It’s a common concept amongst both scientists and storytellers, and it may be summed up best by a quote from the 1978 Battlestar Galactica: “There are those who believe that life here began out there.”  Numerous theories of the creation of life on Earth – mystical, scientific, divine and sometimes even a mix between the three – have appeared over the millennia of human existence, with one similarity among them: life began on Earth.  But what about the alternative to those theories that propose a localized beginning?

     There are two terms that scientists and avid fans of science-fiction both know: Panspermia and Exogenesis.  While the two words are close in concept, they are infinitely different in definition.

     Panspermia describes the process of sowing the seeds of life throughout any local area of space through either predetermined technological methods or random, naturalistic ones.  For example, an intelligent, extraterrestrial race outside of our own star system may be facing an inevitable extinction. In order to avoid the cruel outcome of complete genetic disappearance from the universe, this race sends a million probes into space at velocities close to light speed. These probes would find suitable worlds and place specific cellular and molecular structures in proper environments.  By this method, the implantation could trigger successful evolutionary processes to result in the appearance of the same species that first orchestrated this panspermia.  This movement would take place all within the course of a few million years.

     Panspermia has been considered as a possible operation by numerous space programs of our own world, including NASA.  By constructing self-replicating probes and accelerating these tiny spacecraft to velocities just below the speed of light, the Milky Way galaxy could be entirely seeded with the forerunning microorganisms that would one day become Homo sapiens, or something significantly similar.  The difficulties with this theory are numerous. The advanced biology needed to predetermine this artificial genesis is ages from invention and ethical issues– like cancelling out the evolutionary processes of life that may have already begun to develop on an alien world- present large hurdles.  Because of these obstacles, this mission will most likely not be undertaken by the people of this millennium.

     Exogenesis is a concept that seems to be more preferred by writers because of its openness to various story plots, but scientifically speaking it is just as theoretical – if not hypothetical – as panspermia.  This theory of life states that some sort of organized system of plants and/or animals was taken from one or more habitable planets by unknown means and transferred to another planet, either to sustain these species on a world already capable of supporting that life or to reshape a planet into something habitable, preparing it for the arrival of another string of life-forms.

     Another method of exogenesis could be the transfer of higher life – like that of Homo sapiens – from their home world to another planet that may be environmentally different in few ways.  Over the eons these life-forms would most likely adapt to better suit their slightly altered biosphere.

     Both exogenesis and panspermia have been used to suggest the origin of life on Earth, but neither has been proven or disproven. The reason for these inconclusive results is rooted in the fact that we as a species are limited in what we can and cannot test.  The best scientists in the world will admit that the scientific method is incomplete, in that the results of laboratory testing can only be applied to the specific variables tested.  For example, we know that the sun burns with yellow-green colors because we have seen those same spectroscopic results during the fusion of hydrogen into helium.  Therefore, the sun must be fusing hydrogen into helium.  However, while this is more than likely, we will never truly know unless we can see for ourselves. And while setting foot on the sun may not be the best idea to fully understand a star’s fusion processes, the point still stands that the only facts in our scientific world come from variables directly tested.

     Panspermia and exogenesis suggest theories for random or even predetermined origins. The origin of human life – and all Earth life for that matter – is still an enigma to this world, but with every passing decade science makes great strides in hypothesizing logical ways that life on this world could have originated.

     There are many more theories that discuss the appearance of life on Earth, and while panspermia and exogenesis may be the most appealing to science fiction writers, they are not necessarily the most concrete.  Further study is needed before the truth can ever be known.  But don’t be discouraged, there is a guarantee at the end of the road of discovery, no matter what the truth is, it will be astounding.