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Topic: A math problem
Replies: 6   Last Post: Mar 15, 2013 8:06 PM

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David Bernier

Posts: 3,892
Registered: 12/13/04
Re: A math problem
Posted: Mar 15, 2013 4:34 PM
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On 03/15/2013 01:07 AM, Martin Phipps wrote:
> Let's imagine that we are the grand designers of life. Animal life as
> we know it consists of two sexes, male and female. This is,
> presumably, the most efficient way of mixing the chromosomes amongst
> different creatures, one male and one female, so that the offsping are
> immediately different from either of the parent, thus speeding the
> process of evolution.
> While this may be the most efficient way to mix chromosomes, one might
> ask if it were the only way. What if instead of two sexes, one with
> two X chromosomes and the other with an X and a Y chromosome, we
> instead had various sexes due to a combination of chromosomes. The
> simplest situation to imagine would involve two chromosome pairs
> instead of one: for instance we could imagine that to be male would
> require one to not only have an X and a Y chomosome but also a W and a
> Z chromosome whereas females would have either two X choromosomes or
> two W chromosomes.
> Well, did the math: the first generation would have males with the
> XYWZ chromosomes breeding with females with either XXWW, XXWZ or XYWW
> chromosomes. Alas if males breed with females with either Y or Z
> chromosomes then they can get offspring with two Y chromosomes or two
> Z chromosomes. These offspring would be either male (YYWZ or XYZZ) or
> female (YYWW or XXZZ).
> It gets even more complicated when all the different types of males
> breed with all the different types of females. For example, the males
> with two Y chromosomes or two Z chromosomes breed with females at
> random then they have mostly males. Indeed, I calculate if there were
> an equal number of such males and a equal number of regular males as
> well as an equal number of females with either two Y chromosomes or
> two Z chromosomes and females with neither a Y chromosome or a Z
> chromosome then what you would get, all things otherwise being equal,
> is an equal number of males in females born as a result.
> Basically then I just considered two generations and already there's
> an indication that there would eventually be an equal number of males
> and females. I'm wondering if this is inevitable. I mean, if you
> separate people into male in female based on their chromossome makeup
> are you eventually going to get a 50% male and 50% female population?
> It isn't really a biology problem: it's a math problem and maybe it
> has already been effectively solved elsewhere.
> Martin

Fungi can have many genders:
"Scientists discover why fungi have 36,000 sexes"
(and humans not)

The Independent, 15 September 1999:


David Bernier

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