We have little enough evidence about the pre-socratics, and if there were precursors, nothing of their writings exists. Thales (c. 585 B.C.) is roughly contemporary with the collation of the Torah from older sources, and the various recensions of the Book of the Dead seems to be based on writings in the beginning of the Old Kingdom.
It is, moreover, difficult to say with any accuracy how strong the alliance between various religions and what we call philosophy was before the time of Thales and the other Ionian writers.
It is enough to say that during the period of intense activity (600 to 300 B.C.), that is from Thales to Aristotle, Western philosophy took its decisive form. These dates would, obviously, eliminate Christianity as a source of influence, and would suggest that (despite the commerce and travel along the Levantine shores), the monotheism of the Jews would have but second-hand influence compared to, for example, the more direct influence of local or Persian religion.
We may be able to say that the three hundred years saw a succession of writers who contributed to the separation of religious thinking by creating a tradition of rational, speculative thought about the world and the place of humans in it that generally remained operative up to the present.
While diverse in the answers the presokratics provided, they seem to share a common set---or perhaps family resemblance---of characteristics that set them apart from religious speculation:
1. A commitment to argument and dialogue as a means of inquiry instead of uncritical belief and dogma.
2. A view that reason, common to all men, was the appropriate justification for an explanation
3. A belief that the natural world could only be explained in terms that do not refer to sources outside of nature. Given the crudity of explanations, it is still worthy of notice that the fundamental reality of the world was an element or strife or the collision of atoms, and not the divine intervention of the godhead and its miracles.
So much was the general opinion of Frankfort (1946) and of Kirk and Raven (1964). It is certainly instructive, moreover, to consult Aristotle (Metaphysics, Book I) and to consider his views of his precessors---even more importantly, the kinds of criticisms he levels at each of them; his arguments are far from disputations on religious grounds, but are presented from the position of one philosopher (as we know it) criticising the theories of others.
Now it may be argued against this view of philosophical history, that nevertheless many of these same Greeks wrote about God. But if one attends to what they say, or how Plato and Aristotle concieve of the godhead, it becomes I think very clear that their conception is far from the traditional religious one: not Yahwah sending plagues and floods, but the unmoved mover.