Hypothesis paper
Von Neumann probe and the origin of life on earth
Hypothesis: Life on earth goes back to a special form of alien “von Neumann probe” or “von Neumann Assembler”. This probe consisted of artificial (synthetic) microorganisms able to survive even interplanetary travel via comets, planetoids etc. A possible purpose of such an alien probe could be terraforming of planets and moons able to support this kind of life for later colonization or exploitation.
Von Neumann probe
What is a von Neumann probe? John von Neumann (1903-1957) was an exceptionally gifted mathematician. Many of his hypotheses have been used as idea for science fiction literature. One of his hypotheses was a machine or program able to reproduce itself. In secondary literature this machine was called von Neumann machine or von Neumann probe (in science fiction literature if it is to be used for interstellar exploration). It is a construction capable for self-replication and able to overcome interstellar distances. After reaching a new solar system, von Neumann probes start to use raw material (comets, asteroids or even planets) and energy sources of the system to reproduce itself and later starts to send copies to other solar systems as well as to start with its mission in the solar system – whatever that might be. Reproduction, consumption of raw material and energy rich sources, data processing and transmission to its offspring and ability to respond gave such a hypothetical machine characteristics of life and might be considered as a form of artificial life.
It is a convincing thought to understand life on earth itself as the very late descendants of an organic self-replication machine – life as the descendants of an artificial (synthetic) living von Neumann probe. What makes this hypothesis charming and are there any hints in the structure of life which might substantiate this thesis? This is discussed in the following text.
Von Neumann probe in contrast to the panspermia hypothesis
A “simple” hypothesis of the origin of life on earth is panspermia. Panspermia is a hypothesis that life is widespread in the universe and that it is distributed by comets, asteroids, planetoids and entire planets (“Some Stars Capture Rogue Planets”; Harvard-Smithsonian Center for Astrophysics) from one solar system to the other. It has been shown that microorganism like special archaea and bacteria are principal able to survive space condition. The Living Interplanetary Flight Experiment, which was developed by the Planetary Society, intended to send selected microorganisms on a three-year interplanetary round-trip in a small capsule aboard the Russian Fobos-Grunt spacecraft in 2011 but unfortunately fell back to earth soon after launch - so the experiment was never carried out. The experiment would have tested one aspect of transpermia, the hypothesis that life could survive (interstellar) space travel, if protected inside rocks blasted by impact off one planet to land on another ("Projects: LIFE Experiment: Phobos". The Planetary Society. https://www.planetary.org/programs/projects/innovative_technologies/life/).
A new result from ESO's HARPS planet finder shows that rocky planets not much bigger than Earth are very common in the habitable zones around faint red stars [1]. Giving the van Neumann probe some attributes of the microbial panspermia hypothesis has some charm: To think of a von Neumann probe as a classical, complex machine that needs artificial intelligence, advanced sensor, an extreme advanced drive and very robust engineering to “survive” long enough and to be able to operate autonomic and able to repair and reproduce itself might be not impossible but hard to believe. But to think of such a probe as microbial life that flourishes wherever it falls on fertile ground (planets and moons with liquid water and some common elements), with no directed expensive drive, more like a pandemia that infects one solar system after the other even when it will take millions of years, is charming from the point of view of a biologist. Sure, panspermia or the idea life as descendent of a “living” van Neumann probe will not solve all the questions because it is not answering the question where and how (or who) life developed but it can expand our view for novel thoughts and overseen signs. At this point I distance myself clearly from creationism. I want my approach is seen as a purely scientific approach.
What would prove panspermia and what would proof the hypothesis of life itself as a special form of von Neumann probe? If the hypothesis panspermia or the living von Neumann probe are right we will find microbial life or the fossil record of life also on other objects of our solar system but also on all objects of other solar systems around us which are capable to support life or were once in their past capable to support life. Another thing would be in common: We would only find family members. They should be made of the same molecular building blocks and processes as we are. If so it is very unlikely to find any forms of complete alternative life. But what could be a distinctive feature between naturally occurring and spreading life of the panspermia hypothesis and the living van Neumann probe? If we are able to explain the natural origin of life in context of its environment, a hypothesis of an extraterrestrial origin is obsolete. Signs of artificiality of life would be strong features confirming an alien origin. But are we able to identify signs of artificial (synthetic) origin of life or not? Do we have to analyze genomes of putative primordial life (archaea, bacteria) much more carefully from that perspective? Sure it will be difficult to proof signs of artificiality in genomes of evolutionary old organisms, despite its originality they have also evolved for 3.7 billion years [2]. There are certain attributes of life which are under discussion: (1) The asymmetric spread of certain isomers of amino acids and sugars (chirality) used and produced in life forms on earth (homochirality) in contrast to the fraction of both possible isomers when produced under archaic abiotic conditions in a putative prebiotic world (e.g. in Millers-Urey primordial soup experiment where a racemic mixture of amino acids occurred). Nevertheless there are approaches to explain the occurrence of homochirality in the process of abiogenesis [3]. (2) The very early emergence of life on earth short after formation of earth itself and – much more surprising – the even shorter period after formation of conditions supporting organic matter, abiogenesis and life on earth in contrast to the unknown relative probability for life to originate and only poorly understood conditions needed for life to arise from inorganic matter [4]. (3) All life on earth seems to be monophyletic. All life forms share the same fundamental processes and “conventions” on many areas of structural and mechanistic level of cell function (universal genetic code of all organisms on earth, usage of 21 specific amino acids, 2 specific forms of nucleic acids in life, several principals of metabolism and cell architecture etc.). Therefore it is believed that the development of life was a single event on earth. There have not been found sign of multiple alternative forms of life in the early history of earth in the fossil records so far nor do such forms of alternative life seem to exist or (have a chance to) develop now on earth (maybe with exception of futurity synthetic life made by human). I frankly think that these phenomena can be regarded as evidence of an artificial origin from outside. Progress on the area of synthetic biology might give us in future indications of possible features of synthetic life.
A plan behind…?
If life´s origin is artificial what is the plan behind a living von Neumann probe? A living von Neumann probe in form of synthetic microorganisms is not able to fly actively and fast to solar systems and special targets within these systems. Such a probe does also not collect any information apart from the fact of sending them to a receiver (except life becomes able to build machines sending signals!). But all life on earth transforms energy to sustain its order / self-organization (key words life and entropy/negentropy). So, life can make a complete reshape of a planet surface, a highly unbalanced atmospheric composition and an amazing diversity of material complexity and cycle of matters. The result is a serious transformation of its environment a foreign observer can´t explain by known abiotic processes in its specific combination. Exactly that is what we would call Terraforming. Terraforming is a process of modifying the atmosphere, temperature, topography and especially the ecology to make it habitable for those who have started the process. A spreading civilization with great foresight could have prepared its spread with these von Neumann probes to increase the likelihood of finding habitable places in former solar systems - especially if one does not expect indigenous life in those systems. Even the culture of engineers of the probe was already set, the process would run away…and billions of years later: Here we are! But even that could have been the plan of the engineers. Wouldn´t it be a great feeling to spread life all over the galaxy?
Also a living von Neumann probe (modified or synthetic microorganisms) is a cheap and very robust design. Since life spread on earth even environmental disaster of global impact never brought life to extinction. Life is also highly adaptive: The microbial von Neumann probes are able to mutate during the process of replication allowing a selection process which helps to adapt to the special and changing environmental conditions of the planet or moon.
Von Neumann probe and implication for the Fermi paradox
The Fermi paradox is a very popular explanation for the lack of evidence for alien civilizations. A common definition is: “The apparent size and age of the universe suggest that many technologically advanced extraterrestrial civilizations ought to exist. However, this hypothesis seems inconsistent with the lack of observational evidence to support it.” Frank Tipler for example hypothesized that the absence of von Neumann probes is a clear proof that there is no other and was no other intelligent life despite humans so far because self-replicating probes would have been inundated the universe [5]. A response was given by Carl Sagan and William Newman: “Any intelligent race would therefore not design von Neumann probes in the first place, and would try to destroy any von Neumann probes found as soon as they were detected” [6]. A von Neumann probe in form of (synthetic) life (modified or synthetic microorganism) would offer a nice solution for this conflict and the Fermi paradox in general due to the fact that life is restricted to very special environmental conditions and not able to reproduce aggressively under all circumstances. Therefore is it possible to construct a von Neumann probe without “destructive potential”. Needless to say that life itself would be the proof for at least one intelligent extraterrestrial civilization.
See also (key words): John von Neumann, John von Neumann probe, self-replicating machine, Common decent, Entropy and life, Homochirality, Panspermia, Fermi paradox, Synthetic life / -biology, Terraforming, Abiogenesis
Reference
[1] Bonfils et al. The HARPS search for southern extra-solar planets XXXI. The M-dwarf sample. Astronomy & Astrophysics, 2012
[2] Fedo CM, Whitehouse MJ, Kamber BS. Geological constraints on detecting the earliest life on Earth: a perspective from the Early Archaean (older than 3.7 Gyr) of southwest Greenland. Philos Trans R Soc Lond B Biol Sci. 2006 Jun 29;361(1470):851-67. Review.
[3] Erives A (2011). "A Model of Proto-Anti-Codon RNA Enzymes Requiring L-Amino Acid Homochirality". J Molecular Evolution 73: 10-22. doi:10.1007/s00239-011-9453-4. PMID 21779963
[4] Gerald F. Joyce. Bit by Bit: The Darwinian Basis of Life. PLoS Biology, 2012; 10 (5): e1001323 DOI: 10.1371/journal.pbio.1001323
[5] Extraterrestrial Beings Do Not Exist", Quarterly Journal of the Royal Astronomical Society, vol. 21, number 267, 1981
[6] Sagan, Carl and Newman, William: "The Solipsist Approach to Extraterrestrial Intelligence", Quarterly Journal of the Royal Astronomical Society, vol. 24, number 113, 1983
© Sascha Eilmus, Biologist, Germany
“…More likely, it will be the handiwork of an intelligent species that has discovered the principles of Darwinian evolution and learned to devise chemical systems that have the capacity to generate bits on their own.” Gerald Joyce
