab’s story, “Stella Infantes,” and Dan Hoyt’s story, “Exodus”), or will embryos be preselected through exhaustive genetic screening? Will they belong biologically to one or two crew members or derive from preserved Earth sperm and ova in order to preserve genetic diversity? As discussed, many negative traits can be out-screened but positive ones are simply too complicated to select for with any real predictability, never mind the social implications.
Even before involving the consequences of genetic engineering, we must contend with the fact that few desired traits “breed true.” Heritability for intelligence is pegged at about 0.7; thirty percent of the variation lies outside of genetics. On average, the children would likely have a greater range than the parents. In other words, the least intelligent child will be substantially less intelligent than the least intelligent in the parents’ generation—an example of “regression to the mean.” On the other hand, you can have too much of a good thing. There is now genetic evidence to support the assertion that, genetically speaking, the old adage about a thin line between genius and madness holds true, at least regarding such illnesses as ADHD, bipolar disorder, and autism spectrum disorder. There appears to be an optimum number of “good” alleles with respect to intelligence, with too many being just as problematic as too few. Similar properties apply to the immune system and physical robustness.
In a crew selected for exceptionalism, each subsequent generation will trend back toward human baseline. Those who become colonists, potentially several generations downstream, may be far less capable than their predecessors, even with careful manipulation of the factors within our control.
Regarding reproduction, artificial wombs would be an incredible advancement, but they ignore the dyadic nature of the biopsychology of mother and infant. This involves complex hormonal interplay between the two which affects the infant’s development and prepares the mother to become the primary attachment figure. On the day of birth, a newborn can identify its mother’s voice as distinct and calms more quickly to her touch than others. The mother produces milk tailor-made to her baby’s immune system and neurodevelopmental needs. The role of pregnancy in the attachment process is such that even when adopted at birth to good homes, adoptive children’s outcomes lag. Attachment figures are important. For infants and children, the ability to identify a primary caregiver, someone whose primary responsibility is their safety and emotional well-being, relates to a range of positive outcomes, from emotional and physical resilience to intelligence. Absence of a primary caregiver likewise has striking effects.
Children need enriching environments, full of things to explore and learn about and to facilitate self-exploration. This requires space and supervision. Children also need varied environmental contaminant exposure, which could be challenging or otherwise problematic on a spacecraft. The “hygiene hypothesis” states that healthy immune functioning and low allergic tendencies are linked to dirt exposure, different foods, and a range of pathogens, without which children are at greater risk of allergic response to alien environments or immunoincompetence to mutated or xenopathogens.
Psychology
The basic personality structure of an ideal colonist is clear. In daily life they must be measured, agreeable, conscientious, and tolerant of boredom. Yet on longer scales, they must stomach risk, think adaptively and problem solve in the moment, and be self-reliant. However, no matter how carefully our early explorers are screened, generational timescales mean further thought is required.
The highly controlled environment may also lead to sensory processing disorder, in which the normal unconscious filtering of stimuli becomes impaired. Light sources that don’t match the characteristics of shipboard lights will be jarring and even headache inducing. Sounds not normally heard, hums of a different pitch or intensity, will sound like nails across a chalkboard. This can be managed by carefully varying our background noises and lights in a way that keeps these filtering pathways active.
Humans can set aside personality differences to get extraordinary jobs accomplished. Natural disasters, heroic projects (e.g. space missions) and harsh environmental colonies (e.g. Antarctic bases) unify people who normally wouldn’t give each other the time of day. But there are people who do not or will not continue to put the mission first. They might evade psychological screening, which remains an imperfect “science.” Problems might first occur in children of the original explorers, beyond the careful control of pre-mission planning. Like a speck of grit against a bearing, small differences can magnify, insults and friction growing larger. Humans, for all our vaunted rationality, can reach points at which emotions and relationships cannot be saved by logic, facts, or by the dire consequences of irreconcilable differences or antisocial behaviors. It might not even be intentional, just an inability to function at the level demanded of the closed, high-stakes system of exploration and colonization.
Stellaris: People of the Stars Page 31