Assumptions about the origin of tardigrade
The extraordinary features of the tardigrade resistance could allow it to withstand space travel via a meteorite.
Overadapted to withstand all conditions, the tardigrade has all the characteristics to survive space travel even very long, through a meteorite for example.
It also has features that permettraientt him to resist the bit tricky landing of the meteorite on the earth's crust. Suppose the surface of a planet to be hit by an asteroid, which by the shock inherent in contact, breaks the surface into small pieces, some of which sent in the cosmos become in turn meteorite, or through any another process that would become part of the crust of this planet, a meteorite.
Suppose also that this part of the superficial layer which has become a meteorite, also contains tardigrade in cryptobiosis. If they withstand the mechanical, physical and thermal stresses of the shock, they could "easily" withstand the lack of oxygen, absolute vacuum and cold space for a long time.
If these tardigrades are present in a layer that is not entirely superficial, but a little more in depth meteorite, they might well withstand the intense heat, and the alteration of the surface layer of meteorite that flow from its high-speed passage through the Earth's atmosphere and friction and air friction against the meteorite. Then just as the meteor falls in a region favorable to his reminiscence, or erosion and other phenomena can alter the surface of the meteorite to reach the place are, freeing them of their mineral prison. If conditions are sufficiently lenient the tardigrade may arise from its long lethargy and miraculously come back to life.
This theory is quite plausible and nothing fantastic or supernatural. She joined that of nanobacteria in particular which could also have an extraterrestrial origin and whose structural feature are also amazing. It also joins the hypothesis that raw organic materials appeared on earth are from space, knowing that at present it was not clearly demonstrated, and far from it, the way they were originally developed and how they have been despite the very interesting work of scientists who have studied the issue as Stanley Miller and Sydney Fox, for example.
Anyway, the tardigrade like any living being needs water to live or at least out of his cryptobiotic state, so it is anyway a place where gold transparent biology is present or was present. The tardigrade it be the common ancestor of all living species?
It would be almost "accommodating" that this is the case, because that would allow us to explain in part one of the greatest questions of humanity: How did the first living cells appear on Earth? The tardigrade being a eukaryotic organism, the biodiversity that would result from its evolution could be all the more important. It is also possible that the protists all stem from the arrival of bacteria, nanobacteria, or prokaryotic cells from space and that eukaryotes arise from the arrival on earth of an animal such as tardigrade.
Taking this hypothesis to the extreme, one could imagine that they would have made the trip together and their respective developments are due to a symbiosis for example. To verify or refute this hypothesis, we must know or estimate the time of occurrence of the tardigrade on earth, and about this missing data. It should also study the karyotype and genotype tardigrade to evaluate their relationship and similarities with other species. However, it seems that its taxonomy already poses serious problems for biologists are not sure how the associated branch, which could confirm the mysterious side of its origin. All data that would allow us to push this hypothesis further we are sadly lacking. Cryptobiotic the specificity of tardigrade, by cons, could help explain easily why some tardigrades has little or no advanced.
Indeed, the fact that some people can survive for long periods with very low metabolic rate, does not play in the favor of their evolution and their possible mutations. Its habitat is so ubiquitous that it is possible that some environments promote its evolution while others can, however, suspend it by bringing into cryptobiosis.
We do not know yet at present it is the true source of tardigrade, someday surely, technical and intellectual resources will allow us to solve this mystery, in the meantime, we can only speculate and think about what that mystery nature has a secret, and all theories must be heard and respected until we get some convictions by the weakness of some and the plausibility others.