The battle of the white bull and the dun bull which forms the basis of The Táin is pivotal in Irish myth and many have noted that it seems to reflect a creation myth, with the white bull torn to pieces and scattered over the land. Bit it fits into the mold of a creation myth also because the two bulls are in fact two brothers, transformed into bulls after going through a variety of other forms. In indo-european myth, creation seems to center around a battle of two brothers, with one being killed.
The Rennes Dindsenchas identifies the brothers as Cu and Cethen, the two brothers of Cian, father of Lug. It also identifies Cu and Cethen as wolves, and thus we should think no different of Cian, thus making Lug a son of a wolf. It also identifies them as sons of Cronn, presumably the Cronn river which plays a pivotal romm in the story and which comes to the aid of Cuchulain.
"the story of the two swineherds, who were (incarnate) in seven shapes, a full year in each of them. And those were Cronn son of Agnoman’s two sons, named Rucht and Rucne (when they were swineherds), Ette & Engan (“Wing and Talon”) were their two names when birds. Cú and Cethen were they when wolves. Bled and Blodwere they when trout of the Boyne. Crunniuc and Dubmuc (leg. Duinniuc, Tuinniuc?) when they were worms."
A counterpoint could be made that this is a later idea and the bard is just searching for names to call them in different forms. Even if this were the case it must have been that the idea existed that Cu and Cethen were wolves. But the significance of this also ties in Lug to the creation of the cosmos and it is likely that The Tain and Cuchulain's role there is in some way a heroic reflection of the roll Lug played. The white bull represents underworld forces of death, the dun bull the forces of worldly life and fertility.