Hi, Dennis.
Can you please use the qs dBCodes for quotes. Click on the peek button at the bottom of this message to see how I make this quote box:
dennis780 writes:
Both mutations still have to occur at the same time. If the female lays eggs, but no males have developed, no fertilization. If male developes but no eggs, nothing to fertilize. Same problem.
Let me take you through the evolution of sex, from the beginning, to the end.
Single-celled organisms can reproduce sexually by fusing with another member of their species, or injecting copies of their DNA in another. This requires only one organism to develop a new trait, because only one of them need initiate the transfer: all that is required of the other is that it doesn’t stop the transfer. This could lead directly to two sexes, or it could result in a population full of cells that can initiate transfer.
As organisms became more complex (e.g. animals), different cells within the body of the organism become specialized to take on different functions. Some cells within an individual retain the ability to merge with other cells. These cells are referred to as gametes. At first, there may only be one kind of gamete.
Some individuals in a population may produce gametes that can initiate transfer. Some individuals’ gametes may lose this ability (or may never have had it), and are therefore only capable of merging when another gamete initiates transfer, but may evolve means to promote transfer. So, some individuals will produce gametes that can
initiate transfer, and others will produce gametes that can
accept transfer. This is the beginning of bisexuality.
Originally, the gametes with the ability to initiate the transfer (we’ll call them sperm) would be able to detect and swim to female gametes (which we’ll call eggs). However, the organism will tend to retain traits that make the sperm’s job easier, because it will increase reproduction, and will thus lead to higher numbers of organisms that have those traits.
So, the male might gain behaviors that bring the sperm closer to the egg (e.g.
amplexus), or might gain morphological adaptations that allow him to place the sperm
inside the female while the egg is still inside her. Again, this only requires one sex to develop a new trait or organ: all that is required of the female is that she not prevent it from happening. Eventually, we would expect the female to be altered in some way to help facilitate the male’s new mode of sex, but it would not require her to be altered significantly at the exact same moment as the male is altered.
Does this make it clear what Dr Adequate was saying?
Basically, sex predates sexual organs (or
any organs, for that matter) by a long time, and sexual organs are later adaptations that increase the rate of success of sex.
Also, each step can be explained by just some members of the population (comprising one sex) mutating away from the initial condition, and other members of the population (the other sex) evolving in response to the first group. This leap-frogging style of evolution is referred to as coevolution.
Edited by Bluejay, : Typography.
-Bluejay (a.k.a. Mantis, Thylacosmilus)
Darwin loves you.
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