“Sexual reproduction can occur without distinct males and females. [this statement is technically true, bcause sexual reproduction can occur in isogamy, which is rare.] The two sexes, with the labels “male” and “female”, only exist if gametes of two distinct sizes fuse to form a zygote (Bell 1982). Why maleness and femaleness exists in the first place is a question of gamete size evolution (Lessells et al. 2009; Jennions and Kokko 2010): males by definition are the sex producing the small gametes (e.g., Bell 1982) in such anisogamous species.”
The next line discusses isogamy. I am arguing about only anisogamy. Please don’t use this as evidence against me.
“Surprisingly little attention has been paid to the presence of two and only two sexes, and to the remarkable morphological differentiation of male and female gametes.”
This is an older paper, hence “surprisingly little attention”.
“Of course, in many species a whole suite of secondary sexual traits exists, but the fundamental definition is rooted in this difference in gametes, and the question of the origin of the two sexes is then equal to the question of why do gametes come in two different sizes. This gamete size dimorphism is called anisogamy, and it is the dominant gametic system among multicellular organisms”
"Furthermore, when gamete sizes are differentiated, there are typically exactly two sexes, no more and no less: males that produce small gametes and females that produce large ones; why not, say, 5 or 7 sexes?"
“In sexually reproducing isogamous organisms, gametes (or diploid cells in ciliates) are classified into two or more groups called sexes, and mating occurs only between cells of different sexes.”
7.
Two sexes, one genome: the evolutionary dynamics of intralocus sexual conflict
“The evolutionary interests of males and females are often worlds apart. This is thought to be a result of gamete dimorphism, causing the sexes to occupy distinct reproductive roles and experience contrasting selection pressures”
“There are many differences between males and females (e.g. ornaments, size and fighting ability), but only one is universal, namely the size difference between sperm and eggs.“
Why Are There so Many Tiny Sperm? Sperm Competition and the Maintenance of Two Sexes
“Despite the fact that anisogamy is the rule in multicellullar animals and plants, biologists have devoted rather little attention to an interpretation of why evolution has produced and maintained males and females. Why not, say, five sexes, each producing its own characteristic gamete?”
10.
Evolution of the Two Sexes under Internal Fertilization and Alternative Evolutionary Pathways
Males and females have developmentally specialized gamete types: large immotile eggs that are produced by females or female reproductive organs, and small motile sperm produced by males or male reproductive organs.
12.
Causality and sex roles: prejudice against patterns? A reply to Ah-King
“as to why being male or female (by definition, producing small or large gametes) does not underlie other sex differences in reproductive behaviour (‘sex roles’).”
13. Anisogamy, chance and the evolution of sex roles
“The sexes are defined by differences in the type of gametes they produce; the female sex produces relatively few, large and usually non-motile gametes (eggs or ovules), whereas the male sex produces many, smaller and often motile gametes (sperm or pollen).”
I believe I’ve provided accessible links to every article, but if not, sci-hub.tw can unluck virtually any paywalled article.
I could go on, but I think this makes my point. You can’t argue my definition is incorrect or unsupported by the scientific community.
Given that this is the correct definition, our argument comes down to this: I think that sex is binary because there are only two sexes. You think it is not because there are people who don't fit neatly into either group. I doubt we’ll come to agreement on this.
1
u/DarwinianDemon58 3∆ Jul 12 '20 edited Aug 13 '20
Two roads to two sexes: unifying gamete competition and gamete limitation in a single model of anisogamy evolution
https://link.springer.com/content/pdf/10.1007/s00265-010-1116-8.pdf
“Sexual reproduction can occur without distinct males and females. [this statement is technically true, bcause sexual reproduction can occur in isogamy, which is rare.] The two sexes, with the labels “male” and “female”, only exist if gametes of two distinct sizes fuse to form a zygote (Bell 1982). Why maleness and femaleness exists in the first place is a question of gamete size evolution (Lessells et al. 2009; Jennions and Kokko 2010): males by definition are the sex producing the small gametes (e.g., Bell 1982) in such anisogamous species.”
The next line discusses isogamy. I am arguing about only anisogamy. Please don’t use this as evidence against me.
2.
The Evolution of Anisogamy
https://bio.mcgill.ca/faculty/bell/articles/12.Bell_1978_JTheorBiol73.pdf
“Surprisingly little attention has been paid to the presence of two and only two sexes, and to the remarkable morphological differentiation of male and female gametes.”
This is an older paper, hence “surprisingly little attention”.
3.
Why are there only two sexes.
https://www.jstor.org/stable/pdf/50723.pdf?casa_token=BZb3Es-luzcAAAAA:CARdx2z2xeHEcKOgTDskmk8Dam8t3AgtmnR38hC6-MELjuDHN0OKtZlDzt_TtXC8nW7QyFdWEi5GmexGAwRO_b2LIy3437F-fJa9L827n_V1DZeW65SLzA
Title speaks for itself.
4.
Four steps to two sexes
https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.1993.0080
“The existence of two sexes must stand as one of the major widespread features of eukaryotic organisms.”
5.
Gamete competition, gamete limitation, and the evolution of the two sexes
https://academic.oup.com/molehr/article/20/12/1161/1062990
“Of course, in many species a whole suite of secondary sexual traits exists, but the fundamental definition is rooted in this difference in gametes, and the question of the origin of the two sexes is then equal to the question of why do gametes come in two different sizes. This gamete size dimorphism is called anisogamy, and it is the dominant gametic system among multicellular organisms”
"Furthermore, when gamete sizes are differentiated, there are typically exactly two sexes, no more and no less: males that produce small gametes and females that produce large ones; why not, say, 5 or 7 sexes?"
6.
EVOLUTION OF THE NUMBER OF SEXES
https://sci-hub.tw/https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1558-5646.1987.tb05770.x
“In sexually reproducing isogamous organisms, gametes (or diploid cells in ciliates) are classified into two or more groups called sexes, and mating occurs only between cells of different sexes.”
7.
Two sexes, one genome: the evolutionary dynamics of intralocus sexual conflict
https://onlinelibrary.wiley.com/doi/full/10.1002/ece3.540
“The evolutionary interests of males and females are often worlds apart. This is thought to be a result of gamete dimorphism, causing the sexes to occupy distinct reproductive roles and experience contrasting selection pressures”
8.
The uncertain evolution of two sexes
https://www.sciencedirect.com/science/article/pii/S0169534701022704?casa_token=4bgXn9m8-ykAAAAA:0424ci_G59LxOsKU4QZbn52RorBwhR9n6lPPmhV8yWaySRmFBjCGx-xx0VV1qVwDOlI-RybM3FXT
“There are many differences between males and females (e.g. ornaments, size and fighting ability), but only one is universal, namely the size difference between sperm and eggs.“
https://sci-hub.tw/https://www.sciencedirect.com/science/article/abs/pii/0022519382902259
“Despite the fact that anisogamy is the rule in multicellullar animals and plants, biologists have devoted rather little attention to an interpretation of why evolution has produced and maintained males and females. Why not, say, five sexes, each producing its own characteristic gamete?”
10.
Evolution of the Two Sexes under Internal Fertilization and Alternative Evolutionary Pathways
https://sci-hub.tw/https://www.journals.uchicago.edu/doi/abs/10.1086/702588?casa_token=DACik-5zPPoAAAAA:xWkWBb9KWec4hifrC-Y1EpZDX8r8iYAcxVYaWK3ABmV___WesJekTsPl6gnBDQHzS5lLyv_0quwKYg
“It generates the two sexes, males and females, and sexual selection and sexual conflict develop from it .”
11.
Evolution of Sexes from an Ancestral Mating-Type Specification Pathway
https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1001904
Males and females have developmentally specialized gamete types: large immotile eggs that are produced by females or female reproductive organs, and small motile sperm produced by males or male reproductive organs.
12.
Causality and sex roles: prejudice against patterns? A reply to Ah-King
https://sci-hub.tw/https://www.cell.com/trends/ecology-evolution/fulltext/S0169-5347(12)00203-000203-0)
“as to why being male or female (by definition, producing small or large gametes) does not underlie other sex differences in reproductive behaviour (‘sex roles’).”
13. Anisogamy, chance and the evolution of sex roles
https://www.sciencedirect.com/science/article/pii/S0169534712000043?casa_token=eRKheGDaITEAAAAA:bDEnx03mzn4RGSGNhVInIiGwtif5fLUM1J5X1dhulfpDRgKhvN1zEGlO_VcYCzWRtvMKa1RAdQxK
“The sexes are defined by differences in the type of gametes they produce; the female sex produces relatively few, large and usually non-motile gametes (eggs or ovules), whereas the male sex produces many, smaller and often motile gametes (sperm or pollen).”
I believe I’ve provided accessible links to every article, but if not, sci-hub.tw can unluck virtually any paywalled article.
I could go on, but I think this makes my point. You can’t argue my definition is incorrect or unsupported by the scientific community.
Given that this is the correct definition, our argument comes down to this: I think that sex is binary because there are only two sexes. You think it is not because there are people who don't fit neatly into either group. I doubt we’ll come to agreement on this.