# Migration from Earth: Human Evolution and Space Colonization

Book Review:
Going Interstellar, edited by Jack McDevitt and Les Johnson.
ISBN-13: 9781451637786
Publisher: Baen Books
Publication date: 5/29/2012

The Man in the Moone

When space shuttle Atlantis rolled to a stop on its runway last year, it did not mark, as some worried, the end of human space flight. Rather, it opened the gates to the continuation of human evolution on the largest scale, the migration of our species away from our home planet.

For half a century, governments controlled access to space with exclusive technologies, but today the technologies have migrated into the public sphere. Half a dozen companies are building spacecraft for private access to space. This is a Wright Brothers period: crazy contraptions will be tried and tested, many will fail, some will fly, and in the end they will be transformed from playthings of the rich to common commuter vehicles. And ultimately, people will want not to just visit space (in such extravagances as Bigelow Aerospace s inflatable orbital hotels), but to live there; Elon Musk, of PayPal fortune, has publically stated that his long-term goal is to privately fund the colonization of Mars, polar explorers Tom and Tina Sjogren are currently designing a private flight to Mars, and recently, the Europe-based MarsOne project announced its goal of establishing a human colony on Mars in 2023, funded entirely privately, with No political mumbo jumbo [and] no taxpayers dollars involved. The colonization of space is beginning now.

There will always be those who label such ideas as fantasy. In the 1620 s the Englishman Francis Godwin wrote The Man in the Moone, or, a Discourse of a Voyage Thither, prefacing wryly that while it was simply an entertaining fancy, it had once been a fancy that the Earth was spherical. Travel to the moon, Godwin held, was inevitable. I think the same of human space colonization. Throughout human history and prehistory, whenever the material and social conditions for inhabiting a new environment arose, people have taken advantage of them. The geographic range of our species ensures its survival, and the same will be true in the future.

For the past 23 continuous years human beings have already lived off of the surface of the Earth in various orbital stations: Sergei Krikalev has spent over 800 days in space, and Valeri Polyakov once remained continuously in orbit for well over a year. Clearly, the essential technologies for long-term stays in space are well-understood. The peppery space engineer, author and president of the Mars Society, Robert Zubrin, whose 2001 book The Case for Mars: the Plan to Settle the Red Planet and Why We Must has convinced many that Mars (in contrast to the moon) is rich in oxygen and water, is suitable for building farms, and has sufficient resources to manufacture building materials, such as glass and metals, on-site.

Others, notably the late American physicist Gerard O Neill, developed the idea of giant orbital space colonies, in which as shown in delightful NASA schematic paintings people could live in health and plenty, off of Earth, riding bicycles and flying hang-gliders in orbital cities. With engines, such colonies could be turned into Space Arks sent out to the stars. Recently several research groups have begun to design a 100-Year Starship to get to grips with the challenges ahead.

But as important as they are, the technological dimensions of space colonization are only a prerequisite; they are necessary to make space colonization work, but not sufficient. No matter how well planned, space colonies either in great Arks on the way to other stars, or inhabiting bodies such as Mars or asteroids are not going to survive in the long term if important issues in human biological and cultural evolution are not as carefully considered.

It is time to build a realistic science of the human dimensions of space colonization, one that grapples with the fuzzy, messy, dynamic and often infuriating worlds of genes and people. After all, if it is to succeed in the long run, space colonization cannot be about rockets and robots, it will have to be about living things; bodies, people, families, communities and cultures. And if it is to be about living things, it must be planned with the clearest fact of all regarding living things in mind; that they change through time, by evolution.

Human Evolution, Adaptation and Space Colonization

This new science of human adaptation to off-Earth environments (what I like to call the Extraterrestrial Adaptation) will be heavily influenced by the collective wisdom of anthropology, the scientific study of our species. One of anthropology s central discoveries has been that humanity has not ascended a ladder of civilization, from Savagery to Barbarism to Civilization in any internally-directed and inevitable way.

Rather, human populations in the past 100,000 years have adapted to a wide array of environments, devising new cultures that match human action to a variety of landscapes. And, we have found that humanity doesn t rely on biology to adapt. Indeed, cultural behavior (including the use of technology) allows us to live wherever we please despite our relatively frail biology.

Understanding how our species evolves and adapts will be central to shaping intelligent and adaptive space colonization. We cannot assume that humanity is destined for the stars , or that our species will conquer space . We must proactively make space colonization the extraterrestrial adaptation–happen, and to give it the best chance of success we must understand human adaptation.

The raw material of human biological adaptation is genetic variation. A super-race of clones or genetically very similar people would be a catastrophe in the making because when a single disease or other new variable strikes, all would be subject to the same disaster, with no mutants capable of surviving. For this reason, we will have to ensure that off-Earth colonists are genetically diverse.

Humans have done this for thousands of years, but mainly in large populations that travel freely, mixing genes worldwide. But in the earlier stages of space colonization, populations will be smaller rather than larger, and there will be fewer people with whom to mix genes, such that inbreeding will be a significant danger.

In the same way, cultural adaptation requires flexibility. Cultures must be willing and able to accommodate new conditions by reshaping traditions, religious beliefs, and such technicalities as rules regarding marriage and inheritance. In ancient Polynesia, for example, only a chief s first son inherited anything, prompting other sons to disperse and explore the ocean for more land where they could built their own fortunes. This was a cultural adaptation that fit human action to the conditions of Oceania.

Clearly, off-Earth cultures will have to maintain the human Ace-Up-the-Sleeve of diversity genetic and cultural–despite the fact that small, colonial populations can drift towards fundamentalism in an attempt to force a traditional Norse way of life in an alien environment: this is what the Vikings attempted in early Medieval Greenland, and they perished.

Selecting the Colonists: Genetic Lotteries?

Who will be the space colonists? Here we must ditch the old concept of crew selection . Dispersing populations of humans are not ship s crews with strictly-defined roles, they will have to be normal families and communities for whom space colonization is not a finite goal or end, but a beginning. They will not be on a mission, but living out lifetimes.

Even early off-Earth populations will have to be large small populations are particularly susceptible to single catastrophes, disease in particular won t \be in the billions we have on Earth. The genetic composition of these populations will be critically important because individuals carrying genetic maladies could threaten the future in ways that don t normally play out in a population of billions. This will apply more to a closed system, such as the 100-Year Starship being designed by several teams worldwide.

In this case, no new genetic material could be directly introduced. This might be overcome by carrying stocks of sperm and egg sampled widely from Earth before beginning the voyage, and/or the inducing of mutations at an Earth-comparable rate. In a Mars-colony scenario, people will presumably continue to migrate there from Earth (and back), and this might preserve gene pool diversity. But, as we are about to see, there is no getting around the fact that complex issues of reproductive rights and genetic screening will be a part of human space colonization.

Determining which humans can and cannot participate in off-Earth colonies will be morally complex and a process ripe for misuse and mischief, but we cannot ignore genetics. We should remember that this is nothing new: over thousands of years human cultures worldwide have devised many and elaborate kinship systems and sexual regulations that prevent the genetic disorders associated with close inbreeding.

The main purpose of genetic screening related to space colonization will be the detection of genetic disorders that might send a biological time bomb into future populations. In practical terms, this is evident in a depressing poster generated by the federal Genomic Science Program (https://public.ornl.gov/site/gallery/highres/GenomePoster2009.pdf), a rather gruesome document pointing out the location–on each of our chromosomes–of hundreds of genetically-controlled disorders, from cancers to deafness.

Screening for space suitability here seems simple enough: if you re carrying certain genes, you remain Earthbound (recently researchers announced that they could screen for over 3,500 such traits in human fetuses, opening whole new domains of moral philosophy). The complication, and it is substantial, is that while some genes are strongly implicated in some genetic disorders these are called Mendelian traits more disorders are not so easily pinned onto just one genetic marker. Many disorders are polygenic, the complex result of the interactions of many genes, and single genes can be pleiotropic, affecting multiple characteristics of the individual organism!

And even though one might carry the gene or genes for a certain disorder, environmental factors encountered during the course of life can determine whether or not those genes are activated in such a way as to express the genetic disorder. In short, genetic screening is, and will always be, probabilistic, not deterministic. This particularly applies to the genetics of behavior, where screening, according to Harvard geneticist David Altshuler, is especially prone to misinterpretation and misguided policy.

Considering all this, in the short term a modern screening process would first filter out individuals carrying the best-understood and most debilitating or lethal Mendelian disorders. Next, we would filter out individuals carrying genes known to be most likely affected by the environmental conditions on Mars, or in deep-space colonies, such as different mixes of oxygen and other breathing gases, different gravitational fields and exposures to sunlight and radiation and different food and water supplies than we consume here on Earth.

Despite this screening we must ensure genetic diversity of the gene pool because genetic diversity is a species’ health indicator. Early colonial populations,then, should represent human adaptations worldwide (cold, hot, high altitude and so on), to give future populations the best chance of having on hand genes that might be adaptive in these new environments, seen and unforseen.

Finally, we must consider humanity’s Minimum Viable Population, the population needed to maintain a healthy gene pool. This figure has been much debated, but a ballpark of figure in the low hundreds or perhaps 500 is reasonable. I would suggest erring on the side of larger populations, starting with at least four times that. Space colonization should be planned with ever-increasing populations in mind, not with a paradigm of small colonies, which are are at higher risk of extinction. For humans in space, strength will indeed be found in numbers.

First From Earth: The Return of Natural Selection

No matter how ingenious are our technological and cultural adaptations, life off of Earth, at least at first, will be more dangerous and perhaps shorter than on Earth, a planet that we have actively shaped to be as benign as possible for our species. Off of Earth, humanity will again be subject to the natural selection that we have in many ways buffered out of daily life with technology. Not much of this selection will not play out in the dramatic ways we might expect from science fiction movies. Rather, much will occur on the genetic and tissue-development levels.

For example, consider that the most important time in a person s biological life is arguably during early development of the fetus, when few errors are tolerated. Now consider that the human body evolved under roughly 15 pounds of atmospheric pressure per square inch for several million years, breathing a mix of roughly 80% nitrogen and 20% oxygen. Of course, in free space and on Mars, there is close to a vacuum and since pressure vessels are hard to construct, the lower the pressure they need to hold, the easier and cheaper they will be to build, so atmospheric pressures in a Space Ark or in Mars structures will probably be lower than on Earth. But if you lower atmospheric pressure, you must increase oxygen as a percentage of what you are breathing. Is this solution sustainable over the long term?

Since the 1940 s it has been known that lower atmospheric pressure and elevated oxygen levels interfere in the development of vertebrate embryos. It seems inevitable that in new conditions natural selection will preserve the genes suitable for these new conditions and remove those that are less suitable. For some time, this will play out in increased infant mortality compared to what we are used to today, at least in developed countries, as the off-Earth genome is shaped by its new environment.

Over time, extraterrestrial humans will be shaped by their environment just as Earth humans, including native Andeans or peoples of the Tibetan plateau, who have independently evolved more efficient oxygen-transport systems in the blood; however, they do sustain higher death rates for infants born at altitude, and actually mothers nearing delivery often descend to oxygen-richer altitudes. We can expect similar natural selection, and attempts to curb it, off of Earth. Women nearing birthing, for example, might ascend from 1/3-g, low-oxygen Mars surface colony to a rotating orbital birthing station that provides a full 1g and richer oxygen breathing mix, to give birth and allow early development to go less impeded.

And we must remember that humans are only one species that will go into space. Thousands of domesticates plants and animals for food and materials will accompany us, and they will be subject to new natural selection as well. Finally, so will all of the unseen millions of microbial species that ride on, and in human bodies (see Scientific American Your Inner Ecoyssystem , June 2010) as well as those of our plant and animal domesticates. Many of these invisible genetic hitchikers are critocal to our health, and that of our domesticates, so their genetic health must be undersood and safeguarded as well.

150 Years From Now: New Dialects and Cultures

In either the Mars or Space Ark scenarios, Earth- and non-Earth populations will differentiate over time. There is no stopping this, and rather than resist it, we should accept it as entirely natural and, in fact, a sign of healthy adaptation. If we look ahead 150 years, or five, 30-year generations –considering all that anthropology knows about humanity– we can expect some significant biological and cultural change.

Human survival to date has been a result of our species’ ability to rapidly adapt our cultural practices according to local conditions. In a Space Ark, for example, new concepts of both space and time will change to reflect the reality of living in a closed environment that lacks natural seasons. If cars, for example, are not in general use, what would be the use of the mile or kilometer? People might return to the use of a league, for example, a unit of distance first recorded in Roman documents, of about an hour s walking.

In time, such new ideas would become the norm. Or on Mars, for instance, people will presumably tire of naming everything with reference to Earth New New York, New Grand Canyon, New Antarctica. And not just place names, but words for specific phenomena will appear; Martian landscapes include flow features and ice cap topographies that have no convenient or even descriptive equivalents on Earth, and they will be described in new ways.

In the same way, new dialects will arise. In low-pressure, oxygen-rich atmospheres sound will propogate differently even if subtly–and this could alter pronunciation and perhaps even the pacing of off-Earthers speech, which will also have liniguistic biases based simply on the language constitution of the founding populations. And it is sure that cultural arrangements related to mating, family structure and inheritance will change over time. Culturally, we should not expect to replicate, for example, suburban Western culture off of Earth; in an environment of resource scarcity (at least at first), that simply will not work. Even religious traditions that bear on the relationship of humanity to the natural world will be subject to adjustment to new understanding of the universe.

Regarding biology, it seems impossible that human reproduction, embryo development and bodily growth will be identical off of Earth as on our home planet. Different gravity conditions and even ambient temperatures and humidity conditions in colonial habitats could all affect human development. In the short term, though it is unlikely that these would lead to speciation, off-Earth humans will begin to look somewhat different than Earth people, and they might well be unsuited to a return to Earth.

300 Years From Now: New Bodies and Languages

Significant genetic change occurs with genetic fixation, when new genes become widespread in a population. How long this takes depends on many factors, but my calculations suggest that a likely time for gene fixation in colonial populations is around 300 to 600 years, or 10-20 generations. If so, in as little as ten generations we should expect significant genetic divergence of terrestrial and extraterrestrial human populations (not to mention those of our domesticate species). In particular, I would expect significant selection against genes that result in poor embryo development in new gravity, pressure, breathing gas and radiation environments, and, concomitantly, selection for (and spread of) genes that allow better health in these conditions.

Within these few centuries I would expect Mars or Space Ark people to look somewhat different from Earth people, with different statures, skin hues, hair and eye colors and, more important than these superficial differences, different genes, different epigenetic issues, and different gene regulation and developmental schedules. People might well evolve new metabolic sytems; on Earth, the ability to digest lactose into adulthood spread rapidly with the domestication of milk-bearing animals around 10,000 years ago, originating simply with mutations that allowed digestion of lactose past the weaning age. It is entirely possible that such new genes will arise and spread off of Earth.

Because of human experience to date, however, I would not expect these distinctions to cause actual speciation; that is, if terrestrial and extraterrestrial people mated after this time, I think on this scale they would likely be able to have healthy offspring. Rather, the differences would be on the level of geographical variations we see in humans today (once referred to as ‘races’).

Along with new bodies we can expect new languages. Early exploration of both Asia and the New World resulted in dozens of new words not to mention ideas in the languages of Western Europe. Extraterrestrial people will similarly devise new accents, dialects, words and entire vocabularies to describe new phenomena. What metaphors will arise on Mars, where the wind can blow at hundreds of miles per hour but because of the reduced atmospheric pressure, its effect is hardly noticeable? When the human experience is so modified by new experiences that new grammars (structures of speech) are required, we will see the evolution of new languages off of Earth. Several centuries is a good ballpark figure for such emergence.

The Distant Future: Speciation and the Evolution of Homo extraterrestrialis

When will we see even more fundamental biological change–speciation? Speciation is common in nature when sub-populations of a single kind of life become separated or reproductively isolated, adapting to their own conditions to the extent that they may no longer interbreed.

Mammalian speciation can occur as quickly as over a few thousand years (though normally takes much longer). In the case of Homo, we have gone over 150,000 years migrating into a wide variety of environments, from desert to open ocean without speciation (the possible exceptions are many thousands of years past, including the cold-adapted Neanderthals, and the apparently miniaturized hobbit humans of the island of Flores in the southwestern Pacific). This is because we normally adapt more culturally than biologically. But as we have seen, we can expect that the return of natural selection and adaptation in Homo will in the long run result in significant biological evolution.

What will Homo extraterrestrialis look like? Will it grow wings, or a hard shell with which to actually survive for a time outside a spacecraft? Will people of Mars grow structures that could split the oxygen from the carbon dioxde in the atmosphere in the way that fish gills separate gaseous oxygen from water? The answer seems to be no, or not for a very long time. This is because such large, structural changes are quite rare in evolution due to a species genetic heritage, which constrains the innovations that can occur. It seems that humanity will for a long time retain an essentially bipedal primate form. Speciation, then, will more likely have to do with less visible divergence of internal mechanisms, with perhaps a few visible correlates.

On the other hand, if off-Earthers decide to harness the staggering replicative potential of DNA, and control it four their own purposes, it seems likely that in the long run they will design their own bodies for very different environments than on Earth. Humans might well be engineered to have novel metabolic and even locomotor capabilities. Before this, or along with it, humans might also transfer intelligence and even consciousness to non-biological substrates; conscious, exploring systems much more resilient than our current biological form.

Ensuring the Success of Human Space Migration

Human space colonization, as a long-term beginning rather than a short-term goal, is an insurance policy for the human species. It will require plenty of technical advance, but equally important will be to develop an understanding of how human biology and culture adapt to new conditions, and use that knowledge to make space colonization succeed. There is plenty to do, and we may as well begin now, by applying what we know from anthropology to the breathtaking goal of ensuring human survival by migrating from Earth.

Follow Scientific American on Twitter @SciAm and @SciamBlogs. Visit ScientificAmerican.com for the latest in science, health and technology news.

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