As a result of studies of To'u'lese biochemistry and cytology, a number of xenologists, beginning with the influential school of Seniis-2.
Seniis-2, a human from the Eden Institute argued that the To'u'ls are not even be natural organisms, but rather the result of biogenetic engineered life-forms from a lost race (the "To'u'logenitors") that decided to seed a number of To'ul'hian-type planets.
Critics point out that no other To'ul'hian worlds with to'ul'h-like intelligent races have ever been found, nor does To'u'lese culture and folklore does not make reference to any founders, progenitors, first ones, etc. Seniis-2's ideas were quite influential during the late Empires period, but as time went on and no further To'u'lese lifeforms were discovered he began to fall from favour among the academia, although some of interactives remained strong among the less educated, where they were combined with more and more disinformation.
An ironic result of this is that the Seniis-3 clones spent some futile decades trying to combat this distortion of his clonefather's theory, before giving up and going into lucrative business as a Biotech consultant with Cyrus Ecohabitats.
The To'u'l still refer to Seniis-2 as "Our Terragen Friend", and seem bemused by what all the fuss is about
Today To'ul'ese biology is regarded as having evolved naturally, especially since several alternative Cytherean ecologies have been discovered.