I want to ask why complex animals are usual divided into sexes and are
not intersexual. I know some evolutionary explanation for advantages
of sexual reproduction against asexual, but I've never heard
explanation why sexual reproduction is not made by pairs of
intersexual individuals. I now it is popular among invertebrates why
it disappeard for vertebrates?

I will be appreciate for any help like link to a book where is an
explanation or even name of author .

On Jul 2, 12:05=A0am, Adam Skrodzki <adamskrod...@gmail.com> wrote:

I want to ask why complex animals are usual divided into sexes and are
not intersexual. I know some evolutionary explanation for advantages
of sexual reproduction against asexual, but I've never heard
explanation why sexual reproduction is not made by pairs of
intersexual individuals. I now it is popular among invertebrates why
it disappeard for vertebrates?

I will be appreciate for any help like link to a book where is an
explanation or even name of author .

I have a page on that topic:

http://alife.co.uk/essays/gender_division/

"Tim Tyler" <seemysig@googlemail.com> wrote:

http://alife.co.uk/essays/gender_division/

Nice essay, Tim.

But there are two features of animal hermaphroditism
that you ought to mention and include in the essay.
1. Some hermaphroditic animals require reciprocal coitus. But plants
don't/can't use this strategy. Instead, they broadcast the male pollen.
Why don't plants engage in coitus? My guess is because they don't
have a fixed shape. (Well, also because they are immobile).

2. Other hermaphroditic animals are serial hermaphrodites. But I don't
think that any (presumably perennial) plants are. Note that a serial
hermaphrodite is automatically sexually dimorphic and subject to
both male-combat and female-choice forms of sexual selection. My
own speculation is that serial hermaphroditism is the evolutionary
precursor of dioecious sexuality.

"Tim Tyler" <seemy...@googlemail.com> wrote:
On Jul 2, 12:05=3DA0am, Adam Skrodzki <adamskrod...@gmail.com> wrote:

I want to ask why complex animals are usual divided into sexes and are
not intersexual. I know some evolutionary explanation for advantages
of sexual reproduction against asexual, but I've never heard
explanation why sexual reproduction is not made by pairs of
intersexual individuals. I now it is popular among invertebrates why
it disappeard for vertebrates?

I will be appreciate for any help like link to a book where is an
explanation or even name of author .

I have a page on that topic:

http://alife.co.uk/essays/gender_division/

Nice essay, Tim. =A0But there are two features of animal hermaphroditism
that you ought to mention and include in the essay.
1. =A0Some hermaphroditic animals require reciprocal coitus. =A0But plant=
s
don't/can't use this strategy. =A0Instead, they broadcast the male pollen=
...
Why don't plants engage in coitus? =A0My guess is because they don't
have a fixed shape. =A0(Well, also because they are immobile).
2. =A0Other hermaphroditic animals are serial hermaphrodites. =A0But I do=
n't
think that any (presumably perennial) plants are. =A0Note that a serial
hermaphrodite is automatically sexually dimorphic and subject to
both male-combat and female-choice forms of sexual selection. =A0My
own speculation is that serial hermaphroditism is the evolutionary
precursor of dioecious sexuality.

Perplexed in Peoria wrote:
"Tim Tyler" <seemysig@googlemail.com> wrote:

http://alife.co.uk/essays/gender_division/

Nice essay, Tim.

Thanks. It needs rewriting - but it makes a basic point and has some
references.

But there are two features of animal hermaphroditism
that you ought to mention and include in the essay.
1. Some hermaphroditic animals require reciprocal coitus. But plants
don't/can't use this strategy. Instead, they broadcast the male pollen.
Why don't plants engage in coitus? My guess is because they don't
have a fixed shape. (Well, also because they are immobile).

This is true. However, how this relates to separated genders is not
immediately obvious to me. It could be implicated - but you haven't
proposed how.

2. Other hermaphroditic animals are serial hermaphrodites. But I don't
think that any (presumably perennial) plants are. Note that a serial
hermaphrodite is automatically sexually dimorphic and subject to
both male-combat and female-choice forms of sexual selection. My
own speculation is that serial hermaphroditism is the evolutionary
precursor of dioecious sexuality.

That is interesting and relevant. It weakens the argument for
the "different roles" theory a bit. However, it doesn't weaken it
terribly much. Control over development from birth provides more
in the way of options for specialisation than is present with
sequential hermaphrodism - which I understand is called "dichogamy".

See: http://en.wikipedia.org/wiki/Dichogamy

....for the story with plants.

"Tim Tyler" <seemy...@googlemail.com> wrote in messagenews:h2r72u$5lr$1@d=
arwin.ediacara.org...
Perplexed in Peoria wrote:
"Tim Tyler" <seemy...@googlemail.com> wrote:

But there are two features of animal hermaphroditism
that you ought to mention and include in the essay.
1. =A0Some hermaphroditic animals require reciprocal coitus. =A0But pl=
ants
don't/can't use this strategy. =A0Instead, they broadcast the male pol=
len.
Why don't plants engage in coitus? =A0My guess is because they don't
have a fixed shape. =A0(Well, also because they are immobile).

This is true. =A0However, how this relates to separated genders is not
immediately obvious to me. =A0It could be implicated - but you haven't
proposed how.

In the absense of reciprocal coitus protocols, non-sequential hermaphrodi=
tism
is unstable because desirable mates in terms of female choice may not
match the desirable mates for male-choice. =A0You, yourself, may find tha=
t
you are scored as a desirable male partner, but an undesirable female one=
...
Hence you may have the incentive to focus your resources on one role
over the other.

But with reciprocal coitus protocols in place, if cheating can be prevent=
ed,
there is no instability. =A0A standard argument shows that resources shou=
ld
be equally divided between the sex roles.