Project Nettie calls on scientists to defend biology

Please spread widely, and sign, to support science and rationalism over the new irrationalism sweeping universities and a range of other institutions. 


Sexual reproduction, the generation of offspring by fusion of genetic material from two different individuals, evolved over 1 billion years ago. It is the reproductive strategy of all higher animals and plants, including the mammalian class to which humans belong.

Humans can be differentiated into two categories by their reproductive roles. Females make eggs and gestate live young. Males generate sperm to fertilise the female egg. In accordance with their respective roles, females and males have different reproductive anatomies (“biological sex”).

No other reproductive mechanism exists in humans.


In contradiction of evolutionary history and millennia of human observations, highly-esteemed scientific periodicals are running articles undermining the observable reality of biological sex.

“Biologists now think there is a larger spectrum than just binary female and male.”

Scientific American, Oct 22 2018

“The research and medical community now sees sex as more complex than male and female.”

Nature, Oct 30 2018

In response to these claims, Project Nettie was born.


What is Project Nettie? Project Nettie is an online and regularly updated record of scientists, medics and those in related disciplines who, by signing their support for the Project Nettie statement (below), assert the material reality of biological sex and reject attempts to reframe it as a malleable social construct.

How can you be a part of Project Nettie? If you are a scientist, a medic or other healthcare professional, a science educator, or in another relevant field, you can sign the Project Nettie statement. Other academic and professional signatories are welcome but will be listed separately. Please click here to access our signatory form. All signatories will be verified by the team.

What is the aim of Project Nettie? The aim is to simply reassert the definition of biological sex. We do not extend our claims regarding biological sex beyond the scientific fact of biological sex. We do not feed into any political ideology.

Why ‘Project Nettie’? Sex chromosomes were, in 1905, discovered by a female geneticist called Nettie Stevens. We hope, in some small way, to honour her achievements.

Nettie Stevens, the female geneticist who discovered sex chromosomes in 1905


The Project Nettie statement:

“Biological sex” is a scientific description of the reproductive anatomies that have evolved to fulfil the function of sexual reproduction. Biological sex exists independently of humans and society.

In mammals, there are two types of gamete and two classes of reproductive anatomy. The male sex class produces many small motile gametes – sperm – for transfer. The female sex class produces few large immobile gametes – ova – and gestates/delivers live young. In any individual, reproductive anatomy is almost always unambiguously male or female and observed correctly at birth, regardless of ultimate sexual function or dysfunction.

Male and female reproductive anatomies differ qualitatively, not quantitatively, and there are no intrinsically-ordered states between male and female reproductive anatomies. Biological sex does not meet the defining criteria for a spectrum.

Although rare, some individuals have disorders of sex development (also referred to as intersex conditions). Most of these disorders are male or female specific and do not cause ambiguous biological sex. Some individuals have reproductive anatomies with both male and female features; here, biological sex classification is a complex process with input from medical professionals and parents. Not one of these individuals represents an additional sex class.

Reproductive anatomies differentiate and mature under the control of genetic and hormonal signals, and measurements of these factors have strong predictive power, but do not define the sex of an individual. Biological sex is fundamentally defined by male and female reproductive anatomy.

Attempts to recast biological sex as a social construct, which then becomes a matter of chosen individual identity, are wholly ideological, scientifically inaccurate and socially irresponsible

See signatories here