I revisited "the selfish gene" by Richard Dawkins and this post is in special reference to Chapter 9 in the book titled 'Battle of the sexes'. In this chapter Dawkins tries to explain the difference between what fundamentally is male and female. In the animal and plant kingdom in general the criterion for judging the sex of an individual are based on how large the sex cells are. In general the egg cells of the female are many times larger than the male sperm and this can be used as a general yardstick to interpret the differences between the sexes.
He goes on further to talk about the contribution of the males and females during reproduction. The egg essentially is the major contributor, the sperm on the other hand is just a vehicle that transfers information, it is not a good food source. All the food for the developing embryo is provided for by the egg. In primitive organisms like fungi sexual reproduction occurs between isogamous individuals those that cannot be distinguished into two sexes. The contribution of both donating individuals in such a scenario is equal. So, during evolution one of these two isogametes must have turned into a larger cell and thus cells with larger gametes would become suitable embryo support systems. This is where female exploitation started evolutionarily according to Dawkins.
A few lines from the chapter that describes evolution of sexes…
"In the days when all sex cells were interchangeable and of roughly the same size, there would have been some that just happened to be slightly bigger than others. In some respects a big isogamete would have an advantage over an average-sized one, because it would get its embryo off to a good start by giving it a large initial food supply. There might therefore have been an evolutionary trend towards larger gametes. But there was a catch. The evolution of isogametes that were larger than was strictly necessary would have opened the door to selfish exploitation. Individuals who produced smaller than average gametes would cash in, provided they could ensure that their smaller gametes fused with the extra-big ones. This could be achieved by making the small ones more mobile, and able to seek the large ones actively. The advantage to an individual producing small, rapidly moving gametes would be that he could afford to make a larger number of gametes, and therefore could potentially have more children..."
In the lines above Dawkins has beautifully pointed out how females have been exploited by males through evolution to spread their genetic information, it is interesting how selfishly genetic selection makes the females the exploited species. Males according to Dawkins are worthless fellows, and it would be good for a particular species to have more females than males. There are many more interesting aspects to this particular chapter that discusses about the advantages of being a male and the disadvantages of being a female. I have recently been visiting this blog and witnessing a battle of sexes of sorts. I hope that the battle of sexes stops, coz after all we (males and females) were all once isogamous!