Ask Mr. Smarty Plants

Apparently so, because from this article, The Pecan Tree, by P. C. Andersen and T. E. Crocker, from University of Florida IFAS Extension we learned that they were harvested and eaten by Native Americans for many years before Europeans came to North America. However, you would have to be very patient, as Carya illinoinensis (pecan) rarely fruits before it is 20 or so years old, and much older trees are the best producers. And then, of course, you'd have young trees beneath the parent tree competing for space and nutrition. And since members of the Hickory family are capable of producing allelopathic substances and discourage competition beneath them, the parent tree might very well be committing nuticide on the babies below. 

If you were thinking of doing this in your own garden, you need to be aware that pecan tree propagation now is almost exclusively done through grafting procedures. Plants that have been grafted will not breed true through the seeds they produce. In our experience, squirrels would get pecans from pecan trees down the street, industriously hide them in our flower garden, and promptly forget where they put them. We just yanked them out when they appeared because we knew they would not be the same kind of pecan that was growing elsewhere. Our property, at that time, was on what had once been a pecan tree nursery, and the trees lining the street were all the products of grafting. 

Carya illinoinensis

Carya illinoinensis

Carya illinoinensis

Carya illinoinensis