Darkness you mean?
that's the only chain of events that could of
occurred. Darkness in the heart was what
Ansem was researching, but that darkness
became flesh when Xehanort concentrated
darkness within a pure heart, hence the pureblood,
and then the purebloods were replicated through
a machine in which he bore the insignias on.
It is the creation that may hold some resemblance
to what may have brought the unbirths into
existence, but of course their is no evidence
until the game and info itself is released. As far as
i've mentioned before (which was brutally butchered
by nonsense), The basic unbirth does not bore an
insignia, but the the actual symbol that the other
forms of unbirth have implemented on them can
actually be formed with the tentacles of the basic
unbirth. With this being said it gives was to believe
that either MX truly made these creatures, or that in
fact, he merely replicated them, by identifying the
unusual pattern the tentacles made crossed together
and creating an insignia through it.