Your insinuations that the origin of the christian scriptures is involved in fable and mystery, should have been accompanied with a clear refutation of the arguments used by Lardner, Paley, and others, who have with much learning and labour traced the stream to its fountain.
I must say something on the subject which you introduce concerning man, as a species of being, or you may think me inexcusable for the neglect. There seem to be two main questions suggested on this subject; the first inquires what man was farther back than history reaches; and the other directs the mind to a "line of demarcation" between the human and the brute.
We have no account that I know of when the use of fire was not known. We read Gen. iv. 22, that Tubal-cain was an instructor of every artificer in brass and iron, and if reason has any thing to do in this case, we may suppose that the use of fire was known to these mechanics. The date to which this reading belongs, is 3875 years before Christ; but there can be no reasonable doubt but that the use of fire was known long before, and that it was used in the offerings which were made by Cain and Abel.
That the discovery of arts and the progress of science have changed man from what he originally was, is no more reasonable, than to suppose that the education which a child acquires by degrees, by the same degrees changes him in respect to his nature. That the arts and sciences serve to improve and extend the human intellects is reasonable enough, but that they add any thing to the natural principles or faculties of man is not conceivable.
In fixing the "line of demarcation" between the human nature and the brutal, I will suggest two characteristics which you have noticed by which the distinction may be ascertained.
The first is the power or faculty of improving from generation to generation his condition by means of art, and knowing how to advance from one degree of science to another. This I will suppose belongs to man and is peculiar to our race of being. We know of no other animal on earth that has ever improved his condition by the discovery of the arts or an increase of science.
The other characteristic is one of your propositions, on which you build your system of doubting, viz. _Superstition_. This is found in no creature but such as is susceptible of religion. Man is the only religious animal, if I may be allowed this form of expression, found on the earth.