We have Met the Aliens and They are Us!

                One of the more interesting futures would be one in which humanity's search for life in the universe is the cause of the alien civilizations and alien life that we do find.  Let's say earth life begins to spread through the universe at ... oh say 5% of the speed of light. It is an interesting speed in that a light year takes 20 years to cross, roughly a human generation.  New settlements succeed or fail, and at least a few of those that do succeed produce the next wave of interstellar settlement. This is sometimes called, “Crawinization.”

At theses speeds each system settled becomes a genetically isolated population. Through the founder effect, genetic drift, and natural selection, the process of speciation begins. This completely ignores the possibility of engineered selection. Even new arrivals from the mother civilization are either reestablishing a failed effort, and thus starting the clock over, or are encountering an existing population to which, assuming small crew sizes, they can make only a limited genetic contribution.  Some estimates put the time for one species to transform through accumulated mutations into a different species at 2 million years, but in some African fish species as little as 15,000 years. That said each wave of settlement starts with a small population, one genetic choke point after another driving speciation not through time but through distance.

Settlement thus moves as a wave front through the galaxy, but how fast? Upon arrival let’s estimate the time for the daughter civilization to build the population and industrial base to repeat the process is about 500 years.  Some will be faster, some will be slower, but it is the faster that will seize the colonization opportunities.  The mother civilization has a 500-year head start on reaching any settlement target. At 5% of the speed of light this amounts to about 25 light years beyond he daughter settlement.  Beyond that, at least one of the daughter civilizations (assuming many successes) will be closer to any given settlement target, still at 5% of the speed of light. 

Where is this settlement front headed? Sol is about 26,000 light years from the center of the galaxy and in the middle of the galactic habitable zone, an annulus about the disc of the galaxy where stars form and the necessary elements for life are being generated in the deaths of supermassive stars.  A circle of radius 26,000 ly is roughly 160,000 ly in circumference.  The waves of settlement will proceed in both directions and each covering half that path, 80,000 ly and meet on the other side of the galaxy. At 0.05c this takes 1.6 million years, or 80,000 human generations.

As we colonize the galaxy, we are going to take our allied species with us. The producers of food, oxygen, companionship, and even the microbes in our gut. Oh, heck with it. Let’s take all species with us just in case. 

In addition to going through a genetic choke point every 25 generations or so, consider also that we will have full control over our genetic future.  It is difficult to imagine using that freedom to deliberately produce the diversity of say the Star Wars Universe, but what about unintentionally? We need to think about 1.6 million years with small deliberate decisions made in each generation.  In one generation, we eliminate a genetic disease, in the next we ensure our children are just a little more resistant to depressurization than their parents.  How many generations of small deliberate adaptations until vacuum exposure is a survivable experience?  How long till we are as adapted to vacuum as we are currently to the heat of the Australian desert, with vacuum adaptations are just one possible choice. 

What about metabolic needs? These needs drop roughly as the cube root of the scale, a 1/2 sized human takes up 1/8 of the space and food, water, and air resources.  Why stop at 1/2?  How far down could we go and still support human cognition?  What about temporal adaptations? What advantages accrue to a human clade with a clan that metabolizes, moves, and thinks at 1/100^th of normal speed in order to pilot interstellar voyages? To such a human a 500 year voyage is still a grueling 5 subjective years, but not endured on a generation ship.  In the end, different branches of humanity meeting again after thousands of years may be as alien to each other as anything imagined by George Lucas. 

--- posted by Y.H.N.