Anne Frank once taped over two pages in her diary with brown sticky paper, leaving a small puzzle as to what material the Jewish teenager, who had no idea of how famous her diary would later become, wanted to exclude. He said these pages were important because they show Frank's first foray into trying to write in a more literary tone.
He said the jokes "make it clear that Anne, with all her gifts, was above all also an ordinary girl".
Researchers using digital technology deciphered the writing on two pages of Anne Frank's diary that she had pasted over with brown masking paper, discovering four naughty jokes and a candid explanation of sex, contraception and prostitution.
The pages were part of one of several diaries penned by the Jewish teenage diarist during her time hiding from the Nazis in Amsterdam, the city's Anne Frank House wrote in a statement Tuesday.
Anne Frank House museum executive director Ronald Leopold, says that 'like every adolescent she is curious about this subject [of sex]'.
Experts on Anne's multimillion-selling diary said the newly discovered text, when studied with the rest of her journal, reveals more about her development as a writer than it does about her interest in sex. Anne and her family were betrayed and deported to Germany.
"She was probably afraid that other people she was hiding with, either her father, her mother or the other family would discover her diary and would read these things", Leopold said.
The pages, dated to September 28, 1942, were contained in the red-and-white checkered diary Anne had received for her birthday in June of that year, shortly before they went into hiding.
"She starts with an imaginary person whom she is telling about sex, so she creates a kind of literary environment to write about a subject she's maybe not comfortable with", he said.
One of her jokes was this: "Do you know why the German Wehrmacht girls are in Holland?"
Anne wrote her diary while she and her family spent two years in hiding in an Amsterdam canal-house, in an attempt to avoid Nazi occupiers during World War II.
She also related this joke: "A man had a very ugly wife and he didn't want to have relations with her".
Anne died at the Bergen-Belsen concentration camp in 1945, aged 15. Only Anne Frank's father, Otto, survived the Holocaust.
Her diary was published two years later and has been read worldwide and translated into at least 60 languages.
The house where the Franks hid has been turned into museum, making it one of Amsterdam's most visited attractions.