Excerpt from Bitch by Lucy Cooke, plus links to reviews, author biography & more

In the 1980s Peter Goodfellow's lab in London finally unmasked this unassuming piece of genetic code as the elusive testis-determining factor in humans. His team discovered that the switching on of SRY proved to be the crucial first genetic step in triggering the neutral fetal gonad sex cells to develop into testes and start pumping out testosterone. In its absence, the unisex primordial kit matures at a more leisurely pace into embryonic ovaries.

This time there was much fanfare. The master switch for mammalian sex determination had finally been revealed and the 'essence of maleness' located. SRY was the missing trigger for the cascade of genes that code for testes development – the male sex-determining pathway.

I spoke to Jennifer Marshall Graves, the distinguished Australian professor of evolutionary genetics who was part of the international cohort of scientists hunting for this crucial male sex-determining gene. Her work on marsupial chromosomes prompted the search to switch direction to a fresh section of the Y, where the SRY gene was eventually located. Graves explained why their triumph at solving the puzzle of sex was, in fact, short-lived.

'We thought it was going to be the Holy Grail,' she confessed over Zoom from her home in Melbourne. 'When my student found the SRY gene we thought it would all be really simple. A kind of switch. But sex determination turns out to be much more complicated than we thought.'

The way sex is taught, you'd be forgiven for assuming the genes for creating testes inhabit the Y and the genes for ovaries reside on the X.That would be helpful. But evolution has done nothing to make the work of geneticists easy.

Excerpted from Bitch by Lucy Cooke. Copyright © 2022 by Lucy Cooke. Excerpted by permission of Basic Books. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.