On Bagpipes & Blowguns
[Updated as of Aug. 31, 09 with addition on mumps, omnivory & air sac transition to diving]
Respiration in surface float feeding vs deep benthic diving
Float/surface foragers have a bagpipe-like system of breathing & vocalizing
The lungs and/or the air sac are always aerated (buoyant), nostril-up or closed
Dive/benthic foragers have a blowgun-like system of breathing & vocalizing
The lungs and/or the blood/muscle are oxygenated, nostril-down or closed
This is parallel in: [surface vs benthic foraging]
lily pad sitting frogs vs deep sub aquatic frogs
surface foraging right whales vs benthic foraging sperm whales
nostril-up wading reindeer/caribou vs nostril-down moose/muntjac
nostril-up gorillas/chimps vs nostril-down humans
Nostril-up usually indicates laryngeal/throat air sac (frog/gorilla/chimp)
Nostril-down usually indicates lack of throat sac (human/sea otter/nasalis)
Allopatric speciation in humans and chimpanzees:
Hominoid to human: From sit-float to backfloat to boat
The link from laryngeal air sac inflated sit-floating hominoids 20ma to forage diving - backfloating humans 1ma, connecting mumps, milk, weaning, hydrodynamics.
I think human laryngocoeles indicate at least a small throat air sac ancestrally (like dolphins). I doubt they had very large air sacs equal to large adult male gorilla. Human females in some areas low in Iodine can develop goiters, there may be a link, since the thyroid cartilage is adjacent. Goiters are usually mild, but can become very large. I've never heard of any non-human hominoid having a goiter. Both male and female apes have air sacs, only males may have huge ones.
We know that 3 year old Selam (dikik-1) of about 3ma had a hyoid bone (tongue base bone) indicating a laryngeal air sac, we don't know her exact species, though similar to Lucy the Apith afarensis. The hyoid is a small weak bone, usually it breaks down long before the skull does. The air sac itself doesn't last long at all. All Genus Homo hyoids found lack air sac indications, which fits with diving/submerged crouching but not much arboreal-terrestrial-swamp mix. Human ancestors after gorilla, chimps split didn't stay in wetlands, they were somewhere else, no more upright sit-floating. Most likely seashore beaches and no more thick forest canopy.
The correlation of fused tail bone and enlarged throat air sac is strong in non-quadruped tetrapods. Waterside foragers which don't dive tend to have shortened tails, whether they have air sacs or long prehensile nose-lip tools. I think our ancestors changed from sit-floating in lukewarm brackish water to backfloating in sunwarmed saltwater with face submerged, so air sacs became disadvantageous and the male beard became fuller, possibly females had slight goiters, possibly post-weaned kids had mild mumps swellings before puberty (post-milk, chewing-salivation immuno-reaction, triggered by contagious mumps
virus which might otherwise be present but non-infectious?).
More on mumps, milk, air sacs, goiter, saliva, defensins:
Gorillasw are herbivores, they get their protein from floating herbs. A mother gorilla and mother rabbit both feed their infants fecal pellets, I think deer also do this, to provide symbiotic gut bacteria and pre-digested plant material and probably some maternal hormone and immuno-defensins. Carnivores and omnivores don't do this. Instead they chew, partly swallow, then regurgitate the food for the infant (birds and wolves). Human mothers just chew and spit out some foods, Marc has noted that kissing may have begun this way ancestrally,
notably some tribes don't kiss but do alternatively rub noses, foreheads or cheeks.
Pre-birth, fetus gets food and defensins via blood.
Post-partum, newborn gets food and defensins via milk.
Human babies at weaning get food chewed by the mother, mixing her saliva containing defensins (anti-biotics & pro-biotics).
So I think that mumps and probably goiters only originated after the move from fresh-brackish wetland herbivory float-sit-foraging to increased upright submersed crouch-plucking lily seeds and invertebrates and early shallow diving.
So in Genus Homo (and maybe only partially in Genus Pan, see bushbaby spearing by female fertile chimps) there is a combined correlation of increased omnivorous nutrition, salivary defensin transmittance at weaning, improved submerged hydrodynamic form of throat area but male-only beards, reduced plant protein consumption but still Vit C dependence on fruits-plants so PTC gene still selected for, contagious but mild form of mumps after weaning but before puberty, mild form of goiter hypothyroidy in fertile females but not
pre-pubertal females or males, effect of osteoporosis in elder females(?), weaned children chewing more, activating salivary glands, but also suction feeding at puberty (raw oyster as aphrodisiac).
So, I think the early speculation that mumps correlates to the diving transition is further confirmed. The loss of the laryngeal air sac and AHV herbivory resulted in increased general diet including seafood high in Iodine and Omega 3 fatty acids, supplementing shore foods, with effects on jaw, dentition, tongue, larynx, facial hair, "childhood diseases". (Chicken pox may correlate to hair loss or sun UV or eccrine sweating protection in some way.)
(Marc V. had the idea about the goiter-hydrodynamic-diet-temperature link.)
Air sac & tidal lung breathing and buoyancy in dinosaurs, birds, crocs & snakes
"mauka to makai" Hawaiian for 'inland to oceanside' is a science/nature/marine blog
Laryngospasm & Shallow Water Blackout: When divers attempt long dives, they may run out of oxygen, which causes SWBO and associated laryngospasm (safety closure of larynx at glottis valve). The diving buddy needs to recover the unconscious diver, get them to the surface, and if the diver does not awaken within a few seconds, do the BTT: Blow (remove mask) across the eyelids, Tap the cheek, Talk to wake up the diver. The eyelids link to the trigeminal nerve, the cheeks to the facial nerve, the ears to the auditory nerve. The BTT informs the diver that oxygen conservation is completed and to breathe. Presumably in ancient human divers, sunlight in the eyes did the same thing.