For the first time since 1995, the Karolinska Institute in Sweden has added a woman to the short list of female winners of the Nobel Prize in Physiology or Medicine. A database of more than 4,300 nomination letters available on the institute's website in part explains the dominance of male winners in the field.

On 4 October, the Nobel Assembly awarded the SEK10 million ($1.4 million) prize to US researchers Linda Buck and Richard Axel for deciphering how mammals, including humans, identify thousands of smells. Buck is the seventh woman to win in the category since 1901, adding up to just 4% of 182 winners.

Reviewers at the Karolinska Institute have in the past attributed that scarcity to male dominance within the biomedical field. The institute's database supports that assertion. Covering only the years 1901–1949 because of confidentiality rules, it reveals that only 1.2% of nomination letters mentioned 12 different female nominees. Of those, biochemist Gerty T. Cori became the lone female winner among 56 laureates over that period. University of Chicago bacteriologist Gladys Dick, together with her husband George Dick, was nominated by 24 colleagues for findings on scarlet fever, but never got the award.

What's more, only 0.3% of nominations came from women. Many female scientists at the time couldn't get formal research positions, a prerequisite to be invited to nominate, says Sharon McGrayne, author of the book Nobel Prize Women in Science. “Through the years, many factors have come together on many levels, making the problems of women in science such a persistent thing,” she says.

Even now, boosting female representation is difficult because professorial positions in many countries are still occupied mostly by men, notes Hans Jörnvall, the Assembly's secretary. “We can't dictate whom people should nominate,” he says.

The selection process for Nobel Prizes has historically been a heavily guarded secret. Nomination letters, evaluations and deliberations are kept secret for 50 years, and only qualified researchers are allowed access to documents from earlier years. The Karolinska Institute, which awards the Physiology or Medicine Prize, was the first to go online in 2002 with a searchable nomination database.

The records offer details such as gender, university, city and country of nominators and nominees, and indicate whether and by whom the nomination was evaluated. The database also reveals that, at least up to 1949, researchers from Japan, the US and France primarily nominated scientists from their own countries. Jörnvall says it is unclear whether the database will continue to be updated.

Israelis Aaron Ciechanover and Avram Hershko and American Irwin Rose shared the 2004 Chemistry Prize for discovering how cells dispose of unwanted proteins. Controversy erupted over Peace Prize winner Wangari Maathai, Kenya's deputy minister for environment and natural resources, who was quoted in a Kenyan newspaper as saying that HIV “is a tool to control [Africans or black people] designed by some evil-minded scientists.”