Re: Statutory rape question?

mkkuhner@xxxxxxxxxxxxxxxxxxxxxxxxx (Mary K. Kuhner) wrote:

In any case many sexual organisms make no attempt to avoid inbreeding,
even selfing. Obligately selfing plants are common. Parthenogenic
reptiles, amphibians, and insects are not rare. And there's a mite
(so I am told) which only has sibling mating, because mating takes
place before the mating individuals are born. So even if sex arose
to prevent inbreeding, inbreeding avoidance is clearly not obligatory
for all species.

Drawing on Dawkins (Ancestor's Tale) and Zimmer (Parasite Rex): it'd be
tempting for a female to go parthenogenetic, because more genes are passed on,
and as you say this in fact happens. But apparently it usually doesn't
spread; Dawkins says that in general, if you look at the Tree of Life,
parthenogenetic species are isolated twigs, suggesting they don't become
ancestors of lots of species, but go extinct when parasites catch up to them.
He also noted there's one exception, a whole family of tiny marine species,
which baffled him; I'd guess they've hit upon some killer defense against
parasites, like a protective shell or something.

Zimmer said there are species which switch between sex and parthenogenesis,
and a species (snails in Australia?) were looked at and found to be more
parthenogenetic in an area with lower parasite load. I don't remember if they
did an experiment of adding parasites to see if the sex increased.

It is also formally possible that there is no innate tendency to
avoid inbreeding, and that the common cultural avoidance has arisen
for purely cultural reasons.

Formally; it seems like evidence from kibbutzim and Chinese families strongly
indicates an aversion to mating with others who were too close in early
childhood. These give cases where the culture would have supported mating,
but the children avoid each other.

Critters do really odd things that resist simple evolutionary
explanations, as I learned as a fairly young child when my
aquarium fish ate all of their own offspring. So I am cautious
about assigning evolutionary explanations to behaviors.

Well, that one seems simple enough -- if the fish would normally disperse
enough so there's no need to waste resources on offspring recognition.

-xx- Damien X-)
.

Relevant Pages

  • Re: The "fuel" of evolution
    ... >>Consider the case of a sexual species into which a parthenogenic female is ... Assuming that she and her immediate offspring ... Unless of course the mutation that causes parthenogenesis simultaneously ... Sexuality survives by default. ...
    (sci.bio.evolution)
  • Re: Two of a kind.
    ... asexual reproduction would be the means of propagation. ... You'll be happy to learn that there are hundreds of species of ... I wasn't aware that these species were mammals. ... I wonder if he'll accept parthenogenesis induced through experiment in lab ...
    (talk.origins)
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