Re: Origin of female

On Mon, 10 Dec 2007 23:27:38 GMT, John Harshman
<jharshman.diespamdie@xxxxxxxxxxx> wrote:

r norman wrote:

On Mon, 10 Dec 2007 03:11:42 GMT, John Harshman
<jharshman.diespamdie@xxxxxxxxxxx> wrote:


r norman wrote:


On Sun, 09 Dec 2007 16:26:14 -0600, Ferrous Patella
<FerrousPatella@xxxxxxxxxxx> wrote:



Lauren <laurenh@xxxxxxxxxxxx> wrote in news:d8f1eb29-4f63-4644-88c4-
898f222cb9cc@xxxxxxxxxxxxxxxxxxxxxxxxxxxx:



Not so long ago I read a post in one of the threads in this group
giving an explanation how the original cells of abiogenesis split to
form what is now known as the first female. I can not find it again.
Will someone please help me find it? If the original poster sees this,
please help me to find it. If someone can put me on track to find
something similar, I shall be very grateful.
Tnx,
Lauren


I think females are like atheists. The concept would not exist if it
weren't for males/theists. Life was happily reproducing before genders came
along. Even sexual recombination was possible without sexual dimorphism
(see earthworms). So I see the whole baby-carrying state as being the
default mode (again like atheism) until someone comes up with this bizarre
divisive concept to mess with our heads.


Sorry about the blank post ---

You are sort of wrong about earthworms. They are fully sexual, with
male and female sex organs and produce fully functional sperm and
eggs. It is just that they, like very many other organisms,
especially plants, have single individuals that carry both male and
female parts. Some the individual is not sexually dimorphic, but the
organs or distinctly sexual in morph. Still, they have aspects that
are distinctly male and other aspects that are distinctly female.

There are, indeed, eukaryotes like Chlamydia who go through full
sexual reproduction: fertilization (or, more technically, syngamy) and
meiosis, with no morphological distinction at all between different
sexes (although there is a biochemical-molecular biological
distinction between mating groups).

But more fundamentally, as you indeed suggest, the real question is
not the origin of 'female' but rather the origin of 'male'.


I wouldn't say that. It's more the origin of distinct gender
reproductive cells, one (the egg/megaspore/whatever) specialized to
provide nutrients to an embryo and the other (the
sperm/pollen/microspore) specialized to move around and find eggs. You
don't get one without the other (you can lose the male, but all such
cases are secondary loss as far as I know).


I must protest. In cases of syngamy, where the two gametes seem
indistinguishable, they each look like and act like the egg form
stuffed with appropriate nutrients and with all the organelles and
cytoplasmic structures necessary for complete development.

I wouldn't say that. I would say that they each look like half an egg
form stuffed with half the necessary nutrients, and they look rather
like sperm too, in having some means of motility. Undifferentiated
gametes are neither sperm nor eggs.

The sperm
is lacking in all of that. Two eggs can fertilize each other with the
development of a new diploid individual; two sperm cannot.

And I disagree. When gametes are differentiated, two eggs can't
fertilize each other as far as I know. If you know of any species in
which this does happen, you may disabuse me.

I would guess that sexual reproduction first arose through the
development of alternating haploid and diploid states, alternating
occurrences of syngamy and meiosis within the complete life cycle.
That is true "sexual reproduction" without any sign of separate sexes.

I agree.

Only later did the differentiation of gametes into nutritive and
developmental vs. motile occur which probably happened with the
specialization of the sperm from what was originally a nutritive and
developmental precursor, that is, the development of "male".

Now here I disagree. I would bet that both gamete types would have had
to evolve in tandem. I would envision two mating types starting to
specialize, with one getting a bit smaller, the better to be mobile, and
the other getting a bit larger in necessary compensation (if we want a
viable zygote, thus becoming a bit less mobile.

And only
later still did the differentiation occur to produce an organ to
produce sperm (testes or antheridium) separate from one to produce
eggs (ovary or archegonium). The final step is a whole individual
that is exclusively male vs. one exclusively female.

I see no a priori reason to suppose that dioecy is necessarily
primitive. I can see two mating types beginning to specialize for
individual roles as being at least as sensible, a priori. And I see no
reason why the two (or more?) independent inventions of male/female
might not have followed different pathways. The best test is how it maps
onto the tree, and offfhand I don't know how that test would come out.

My error in part: two eggs _could_ conceptually fertilize each other
because each has the full complement of stuff necessary to initiate
successful development and maintain full cell function.

On the question of isogamy, I don't know how you can think of two
isogametes as each having only "half" the necessary equipment. I
can't see much difference, if there is any at all, between one of the
two isogametes and a primitive ovum other than a trivial loss of a
flagellum (or two). Note: many eggs do not have a large nutrient
supply, not more than you would find in an isogamete anyway.

The virtual universal prevalence of dioecious types leads me to
believe that it is the primitive type. Certainly it is in plants. I
don't know about the developmental biology of sex organs throughout
the animal kingdom (I am too lazy to look it up), but certainly in
vertebrates including humans, we start with the full capability to
produce both types of sex organs. That is, we are primitively (in the
developmental sense, not the evolutionary) dioecious but only allow
one set to mature. And all those examples of animals who switch sex
indicate that they have both capabilities inherent in their genetic
composition.

But it seems to me that we are searching for very fine points to
disagree about so we can argue, agreeing on everything essential. No
mind, that is the game and I can keep it up another round or two. You
have the stamina to go after UC, for example, thousands of
exchanges.


.

Relevant Pages

  • Re: Origin of female
    ... form what is now known as the first female. ... sperm/pollen/microspore) specialized to move around and find eggs. ... like sperm too, in having some means of motility. ... produce both types of sex organs. ...
    (talk.origins)
  • Re: Origin of female
    ... form what is now known as the first female. ... distinction between mating groups). ... sperm/pollen/microspore) specialized to move around and find eggs. ... like sperm too, in having some means of motility. ...
    (talk.origins)
  • Re: Origin of female
    ... form what is now known as the first female. ... sperm/pollen/microspore) specialized to move around and find eggs. ... like sperm too, in having some means of motility. ... produce both types of sex organs. ...
    (talk.origins)
  • 00 de puliot si sperma de A$kie
    ... Are male eggs and female sperm on the horizon? ... and female cells into sperm. ...
    (soc.culture.romanian)
  • Re: Origin of female
    ... form what is now known as the first female. ... sperm/pollen/microspore) specialized to move around and find eggs. ... like sperm too, in having some means of motility. ... don't know about the developmental biology of sex organs throughout ...
    (talk.origins)