Discussion on hypothesized ancestral human cyclical ARC dive-foraging

Review of above article on mysticete whale with osteosclerosis.
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[Ancient benthivorous baleen whale (and tapir) from US Virginia coast, with osteosclerotic (enlarged dense bones, parallel to, but more distinct than, ancestral humans at coasts) and mandible injury. The authors speculate that many oligocene whales may have fed on benthic (bottom) foods, and baleen (mouth whiskers) may have developed there, and later whales became more pelagic and surface foraging, losing their dense ribs like today's whales. My speculation is that all early whales had dense bones (cf Indohyus, walrus, manatee, H. erectus costa) to counter buoyancy from air held in lungs while foraging in shallow benthic zones of coasts, and as their oxygen carrying abilities via hemoglobin and myoglobin improved, their volume of air in lungs reduced and the osteosclerosis also reduced, resulting in modern whales with porotic ribs and muscles/blood highly capable of oxygen conservation, and some baleen whales with enlarged laryngeal air sacs for surface foraging while baleen whales which still feed on benthics not developing enlarged air sacs.]
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Osteosclerotic bones (rib, pelvis, occiput) occur in slow benthic divers.

MV: AFAIK (back-floating requires less dense ventral bones: claviculas, ventral ribs...).

Yes, from an upright surface forager, upright crouching plucking benthic-surface forager to a vertical diver/backfloater, rather than a horizontal qpal forager to horizontal benthic forager (Indohyus, early mysticetes).

MV: Heavy ventral ribs (seacows) suggest pronograde slow swimming (always bottom??). Heavy limb bones (hippo, sea otter...) suggest wading/bottom-walking. Heavy leg but not arm bones (A.robustus??) suggest
vertical wading?bottom-walking?floating?? --marc

Yes, thanks. Uprightness in float-sit-feeding and wading (air sac) and crouch-pluck feeding and wading (hooded nose) would not select for dense ribs at all, but for dense femur and large feet. Regular part-time diving/backfloating would select for dense occiput, dense femur, paddle-like feet and hands, improved streamlining.

Osteoporosis in older females, and secondary scalp loss in older males, may indicate a slightly more pelagic condition in human ancestors (parallel to later whales) after the osteosclerotic femur/occiput (large air-filled lungs) had developed, which indicates to me an improved diving cycle of near-empty lung diving (less need for dense bones), better rhythmic timing (synchronised swim & dance) & communication (clicking cf dolphins, humming cf humpbacks), and specifically the advantage of tool use (fiber nets cf humpback bubblenets, spears/swords cf swordfish), as technology improved. Social herding using vocal and visible signals, group ambush techniques, mass harvesting (fishing cf fish/krill gulping in mysticetes), tools functional both underwater and on land (spears, tomahawks vs clubs) all combined to bring a sessile foraging slow diver/walker/climber to a fast killer, pelagic bait trapper and missile toting long beach jogger.

Of course, mysticetes and sirenians developed dense ribs, since their pelvis and femur bones became vestigial when the tail became the propeller and the arms became mere rudders. Human ancestors always returned inland seasonally during the rainy season, (cf emperor penguins in winter), and since the tail was long gone due to surface hydrostatic foraging (cf frogs), the legs became longer and more tail-like in the water, while improving the mechanical efficiency in the striding cadence of the pendulum walk.
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An aside, the nearby (Humboldt County, CA) North Coast Natural History Museum may be closing due to budget problems, more info here: http://the-arc-ddeden.blogspot.com/2009/08/humboldt-natural-history-museum-closure.html

A thought on the diving/backfloating cycle: Based on the Diving reflex and the (hypothesized) sun sneeze exhalation acting as the respiratory cycle mechanism at the trigeminal nerve, and its correlation to both dark adaptation-visual accomodation at depth and pupillary light response at surface, ARC diving has been assumed to have taken place during mid day hours, never at night (like sea otters but unlike dolphins which seek the nocturnal rise of fish schools).

It has also been assumed to have not taken place during the rainy season of the monsoons, due to both inconsistent sunshine lighting and more significantly, due to murky water full of silts from inland river flooding, and the increased amount of sharks and crocs that are able to hunt in muddy water. Most likely these were the months of inland foraging on fresh sprouting herbs, and easily obtainable and abundant rainwater puddles, as opposed to the dry season's limited stagnant overused waterholes.

Note that in the tropics, the non-rainy season may have brief showers daily, usually in the late afternoon, due to the humidity of the tropical rainforest rising and meeting cooler air above, resulting in rainfall at nearby coasts as well. This micro-climate cycle was probably part of the adaptive dive foraging and beach combing cycle, using the shells from the shellfish gathered to capture fresh rainwater on the beaches, in little sand divots.

These brief mild rains were unlike the storm season floods, and wouldn't have prevented swimming, diving, backfloating and wading, though diving would have been limited to warm shallow water using voluntary apnea, rather than deep ARC diving based on physiological reflexes.

Sea otters during rains also move to shallower areas, and during storms will come ashore and make sleep dens in the rocks and driftwood above the tideline, rather than backfloat in the heavy surf and relatively less dense freshwater ponding at the surface.

Baby backfloating

Why ISR? - Go Swim Baby - ISR Training

Carl Sagan on the human brain

from his book Dragons of Eden

- speculated that dolphins communicate by clicking specific patterns to others in the pod. An example, a sighting of a shark, would result in a dolphin producing a click train echo scan of a shark profile, so others hear the "shark" message, even if they can't see a shark. This message is the equivalent of a vocalized word. That is more complex than I'd expect ancestral human divers were capable of, but even a few consistent clicks as sub-aquatic warnings were advantageous, it would have changed the vocal/aural patterns in an otherwise silent submerged hominid. Sound carries well downwards from the surface (humming, splashing) but sounds from the depth would be heard only by those with ears submerged (backfloating, diving) to hear the click warning, all others would be 'sitting ducks' including those treading water and those wading or floating vertically in otherwise safer shallower areas. If these 'sitting ducks' had sharpened hollow bamboo spears/probing sticks, they would still be relatively safe, but vulnerable to the initial attack, the shark's 'taste test', if not attentive.

Re: Diving & Surfacing efficiently

BBC - Earth News - Killer whales visit 'social clubs'

Fish-eating Orcas gather in multi-pod social groups, speak different dialects.

The Pip and Pop Effect: Sound helps us find visual changes : Cognitive Daily

(Testing correlation of click tones and locating visual images on dark screen)

Sound helps us find visual changes [Category: Attention • Perception • Research]

"So while an audio cue helps viewers find the dot, a visual cue does not.

Even when the clicks were relevant just 20 percent of the time, the students were still significantly faster at recognizing the horizontal/vertical line during relevant clicks.

The researchers say this suggests that the connection between the audio cue and visual search is automatic. Even though the sound has nothing to do with the location of the change, just hearing a sound while the relevant object changes helps viewers to spot it more quickly."

Van der Burg, E., Olivers, C., Bronkhorst, A., & Theeuwes, J. (2008). Pip and pop: Nonspatial auditory signals improve spatial visual search. Journal of Experimental Psychology: Human Perception and Performance, 34 (5), 1053-1065 DOI: 10.1037/0096-1523.34.5.1053

Commenter: "Obvious interpretation: a disembodied click primes the attention system (which is multimodal) at those particular times, making that particular blinking point stand out further. A visual blink - with a definite spatial position - also primes the system but distracts from the correct point."
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"the correct point", IMO, would be Diving & Surfacing efficiently, in reference to click warning during dive foraging and surface backfloat resting in the presence of environmental hazards typically encountered by archaic forage divers entering the deep blue.

Yahoo! Groups

Chimp infants don't get colic, human infants do.
Confirmed. This indicates that unlike chimps, but like sea otter pups, human infants underwent natural selection for retained gastrointestinal tract gases which provided additional buoyancy while backfloating for short periods while the mother was foraging below or near rocky reefs. If babies could burp while backfloating they would sink lower and the nose might go under the surface. Instead, when too much gas accumulates, the baby cries while immobile, the mother returns and holds baby vertically allowing gases to escape while safely held. Thus, like mumps and goiters, colic was once a beneficial condition when human ancestors lived at tropical seashores 1ma, dive-foraging and backfloat-resting mid-day during the long monsoonal dry seasons.

Human infants should be put on their backs to sleep, to prevent possible SIDS (Sudden Infant Death Syndrome). This is not typical for other primate infants like monkeys or chimpanzees.

Both of these relate to maternal nursing while the mother reclined, and also to sleep apnea, both of which are typical in humans but not in other hominoids.

Humans are the only seashore hominoids, (60% live at coasts today) all others live in inland tropical rainforests or woodlands and avoid the sea or moving water when possible, but may wade into shallow ponds for AHV as Congo gorillas do.

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Baby chimps show same emotional range as human babies but cry less - Times Online

Bard, K.A. (2004). What is the evolutionary basis for ‘colic’? Behavioral and Brain
Sciences, 27, 459

Arjen said:

Research

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Research on why humans have some disorders/diseases while the other hominoids do not. These often seem to correlate with spending time in water, such as colic & SIDS (hydrostatic eupneic buoyancy advantage when parent is unavailable), mumps (mandibular parotid salivary glands affected, not maxillae, hydrodynamic advantage), laughter (human exhale only, other hominoids both inhale and exhale laughing, expected since primitive hominoid inflated laryngeal air sac would always keep face above water surface disallowing submersion), mild hypothyroidy (submandibular goiter gives hydrodynamic advantage where facial beard would be problematic in infant nursing, 'cold-bloodedness' to receive warmth of surface water when backfloating but not in apnea when submersed, associated with subcutaneous fat layer deposition), sun sneeze after dark adaptation (fast exhale/inhale cycle at sunlight-air surface), etc. Even infant sleep-smiling (noticeable to new mothers) correlates to the level of gas in the GI tract, something of critical importance in the past when infant buoyant fat levels were still amassing in an envelope around the baby, and covered in waterproof vernix just as a harbor seal is (but no other hominoid, which are instead licked cleaned and fluffed).

(Even the ancient pre-Indo-European word for float was the same word for bloat.)

Arjen said:

other thread

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This is the Diving & Surfacing efficiently thread, not the Elaine Morgan TED thread. I let Arjen & Trux duke it out on that thread, small eared factual aquatic gorilla vs big eared principled swimming chimp. :ko

This thread is strictly about ancestral diving backfloating humans that foraged efficiently at sub/tropical shores after the wetland float-sit-feeding phase, after but inclusive of the estuarine/mangrove upright crouch-leap-benthic plucking phase but before the development of dugout boats and nets and complex harpoons. It includes development of hollow bamboo probing spears and basic hand axes (Achelean bifacial hand axe tomahawks and plausibly bait traps) and pachyostotic coastal H erectus/H antecessor skeleton fossils. [See fossil and knapped limestone artifacts of both in southern Spain from 1ma, associated with caves and marsh-ringed lake, and others in west Asia and the African Rift].

The abundant (uncut) long scalp & facial hair in humans (vs fur in other hominoids) completely cover the ears providing hydrodynamic profile, when the face is (mostly) forward, rather than looking downward. Seals etc. lack this scalp hair and have quite small ears, but sea lions ear pinnae protrude out about as far from the skull as humans with soaked hair, some sea lions do have ruffed fur around the throat and neck area improving hydrodynamics similarly. Most likely human ancestors 1ma did have much smaller ear pinnae than today, smaller than today's gorilla pinnae, but probably similar rounded form. Recall that they were largely shore based, not aquatic dolphins, but spent much time foraging partly and fully immersed, they did not develop fully aquatic ears. However the ability to produce and hear splashing, clicking below and humming/speech above, and the ability to move in 3 dimensions, meant some changes to the inner, middle and outer ear, and to the external pinnae would be expected, and largely confirmed via fossil and genetic evidence. I'll let others answer your other questions.

trux said:

As for the farting / burping theory - I am not sure if the author ever had kids. But I can assure you that kids can perfectly fart even when laying on their backs. In contrary they often need to burp just after brestfeeding, because they swallow some air. So that completely violates your theory about gastric gases as floating help - they burp in the presence of the mother (during or just after feeding), and they fart even on their backs when left alone. Hence if they were really backfloating only thanks to the cummulated gases, they would drown.

Besides it, the burping/farting theory does not explain how the infants go on backfloating when mother comes to them, and makes them burp. Must she then stay keeping them afloat until they fill with gases again to make them sufficiently buyant?

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I don't know where to begin. The GI gases result mostly from the stomach acids decomposing the milk components (eg. CO2, sulfurous gases), not from swallowing air (though there is some incidental air). While a backlaying baby relies on gravity, a backfloating baby relies on buoyancy, a bubble of gas in water tends to go upwards (ventrally to the belly button), not outwards (posteriorly) or downwards (to the pharyngeal canal and the mouth).

An infant simply can't burp while backfloating right after nursing, so to alleviate the growing discomfort, it cries (but sheds no tears) on and on until lifted vertically or it climbs (like a sea otter pup) onto the parent's stomach.

Farting differs, because most gas is already burped out, what is sent far down the GI tract being pushed by both internal muscle contraction and later food intake out the posterior lifts the wrong end of the body (the pelvis) which pushes the face and little pug nose down rather than up.

Note also that ancestral adult humans had very dense bones (pachyostosis) but their infants had very little mineralized bone, so naturally floated higher in calm warm lagoon seawater.

seawater is highly dense in mineralized salts in solution.
freshwater is low dense in mineralized salts in solution.
osteosclerosis/pachyostosis is highly dense in mineralized salts in bone.
osteoporosis (elderly) & infant cartilage is low dense in mineral salts.

So despite the jokes, colic was indeed a baby lifesaver, only selected amongst seashore diving hominins where infants were regularly in water, not amongst forest freshwater swamp apes or savannah waterhole babboons which keep their infants out of the water, putting them in sedge bank or tree fork or let them climb on their fur and cling. Human infants are very poor clingers but very good at immobile crying loudly when uncomfortable, most species which hide their infants depend on scent to find them and the infants cry only when they detect the parents, rather than loud persistent crying sight unseen, which would attract predators.

Humans unlike most mammals must feed many times a day consistently, not because of nutritional need (milk is mostly water) but because of combined freshwater intake, food and associated gas production. Some animals feed twice a day. The more often and more consistent nursing, the more regular and small GI tract gases would be available. The infant is already floatable, the gas in the belly just keeps the hooded nose at the right angle, the dense bony backbone and occiput at the bottom (before the ventral ribs and facial bones are well ossified), the infant larynx high behind the nose rather than low in the throat.

Don't view the entrapped GI gas solely as a buoyancy mechanism, but as a consistency mechanism, allowing the mother (parent/auntie) to leave for short periods in relative safety, knowing that even if she dove 20m deep she would hear cries or splashes, and her clicking (might) communicate impending arrival at the surface.

Quite different from arboreal apes, due to the buoyancy/gravity difference, though there are parallels.
In case anyone is wondering, the father/s would have alternated in the diving cycle, but usually would have been further away diving deeper, climbing sea cliffs, ambushing and patrolling against predators ashore, making spears and axes etc.

trux said:

because they swallow too much air.

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Not likely.

So that's usually still when mother is there. And when we already speak about breastfeeding - how did the aquatic ancestors do it? Backfloating? Or was it in another position? Or did they breastfeed on the shore only?

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Yes, backfloating and ashore, semi/reclining, though able to nurse vertically (like chimps) as well.

Other questions already answered in other post.