An Istanbul court judge on Wednesday said Muazzez Ilmiye Cig's writings had not insulted religious honour nor incited hatred and enmity as charged by the prosecution.
Turkey is an overwhelmingly Muslim, but officially secular, country and a candidate for European Union membership.
Dozens of intellectuals, notably the Nobel literature prize winner Orhan Pamuk, have been prosecuted over the past year for insulting concepts held dear by Turks, such as the ''Turkish identity'' or the founder of the republic, Mustafa Kemal Ataturk.
Flanked by 15 lawyers who came to support the Sumerian historian, Cig speaking to the court said:"I am a person of the Ataturk revolution and as a Turkish woman I try to bring people together, I'm not someone who is trying to incite hatred."
Cig, who has translated 3,000 stone tablets and published her findings last year, had faced up to three years in jail if convicted of all charges.
She was applauded by supporters as she left the court house.
Lawyer Yusuf Akin brought the case against Cig, saying her conclusions about the headscarf insulted Muslim women.
The Ataturk revolution greatly
expanded women's freedoms
In its annual progress report on Turkey due to be published on November 8, the European Commission is expected to sharply criticise Turkish prosecutions of intellectuals and journalists for expressing peaceful opinions.
Brussels is particularly critical of Article 301 of the penal code, which makes it a crime to insult Turkish identity.
Cig was charged under a separate article in the law.
Turkey's centre-right government has resisted EU pressure to modify articles criticised as curbing freedom of expression, saying more time is needed to build up a body of case law.
A supporter of Cig speaks to the
media after her acquittal
Most cases involving freedom of expression are dropped, it says.
The Sumerians were among the first settled societies considered a civilisation, ruling southern Mesopotamia, in what is now Iraq, from 3000 to 2000 BC.
In her book, My Reactions as a Citizen, Cig said headscarves were worn by women who worked as prostitutes in temples during the Sumerian period to differentiate them from women who worked primarily as priests.
Females often presided over the temples in the polytheistic society, Cig said.