The (usually infertile) off-spring that results from the mating of two distinct species.

Interbreeding between two distinct species or clades may result in a hybrid, which may or may not be fertile. Even non-fertile hybrids can be very vigorous, like mules.

Some clades won't mate because of culture but would be viable if they tried it (like certain duck species, or several exclusive Genen clades, known as Families).

Some clades are unable to mate because of physical limitations (Goliaths and Clade Secha , big and little, for instance) but are fertile in vitro.

But it is genetic difficulties that are the most interesting. How the genetic engineers of various cultures achieve their results affects the viability of crossbreeding. If it affects the number or structure of the chromosomes it could cause postzygotic mortality, where the process of mitosis (chromosome pairing in cell division) is made impossible in a hybrid.

If it achieves adulthood, the hybrid could be weak, or ill adapted to any conceivable habitat, or be infertile, or infertile in the F1 or F2 generation.

This would definitely be speciation under natural conditions, but any of these incompatibilities could perhaps be part of the design, or conversely two widely different clades could be designed to easily interbreed to produce useful characteristics, like the infertile hummingbird/tortoise splice hybrids that are sometimes used for pilots of relativist Biopolity ships. Long periods of inactivity coupled with speed and agility on demand makes them valuable, as does their rarity.

Generally, provolves are not able to breed with human baselines, although they might be able to breed with baselines of their original stock (i.e. bonobos or African greys). The typical provolve genome might not have much Human in it at all, but instead have direct neogene improvements to make the creatures more intelligent in their own way...

Most provolves have at least a few human genes, but generally the gene complexes will be the same in many terragen creatures, so it is difficult to say where they came from.

Hu-dog splices for example, where viable sometimes also interbreed with humans and or dogs, with the cross species traits becoming diluted or perhaps dominant/recessive...

On the whole geneticists have all or nearly all the consequences of well known terragen species mapped out including hybrid viability. However there are always new species being discovered, both xenobionts and naturally evolved terragen species on isolated habitats, to say nothing of the huge number of neogens and xenosplices that flood the market .
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Development Notes
Text by Steve Bowers
Initially published on 02 September 2002.