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Quote by: CrochityOldMan  I have wondered about how sex evolved for quite some time, if anyone could shed some light on this issue it would be appreciated, because it seems to be a legitament problem. |
And it is a very good question. But your thinking is quite limited. You first try to limit it to mammals and then you talk about plants that don't reproduce in any similar way. By the way, not all plants have both sexes.
However, it is true that it is a perplexing question and the answer is still being sought. In asexual an asexual species, every individual produces offspring, even among the few species of asexual animals. However, in sexually reproducing species, only half bear offspring. It can easily be seen that the asexually reproducing species seems to have a distinct advantage. When other factors are taken into account, it is apparent the sexual reproduction is very expensive. And yet, only a small percentage of vertebrates reproduce asexually. There must be some advantage in sex.
Relatively recently biologists have been finding evidence for a surprising hypothesis: sex fights helps organisms shed parasites. The hypothesis is known as the Red Queen Hypothesis. You can find information about this hypothesis at the following sites:
Evolution: Library: The Red Queen Red Queen Hypothesis
A second hypothesis (and slightly older one) is also known as the Red Queen Hypothesis. It involves the evolutionary arms race between predator and prey. You can get more information on this hypothesis at the second url above and at the following:
Red Queen - Wikipedia, the free encyclopedia
There are lots of sites that have information that will be helpful in informing you. Just Google "red queen hypothesis" and check out a few for information on both hypotheses.
You might also read Ridley, Matt.
The Red Queen. 1995. Penguin Books, New York. 405 pages. ISBN 0140245480
That's the U.S. paperback. The book was first published in Great Britain in 1993, and in the U.S. by Macmillan Publishing in 1994.
Happy learning.