The Rabbis tend to accuse Karaites of being nothing more than modern Sadducees. The Rabbis demonize the Sadduces for rejecting the premise of the Oral Law and thus the Talmud. According to the Talmud the Sadducees are virtual apostates who went after a Greek lifestyle. They rejected the resurrection of the dead, the afterlife, and the magical Meshiach (Messiah). The Sadducees seem to have come into existence in one form or another shortly after the return from the Babylonian Exile. The Targumim (Torah and Hebrew Bible translated into Aramaic) immediately fall into two categories during this period: a literal translation and one containing significant pseudo-Talmudic commentaries. The Sadducees leave the scene after the destruction of the Temple in 70 CE.
Another Rabbinic claim is that the Karaites were created by Anan Ben David after he had a quarrel with the Rabbis in Baghdad. According to other Karaite sages, such as Jacob Al-Qirqisani, the Karaites appreciated Anan’s help in securing recognition of Karaite Judaism as a separate from of the religion from the Islamic authorities. This meant freedom for Karaites from the Rabbis who were until then using the Islamic authorities to oppress the Karaites. Yet, Karaites also disagreed with Anan’s interpretations of scripture and occasionally belittled his followers. In fact this suggests that Karaism already existed and that Anan provided political assistance but little more to the movement.
Which is it? As in many cases with the Rabbis, they have conflicting stories. With the latter story it is one we have heard before. As Nehemia Gordon points out in his book Hebrew Yeshua vs. the Greek Jesus, the Rabbis claim that every religious movement was established because someone had a quarrel with their Rabbi! Whether it was Jesus or Mohammed the Rabbis claim that disagreements with the rabbinic authorities led these men to establish new faiths. There is a story about the Sadducees in which two followers of a wise man have disagreements with his teachings. One is supposed to have founded the Pharisees and the other the Sadducees. In this case the story about Anan does not pan out as the beginning of the Karaites.
It is true that any existing Sadducee leaning congregation would have joined the Karaites. All of the congregations that rejected the Talmud of the Pharisees (Rabbis) were eventually molded into the Karaites (except for the Samaritans). Karaism continues to use the Sadducee calendar, they celebrate Shavuot on the day prescribed by the Sadducees, and interpret the Torah directly just as the Sadducees did. Nevertheless, Karaism is not Sadducee Judaism.
The Sadducees were known to have two major factions, one faction that did not believe in an afterlife or angels (except as they appear in the Torah [that is as men delivering messages from YHVH]); while a second faction believed in the afterlife to the extent that it is referenced in the Torah and Tanakh (except for Daniel) and that angels existed as described in the Torah and Tanakh. The claim that the Sadducees went after a Greek lifestyle is ridiculous given that almost all Greeks believed in “Hades” as Josephus called the afterlife. In fact those Sadducee homes that have been unearthed by archaeologists contained few if any Greek artifacts. They contained all the necessaries for a simple Jewish lifestyle. So it appears that the Sadducees were not as “evil” as the Pharisees and their Rabbinic descendants would have you believe. In that case being called a Sadducee is far from an insult, and I respect the Sadducee movement as an important element in the formation of Karaite Judaism. Much like the Federalist and Whig parties helped to form the Republican Party in the US, and the Democratic-Republicans and National Republican Parties helped lead to the Democrat Party.
Karaites have grown over the nineteen centuries since the Sadducees disappeared from history. Karaite Judaism contains many of the teachings of the philosopher Philo and has more than a dozen sages and scholars of its own such as the afore mentioned Jacob Al-Qirqisani. Modern Karaism can also be defined by those elements of foreign philosophies that it did not incorporate. Not having followed Maimonides, for example, the Karaites never adopted Aristotelianism.
In short, Karaites today are Karaites.