Xenogenesis

Xenogenesis is the now-commonly-accepted theory that Human-type life (known to biology as neobiota) did not originate on Galhaf, but on some other planet.

History

It had long been recognized that humans and a few other animals had a distinctive bodyplan that was not shared with other, more diverse, groups, and likewise that some important plants were also rather distinctive from other groups. Various explanations existed for this observation through the history of science. As paleontology gradually developed, a further mystery was revealed in that the human-type organisms appeared to have been a very recent development, while all other groups had ancient roots (which lead to their being named paleobiota). But, in general, it was not seen as a major problem until the development of the theory of evolution when the seemingly-sudden appearance of Human-style life was taken as a major problem with the theory.

It was recognized that plants and animals from different parts of the world had different characteristic traits, and so an obvious explanation was that human-style life was native to some other place. As plate tectonics had not yet been developed, one early theory was that there had once been another continent, one well-isolated from the others, on which humans and related organisms evolved. According to this early version of xenogenesis, this continent subsequently sank and a few refugees fled to other continents, bringing with them some plants and animals. This theory became increasingly tenuous as the magnitude of the differences between the different groups of organisms became more apparent, and as the development of plate tectonics discredited the idea of a sunken continent.

Subsequently, a controversial assertion was made that the human-style life had evolved on a different planet. The most obvious choice was Ufsandakh, known even then to have liquid water on its surface, though very little land. It was though that some disaster had forced humanity to flee that planet, but the sparseness of dry land and the fact that Ufsandakh is tidelocked to Chihazh called that idea into question. It was finally accepted that humanity's origin was extra-Chihazhan.

Biochemistry Question

A major riddle exists in the fact that both neobiota and paleobiota use fundamentally similar biochemistry, including the use of the same set of amino acids. The mystery was reinforced when samples of Ufsandakhan life were obtained, revealing a different biochemistry, and thus discrediting the notion that perhaps only one biochemistry was possible. One possibility is that there are only a relatively small number of possible biochemistries, and that the human settlers had explored multiple possible worlds for colonization before they found one that shared their biochemistry