Re: theme for a fantasy campaign
 

In the fourth place, trolls aren't distance runners. Which means that there is not such a strong selective pressure to keep their pelvises narrow for an efficient running gait as there is with H. sap. sapiens. Which means that large foetal craniums are not necessarily so much of a problem. Neanderthals had larger heads, and probably easier labour despite them because of wider pelvises; but it looks as though they couldn't run down an antelope. Frighten heck out of a buffalo in hand-to-horn fighting, yes. Run the buffalo to exhaustion, no.


It has long puzzled me how birds are able to get comparatively sophisticated behaviour and visual processing out of a comparatively small brain, comparisons being made to other vertebrates. Crows and some parrots seem to rival dogs in at least some behaviours (visual recognition and spatial perception, mostly — I suspect that canines have a lot more emotional depth and probably better ability to model others' behaviour). Flight has of course put them under intense pressure to lower the weight of the brain and skull — look what happened to their teeth! Very likely they have made some trade-off to expand the weight-performance envelope of their brains, but if so, what is it? And since H. sap. sapiens are also manifestly pushing on the size-performance ratio of our brains hard enough to alter pelvic anatomy I wonder why we haven't evolved notably more compact brain tissue, which birds seem to have done. Perhaps we have started, and just hadn't got very far when we invented obstetrical forcepses, the Caesarian section, and induced labour.

Re: theme for a fantasy campaign
 

Okay, got it.

Have you given any thought to how this relates to your theme? Your theme is biome competition, with each hominid species or subspecies moulded by, and its survival chained to the persistance and success of, a biome. That makes extrapolation of form and way-of-life from environment integral to your theme? Where does this fit in? Are you confident that it won't end up as another Chekov's Gun? Are you confident that it won't obscure your theme?

I don't know that passage. Where is it from?

Re: theme for a fantasy campaign
 

I don't know much about the structure of bird brains. Mammals have the laminar cortex, six cell layers thick, and massively folded up to squeeze it into the skull (in humans, anyway). Do birds have that many layers? How much of their information processing even uses the cortex?

It looks as if the song control centers are in a structure called the nidopallium that handles higher cognitive and executive functions in birds—but mammals don't have it; it corresponds most closely to part of the brainstem. There's something that looks like cortex, but it's a smaller part of the brain and doesn't seem to monopolize higher cognition. Weird.

Bill Stoddard

Re: theme for a fantasy campaign
 

Okay. I think that the only available models of vertebrate eusociality (naked mole-rats and Damaraland mole-rats) are life-insurers, but that's okay. I can do things with non-vertebrate models, and I have been known to extrapolate in my time.

Another distinction among eusocial species is between the diploid and the haplodiploid. It is the haplodiploid ones (particularly ants and bees) that were so fruitfully analysed by Hamilton (W.D. [1964], "The genetical evolution of social behaviour" (I and II), Journal of Theoretical Biology 7, 1–16 and 17–56), but those are also the ones that produce the grossly-biased sex ratios and diploid sex that is more closely related to its same-sex siblings than to its own offspring). If you have an equal sex ratio and workers of both sexes then we are probably in the diploid range, where termites and mole-rats are better models. I'll have to look carefully to see whether analogues of slave-making ants and regicidal ants make sense, but on the other hand I think it won't be quite so challenging to fathom individuals' motives.

Two or three different ones, I think. Among bees the workers feed royal jelly to a larva to grow a new sister-queen (or niece-queen). Among naked mole-rats sterile workers of the appropriate sex (brothers or sisters) fight over which of them will complete adolescence and regain his or her suppressed fertility. Among Damaraland mole-rats I think the colony tends to break up, with multiple workers seceding.

Also, eusocial animals have at least three different ways of founding a new colony. The social bees (not solitary bees, of course) send out swarms, each with one fertile member and a power of workers. Ants tend to send out fertile offspring (of both sexes) to seek mates and start small. In those examples members of the fertile castes are specially prepared for the process, so that the colony is an analogy to an organism reproducing by fission (swarming) or broadcasting gametes (nuptial flights). But among Damaraland mole-rats an individual can leave the colony, whereupon it recovers its fertility (or completes adolescence) and can seek a mate and establish a new nest. Colonies still look like families and one is not tempted to analyse them as discontiguous organisms.

I reckon that this will depend crucially on how the colonies produce new colonies, on whether the sterile worker is potentially fertile, on whether he or she is more like a somatic cell or a non-rebellious teenager.

Re: theme for a fantasy campaign
 

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Re: theme for a fantasy campaign
 

It's an attempt at getting started toward the primary goal by using an intuition pump. I'm not proposing to make it a separate goal; I'm trying to use it as a tool. I'm not enough of a mathematical population biologist to actually derived optimal strategies from equations, but I'm perfectly willing to pay attention to suggestions from people who know more than I do. That's why I raised the subject here—I was hoping to lure people like you in.

It's in the chapter of The Hobbit where Thorin & Co. stay at Rivendell.

Bill Stoddard

Re: theme for a fantasy campaign
 

Haplodiploid genetics seems unlikely in mammals. I'm not sure if it's possible. I need to think about that.

Re: theme for a fantasy campaign
 

There is a SF short story about haploid people. Your Haploid Heart by James Tiptree, Jr. .

Re: theme for a fantasy campaign
 

Vertebrate sex determination is capable of getting screwed around. Mammal males are XY and females are XX; but bird males, I believe, are ZZ and females are ZW. But I would just as soon go with diploid eusociality.

Bill Stoddard

Re: theme for a fantasy campaign
 

Certainly but I'm not sure it's very likely in mammals. I need to review some stuff about chromosomal structure and meiosis in mammal gamete formation.