Re: A Question about Sex

On Dec 21, 8:59 am, Treus <treusd...@xxxxxxxxx> wrote:
What process of natural selection acting over time on an originally
asexual population will produce a first generation of sexually
differentiated adults?

Let's teach you the facts of life.

In the beginning, well, maybe there was no
beginning because this process may have
started very near the origins of life, ... so
maybe very near the beginning, life might
not have had the ability to share genetic information
between organisms.

This produced a severe disadvantage to the
species, not allowing it to adapt to new
changes very rapidly.

Think about why this is so.

Say you had an organism with only 5 genes.
(This is very simplistic.) G1, G2, G3, G4, and G5.

Now G1 has a possible mutation that could generate
a severe benefit to the species - G1A.

Gene 3 (G3) also has another possible mutation that
could generate a severe benefit to the species - G3A.

G1A happens in one organism through random
mutation. How much time would it take to produce
an organism with both G1A and G3A in it? What
would need to happen is that all of the descendants
of the G1A mutant would have to gradually come into
existance and die off, and keep reproducing, until
one of them randomly again produced the G3A gene
by random chance.

What happens if you have to sets of organisms, one
with the G1A beneficial gene, the other with the G3A
gene, and not genetic recombination. Both populations
of organisms are competing with each other, but neither
could take advantage of holding both sets of beneficial
genes, until each of the populations were able to acquire
them through random mutation again. It could be thousands
of even millions of years before the mutation combination
could appear depending on the generation time of the
organism.

If genes are shared between organisms of a species,
however, the net result is that the G1A G2 G3A G4 G5
superorganism could come into existance in only a few
generations. The species could thus more rapidly
adapt, because random beneficial mutations in
several genes existant in different organisms of
a species, and not simply a single one in an
individual member of the species. This thus enables
a species to more rapidly adapt, without exposing
the genes as much to the more hazardous aspects of
random mutation, which can also have destructive
effects. This also has the advantage over cellular
fission alone and reproduction using the genetic
material of one parent only in that bad genes could
not piggyback off of good genes. The recombination
in the next generation might produce organisms
that might also have bad genes but miss the good
ones. They would have a chance of dying off more
quickly and could not continue to propagate because
of other good ones in the entire gene set.

That is why the sharing of genetic material exists.
Even bacteria do it. It is called 'plasmids'.

Many worms and other more simple macroscopic
multicellular organisms do share genetic material,
but do not differentiate the sexes. They are
hermaphrodites. (They have both male and
female sex organs.) When they reproduce,
they can combine both organs with the opposite
organs on the other organism they are having
sex with using both eggs and sperm.

Possibly slightly later on, however, something
called sexual differentiation occured, along
with sexual dimorphism. Some individuals
within the species had only male organs,
whereas others had only female organs.
This allowed certain members of the
species to specialize in the creation of
new organisms, and others to specialize
in other ways (sometimes body strength
or something else). This however
has varied a lot from species to species
throughout the animal kingdom.

What caused this genetically throughout
the animal kingdom also varied. Birds with two
of the same type of sex chromosomes produce
males, and birds with two different types of
sex chromosomes produce females
(the opposite of mammals).

There you have it. Those are the facts of
life.





.

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