Was Gamaliel VI (ca. 370 – ca. 425) the last nasi of the 'ancient' Sanhedrin?
Note I've just recently come across a fascinating piece by Dr. Alan Applebaum entitled Hillel II ; Recovering an obscure figure of Late Antiquity, The Jewish Studies Quarterly (Vol. 20, 2013). That article sheds further light on this murky period of Jewish history and I will update this post once I transcribe the relevant parts.
Wikipedia would have you believe that:
"Gamaliel VI (ca. 370 – ca. 425) was the last nasi of the ancient Sanhedrin"
This is a blatant error.
Due to intermittent persecutions and upheaval in the Holy Land, the Sanhedrin and the central Yeshibha/Academy of The Land of Israel (heretofore referred to as EY), would often move around (sometimes it would be forced to uproot to locales as far away as the coast of Lebanon and Old Cairo). What we do know for certain is that both institutions (The Sanhedrin and the Yeshibha) stayed alive way after the death of Gamaliel VI. The subsequent Nesiim (Patriarchs) may not have been descendants from the House of Hillel (although Aharon ben Meir, who flourished in the 10th c. and functioned as both Rosh Yeshibha and Nassi, did claim descent. See note where I express skepticism regarding that claim) but the post of Nassi was not abolished as can be clearly evidenced from the Genizah findings and the extant responsa of the Gaonim.
We unfortunately do no possess an equivalent of Iggeret Rav Sherira Gaon for the Gaonim of the Eretz Yisrael Yeshibha. The closest we have to that is Megilat Ebiathar, penned by the 12th c. Gaon Rabbi Ebiathar b Eliyahu Hacohen, Rosh Yeshibha and Nassi of Eretz Yisrael (and a descendant of the aforementioned Aharon b. Meir).
The community in EY was drastically reduced in size by the end of the Millenium and as a result both the Yeshibha and Sanhedrin often lost its prestige. It may be said that they suffered from an inferiority complex and when given the opportunity, they would assert the primacy of the EY authorities as can be seen with the Ben Meir affair and most tellingly the biting words of his descendant, the Nassi and RY, the aforementioned Rabbi Ebiathar Ben Eliyahu Gaon:
ארץ ישראל אינה קרואה גולה שיהא ראש גולה נסמך בה, ועוד שאין עוקרין נשיא שבארץ ישראל, שעל פיו מעברין את השנה וקובעין את המועדות הסדורים לפני הקב"ה קודם יצירת העולם, דהכי גמרי בסוד העיבור
The basic gist of it is that Eretz Yisrael is not termed exile (and by implication is not under the jurisdiction of the Exilarch in Babylonia or the Academies there).
There were sporadic comings and goings to and from the Babylonian Diaspora however during virtually all periods of Jewish history.
Take for instance this:
In the year 520, the Davidic Mar Zutra III , son of the Babylonian Exilarch, established himself at the helm of the Eretz Israel Sanhedrin and Yeshibha. Seven generations of his descendants succeeded him at this post.
I have yet to study the exhaustive writings of S.D. Goiten and Moshe Gil but they are the preeminent experts on EY during the Geonic Period. Much of the history of that period seems to be shrouded in obscurity but there are tidbits that can be culled from various non-Jewish sources. An example of something very interesting I came across was the Sanhedrin's involvement with the failed Samaritan Revolt led by Justus.
One interesting detail about that revolt was that they invited the Jews to participate and the issue of whether to join the Samaritans or to stay neutral went before the then Sanhedrin (which was then operating in Tiberias). Most of the members of the Sanhedrin voted against the alliance except for one young member (IIRC his name was R. Uzi b. Berekyahu). He claimed that based on one opinion in the Talmud the 'kuthim' (a Rabbinic term used to describe Samaritans) are kosher Jews and therefore Jews should come to their aid. As mentioned, his opinion was a lone one and it was just as well because the revolt was cruelly crushed shortly thereafter.
(I recall reading about this years ago in Monroe Rosenthal's Wars of the Jews).
Be it as it may, as can be seen from these early sources (and there is no reason to doubt their veracity), there was a fully functioning Sanhedrin with a Nassi at its head, way after the deposing of Rabban Gamaliel VI.
There were some who claimed that Aharon Ben Meir (who was a Cohen) claimed descent from the line of Hillel II (the alleged composer of the so-called Hillel Calendar which is still in use today). However, as mentioned Ben Meir was a Cohen and I am not sure what setting the Calendar has to do with being descended from Hillel. Yes, the Chairman (Nassi) of the Sanhedrin has the final vote on such important issues as setting down the dates of the new moon and holidays, but how does being a descendant of a Nassi (and certainly not a patrlineal one) add any power of authority?
Parenthetically, the founder of the Hillelite line, Hillel I, himself the Nassi of the Sanhedrin of his time is alleged to have claimed descent from King David, yet there is contradictory evidence in the Talmud regarding his alleged royal credentials. Suffice it to say that the first one who tied him directly to King David was Ibn Daud (Raabad) in his Book of Tradition (he flourished in Medieval Spain). In the Talmud itself we found evidence of a weak connection through matrilineal descent (since when was any importance attributed to matrilineal Davidic descent?!).
One should also bear in mind that while the Exilarchs in Babylon needed to prove their Davidic credentials in order to attain the aforementioned position, the Patriarch (Nassi) in Eretz Israel did not need it all; his position was based solely on his ability and knowledge (although such a claim, whether authentic or not, probably helped him gain prestige and support). Of course, we should likewise bear in mind that the Nassi in Eretz Israel was also the head of the Sanhedrin--the most important Jewish legislative body in ancient Byzantium, while the Exilarch was very often only a (royal) figurehead for the Jews residing in the rest of the Diaspora.
*I must qualify my previous statement about the Nassi being elected solely on account of his qualifications and not pedigree. This is isn't particularly true in the case of the House of Hillel. The Hillelites maintained a stranglehold on the Nesiut beginning with Hillel I at the start of the common era until the 5th c. CE. Not all the Hillelites were necessarily fit for the job. The latter turned the Nesiut into an hereditary institution (it was not like that before they were at the helm, e.g. Elazar ben Azaryah, Bnei B'teyrah, etc.). After the death of Gamaliel VI (some claim he was executed by the Byzantines but I haven't seen any corroborating sources. Also oddly enough this is also said of the 'last Exilarch' in Babylonia, Hizkiyahu. See following post), there was a gap, probably due to renewed persecutions but the Nesiut and Yeshibha were reestablished not long after and it lasted until close to the 14th century.
In addition it should be pointed out that sometimes the post of Nassi and RY were combined (as was the case with Ben Meir). In Babylonia too, the Exilarch could also simultaneously function as the powerful Rosh Hayeshiva as well (as was the case with the Exilarch Hizkiyahu who in 1038 became the RY of the Babylonian Academy at Pumbeditha).