Some claim that rare chromosome combinations prove there are more than two sexes, yet these combinations still result in males and females, not new sexes.
Sources:
[1] Scharer, L. (2017). The varied
...
ways of being male and female. Molecular Reproduction & Development, 84.
[2] Lehtonen, J., Parker, G. (2014). Gamete competition, gamete limitation, and the evolution of two sexes. Molecular Human Reproduction, 20(12).
[3] Lehtonen, J., Parker, G. (2019). Evolution of the two sexes under internal fertilization and alternative evolutionary pathways. The American Naturalist, 193(5), 702-71.
[4] Bachtrog D, Mank JE, Peichel CL, Kirkpatrick M, Otto SP, Ashman TL, et al. (2014). Sex Determination--Why So Many Ways of Doing It. PLoS Biol, 12(7).
[5] Eggers, S., Sinclair, A. (2012). Mammalian sex determination--insights from humans and mice. Chromosome Res, 20.
[6] Kimball, J. (2020). Sex chromosomes. LibreText.org.
[7] Sekido, R., Lovell-Badge, R. (2009) Sex determination and SRY, Down to a wink and a nudge. Trends in Genetics, 25(1).
[8] Rey, R., Josso, N., Racine, C. (2020). Sexual differentiation. In--Endotext. South Dartmouth, MDText, Inc.
[9] Witchel, S. (2018). Disorders of sex development. Best Practice and Research in Clinical Obstetrics and Gynecology, 48.
[10] NIH. (2020). Turner Syndrome. Genetics Home Reference, National Library of Medicine.
[11] NIH. (2020). Triple X Syndrome. Genetics Home Reference, National Library of Medicine.
[12] NIH. (2020). Klinefelter Syndrome. Genetics Home Reference, National Library of Medicine.
[13] NIH. (2020). 47:XYY Syndrome. Genetics Home Reference, National Library of Medicine.
[14] NIH. (2020). 48:XXXY Syndrome. Genetics Home Reference, National Library of Medicine.
[15] NIH. (2020). Tetrasomy X. Genetics Home Reference, National Library of Medicine.
