The theory of cosmic ancestry states that life on Earth originated in space, and that life as a whole has always been present within the universe, having no single identifiable point of origin (or, for that matter, point of ending in the distant future). Cosmic ancestry is a theoretical outgrowth of the theory of panspermia, which states in general that life on Earth was seeded by living material which originated elsewhere in the cosmos.
- Background: Panspermia -
The theory that life on Earth actually began somewhere else is technically separate from the religious or intelligent design argument that life began through the intervention of an outside creative force, like God (since cosmic ancestry argues that life has always been present and had no designer). It is also separate from the current biological view of our origins, which states that there was a definite point at which life came together from complex organic compounds, a process known as abiogenesis.
Initially, panspermia was open to either of these options, although it insisted that wherever life originated, it was somewhere other than Earth. This is essentially an untested hypothesis, because while we cannot confirm the precise mechanism by which life began on Earth (we can only note that the first fossils appear after a few hundred million years), we also cannot point to a source from which life could have come - especially if that source is not only off the Earth, as many suggest, but indeed outside our solar system, as a few suggest. Nevertheless, this limited form of panspermia, also known as exogenesis, does not actually eliminate the question of where life originated: it simply moves it from the surface of the Earth away to some distant and unspecified location in the cosmos.
- Cosmic Ancestry -
The theory of cosmic ancestry goes one step further. It states that not only did life not originate on Earth (either through religious creation or through natural abiogenesis), but it did not "originate" in this sense anywhere else, either. Instead, life has always been one of the fundamental constants of the universe, and presumably always will be. Within the universe, sometimes this life has evolved greater levels of complexity, however, as it has on Earth. However, ultimately the evolution of life on Earth, including human beings, was not the result of creation of new life, merely recombination of existing material.
The theory of cosmic ancestry thus rests on the fundamental lack of a clear, coherent explanation of the natural process (either scientific or otherwise) by which non-living matter turned into living matter at some point in the distant past. Without an explanation of how this could have happened, advocates of the theory of cosmic ancestry state, the only rationally appropriate response is to reject a theory that relies on abiogenesis as being fundamentally unsound. This then leads to the alternative theory that some form of life has always been present in the universe. How that life arrived on Earth is, of course, another question, and here cosmic ancestry can turn to the classic exogenesis arguments that life here was seeded by life from elsewhere.
- Scientific Credibility -
Ultimately, the strongest case for the theory of cosmic ancestry comes from its challenge of abiogenesis, in much the same way that intelligent design advocates have gained some ground by criticizing what they call the concept of "macroevolution." Unfortunately, cosmic ancestry proponents have not been able to put forward strong evidence to support their alternative theory. To date, no analysis of comets, asteroids, or the solar wind has shown evidence of microorganisms there, like bacteria or viruses, and the only evidence of continuing life on Mars is a handful of disputed and inconclusive readings from the Viking program of the 1970s. (Today's rovers have not uncovered anything more than evidence that the building blocks for life were present in the distant past, and that it might have existed then.)
In addition, and more seriously, the theory of cosmic ancestry does seem to be at odds with another and more fundamental body of scientific theory: the cosmological explanations of the origins of the universe. The idea that life is an ever-present component of the universe implies that the universe itself is likely timeless or unchanging - known as the "steady-state" theory of the universe. However, the vast majority of scientists working in cosmology and astronomy now believe that the universe did have a coherent beginning (the so-called Big Bang), which was followed by a period of expansion that continues today and will possibly continue until the ultimate end of the universe.
If the universe itself is not timeless, but has a decisive beginning and ending, it would logically follow that life within the universe had a coherent beginning point as well. Moreover, since we believe that for its first moments the universe consisted of a soup of material devoid of the larger and more complex structures on which we know life relies, like atoms and molecules, it would also follow that life originated some time well after the origin of the universe. Note that this has implications for the strong form of the theory of cosmic ancestry; it does not necessarily follow that, having once originated elsewhere, some form of life did not spread to a vast number of planets, including Earth.