Fundamental Differences Between Females and Males?
What, if any, are the fundamental differences between females and males? All the usual suspects are wanting. There is no female-male dichotomy when looking at diploid individuals (those with two copies of each chromosome) because there are numerous hermaphroditic species, including numerous intersex human individuals, and species with environmental sex determination. Not all males have an intromittent organ, such as a penis. More surprisingly, female-male dichotomy is even illusory when looking at haploid individuals (each nucleus with one copy of each chromosome), such as eggs and sperm. Not all sperm have Y chromosomes.
The fundamental differences between females and males are only to be found in the nuclei of eggs and sperm, that is, only in small portions of single haploid cells. Sperm nuclei are the only nuclei lacking pores in their nuclear membranes. Furthermore, only male’s meiosis is symmetrical, producing four functional sperm nuclei. Female meiosis is asymmetrical, producing only one functional egg nucleus; the other egg nuclei are discarded. The terms female and male fundamentally apply to haploid nuclei, not haploid (nor diploid) cells or individuals.
KeywordsSperm Nucleus Diploid Individual Female Meiosis Mating Flight Haploid Nucleus
Thanks to Marion Blute, Patty Gowaty, Lara Karaian, Amedeo D’Angiulli, Sue Bertram, Pearl Jacobson, and Malin Ah-King for feedback and to the Natural Science and Engineering Research Council of Canada (NSERC) for funding.
A nucleus containing only one copy of each chromosome. A nucleus containing two copies of each chromosome (usually one from the mother and one from the father).
A cell division that results in the production of two identical sets of chromosomes partitioned into two identical daughter cells. Both new cells have the exact same chromosomal content as the cell that produced them. Mitosis is akin to photocopying.
A cell division that reduces the number of chromosomes by half (e.g., a diploid cell produces haploid cells). Each newly produced nucleus contains one copy of each chromosome (either maternal or paternal copy), although crossing over recombination can also produce chimeric chromosomes that are part maternal and part paternal. Meiosis is akin to shuffling cards.
Small completely symbiotic bacterial cells within every eukaryotic cell that are used for converting sugars to chemical energy.
Compact pieces of RNA and protein that translate messenger RNA (which itself was transcribed from DNA) into amino acids and proteins.
Internal cell membranes that form throughout the cell’s cytoplasm and are used to construct the membrane of the cell nucleus. Presence of endoplasmic reticulum distinguishes eukaryotes from bacteria. Ribosomes are attached to a subset of the endoplasmic reticulum and the outer cell membrane.
- 1.Mill, J. S. (1869). The subjugation of women. London: Longmans, Green & Co. (Reprinted by Transaction Publishers in New Brunswick, NJ, 2001.)Google Scholar
- 3.Fausto-Sterling, A. (2000). Sexing the body: Gender politics and the construction of sexuality. New York: Basic Books.Google Scholar
- 8.Zouros, E., Freeman, K. R., Ball, A. O., & Pogson, G. H. (1992). Direct evidence for extensive paternal mitochondrial DNA inheritance in the marine mussel Mytilus. Nature, 359, 412–414.Google Scholar
- 11.Austin, C. R. (1965). Fertilization. Edgewood Cliffs: Prentice-Hall.Google Scholar
- 19.Iwamatsu, T. (2000). Fertilisation in fishes. In J. J. Tarín & A. Cano (Eds.), Fertilization in protozoa and metazoan animals: Cellular and molecular aspects. Berlin: Springer.Google Scholar
- 26.Jordan-Young, R. M. (2010). Brainstorm: The flaws in the science of sex differences. Cambridge: Harvard University Press.Google Scholar
- 27.Margulis, L., & Sagan, D. (1988). Sex: The cannibalistic legacy of primordial androgynes. In R. Bellig & G. Stevens (Eds.), The evolution of sex. San Francisco: Harper & Row.Google Scholar