Okay, I'd like to start by offering my apologies in advance if anything if this nature has been discussed previously. I'm new here (Nu..heh heh) and so far I haven't found the answers to the questions I have in any of the threads regarding Nu, nor in the encyclopedia section, so I thought I would strike up a topic and hopefully generate some analysis.
Since having first played the game, I've been fascinated with the Nu. They stand apart from other creatures that the party encounters as they will more frequently engage in dialogue and are usually encountered in places of importance to the party, rather than the more mundane battles in which Chrono et al face off with less awe-inspiring foes. Not to mention that since in his most potent from Spekkio appears as a Nu, they are clearly creatures of some importance and power.
The matter that I'm curious about is really the simple nature of the Nu. The encyclopedia offers two possible explanations of their origin, but neither seems to satisfy. On the one hand, the Zeal Creation theory posited by ZeaLitY, doesn't seem to account for the existence of Nu in the Hunting Grounds of 65,000,000 B.C. On the other hand, the Quiet Species theory doesn't fully explain the complete nature of Belthasar's Nu in 2300 A.D. While it does suggest that Nu can rather strangely be programmed as one might program a machine, Belthasar's Nu also has a switch to turn the creature off, which would suggest that Nu (or at least Belthasar's Nu) are not organic creatures at all. Nor does it have any explanation for why the Silver Rock Nu is more eloquent that those found in the Hunting Grounds.
Personally I believe that while neither theory goes far enough in explaining the nature and origins of the Nu, a middle ground between the two may shed more light on the subject. Notice that the Nu in the Hunting Grounds of 65,000,000 B.C. speak in a primitive fashion, much like their contemporary human counterparts. This would seem to suggest that they are in an evolutionary stage similar to the humans, and are therefore an organic creature. The exception in this time period being, of course, the Nu who provides the party with the Silver Rock. As for Belthasar's Nu, I would suggest that it is an automaton, created by Belthasar in the image of a Nu, for whatever reason. He seems to have an affinity for the creatures, as his secret room in Enhasa has six of them inside it. Based on his abilities to construct such wonders as the Blackbird and the Epoch, a robotic Nu would not tax his abilities.
Therefore I would state that while the Nu are in fact a quiet species, there are examples of Nu from the Kingdom of Zeal having been gated to other points in time. As for the nature of the Silver Rock-bearing Nu in 65,000,000 B.C., it is unclear it he is a construct of Belthasar as well, but as its contact with the party is limited, the matter is of little consequence. All that one can surmise is that that particular Nu is different from its counterparts in the Hunting Grounds. As for Belthasar's assitant Nu in 2300 A.D., it probably wasn't gated into that era, but at least the man with the knowledge to construct it was.
So there it is. That's my theory on the nature of Nu. Again, I apologize if anyone has already pursued this thread in the past, but I couldn't find anything like it.
Questions? Comments? Concerns? Criticisms?