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Francis (Sid) Dougan Profile picture
Francis (Sid) Dougan
@F_Sid_Dougan
Call me Sid. Evolutionary Psychology PhD student (The @ProfDavidBuss Lab). Zoology/Biology MSci (University of Bristol, UK). 🇬🇧British chavvy in America🇺🇲
May 5 • 13 tweets • 4 min read
1/ 🧵 "SEX BIASES IN PATTERNS OF PARENTAL INVESTMENT"- My latest publication in Human Nature, w labmate @CostelloWilliam & supervisor @ProfDavidBuss
Mother-father investment differences aren’t just “mothers do more.” They vary by domain, as do biases toward daughters vs sons...Image 2/ (Open Access link)


Do parents treat daughters & sons differently?
Do mothers & fathers parent differently?

Previous research has produced mixed results.

I proposed two evolutionary hypotheses to address these questions & resolve the mixed findings...link.springer.com/article/10.100…
Sep 22, 2025 • 16 tweets • 5 min read
🧵 1/15 - "THERE ARE ONLY TWO SEXES AND THERE CAN NEVER BE MORE" - my publication in Archives of Sexual Behavior.
Thread with link and very brief summaries of the main points I cover in the paper...Image link.springer.com/article/10.100…

2/15 - Biologically, sex is determined by gamete type: females produce large gametes (eggs), males produce small gametes (sperm). This definition applies at the level of phenotype. Infertile, prepubescent, or post-reproductive individuals are still male or female, because they belong to a sexed phenotype evolved to produce one gamete morph. They do not contradict the gamete-based definition of sex.
I do not focus on 'gender' or 'identity' in this paper.