another look at Aslan sex ratios

[Ishmael]

in the past, I've puzzled over Aslan sex ratios of 3 females to every male.
I had looked at this as the secondary sex ratio where the natal and primary sex ratios were a Fisher normal 1:1.

There a comment in another forum led me to consider the wood lemming, which has a natal sex ratio of approximately 3:1.

a strange consequence of such a sex ratio may be the evolutionary stability of such when faced with extreme in-breeding.

The evolutionary stability of the female-biased sex ratio observed in the wood lemming (Myopus schisticolor) is discussed. The hypothesis analysed is that the skewed sex ratio is maintained as a result of partial and/or recurrent inbreeding. Fredga et al. (1976, 1977) have suggested that an X-linked mutant gene, X, affects the male-determining action of the Y chromosome, thus converting some XY individuals into females. By a mechanism of selective non-disjunction in the foetal ovary only X-carrying eggs are produced. In particular the stability of that genetic mechanism (or the X chromosome) is analysed by considering the introduction of a "suppressing" sex-linked mutant gene Y. Several deterministic simulation models assuming father-daughter and/or brother-sister matings have been developed and analysed. It is concluded that in the case of extremely strong inbreeding, the hypothesised genetic mechanism may, as a result, be evolutionarily stable. Interpreting field observations on microtine rodents in general it is concluded that only a few species are likely to experience such extreme cases of inbreeding. The wood lemming and the related collared lemming (Dicrostonyx troquatus), another case which seems to have XY-females, are likely to exhibit sufficiently strong inbreeding.

From a paper titled "On the evolutionary stability of the female-biased sex ratio in the wood lemming (Myopus schisticolor): the effect of inbreeding." by J Maynard Smith(1) and N Chr Stenseth(1)

(1) School of Biological Sciences, University of Sussex, Falmer, Brighton, Sussex BN1 9QG, England
(2) Zoological Institute, University of Oslo, P.O. Box 1050, Blindern, Oslo 3, Norway

There are other papers that describe a similar hypothesis.

Sure, the population dynamics are different between lemmings, a prey animal. and the Aslan, an apex predator, but given the importance of existing in a resource poor ecology and the necessity for periodic migrations ( matching ihatei fleets) as resources grow even more scarce might make the Aslan more interesting then being just samurai in lion suits.

 

[rancke]

Sure, the population dynamics are different between lemmings, a prey animal. and the Aslan, an apex predator, but given the importance of existing in a resource poor ecology and the necessity for periodic migrations ( matching ihatei fleets) as resources grow even more scarce might make the Aslan more interesting then being just samurai in lion suits.

You're not going to get migrations with the Traveller costs of interstellar transportation. I once calculated that an Aslan clan can afford to outfit somewhere between 1 and 2% of each new generation as ihatei. And it's by no means certain that they actually do so. The adventure in Aslan features a clan of billions that outfitted an ihatei expedition of 100,000 for the first time in two generations.


Hans

 

[LeperColony]

Given the high cost of travel and the astronomical cost of ships, it would be far cheaper for Aslan clans to simply buy land outside the hierate and ship ihatei in low berth.

 

[RandyB]

You're not going to get migrations with the Traveller costs of interstellar transportation. I once calculated that an Aslan clan can afford to outfit somewhere between 1 and 2% of each new generation as ihatei. And it's by no means certain that they actually do so. The adventure in Aslan features a clan of billions that outfitted an ihatei expedition of 100,000 for the first time in two generations.


Hans

1. Never underestimate the ability of cultural tradition to override pure economics. :CoW:

2. Natal sex ratios would have developed during pre-spaceflight evolutionary periods, when the economic cost of migration was low, relatively speaking.

 

[rancke]

1. Never underestimate the ability of cultural tradition to override pure economics. :CoW:

Actually, nothing is able to override pure economics. Somebody has to pay. Culture can explain why someone spends resources he doesn't have to spend; it can't explain how anyone can spend resources he doesn't have.

2. Natal sex ratios would have developed during pre-spaceflight evolutionary periods, when the economic cost of migration was low, relatively speaking.

Sure, no argument there. But when the economic cost of migration rose sharply, culture had to adapt. Those who could adapt survived, those who couldn't perished.


Hans

 

[Ishmael]

I think its more interesting to consider how this might affect their biological and cultural history.

Why would they have evolved genetics that are stable during periods of massive inbreeding? It would greatly mitigated any negative Allee effects that might arise from excessively low population densities. This allows for a lower critical population density and extinction threshold.

Clearly, the Aslan experienced periods of huge swings in population with near extinction levels bring local population densities to levels that would not have been survivable with-out massive inbreeding. Perhaps they have similarities to arctic stoats in that their prey may have had large periods of growth and collapse analogous to lemmings with populations and densities of the Aslan following as per Lotka–Volterra equations.

How might this situation have influenced the Aslan cultural history?
What sort of environments would gave promoted this on their world?
How would they have adapted after learning to control their own population dynamics?

or else the natal ratio is a 1:1 sex ratio, more like Fisher describes, even though it would then follow that males have an abnormally high mortality rate in order to maintain the 3:1 ratio that is canon.

 

[RandyB]

Actually, nothing is able to override pure economics. Somebody has to pay. Culture can explain why someone spends resources he doesn't have to spend; it can't explain how anyone can spend resources he doesn't have.

I meant the first; the second is clearly self-evident (which is why you had to say it. )

Sure, no argument there. But when the economic cost of migration rose sharply, culture had to adapt. Those who could adapt survived, those who couldn't perished.


Hans

Behavioral adaptation, sure. But I don't think the natal sex ratio would change (i.e. the biological evidence on Earth isn't, to my knowledge, conclusive; extrapolating to extraterrestrial species is speculation at best) without some form of bioengineering.

 

[rancke]

I meant the first; the second is clearly self-evident (which is why you had to say it. )

But that raises the question of how much cultural imperatives would force a clan lord to spend on outfitting ihatei expeditions. I submit that it would be as little as he could get away with. For someone engaged in a 4,000 man Diplomacy game there are far more useful things to spend his resources on than sending his subjects far, far away.

The 1 to 2% I mentioned earlier is based on an assumed 10% of a military budget of 10% of GWP. That is, an average of 1% of GWP goes to outfit ihatei expeditions.

Behavioral adaptation, sure. But I don't think the natal sex ratio would change (i.e. the biological evidence on Earth isn't, to my knowledge, conclusive; extrapolating to extraterrestrial species is speculation at best) without some form of bioengineering.

Indeed. I would go so far as to say that that went without saying.


Hans

 

[RandyB]

But that raises the question of how much cultural imperatives would force a clan lord to spend on outfitting ihatei expeditions. I submit that it would be as little as he could get away with. For someone engaged in a 4,000 man Diplomacy game there are far more useful things to spend his resources on than sending his subjects far, far away.

Generally true. Unless outfitting and sending such expeditions somehow granted dominance in the Great Game of Clans. Then, it's an investment in status. The task then becomes finding the sweet spot of gaining as much status as possible without bankrupting yourself.

 

[Ishmael]

Behavioral adaptation, sure. But I don't think the natal sex ratio would change (i.e. the biological evidence on Earth isn't, to my knowledge, conclusive; extrapolating to extraterrestrial species is speculation at best) without some form of bioengineering.

Indeed. I would go so far as to say that that went without saying.

so, out of curiousity, which natal sex ratio do people use?

3:1 ?
Then people would have to describe how and why such exist and its effect on the culture and behvaiour on the Aslan. A RW example exists as to how and why it might work down on the genetic level, but this may not mesh smoothly with what has already been written in canon.

1:1 ?
Then people would have to explain how and why 2/3 of the male population have effectively ceased to exist sometime after conception, but this may not mesh smoothly with what has already been written in canon.

Even though they are alien, they can eat the same foods as humans which strongly suggests that they are biologically compatible with humans, perhaps having similar/same enzymes and proteins which strongly imply similar/compatible dna sequences.
.

 

[aramis]

Actually, many species have uneven birth ratios. Even a few mammal species do.

Gender selection on Earth is often not genetic - amongst mammals, it's universally XY/XX chromosomal. In avians, it's ZW/ZZ determinant - where the ZZ is male. In a few species, it's XX/X0. A number of species, it's temperature dependent. A handful of species are larval pheromone exposure dependent. And a few are haploid - X_ is male, XX is female, noting that males are generated asexually, while females are sexually generated.

So, it could be set so that male determination is triggered by too high a maternal exposure to female pheromonal concentrations triggering a hormone release that triggers maleness. Or, it could be that there's internal abortion of males when male pheromonal concentrations of males are too high, but there's a natural conception ratio of 1:1. Or it could be that they use an x'y' system, but the ovum penetration chemical is on the x' and y' chromosomes, and is weaker on the y'...

Lots of ways to generate the ratio that require little to no fudging of the science.

 

[RandyB]

so, out of curiousity, which natal sex ratio do people use?

3:1 ?
Then people would have to describe how and why such exist and its effect on the culture and behvaiour on the Aslan. A RW example exists as to how and why it might work down on the genetic level, but this may not mesh smoothly with what has already been written in canon.

1:1 ?
Then people would have to explain how and why 2/3 of the male population have effectively ceased to exist sometime after conception, but this may not mesh smoothly with what has already been written in canon.

Even though they are alien, they can eat the same foods as humans which strongly suggests that they are biologically compatible with humans, perhaps having similar/same enzymes and proteins which strongly imply similar/compatible dna sequences.
.

I don't think there's a canonical answer. I was commenting on the suggested 3:1 ratio. And I have reservations as to whether that ratio would reasonably produce the canonical Aslan culture.

 

[Ishmael]

how many of those would be considered an evolutionary stable strategy?

There is no mention of temperature controlled selection, nor of parasitic controlled selection ( would these be considered stable strategies? ).
And then there has been no explanation as to why they would have deviated from Fisher's 1:1 ratio from 2 sex species.

not that much has been written about female Aslan. This mystifies me considering that they effectively hold control of technology and economics if Aslan culture in addition to being 75% of the poulation.

in any case, this is just an idea based on RW science to make them less rubber-suited-human-like.

 

[Ishmael]

I don't think there's a canonical answer. I was commenting on the suggested 3:1 ratio. And I have reservations as to whether that ratio would reasonably produce the canonical Aslan culture.

and yet the 3:1 ratio is canon (although it is never specified as to whether it is the primary, or secondary, or tertiary sex ratio that is mentioned ).
it seems to me that the biology of Aslan may be at odds with the culture of Aslan.

 

[RandyB]

and yet the 3:1 ratio is canon (although it is never specified as to whether it is the primary, or secondary, or tertiary sex ratio that is mentioned ).
it seems to me that the biology of Aslan may be at odds with the culture of Aslan.

I missed the canonicity of the ratio earlier. IMO, an early CT writer (whomever it was) misapplied the social and cultural implications of that many females.

 

[Dagrill]

Given the high cost of travel and the astronomical cost of ships, it would be far cheaper for Aslan clans to simply buy land outside the hierate and ship ihatei in low berth.

From Rebellion Source Book page 61 this is what they do

Regards

David

 

[rancke]

Given the high cost of travel and the astronomical cost of ships, it would be far cheaper for Aslan clans to simply buy land outside the hierate and ship ihatei in low berth.

They still have to pay the high cost of transportation. It's doable for destinations not too far from the clan holdings. But destinations not too far from clan holdings tend to belong to other clans already.


Hans

 

[FreeTrav]

so, out of curiousity, which natal sex ratio do people use?

3:1 ?
Then people would have to describe how and why such exist and its effect on the culture and behvaiour on the Aslan. A RW example exists as to how and why it might work down on the genetic level, but this may not mesh smoothly with what has already been written in canon.

1:1 ?
Then people would have to explain how and why 2/3 of the male population have effectively ceased to exist sometime after conception, but this may not mesh smoothly with what has already been written in canon.

Even though they are alien, they can eat the same foods as humans which strongly suggests that they are biologically compatible with humans, perhaps having similar/same enzymes and proteins which strongly imply similar/compatible dna sequences.
.

I'd gone with the 1:1 ratio at conception, but fudged the development subsequent to that (I also posted this in The Other Forum where this question is being discussed):

Sex determination in Aslan is a function of TWO chromosome-equivalent pairs. X and Y have the normal meanings; the other chromosome-equivalent pair carries A or B.

If an Aslan gets either two copies of A or two copies of B (i.e., AA or BB), the X/Y combination determines how the fetus will develop - XX, female; XY, male. However, if one copy of each appears in a genetic male (AB), they interact and cause a condition similar to CAIS (Complete Androgen Insensitivity Syndrome) in humans, rendering the 'female' sterile. There is no effect on a genetic female; genetic females are all fertile barring some other condition affecting fertility.

So, XX/anything is normal female; XY/AB is CAIS-equivalent male (genetic male, social/developmental female), and XY/AA and XY/BB are both normal male.

The result of this is an apparent female:male ratio of 3:1, but only 2/3 of the females (XX/*) are fertile. On examination of an Aslan population's chromosome-equivalent distribution, the more "expected" 1:1 ratio of XX:XY will be found.

One can postulate that XY/AB females are somehow racially beneficial; perhaps they proved more capable of managing the transition from a hunter/gatherer nomadic society to an agricultural/technological one.

 

[Ref00000]

wouldn't the higher death-rate in males affect this, somewhat?

and the above post from FreeTrav, are you proposing a sub-caste of biological males who function as females, or hermaphrodites?

 

[FreeTrav]

Definitely not hermaphrodites. In every way except genetic analysis, they are female, but reproductively sterile. Do an autopsy on one, and you'll find [nonfunctional] ovaries, a uterus, external genitalia indistinguishable from those of a genetic female, development of mammary glands and associated subcutaneous lipid deposits, and so on. So, I'd call them genetic males, not biological males, functioning as (and physically indistinguishable from) females.

Socially, once Aslan get to the point that they can do that sort of genetic analysis, I could see there being some problems, given how strongly the idea of sex roles pervades their society - but I could also see them ultimately making a societal decision to, in essence, say "screw it; it takes genetic analysis to tell these ... things ... from normal females, they've been functioning as females for all of recorded history; they have a useful place in society, we'll never cleanse them completely, and trying'd mean infanticide of one-quarter of the population. Leave well enough alone." Not to mention that the medical and social-science roles that would discover this would both be heavily
female-dominated.