Why Sexual reproduction is more popular
Adam Skrodzki
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 ;).
Best Regards
Adam
Tim Tyler
I have a page on that topic:
http://alife.co.uk/essays/gender_division/
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|im |yler http://timtyler.org/ t...@tt1lock.org Remove lock to
reply.
Perplexed in Peoria
> 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/
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
> "Tim Tyler" <seem...@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.
Adam Skrodzki
essay and started to read it :).
Thank you once more.
Vu Ngo
wrote:
> "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/
>
> that you ought to mention and include in the essay.
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
> own speculation is that serial hermaphroditism is the evolutionary
> precursor of dioecious sexuality.
thank
Perplexed in Peoria
> Perplexed in Peoria wrote:
>> "Tim Tyler" <seem...@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.
In the absense of reciprocal coitus protocols, non-sequential hermaphroditism
is unstable because desirable mates in terms of female choice may not
match the desirable mates for male-choice. You, yourself, may find that
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 prevented,
there is no instability. A standard argument shows that resources should
be equally divided between the sex roles.
>> 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.
Thx for the link. My ignorance of botany is again revealed. I had been
thinking in terms of plants expressing female one year and male the next.
I hadn't even considered that the two sexes might be expressed sequentially
in the same flower.
Tim Tyler
wrote:
> "Tim Tyler" <seemy...@googlemail.com> wrote in messagenews:h2r72u$5lr$1@d=
arwin.ediacara.org...
> > Perplexed in Peoria 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.
I had to look up what "reciprocal coitus" meant: in unilateral
mating, only one critter inseminates the other, while in
reciprocal mating, both critters inseminate each other.
I am still not sure I understand the argument. However, the
conclusion seems to involve some animals getting to use
reciprocal coitus sometimes - and those animals being less
likely to have divided genders.
It seems fair enough - but I don't know enough about it to say very
much. I don't know how common reciprocal coitus is. Also, I think
we are supposed to assume that females can usually decide when they
get fertilised - since they are in charge of their own plumbing.
Just because some sperm is delivered, that doesn't mean the females
have to use it. For example, they could do something like what
ducks do - turn their reproductive tract into a maze of twisty
passages for losing bad sperm in.
"Duck genitals locked in arms race"
- http://www.cosmosmagazine.com/node/1277