To the question of Wesley1982:
We have a split between the Sthaviravādins and the Mahāsāṃghikas not long after the Buddha died, and as the legend goes the Mahāsāṃghikas, who went to the east, we more inclined to magic and worship than the Sthaviravādins, who went to the west and focussed more on meditation.
If you read what the japanese scholars usually write you get the impression that Mahāyāna must have started with the earliest days of the Mahāsāṃghikas. This is not entirely impossible, I personally believe that many of the elements that later developed into Mahāyāna are there in the Mahāsāmghika-sources. Especially if one reads the Mahāvastu, the focus of magic, supernatural powers, worship of the Buddha as a deity etc. seems to have it's echo there.
However what we today call Mahāyāna is usually something different. In order to get to the gist of this movement we need some more ingredients, for example the tathāgatagarbha-doctrine. So probably the full development of Mahāyāna-concepts was not complete until the Tathāgatagarbha-Sūtra, the Mahāparinirvāṇa-mahāsūtra and some related texts. The Mahāyāna-traditions themselves seem to have their difficulties in labeling stuff as Mahāyāna, as this was only done at a later point of time. So we end up with the Vaitulya/Vaipulya-confusion and the question what actually is early Mahāyāna, who composed it, why it was done and where it started is until today very much unsolved.
And also the attempt to associate Mahāyāna with one certain school or group seems rather unfruitful to me. I have the impression that Mahāyāna is something that went on across boundaries of certain sects, similar to the anti-war movement in the USA in the 60s (which might was generally associated with the left-winged political parties, but in no way limited to one group or one party) or the nationalistic movement that we have nowadays in Europe. They do generally share a common goal (or at least a direction) but there can be very different when one looks into the details.
Coëmgenu: Yep it is a difficult question. There is also a lot of pre-mahāyāna stuff transmitted in the northern tradition, yet this material has not been widely studied yet. This is partly due to the fact those people who are able to deal with the earliest chinese translations (such as Seishi Karashima) usually have a mahāyāna-background and are not much interested in the study of the non-mahāyāna-material. The few people who do engage in the studies of chinese pre-mahāyāna-material usually are not deeply trained in dealing with chinese sources, so there is some room to improve here.
To give an example the last month I was doing a comparison of the different transmissions of a small portion of the Mahāparinirvāṇa Sūtra. The MPS is not a bad Sūtra to start with since it is quite long, has been well transmitted in a lot of different languages and contains some passages which are of importance for the later doctrinal developments.
My impression is that in order to gain an impression of what the original text might have looked like we usually have to go through comparative study.
In the case of the MPS the northern and southern transmission complement each other quite well, so by comparison it is possible to puzzle together what the original might have been once. The northern transmission seems to be generally the older one in this case, at least concerning the fragment that I went through. This one can see in the fact that the Pāli-Version sometimes has a tendency to simplify, cut down, harmonize and 'arrange' stuff more readily than the sanskrit fragments. This gives the Pāli version a rather dry appearance. the Sanskrit version however suffers from the fact that some of the passages appear to have been written with a sort of 'creative genius' attitude, not always strictly focussed on telling what exactly happened. This is especially true if one looks at the earliest chinese translations (Taishō No. 5 and No. 6, probably 200-250CE).
In general I do however hold the view that the Pāli-canon is preferable to the Mūlasarvāstivāda-material when it comes to antiquity, but in order to get the oldest layer comparison is unavoidable.
By the way, as the master Karashima himself discovered, the term 'mahāyāna' is propably a wrong retranslation of a middle word that once was 'mahājñāna' 'the great knowledge'.
It does make a lot of sense since the southern transmission (and early indian sources in general) don't talk much of vehicles, but are focussed on knowledge and the ways to achieve it.
on buddhism, languages and programming.