Most of the scholarship that I've read on the development of Buddhism agrees that Mahayana sutras were relatively late developments (probably around the 1st century AD, with the Hellenistic world and Central Asia trade routes seen as key vectors for its diffusion). I'm curious to know, however, if there are any academic scholars who argue that some or all of the Mahayana sutras actually date from the time of the historical Buddha, and if so, what is the basis for their argument?
Beyond that, I would like to know more about the current scholarly views on the provenance of the Mahayana sutras. I'm familiar with a couple of theories that have been presented:
1. Paul Williams suggests that Mahayana developed out of a forest hermit tradition in which great emphasis was placed on deep samadhi states, during which the practitioner could encounter a Buddha, ask questions or receive teachings. (See here, pages 40-41)
2. Paul Harrison, along similar lines, suggests “a convergence of meditation and textual transmission in the forest environment, stimulated into a new burst of creativity as a result of a technological development, the advent of writing."
Here the specific circumstances of the real world combine with visions in deep states of meditation or dream to transform received oral tradition into a new kind of Buddhism. The resulting revelations are not completely novel, but deeply conditioned by context and by tradition. Although dismissed as poetic fabrications...or even demonically inspired nonsense by their opponents...
they are in fact creative recasting of material already accepted as authentic buddhavacana [‘words of the Buddha’] by the wider community.
(This is cited in Williams's book; see link above.)
3. Guang Xing argues that Mahayana doctrines developed out of the transcendental Buddha concept of the Mahāsāṃghika, which provided the doctrinal basis for dharmakāya, saṃbhogakāya, and nirmāṇakāya as understood in Mahayana. See here. Guang Xing's thesis also ties in with the views of Williams and Harrison, as Mahāsāṃghika devotionalism/transcendentalism would also provide a context for the samadhi states referenced above.
All three of these scholars are able to suggest ways in which Mahayana may have developed within a framework that allowed for doctrinal innovation while simultaneously legitimizing these innovations with reference to the Buddha -- none, however, go so far as to suggest that they weren't actually innovations at all but actually date from the historical Buddha's time.
I'd be interested to know what other scholarship is out there on the topic. My overall impression -- which could be quite wrong -- is that a great deal of attention has been paid to identifying the contents of Early Buddhism, but relatively little academic attention has been focused on where the Mahayana sutras came from and how.
P.S. Since this is the Academic Discussion forum, I'd like to request that we steer clear of wholesale dismissals of academic scholarship, or rejections of textual-historical methods as a priori irrelevant; I'm specifically interested in academic perspectives on these questions and this seems to the correct subforum for this.