The Gshru seafaring civilisation is an example of a transapient culture which has chosen to move down the toposophic ladder
Although it is very rare, it does occur that trans-singularity entities choose to descend to a lower singularity level for some reason. Such abdicators often stimulate humanist claims that there is something inherently superior or desirable in the subsingularity state, despite the overwhelming tendency for subsingularity entities to move upwards instead.
While it is sometimes a single entity, on several occasions large groups of entities have descended to modosophont level. The most famous incident was the Gshru Colonisation in 5840 (NoCoZo), when aspects of the sentient core markets of Vast Endeavour bought the planet Gshru, created humanoid bodies and downloaded themselves into them in order to create a fairly standard human baseline society. Their stated goal was spiritual, although it might have been aesthetic.
The Gshru civilisation, a mostly seafaring civilisation of hermaphrodites, is apparently slowly developing on its own inside the restriction swarms surrounding the system.
Even more rare are the subsingularity abdicators who descend to toposophic levels lower than modosophont. Most are individuals who for various reasons - ennui, spiritual beliefs, depression or extreme experience hunger - modify their minds and bodies to survive as subhuman intelligences and not just go for rianthhood.
The earliest case of collective subsingularity abdication was the Epimethian movement in the 370's, who voluntarily removed their higher level cognition in order to revert back to average primate intelligence. They became a new species of hominoid ape, known as Homo Epimetheus. The Epimethians believed that this language-less, literal existence would give them back the true "reality as it is" experience mankind lost millions of years ago. The Epimethians were largely dependent on Epimetheus Foundation, an foundation keeping the transformed members in a park in Olemya city. It appears that the foundation and much of the Epimethean philosophy was devised by a group of AIs and humans as a way of making money - the foundation managed the wealth and possessions of the Epimethians, investing just a minimal amount in the park.
Despite public criticism the foundation continued its practices, eventually relocating the Epimethean apes to the automated Locastra Habitats in the asteroid belt in 405. While the foundation vanished in the financial crisis 420, the Epimetheans survived not only that but also the Nanodisaster, protected by the efficient Locastra AI. When the AI joined the Utopia Sphere, the habitats were moved into orbit around New Montana where Homo epimethius continues to thrive to this day.
Another species which has undergone subsingularity abdication is the Snark, a non-humanoid (but largely human-derived) species originating on Bullseye.