Press freedom, the plight of refugees and climate modelling: 12 men and only one woman won Nobel Prizes this year for conferring "the greatest benefit to humankind".

Investigative journalist Maria Ressa was the sole female winner this year as she picked up the Peace Prize alongside Dmitry Muratov of Russia.

Only 59 Nobel prizes have gone to women (6.2% of the total) since they were first awarded in 1901, including two for Marie Curie, who won for Physics in 1903 and Chemistry in 1911.

While four women won Nobel prizes in 2020 -- close to the 2009 record of five -- the awards remain male-dominated as much of the prizewinning work dates back 20, 30 or even 40 years when fewer women reached the top levels of academic research.

In 2019, there was only one woman laureate, and in 2017 and 2016 there were none.

However, the head of the Royal Swedish Academy of Sciences, has ruled out gender quotas and defended the selection of this year's Nobel laureates.

Goran Hansson said: "It's sad that there are so few women Nobel laureates and it reflects the unfair conditions in society, particularly in years past but still existing. And there's so much more to do.

"We have decided we will not have quotas for gender or ethnicity. We want every laureate (to) be accepted... because they made the most important discovery, and not because of gender or ethnicity. And that is in line with the spirit of Alfred Nobel's last will.

"We want to make sure that all deserving women get a fair chance to be evaluated for the Nobel Prize. So we have made significant efforts to encourage nominations of women scientists.

"And we made sure that we know about the problem and also about subconscious bias, etc. in the (prize-awarding) committees and academies. We've had lectures by sociologists, we've had group discussions, we have put quite a lot of effort into it.

"In the end, we will give the prize to those who are found the most worthy, those who have made the most important contributions."

Here are the 2021 winners in each discipline:

Medicine

US scientists David Julius and Ardem Patapoutian won the Medicine Prize for discoveries on receptors for temperature and touch.

Their discoveries "unlocked one of the secrets of nature by explaining the molecular basis for sensing heat, cold and mechanical force," the jury said.

The duo's research, conducted independently of each other in the late 1990s and 2000s, is being used to develop treatments for a wide range of diseases and conditions, including chronic pain.

Physics

Awarded for the first time to two climate experts, the Physics Prize went to Klaus Hasselmann of Germany and Syukuro Manabe of Japan and the United States, as well as to Italian theorist Giorgio Parisi.

Working in the 1960s, Mr Manabe showed how levels of carbon dioxide in the atmosphere correspond to increased Earth surface temperatures. Crucially, he recognised the role of water vapour in trapping heat, which is much more than carbon dioxide alone.

Mr Hasselmann was credited for working out how climate models can remain reliable despite sometimes chaotic variation in weather trends.

Mr Parisi was meanwhile honoured for his work in the 1980s on the theory of complex systems.

His work helped physicists understand apparently entirely random materials, with wide-ranging applications including mathematics, biology and machine learning.

Chemistry

Germany's Benjamin List and Scottish-American David MacMillan won the Chemistry Prize for developing a pioneering type of catalyst.

Working independently of one another in 2000, they created a tool to build molecules that has spurred new drug research, scaled up production and made chemistry more environmentally friendly.

The new technique, called "asymmetric organocatalysis" and which relies on small organic molecules, is used to control and accelerate chemical reactions.

Literature

Novelist Abdulrazak Gurnah, who was born in Tanzania but has lived in Britain for more than 50 years, won the Literature Prize for his portrayal of the effects of colonialism and the trauma of the refugee experience.

The Swedish Academy said Mr Gurnah was honoured "for his uncompromising and compassionate penetration of the effects of colonialism and the fate of the refugee in the gulf between cultures and continents".

He is the fifth African to win the prestigious honour.

Peace

Investigative journalists Maria Ressa of the Philippines and Dmitry Muratov of Russia won the Peace Prize for their work promoting freedom of expression at a time when liberty of the press is increasingly under threat.

Ms Ressa, also a US citizen, is co-founder of Rappler, a digital media company for investigative journalism, and a vocal critic of Philippines President Rodrigo Duterte.

Mr Muratov in 1993 co-founded Russia's leading independent newspaper Novaya Gazeta, one of the few media outlets left voicing criticism of Putin. He has served as chief editor several times.

Novaya Gazeta's opponents have responded with harassment, threats, violence and murder.

Economics

Three US-based economists, Canadian-American David Card, Israeli-American Joshua Angrist and Dutch-American Guido Imbens, won the Economics Prize.

They were rewarded for thier work on the labour market using "natural experiments", or observational cause-and-effect studies, that have revolutionised empirical research in the field.

Mr Card's work has focused on the labour market effects of minimum wages, immigration and education.

Meanwhile, Mr Angrist and Mr Imbens figured out a methodological way to interpret data from "natural experiments", demonstrating how precise cause and effect conclusions can be.