1. Cambrian Explosion
2. expansion of evolutionary theory
6. galactic context
8. Von Neumann Machines
9. molecular assemblers
10. biology or evolved nanotechnology?
1. Cambrian Explosion
The Cambrian Explosion was a relatively rapid appearance, around 530 million years ago, of most major animal phyla, as demonstrated in the fossil record, accompanied by major diversification of organisms including animals, phytoplankton, and calcimicrobes.
Before, the Ediacara biota, ca. 635–542 million years ago, consisted of enigmatic tubular and frond-shaped, mostly sessile organisms. Determining where Ediacaran organisms fit in the tree of life has proven challenging; it is not even established that they were animals, with suggestions that they were lichens (fungus-alga symbionts), algae, protists known as foraminifera, fungi or microbial colonies, to hypothetical intermediates between plants and animals.
Most macroscopic fossils are morphologically distinct from later life-forms: they resemble discs, tubes, mud-filled bags or quilted mattresses. Due to the difficulty of deducing evolutionary relationships among these organisms some paleontologists have suggested that these represent completely extinct lineages that do not resemble any living organism.
Trace fossils of these organisms have been found worldwide, and represent the earliest known complex multicellular organisms. The Ediacara biota radiated in an event called the Avalon Explosion, 575 million years ago, after the Earth had thawed from the Cryogenian period's extensive glaciation, and largely disappeared contemporaneously with the rapid appearance of biodiversity of the Cambrian explosion. Most of the currently existing body-plans of animals first appeared only in the fossil record of the Cambrian rather than the Ediacaran. For macroorganisms, the Cambrian biota completely replaced the organisms that populated the Ediacaran fossil record. The earlier fossil communities disappear from the record at the end of the Ediacaran leaving only curious fragments of once-thriving ecosystems.
Extinction-level events seem to occur priodically in a 62 +/- 3 million year cycle in the fossil record. The last major mass extinction event took place during the late jurassic period approximately 65 million years ago. The implication is that an unknown periodic process has been having a significant impact on Earth’s environment. Although the exact nature of the periodicity remains shrouded in mystery, it has been speculated that the passage of the solar system through the Milky Way Galaxy may be linked to the cause. Two extinction events, late Cretaceous and late Eocene, are associated with evidence for meteorite impacts.
The seemingly rapid appearance of fossils in the primordial strata was noted as early as the mid 19th century, and Charles Darwin saw it as one of the main objections that could be made against his theory of evolution by natural selection. What kind of event might have caused such change and what are the implications for the evolution of life on Earth?
2. expansion of evolutionary theory
Most thinking in genetics has focused upon vertical transfer, but there is a growing awareness that horizontal gene transfer is a highly significant phenomenon. DNA sequences can be shared by viral interaction. Highly sophisticated and specialized phages distribute genetic information across species. There is no restriction to the organism or even the species between which the sequences can be shared. For an example animal DNA can be introduced into plant sequences by viral transfer, wich is a usual procedure in genetic engineering.
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages. The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. Whilst parallel evolution is a possibility, the wide distriution of common traits in nature suggests a different mechanism. The probability for coincidences on this level of complexity is practically zero.
The coding DNA percentage of humans, the part neccesary for reproduction, for an example, is at 1,5%. The other 98,5% is noncoding DNA. Polychaos Dubium, a freshwater amoeboid, may have the largest genome known for any organism, consisting of 670 billion base pairs of DNA, which is over 200 times larger than the human genome. Obviously there is a lot of genetic information floating around wich is not directly releated to reproduction. Evolutionary selection pressures life in maintaining useful genetic information. What purpose is all this genetic information serving?
Every organism carries a considerable payload of the phage code, not just the information neccesary for reproduction of the species. Even if a species becomes extinct fragments of its DNA are retained chopped up in the genome of the surviving species, to arise once again, if the circumstances should favour it. Chances are the context will be quite a bit altered, but the information is preserved by the survivors, ready for further use. Mixing up noncoding with coding DNA slows down genetic degradation, swapping active and inactive sequences by viral interaction, so that selection stress keeps all sequences in a pristine, functional condition.
One indicator for such a mechanism is the acorn worm. The last common ancestor this worm had with vertebrates lived more than 500 million years ago. These worms live most of their brainless lives buried in deep-sea beds. Researchers have probed the genetic patterns of their developing larvae and discovered a set of signals similar to the ones used to build the mamalian central nervous system. Such a set of DNA can not evolve in a brainless host, because it never is used. Therefore no selection can take place. However it may carry a part of the genetic blueprint of the vertebrate brain as a part of the global genetic information and it may exchange such sequences with other species through HGT.
Another example are the central components of muscles of higher wich animals seem to be much older than assumed. A muscle protein core set, including a type II myosin heavy chain motor protein characteristic of striated muscles in vertebrates, was already present in unicellular organisms before the origin of multicellular animals. As this specific myosin has so far only been found in muscle cells, it should be expected that its origin coincided with the evolution of muscle cells. Instead we see that the 'muscle myosin' originated from unicellular organisms, long before the first animals lived. As with the acorn worm, this is difficult to explain, because there is no selection process in place for such advanced concepts in unicellular organisms.
The marine sponge, Amphimedon queenslandica, despite having almost all the genes necessary to build a neuronal synapse, does not assemble any structure morphologically resembling a synapse - it does not have any neurons at all. Its as if the synapse gene network is not wired together. The critical step in the evolution of the nervous system as we know it was not the invention of a gene that created the synapse, but the regulation of preexisting genes that were somehow coordinated to express simultaneously.
Genes that exist before the appearance of the features they encode and identical features that appear to evolve independently, several times over can't be explained by Darwinism alone. Following multiple gene transfer events, the genes would easily appear to have had multiple, independent origins. Necesary stecps seem to be already aviable as "off the shelf solutions" in the global genome information pool, being shared across species.
Evolution does triple duty in this respect by diversification of blueprints for information carriers, thus increasing the probability of survival for genetic information through redundancy, but it also aquires new sequences via slow, long therm mutation, as well as preventing degradation by recombination of existing sequences.
Of special interest is the selection mechanism works wich determines which DNA sequence to share in HGT. It includes a highly sophisticated decision making process capable of determining a threat and selecting a apropriate solution from a cataloge of genetic information. This mechanism is evidently present an was verfied in lab tests by exposing bacteria to hazardous environments. The bacteria shared the neccesary resistance code imedantely, preserving the population through communal adaption of the trait. This is no trial and error approach - its intentional, purposeful ad hoc modification of an existing population.
Mass extinctions are often followed by adaptive radiations as existing clades expand to occupy the ecospace emptied by the extinction. Once the dust settles, overall disparity and diversity return usually to the pre-extinction level. This is not the case during the Cambrian Explosion.
By dating minute glass beads in lunar samples, collected during the Apollo 14 mission, melted debris from the heat of asteroid and comet impacts, scientists made two discoveries, one expected and the other a big surprise.
The ages of many beads, the size of tiny peas or smaller, confirmed the heavy meteorite bombardment of the Moon from 4 billion to 3.5 billion years ago. This was a violent epoch in the young solar system, which formed 4.5 billion years ago. Impacts of asteroids and comets gouged out many of the larger lunar craters and basins that remain virtually unchanged on the waterless, airless Moon.
Describing the findings the researchers concluded that the age data from 155 glass beads "show that the crater production rate has not been constant over the last 3 billion years, as had been generally assumed." The data, they said, also provided evidence for a striking increase in the cratering rate over the last 400 million years. But the most provocative remark by the scientists was the data, they said, "shows an increase in the cratering rate roughly coincident with the Cambrian Explosion of complex life on Earth". This implies that the increased debris influx had a net stimulating effect on biotic diversity, "despite the occasional occurrence of large impacts with destructive consequences".
Why was the "increased debris influx" a stimulating factor? Normally, especially considering other late jurassic extinction event in the fossil record, the assumtion tends twoards the opposite effect.
The only stimulus wich has the potential to produce such a response is the introducion of genetic material into the biosphere. This explains the diversification, because a considerable amount of addition genetic information becomes aviable instantly, feeding an entire library of information into existing genome distribution mechanisms, with predictable results.
Whilst HGT may provide the tools for sharing genetic information across species it doesn't cover the origin of the code. We face the dilemma of new code emerging in accordance with those impact events. If the code didn't evolve on Earth - and there is no previous expression of it in the fossil record - there is a very high probably for extraterrestrial origin, replacing or integrating into the indigenous environment.
"I always thought the most significant thing that we ever found on the Moon was that little bacteria who came back and lived and nobody ever said anything about it."
- Pete Conrad, Apollo 12 Commander
The Surveyor probes were the first U.S. spacecraft to land safely on the Moon.
On November 19, 1969, Apollo 12 astronauts Pete Conrad and Alan Bean made a precision landing on the lunar surface in the Ocean of Storms. Their touchdown point was a mere 163 meters (535 feet) from the Surveyor 3 lander - and an easy stroll to the hardware that had soft-landed on the lunar terrain years before, on April 20, 1967.
The Surveyor 3 spacecraft's camera was recovered back to Earth under sterile conditions by the Apollo 12 crew. When scientists analyzed the parts in a clean room, they found evidence of microorganisms inside the camera. In short, a small colony of common bacteria - Streptococcus Mitis - seem to have had stowed away on the device. The 50-100 organisms seem to have survived launch, space vacuum, 3 years of radiation exposure, deep-freeze at an average temperature of only 20 degrees above absolute zero without nutrient, water or energy source.
Planetary Protection Office still maintains contamination as the most likely explaination, despite biopan space exposure experiments on (notably not aboard) the ISS verified resilience of such stowaways to space. This certainly raises some very interesting questions.
In 1976 two viking landers touched down on Mars. The landers conducted biological experiments designed to detect life in the Martian soil. The Viking labeled release (LR) experiment was one of three biology experiments carried aboard each of the Viking landers.
The Viking lander projects of 1976 produced a positive outcome for the Labeled Gas Release experiment under the guidance of Principal Investigator Gil Levin. However, a negative result in a mass spectroscopy experiment to search for complex organics at the landing site confounded the issue, and the agreed position of NASA was that no life was detected. Gil Levin differed from this consensus, however, and continues to maintain that the 1976 experiments did in fact indicate the presence of microbial life. Most scientists became convinced that the positive results were likely caused by non-biological chemical reactions from highly oxidizing soil conditions.
A recent re-examination of the Viking results appears to further vindicate the position originally held by Levin. The implication is that microbial life does exist currently in viable form, and indeed the high levels of methane that have been detected in the Martian atmosphere further corroborate this conclusion.
The test results and their limitations are still under assessment to this day (36 years). Levin has performed subsequent testing over the years and conclude it impossible to recreate similar results in a lab with any combination of known oxidants.
ALH84001 is a meteorite that was found in Allan Hills, Antarctica on December 27, 1984. Its estimated to be a 4 billion years old originating from Mars, Eos Chasma, a branch of the Valles Marineris canyon system.
Sub-micron sized carbonate globules with surrounding layers of complex organic molecules (PAHs) of presumed biologic origin were discovered – similar to degraded biofilm. In addition, McKay et al found ovoid shaped nanometre sized particles in chains, including magnetite crystals of a type wich are laid down by some terrestrial iron-oxidising bacteria.
The thin atmosphere on Mars may be partly due to it is lacking a magnetosphere. Energy from the solar wind enables particles in the top atmospheric layer to reach escape velocity and leave Mars. However, it turns out Mars had a protective magnetosphere which protected the planet and its atmosphere from the sun's solar winds in ancient times. The presence of an ancient magnetosphere was confirmed in 1997, when the Mars Global Surveyor detected surface magnetic anomalies indicating renemants from a strong martian magnetic field.
An identification with nanobacteria was proposed that has been criticised on the grounds that such small micro-organisms cannot and do not exist in autonomous form because of minimal genome size. Interestingly tests results for terrestrial nanobacteria indicate the objects to be cultivatable (as in reproductive), but of mineral composition, starting a no less controversal debate on its own.
In November 2009, a team of scientists reasserted that there is "strong evidence that life may have existed on ancient Mars", after having reexamined the meteorite using more advanced analytical instruments now available, in light of the objections that had been made since the biogenic hypothesis for the biomorphs first had been put forward. Overall, the team concluded that none of the original features supporting the hypothesis for ALH84001 has either been discredited or has been positively ascribed to non-biologic explanations.
The debate relating to ALH84001 still continues without a satisfactory resolution in sight.
If the structures in ALH84001 are fossilized lifeforms, as proposed by the biogenic hypothesis of their formation, this would represent the oldest fossils ever found, far older than the fossil record of Earth, backing a non-terrestrial origin of life.
Evidence of bacterial microfossils “similar to cyanobacteria", a form of blue-green algae which sustains most of the Earth’s oxygen supply, have been reported by NASA astrobiologist Richard Hoover in 2011. The tiny fossils were discovered in fractured slices of three different CI1 meteorites (named Alais, Ivuna, and Orgueil) and are estimated to be up to 10 billion years old (note: Earth is estimated to be 4,5 Billion years old).
Using an imaging technology called Environmental (ESEM) and Field Emission Scanning Electron Microscopy (FESEM), Hoover investigated the internal surfaces of the CI1 Carbonaceous meteorites, and subsequently produced images of large complex filaments and filament mats wich are very difficult to explain by abiotic origin.
Hoover subjected the microfossils to an additional technique called Energy Dispersive X-ray Spectroscopy (EDS), which indicates that the meteorite filaments are typically carbon rich sheaths infilled with magnesium sulfate and other minerals characteristic of the CI1 carbonaceous meteorites — providing further evidence that the fossilized microbes are from the meteorites or their parent bodies and not the result of terrestrial contamination. The paper is subject of major controversity and NASA officially distanced itself from Hoover's claims.
Chandra Wickramasinghe performed in 2012 a similar research project on the Tissint meteorite, wich is also a Mars rock. He also found carbonate globules and concluded that the formation of nearly spherical C-O rich spheres within the mineral matrix is not easy to explain by any non-biological processes.
On April 10, 2005 air samples were collected from six places at different altitudes from the Earth ranging from 20 km to more than 40 km. Adequate precautions were taken to rule out any contamination from any microorganisms already present in the collection tubes. 12 bacterial and 6 fungal colonies were found in these samples. The fungal colonies were Penicillium decumbens, Cladosporium cladosporioides, Alternaria sp. and Tilletiopsis albescens. Out of the 12 bacterial samples, three were identified as new species and named Janibacter hoyeli.sp.nov (after Fred Hoyle), Bacillus isronensis.sp.nov (named after ISRO) and Bacillus aryabhati (named after the ancient Indian mathematician, Aryabhata). These three new species showed that they were more resistant to UV radiation than similar bacteria found on Earth. For any organism living so far up the Earth's atmosphere or having come from outside Earth, the UV radiation resistance would be extremely critical for survival.
6. galactic context
Its hard to explain the evolution of sufficient tolerance to hazards of space within the confines of Earth.
Bacteria and Archaea are present in environments ranging from deep subsurface to atmosphere, the survial during enhanced gravity has been tested and confirmed. Bacterial spores show reduced water contend, freeze-drying is commonly used to preserve viability during long term bacterial storage. Spores are resistant to DNA and protein damage, DNA repair is performed (notably Deinococcus), additional protection is aquired from adhesion to rock matrix or layering in biofilms. Extreme temperature resistance of thermophilic Bacteria and Archaea has been discovered, as well as heat and cold shock responses, starvation survival capability is given trough dormancy. Advanced hibernation capabilities have been demonstrated, experiments have shown bacteria encased in potassium crystals billions of years ago can and have been reanimated. Metabolic diversity and adaptation of bacteria to alternative nutrients has been confirmed, long therm nucleic acid survival is a given, even broken up DNA sequences can be incorperated into existing genomes, survival during space flight exposure experiments has been confirmed - surprisingly also for more complex organisms, such as water bears and lichen. Lichens were found to successfully survive Martian conditions in the Mars Simulation Laboratory maintained by the German Aerospace Center (DLR). Again the chance for such abilities to develope by coincidence is close to zero.
To use an analogy:
If we study palm trees on a beach and we find palm trees seed coconuts and we find coconuts can float in water, possibly to other beaches - are we going to assume that this beach is the only place where palm trees grow or the source of all palm trees or that this is the only island in existence?
Judging from the evidence uncovered so far, the probability is very high that the realm of DNA is by far greater than we ever expected.
This raises serious questions about life originating from Earth. In addition to that it should be noted that there is no evidence whatsoever in the fossil record that supports the idea of life originating from Earth. It might be missing in the fossil record of Earth because it never happened, as a direct result of colonization.
Earth is estimated to be 4,5 billion years old. The first signs of life appear in the fossil record practically as soon as the environment permits it, about 3,8 billion years ago in its (by no means simple) single cell architecture. There is no evidence in the fossil record of a large scale molecular replication process before that and the conditions on early Earth during the Hadean Eon were anything but favourable. ALH84001, on the other hand, is four billion years old and shows signs of life from ancient Mars. Evidence is mounting that conditions on Mars during the hadean period were far more favourable for life than on Earth.
It is suspicious that such a complex coding mechanism materializes misterously. Aside of the glaring absence of supposedly neccesary steps to establish such a mechanism, it seems unlikely that such a mechanism establishes so early during a planets lifetime (upper limit of planetary lifetime defined by lifetime of its parent star). One would expect it to happen rather later than earlier in the process due to its complexity. To find it emerging so soon is puzzling, to say at least.
Observations taken by the Infrared Space Observatory and the Spitzer Space Telescope of stardust formed in exploding stars called show that the astronomical spectra contain a mixture of aromatic (ring-like) and aliphatic (chain-like) components that cannot be explained by PAH molecules.
By the early 1980’s there was ample evidence for a wide range of complex organic molecular structures being present in the interstellar medium with a possible relevance to biology. Whilst small, low molecular weight organic molecules may have formed by well understood processes, the larger molecules pose a challenge to theorists.
For the last twenty years, this spectral signature has been commonly accepted as being PAHs – polycyclic aromatic hydrocarbon molecules. The Infrared Space Observatory and the Spitzer Space Telescope have shown there’s more there than just a PAHs, it’s a lot more complex: we find signatures resembling complex organics such as coal and pertoleum. Such chemical complexity is only known to arise from living organisms.
The astronomers found that the emissions began to appear in stars in the protoplanetary nebula stage and grew stronger as the stars matured into the planetary nebula phase. The appearance of the spectral features suggests that the organic compounds are made on time scales shorter than thousands of years. The researchers also studied emissions from exploding stars and found that these dynamic cosmic events produced dust even more rapidly. Their spectra changed from a pure gas spectrum to a dust spectrum on a matter of days or weeks.
Theoretically, it is very difficult to understand because of the very low density of the circumstellar environment but, observationally, there is no doubt as we see these spectral features appearing and changing on very short time scales. Coal and kerogen are products of life and it took a long time for them to form. Theoretically, this is impossible, but observationally we can see it happening.
One of the major discoveries from the analysis of comet samples was finding particles rich in organic matter. Comets are believed to have brought water and organic matter to the early Earth, and it is important to understand the nature of these materials because they are necessary ingredients for life. Analyses of the samples from the Stardust sample return mission showed abundant hydrocarbons in many of the collected Comet particles.
Subsequent analyses revealed that some of the organic matter formed in the cold cloud of dust and gas that was the precursor to the solar system. There is little doubt that these organics continuously rain down on Earth at an estimated rate of 30 tons per day.
Although some of the other organics captured by the Stardust spacecraft look somewhat similar to the fairly stable organics found in meteorites, Sandford noted that many of the organic compounds appear to be very volatile. One sample even showed an abundance of material containing alcohols.
A modest development in complexity from acetylene to triacetylene, for example can be explained by a decreasing photospheric temperature, but the transition to much larger aromatic-aliphatic complexes and biopolymers or pseudo-biopolymers cannot be easily explained.
Abiotic synthesis produces a mixture of L and D enantiomers. Each inhibits the polymerization of the other.
Living organisms, on the other hand, use one form exclusively and exhibit homochirality: all amino acids in living organisms are L form while all sugars in living organisms are D form. Biological processes depend on and maintain this asymmetry. The preference of the left-handed forms apparently persists throughout the cosmos, but both forms are found frozen into the meteorites before the right-handed forms could be eliminated. To what extent would all the molecules in the Galaxy be processed by the effect being described? Supernovae by themselves do not come close to being able to do so.
Francis Crick was co-discoverer of the double helical structure of the DNA molecule. Later he became concerned with the origins of the genetic code. Crick found it unlikely that the complexity of DNA could have evolved naturally on Earth so quickly. Crick speculated about the possibility that living systems may be spread on purpose by intelligent life forms using space travel technology, a process he named “Directed Panspermia”.
Micro-organisms organized in separate samples might be the best, most cost effective strategy for seeding life on a compatible planet. Directed panspermia from Earth to new solar systems has been proposed to expand life in the Universe. Fleets of microbial "seeds" can carry extremophiles for diverse environments and cyanobacteria to target destinations. Panspermia, natural or directed (needless to say, choosing targets purposeful with the help of astronomy improves the odds for success considerably), is a practicable mechanism for the spreading life through the cosmos.
The Sun was formed about 4.57 billion years ago from the collapse of part of a giant molecular cloud that consisted mostly of hydrogen and helium and which probably gave birth to many other stars.
As one fragment of the cloud collapsed it also began to rotate due to conservation of angular momentum and heat up with the increasing pressure. Much of the mass became concentrated in the center, while the rest flattened out into a disk which would become the planets and other solar system bodies. Gravity and pressure within the core of the cloud generated a lot of heat as it accreted more gas from the surrounding disk, eventually triggering nuclear fusion. Thus, our Sun was born.
The Sun is about halfway through its main-sequence stage, during which nuclear fusion reactions in its core fuse hydrogen into helium. Each second, more than four million tonnes of matter are converted into energy within the Sun's core, producing neutrinos and solar radiation. At this rate, the Sun has so far converted around 100 Earth-masses of matter into energy. The Sun will spend a total of approximately 10 billion years as a main-sequence star.
It does not have enough mass to explode as a supernova. Instead, in about 5 billion years, it will enter a red giant phase. Its outer layers will expand as the hydrogen fuel at the core is consumed and the core will contract and heat up. Hydrogen fusion will continue along a shell surrounding a helium core, which will steadily expand as more helium is produced. Once the core temperature reaches around 100 million kelvin, helium fusion at the core will begin producing carbon, and the Sun will enter the asymptotic giant branch phase. Following the red giant phase, intense thermal pulsations will cause the Sun to throw off its outer layers, forming a planetary nebula. The only object that will remain after the outer layers are ejected is the extremely hot stellar core, which will slowly cool and fade as a white dwarf over many billions of years. This stellar evolution scenario is typical of low- to medium-mass stars.
As a red giant, the Sun will have a maximum radius beyond the Earth's current orbit, 1 AU, 250 times the present radius of the Sun. However, by the time it is an asymptotic giant branch star, the Sun will have lost roughly 30% of its present mass due to a stellar wind, so the orbits of the planets will move outward. Even if Earth should escape incineration in the Sun, still all its water will be boiled away and most of its atmosphere will escape into space. Even during its current life in the main sequence, the Sun is gradually becoming more luminous (about 10% every 1 billion years), and its surface temperature is slowly rising. The Sun used to be fainter in the past, which is possibly the reason life on Earth has only existed for about 1 billion years on land. The increase in solar temperatures is such that in about another billion years the surface of the Earth will likely become too hot for liquid water to exist, ending all terrestrial life. We are in the last fifth of the period in which life is possible on this planet.
A dying homeworld is a strong motivator for space colonization. We all have to at some point, or die trying. The probability that this is a repeditive pattern is very high.
8. Von Neumann Machines
It has been theorized that a self-replicating starship utilizing relatively conventional theoretical methods of interstellar travel (i.e., no exotic faster-than-light propulsion such as "warp drive", and speeds limited to an "average cruising speed" of 0.1c) could spread throughout a galaxy the size of the Milky Way in as little as half a million years.
This concept is universally known as von Neumann Probe.
In theory, a self-replicating spacecraft could be sent to a neighbouring star-system, where it would seek out raw materials to create replicas of itself. These replicas would then be sent out to other star systems. The original "parent probe" could then pursue its primary purpose within the star system.
There is some confusion within the mission variety depending on the variant of self-replicating starship proposed.
The idea of self-replicating spacecraft has been applied — in theory — to several distinct "tasks". The particular variant of this idea applied to the idea of space exploration is known as a Von Neumann probe. Other variants include the Berserker and an automated seeder ship. The details of the mission of self-replicating starships can vary widely from proposal to proposal, and the only common trait is the self-replicating nature.
A von Neumann probe (first proposal of the concept, hence the general reference) is a self-replicating spacecraft designed to investigate its target system and transmit information about it back to its system of origin. The concept is named after Hungarian American mathematician and physicist John von Neumann, who rigorously studied the concept of self-replicating machines that he called "Universal Assemblers" (a much more fitting description than "probe") which are often referred to as "Von Neumann machines". While Von Neumann never applied his work to the idea of spacecraft, theoreticians since then have done so. The general idea was "simply" a self replicating machine and the mathematical theory behind it.
If a self-replicating probe finds evidence of primitive life (or a primitive, low level culture) it might be programmed to lie dormant, silently observe, attempt to make contact (this variant is known as a Bracewell probe), or even interfere with or guide the evolution of life in some way. Paul Davies theorized the Moon to be an ideal location for such a probe to monitor Earth.
The problem with this concept is its mission design. To think such a powerful tool would be employed to simply collect data and even return to its point of origin, a by no means neglectable efford and also dangerous when considering involved timescales and an exponential growth rate seems unwieldy for its operational mechanics. Even if it makes the return trip, its not even assured somebody might be there to recive the data. Also the probe would almost certainly outlast its creators, defeating its purpose.
It is however ideally suited for mission profiles excluding a return trip. Its simply not suited for being a merely passive data collector. Its a tool wich allows actions on cosmic scales. Thats its true strenght.
Another variant of the idea of the self-replicating starship is that of the "seeder" ship. Such starships might store the genetic patterns of lifeforms from their home world, perhaps even of the species which created it. Upon finding a habitable exoplanet, or even one that might be terraformed, it would try to replicate and adapt lifeforms from stored information using molecular nanotechnology. Such ships might be terraforming vessels, self-replicating colonizers themselves. This would be a very good way for a species to spread throughout the galaxy, maybe even beyond that and reassuring survival for a very long time.
Another variant of the self-replicating starship is the Berserker. Unlike the benign probe concept, Berserkers are programmed to seek out and exterminate lifeforms and life-bearing exoplanets whenever they are encountered.
Berserkers could be created and launched by a xenophobic civilization or could theoretically "mutate" from a more benign probe. For instance, a Von Neumann ship designed for terraforming processes might malfunction and attack inhabited planets, killing their inhabitants in the process of changing the planetary environment, and then self-replicate and dispatch more ships to attack other planets.
Failsafe mechanisms don't tend to do well in Von Neumann concepts because a single probe with a faulty failsafe mechanism could begin unrestricted reproduction. This is practically bound to happen because identical copies are not maintainable. A perfect error correction to assure perfect copies is more complex than the "blueprint" of the probe itself, but still has to be part of the probe, thus elevating complexity ad infinitum. Therefore math doesn't allow perfect error correction in self replicating systems, period.
A safeguard mechanism is not a neccesarity for replication, the only relevant selection mechanism, to produce a probe capable of replication that is, totally neglects to keep any failsafe mechanism in working condition. Quite on the contrary. This can't be altered because this is external error correction, governed by the rules of survival. This means there can be no practicable way to ensure the failsafe mechanism's operation. Its bound to fade away from the "blueprint" over the course of generations, because it is not relevant for replication. Error correction for Von Neumann Machines is the distinction between a reproducing version wich reproduces and a faulty one wich is not reproducing, bound for complete system faliure at some point. Evolution. Self replicating systems are bound to evolve because the only way to get the system to work is by external selective pressure.
Self-replicating machines launched by different species might actually compete with one another (in a Darwinistic fashion) for raw material. Given enough variety of "species" they might even form a type of ecology, or — should they also have a form of artificial or evolved intelligence — a society.
Whilst it is true that this technology is very dangerous, its very likely to be employed by any advanced civilization facing catastrophic annihilation as a last ditch efford of survival. And sooner or later that will happen to every civilization in residing within the terminal vicinity of a star as it ends its life. There are many stars.
In 1981, Frank Tipler put forth an argument that extraterrestrial intelligences do not exist, based on the absence of Von Neumann probes. Given even a moderate rate of replication and the history of the galaxy, such probes should already be common throughout space and thus, we should have already encountered them. Because we have not, he concluded that extraterrestrial intelligences do not exist.
9. molecular assemblers
A molecular assembler, is a "proposed device able to guide chemical reactions by positioning reactive molecules with atomic precision".
To produce a practical quantity of a desired product, the nanoscale size of a typical universal molecular assembler requires an extremely large number of such devices. However, a single molecular assembler might be programmed to self-replicate, constructing many copies of itself. This would allow an exponential rate of production. Then, after sufficient quantities of the molecular assemblers were available, being re-programmed for production of the desired product.
One method to building molecular assemblers is to mimic evolutionary processes employed by biological systems. Biological evolution proceeds by random variation combined with culling of the less-successful variants and reproduction of the more successful variants. Production of complex molecular assemblers might be evolved from simpler systems since a complex system that works is invariably found to have evolved from a simple system that worked. A complex system designed from scratch never works and can not be patched up to make it work. However, most published safety guidelines include recommendations against developing "replicator designs which permit surviving mutation or undergoing evolution". As pointed out ANY self replication design is bound for mutation/evolution, its an integral part of the inner mechanisms wich make the system work. If self-replication of molecular assemblers were not restrained then it might lead to competition with naturally occurring organisms.
One potential scenario that has been envisioned is out-of-control self-replicating molecular assemblers in the form of grey goo which consumes carbon to continue its replication. If unchecked such replication could potentially consume whole ecoregions or the whole Earth (ecophagy), or it could simply outcompete natural lifeforms for necessary resources such as carbon, ATP, or UV light (which some nanomotor examples run on).
Most assembler designs keep the "source code" external to the physical assembler. At each step of a manufacturing process, that step is read from an ordinary computer file and "broadcast" to all the assemblers. If any assembler gets out of range of that computer or when the link between that computer and the assemblers is broken or when that computer is unplugged the assemblers should stop replicating. Such a "broadcast architecture" is one of the safety features recommended by the "Foresight Guidelines on Molecular Nanotechnology".
The fatal flaw in this recomendation, as with the previously discussed Von Neumann berserkers, is that the assembler wich reads the source code is subject to evolutionary selection and might refine the instructions internally enough to break free at one point by evolving its own instruction code on the basis of the input. Safety mechanisms DO NOT WORK in the context of evolution.
10. biology or evolved nanotechnology?
Typically the term "molecular assembler" refers to theoretical human made devices, however some biological molecules such as ribosomes fit this definition. The similarity to the reproduction patterns of bacteria is striking.
Can we really distinguish between an artificial device and an organism on a molecular level? Especially an ancient, self-replicating molecular assembler wich constantly mutates its blueprint?
This in itself is a possible solution for the Fermi-Paradox and Tipler's argument. We simply may have overlooked the "Von Neumann machine", never even recognizing it as such. The solution may reside more within the constrains of our perception and distinction between biology and technology and the concepts of natural and artificial structures than anywhere else. What is natural? Are ants constructing artificial structures? Or is "natural" simply a label we apply to everything of non-human origin?
Its highly probable this strategy of survival has already been pursued by an advanced civilization facing catastrophic annihilation or simply for the purpose of colonization and it probably will and it was employed on a regular basis because of the lack of obvious alternatives. Its a simple matter of suvival and logical action as the normal course of events unfolds.
That being said, life has to be able to emerge on its own in the first place, it has to start. It can't be all artificial, for that requires engineers and engineers have to emerge, too. But that was most likely a very long time ago. It is very likely that the current DNA information present on Earth ran through the process of artificial engineering many times before, as the cycle repeated over and over again. This would easily explain its sophisticated behaviour when it comes to adaptivity and survival. Its not likely to have emerged recently on this world. Chances are its very, very old indeed. Considering the problems of Dark Energy and Dark Matter it might even precede our current model.
Sascha Wageringel firstname.lastname@example.org