Saraswati has been worshipped continuously for about 3 millennia or so. Unlike the Theoi, the Vanir and Aesir, or the gods of the many Celtic lands, she has never been without devotees.
This doesn’t mean that Saraswati’s worship is static and unchanging. Indeed, this is most certainly not the case, as in the Vedic period she was the goddess of a river that is now gone.
The most important change in My Lady’s worship however, was her syncretization with the goddess of speech Vac, which occurred during the Vedic period (ca.1750 BCE – 800 BCE). Today, Vac is mostly forgotten as Saraswati has totally assumed her function.
Vac (whose name literally means speech) was and is still a mysterious and alluring goddess. Her hymn in the Rig Veda(1) sends chills down the spine, as She speaks of her own might, declaring:
I breathe a strong breath like the wind and tempest, the while I hold together all existence.
Beyond this wide earth and beyond the heavens, I have become so mighty in my grandeur!
Rig Veda Book X, Hymn 125, translated by Ralph T.H Griffith(2)
Catherine Ludvik writes extensively regarding the process of Saraswati’s syncretization and ultimately, her total identification with Vac in Sarasvatī, Riverine Goddess of Knowledge: From the Manuscript Carrying Vīnā Player to the Weapon Wielding Defender of the Dharma.(3) She notes that quite early on, Saraswati was identified with the principle of dhi, or inspired thought. (Ludvik pp.32-34) This is evidenced in hymn 3 of the Rig Veda, where She is called upon to bring success to a rite, as the “inspirer of all gracious thought.” (Rig Veda, Book I hymn 3 translated by Ralph T.H. Griffith)
By the time of the slightly later Atharva Veda(4) Saraswati was connected more firmly with speech itself, thus edging into Vac’s domain. (Ludvik p.42.) That identification came in the last of the Vedas, the Yajur Veda(5), where Saraswati began to be truly syncretized with the goddess Vac.(Ludvik pp.52-53)
Just how thoroughly has Saraswati subsumed Vac’s role? The successors to the Vedas, the Brahmanas, contain a number of famous myths starring Vac, including a creation myth involving Her and her father Prajapati, as well as a story called The Barter for Soma. Both these stories survive to this day, with one important change – Vac is no longer in them. Saraswati is, instead.