Its being realistic.
No it isn't. Being realistic is to say that we don't know what the possibilities are\were, thus we cannot say that it was improbable, nor can we say that it was highly likely.
I really fail to understand why the probability issue is so hard to grasp realistically.
Let's say I have three di in my hand. Each one has a number of sides on it, but you don't know how many and each could be different. You don't know if the sides are equal or not, or if they are perpendicular to the center of mass of the di, thus each side could have different metastable conditions affecting likelyhood of balance on that face. You don't know how the di are marked.
What is the probability that I will throw a "7" eh? You can't even calculate how many different possibilities of arrangements there are that affect the calculation of the possibilities of results.
The realistic answer is "we don't know - there isn't enough information to know" and any pretense otherwise is just a logical fallacy of one kind or another.
I have asked the question why nature would have selected sex over asexual reproduction.
The answer that comes back is that if evolution was involved then there was either a survival advantage or a reproductive advantage.
And likely the later, seeing as an organism that develops a feature that allows it to cause other organisms to reproduce its offspring doesn't have to spend its resources and energy on the process, and so it has more time and energy to use causing other organisms to reproduce its offspring.
Also as noted there are bacteria that inject DNA into other bacteria, and there are snails that wage the war of the sexes at a very basic level: whoever impregnates the other gets to play the "daddy" role, they get an offspring without having to spend its resources and energy on the process, and so it has more time and energy to use causing other snails to reproduce its offspring, while the other gets to play the "mommy" role and has to spend its resources and energy to form and bear the offspring before getting back into the battle: there are life forms that exhibit intermediate stages between complete asexual reproduction and complete sexual reproduction.
{abe} see
Message 42 for some comments on the evolution stages of sex {/abe}
In a static population there is usually only one offspring per set of parents survives to adulthood.
Not at all. There are usually way more offspring produced in the course of reproductive life of the parents, even for ones that only bare 1 young per pregnancy (and which is not the norm eh?).
There are usually way more offspring than there are parents, whether the population is static, increasing or decreasing. What controls the population size is natural selection, not birth rate.
... asexual reproduction is twice as fast as sexual reproduction, ...
You are comparing apples and oranges.
Consider a process whereby you would have to split down the middle and progressively fill in the gap with copies of cells from the right side onto the left side and from the left side onto the right side until the two halves could seperate into two new individuals. You would need much more cell division -- PLUS cell migration to the appropriate place -- than occurs in the development of a fetus, and based on time for that cell division ALONE to take place it would take much longer.
Then you have long periods of gestation, ...
Not for the male. The male has zero time for gestation and rarely needs more than a few minutes to be ready for the next mating.
This also means that the males have time and energy to provide defense for their offspring (and any females that are producing them), so that rather than a whole population of individuals incapacitated by dividing down the middle for over a year or so, you have some to ward off predators so the whole population can survive.
How, then, is sexual reproduction less costly than asexual propagation?
For the same reason that having specialized organs within an organism is less costly than having all the cells capable of doing all the jobs: specialization and sharing.
Think of a population of a sexual species as a number of super organisms, where individuals are specialized organs within a {population body} -- it is essentially "asexual" in its reproduction of new {population bodies} of the same species, and the {population body} divides when conditions are right, without input from other {species}.
(hmm. this applies to the
Is death a product of evolution too ... )
Enjoy.
Edited by RAZD, : typo, added ref to Lithodid_Man's excellent post
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