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The current Lead states: "By definition, male gametes are small, motile, and optimized to transport their genetic information over a distance, while female gametes are large, non-motile and contain the nutrients necessary for the early development of the young organism."
While it is true that eggs are much larger cells, and have significantly less motility than sperm even in species where the egg is slightly motile, the true formal definition has to do with how the germ line cell (the precursor cell that divides to form the gametes) distributes its cytoplasm. In a male, each precursor cell divides into 4 gametes with an equal share of the parent cell's cytoplasm. (While it's true that males of most species have "immature" sperm immediately after this division which must then be matured, any loss of cytoplasm from the that maturation process, which varies between males of different species, would presumably also be evenly distributed. By this I mean that all 4 gametes derived from the same parent cell would lose the same percentage of their cytoplasm.) In a female, a single haploid cell claims all the parent cell's cytoplasm, while the other 3 haploid cells are simply nuclei with an outer membrane wrapped tightly around them (no cytoplasm).
In effect, a cell with an equal share of its parent cell's cytoplasm will be small and motile, while a cell that dominated all its parent cell's cytoplasm at the expense of the "polar" cells will be large and less motile even in species where it is not entirely immotile. Although that is the end result, the formal definitions of male and female are in fact equal and winner-take-all distribution of the precursor cell's cytoplasm, respectively. The end result may be convenient for readers, but the mechanism leading to it is in reality the definition, so there has to be a way to clarify this in the Article without going over an average reader's head. The Mysterious El Willstro (talk) 03:41, 22 July 2013 (UTC)
I'm a bit concerned about these edits which substantially changed the article and introduced a theory which is seemingly the editor's own theory. From what I can tell, this isn't a widely accepted theory - the paper about it published in 2010 has only been cited 7 times. Should we remove the information about sex evolving to repair DNA per WP:FRINGE? (The theory is all over the place on Wikipedia and I've started a thread here in case anyone is interested.) Cheers SmartSE (talk) 16:14, 7 December 2013 (UTC)
Flyer22 Thanks for taking a look - I was a bit surprised that nobody else joined in that discussion, but this has been at the back of my mind since then. I'll revert the edits here, but we should probably seek consensus somewhere else like WT:BIOLOGY before removing it from all the articles affected. SmartSE (talk) 19:15, 3 April 2014 (UTC)