Emma Hilton, PhD

Education and career

I am a developmental biologist at the University of Manchester, a world top 50 university. In 1999, I received my Bachelor of Science degree from the University of Warwick, UK, where I studied Biochemistry. In 2004, I received my Doctor of Philosophy degree from the University of Warwick, UK, where I researched early events in the embryogenesis of vertebrate embryos. I have extensive research experience in the field of developmental genetics. My career has focused on the genetic and molecular mechanisms underpinning inherited genetic disorders in humans, including those that differently affect males and females, and that affect nerve and/or muscle development during embryogenesis. In 2007, I was named as an Outstanding Young Investigator by the European Society of Human Genetics, for my work on a sex-linked genetic disorder that causes death in male foetuses. I have authored over 20 peer-reviewed publications in clinical genetics and development journals, received over 1100 citations, and contributed to key medical textbooks.

I am an unpaid director of Sex Matters, a UK-based human rights group that campaigns for clarity on the (UK) protected characteristic of sex in law and in institutions. My area of expertise for Sex Matters is the biology of sex and sports policy. 


Over the last five years, I have applied my developmental biology expertise to the study of sex development, sex differences and sport, particularly regarding fairness and the inclusion of trans-identified males suppressing testosterone in female categories. In 2021, along with Dr Tommy Lundberg (Karolinska Institute), I published a major review of musculoskeletal physiology in trans-identified males suppressing testosterone, assessing whether evidence exists to support the assumption that testosterone suppression in this cohort removes the male performance advantage and thus delivers fair and safe competition. I found that losses of muscle mass and strength are modest, and that significant advantage is retained over reference female metrics. These data, later confirmed in a second independent review, seriously challenge the premise of the International Olympic Committee (and subsequently, many sports governing bodies) that testosterone suppression in trans-identified males delivers fair competition in female categories of sport.  

Published in a world-leading sports and exercise medicine journal (Sports Medicine; five year impact factor 12.2), this paper has, in the first 16 months, received 46 academic citations (Google Scholar; 17th May 2022). The Altmetric score is 4027 (17th May 2022), indicating this review has received widespread global attention (ranked 950 out of +21 million academic publications). It has already been referenced nearly 100 times in the mainstream news, extensively in online media, and in scientific media including Nature and Medscape.

Also in 2021, I joined with Dr Jon Pike (Open University) and Professor Leslie Howe (University of Saskatchewan) to author a policy document commissioned by the Macdonald-Laurier Institute in Canada. We reviewed the importance of sex categories in sport, synthesising knowledge across developmental biology, the physiology of trans-identified males suppressing testosterone, and sports philosophy. We concluded that a female category that excludes all males, regardless of gender identity, is philosophically coherent and necessary to ensure everyone can compete fairly and fully, and that it is reasonable for female athletes to expect that their rights will be upheld by the institutions and procedures of their sports. 

My current research activity is an academic scoping review of transgender athlete policies of the most popular UK sports. 

Selected public activities 

July 2019: I gave a speech at A Woman’s Place is On The Podium, organised by A Woman’s Place UK and Fair Play For Women, where I outlined the poor evidence base for the historic and then-current regulations of the International Olympic Committee.  

February 2020: I was invited by World Rugby to give evidence to the Transgender Working Group, which was tasked with reviewing their regulations for inclusion of transgender women in female categories in international competition. I have since consulted with several sports governing bodies currently examining their transgender athlete policies. I have been invited to consult with sports and athlete groups like the US-based Women’s Sports Policy Working Group and the UK Sports Council Equality Group. 

February 2020: I published an article in the Wall Street Journal with Dr Colin Wright (formerly, Penn State University) called ‘The Dangerous Denial of Sex’, which outlines the harms of gender ideology to women, same-sex attracted people and gender non-conforming children. 

January 2021: I co-authored a letter called ‘The Reality of Sex’ in the Irish Journal of Medical Science (the official organ of the Royal Academy of Medicine in Ireland), where we argue that “Human sex is an observable, immutable, and important biological classification; it is a fundamental characteristic of our species, foundational to many biology disciplines, and a major differentiator in medical/health outcomes.”

September 2021: I gave a speech at a Labour Party Conference fringe event, organised by Labour Women’s Declaration, arguing that sex matters in sport (with a a free basic biology lesson for Labour politicians…). 

December 2021: I was invited to join a webinar, hosted by the independent sports dispute service Sport Resolutions, to discuss the future of sports competition and policy regarding transgender athletes.  

March 2022: I was invited to deliver a presentation at the annual conference of the Canadian Academy of Sports and Exercise Medicine, presenting evidence for the exclusion of male advantage from female sports categories.   

April 2022: I gave a speech at House of Lords on the unfairness of inclusion of trans-identified males in female sports categories. 

May 2022: I published an article in The Australian with Professor David Handelsman (University of Sydney), a world expert in the study of the effects of testosterone in males. Titled ‘What Science Tells Us About Transgender Women Athletes’, we argue that male athletic advantage is retained in trans-identified males, even with testosterone suppression, and that fairness for female athletes must not be compromised.