Discussion on hypothesized ancestral human cyclical ARC dive-foraging

[wet]

Wet, deleted my post. Didn´t mean to break your spirit. :/

Start a new one, with a new topic the AAT is still a interesting theory.

Nobody broke my spirit, just needed to rant a bit. I apologize for offtracking.
DDeden

 

[wet]

Not sure where I dug these up, but IIRC they relate.

http://thesis.library.adelaide.edu....t-SUA20050815.120303/public/02chapters1-3.pdf page 18-152

http://darwin.wcupa.edu/~biology/fish/pubs/pdf/2000PBZ-PlatToWhale.pdf

http://www.archaeocete.org/EAT 2005 Abstracts.pdf

Eye design and function in 2ndarily aquatic tetrapods
Ronald Kroger, Lund Univ. Biology

Warm blooded aquatic animals frequently return to the surface for breathing. On a sunny day [humans typically prefer to dive and snorkle on sunny days and avoid rainy days and nights. DD], this exposes the eyes of deep-diving species to vastly different light levels in rapid succession. Extreme pupillary constriction and fast dark adaptation have been observed in pinnipeds (seals) and may also be present in other groups. [Compare to human occulomotor pupillary constriction, pupillary accomodation for underwater vision in Moken children, sunlight frowning in humans (not in chimps/orangs per Darwin), involuntary eyebrow flash reflex in humans, dark adapted sun sneeze in 20% of temperate Eurasians (occulomotor-trigeminal nerve relay) DD].

Diving mammals also expel a high amount of carbon dioxide with each exhalation, up to twice as much as *humans (Harrison and Kooyman, 1968). [*NOTE: "non-sneezing humans" AFAICT. I've found no data on the quantity of CO2 exhaled during a solar-powered sneezing episode. DD]

The ultimate constraint on body size in organic evolution is imposed by interphasic topology and not body heat [source? DD]

Aquatic specialization in marsupials etc. by Nick Longrich, Univ. Calgary
Eodelphis, didelphodon, stagodont: Similar to otters and mink, heavy tooth wear, durophagy, gastropod & bivalve feeder, resemble sea otter wear, large body size in diverse freshwater semiaquatic habitat. A semiaquatic lifetyle predicts heavy bones to decrease buoyancy during dives, the jaws of Eodelphis and Didelphodon have massively thickened cortices. [H. erectus and H. neandertal had dense occiputs, keeled (He backsculling) or bunned (Hn backfloating), both had thin boned nasal architecture AFAIK. DD] Stagodonts were the largest earliest known aquatic mammals, radiated into 6 species in North America during (dinosaur era) Mesozoic.

add:

Humans lack vibrissae (hypersensitive whiskers), pinnipeds and sea otters have them; these bristles detect physical/water/air pressure. Instead, humans have pressure-sensitive nasal hairs, eyebrow hairs and frontal (but not central or rear) scalp hairs (Trigeminal, opthalmic nerve) (in addition to photic stimuli); all of which when stimulated/irritated can cause a sneeze episode (immediate full exhalation of deoxygenated lung air and inhalation of fresh air). Whales have lost their vibrissae, though some river dolphins have them, possibly odontocetes (toothed echolocating whales) probably use sonar to detect the water surface, while mysticetes (baleen whales) may detect the surface via baroreceptors on their "backwards protruding nose" just in front of the 2 blowholes.
(* THE-ARC *): Diving-Surfacing: Parallel Convergence

 

[trux]

Thanks for the links and information, David.

As for the CO2 exhalation, there are certain limits that are simply physiologically given, and you cannot overpass them even with a very deep exhale or a sneeze. The content of CO2 in alveoli after a prolonged apnea does not correspond to the amount of CO2 produced by the body. The gas exchange of CO2 through the alveoli wall stalls rather early in the breath-hold, and the CO2 then more accumulates in blood and other body liquids than being diffused to lungs.

So even with a very deep exhale after the breath-hold you remove only smaller part of CO2 produced. It allows though starting the diffusion of the cumulated CO2 in the body, which then continues to wash out with the subsequent breaths.

That's actually needed and welcome, because you do not want that the level of CO2 in blood drops too quickly after the end of the apnea, when the hemoglobin is not yet recharged with new oxygen. Due to the Bohr curve shift, it helps oxygenating organs better (releasing O2 easier). The partial drop of CO2 in alveoli is sufficient to bind new oxygen, which is priority in that moment.

With that, of course, I am not telling that the sneeze cannot still offer some advantage in speeding up the process, although I am not quite persuaded this is the real purpose of the photic sneeze. It might also increase the risk of post-apnea blackout, but I guess a specific study would be needed to find it out.

 

[wet]

Thanks for the links and information, David.

As for the CO2 exhalation, there are certain limits that are simply physiologically given, and you cannot overpass them even with a very deep exhale or a sneeze.

The sneeze exhale did NOT remove all the CO2 in the body, only the excess CO2 in the LUNGS. (On average probably 2-3 sneezes) Realize that typically among marine mammals there are two types of dives, one shallow (repeated) and one long deep (unrepeated) dive type. In human ancestors:

Shallow dives (est. 3m depth): dive, surface sneeze, dive, surface sneeze (repeat d,ss 3 more times) then backfloat and respire aerobically, while eating, humming, or chatting. So between the 1st and 2nd shallow dive, the body's blood CO2 level does NOT drop significantly, this is a safety factor that allowed many repeated short shallow dives without risk of SWB. (Mothers with children may have been limited to this form of dive)

Deep dives (est. 12m depth): dive, surface sneeze, backfloat and respire aerobically for a while, probably while eating or humming or chatting, then after body is all flushed, deep dive again. This may have been done by adult males or childless couples diving simultaneously and/or parents diving alternatively eg. father at depth while mother backfloating (singing-nursing) at surface with infant then switching to mother at depth and father (humming-resting) at surface with infant.

The content of CO2 in alveoli after a prolonged apnea does not correspond to the amount of CO2 produced by the body. The gas exchange of CO2 through the alveoli wall stalls rather early in the breath-hold, and the CO2 then more accumulates in blood and other body liquids than being diffused to lungs.

So even with a very deep exhale after the breath-hold you remove only smaller part of CO2 produced.

Right Ivo, that's my whole point, this was a safety factor built-in, they were never selected for hyperventilation, which was a stress reaction, not normal diving action.

It allows though starting the diffusion of the cumulated CO2 in the body, which then continues to wash out with the subsequent breaths.

Yes, aerobic backfloating while humming, chatting, maybe eating.

That's actually needed and welcome, because you do not want that the level of CO2 in blood drops too quickly after the end of the apnea, when the hemoglobin is not yet recharged with new oxygen. Due to the Bohr curve shift, it helps oxygenating organs better (releasing O2 easier). The partial drop of CO2 in alveoli is sufficient to bind new oxygen, which is priority in that moment.

Correct.

With that, of course, I am not telling that the sneeze cannot still offer some advantage in speeding up the process, although I am not quite persuaded this is the real purpose of the photic sneeze. It might also increase the risk of post-apnea blackout, but I guess a specific study would be needed to find it out.

For a slow diver, the more time at the surface = less time gaining food (not significant if they actually eat at the surface). It was optimized respiratory efficiency, in the foraging cycle. Our ancestors were never fast in the water (neither are manatees or right whales), actually Michael Phelps may be a faster swimmer than any of the ancestral human divers, they were in no hurry, but they were faster than mollusks, and really they only had to beat the sinking sun when the water got too dark to see through.

Sneeze = lung CO2|O2 exchange
Backfloat humming/chatting = body-blood CO2|O2 exchange
(I'm sure I wrote all this earlier)

It is, I think, obvious now, right? Any doubts remaining?

DDeden

 

[wet]

There seems to be little interest in this topic.

Can't say I didn't try.

 

[azapa]

5 pages long? no interest????

 

[trux]

David, it is definitely interesting topic, but I am still little bit skeptic about the photic sneezing being optimal for surfacing. I do not really believe faster exhale would help cutting down the surface time. Getting rid of the excess CO2 is relatively quick, unlike recharging with O2, so I do not believe explosive exhale would help here. Also, I already expressed my suspicion that the sneeze might increase the risk of blackout or samba. Also, I am not aware than any aquatic animals sneeze upon surfacing, or do they?

 

[wet]

5 pages long? no interest????

I meant little interest specifically in diving and surfacing efficiently, without modern technology (boats, masks, fins, weights). It may be out of the interest range of many divers today, too arcane I guess.

For me, it's important because it explains the past, clarifies the present and allows provisioning for the future, if we keep the oceans lively and blue.

 

[Mullins]

Sounds like you want to talk about Constant Weight No Fins. Will Trubridge dives and surfaces pretty efficiently. I'll tell him he needs to sneeze more...

Edit: and humm

 

[wet]

David, it is definitely interesting topic, but I am still little bit skeptic about the photic sneezing being optimal for surfacing.

I'll always be skeptical about it, that's my nature.

I do not really believe faster exhale would help cutting down the surface time. Getting rid of the excess CO2 is relatively quick, unlike recharging with O2, so I do not believe explosive exhale would help here.

I think explosive exhales are typical for mammals that habitually dive lengthily, though only whales do so in such spectacular fashion.

Also, I already expressed my suspicion that the sneeze might increase the risk of blackout or samba.

I've never heard of anyone fainting, blacking out or having a samba during or after a sneeze, though people have various conditions (eg. epilepsy, MS) where something like that might conceivably occur.

Also, I am not aware than any aquatic animals sneeze upon surfacing, or do they?

I don't know if marine mammals sneeze at all, I do know they explosively exhale after deep and/or long dives, so likely they are one and the same reflex or very closely related.

Isn't it odd how if your nose is tickled, you sneeze mostly out the mouth, and if your mouth or throat is tickled, you cough mostly also out the mouth? To clear the nose, one has to deliberately blow the nose, there isn't any reflex for that.

Orangutans, cats and dogs sneeze mostly out the nose with their eyes and mouth closed AFAIK.

Humans sneeze out the mouth with eyes and nose (upper soft palate) closed, though there is some exhale through the nose too.

Diving humans generally mouth breathe because it's a lot faster.

[ame=http://www.youtube.com/watch?v=VVkuEpIGYvY]YouTube - Fred Ott Sneeze (Edison, 1894)[/ame]
http://goodbyemailbox.com/blog/uploaded_images/sneeze-742474.JPG
Google Image Result for http://mcaaron.files.wordpress.com/2008/07/sneeze1.jpg

To clarify, I'm not suggesting anyone try this type of diving, rather, to consider it as a possible vestige of past seashore foraging.

DDeden

 

[wet]

Sounds like you want to talk about Constant Weight No Fins. Will Trubridge dives and surfaces pretty efficiently. I'll tell him he needs to sneeze more...

Edit: and humm

You're talking modern diving and sports competition, I'm talking archaic foraging aka food gathering. AFAIK no food gathering is allowed in any AIDA or other official sanctioned event. (Actually I have no idea, but I'd be shocked if it were.)

I've nothing but respect for todays divers and modern techniques.

But my goal was to find out what happened long ago, under very different circumstances. What I've found and conjectured makes basic sense, it fits biological patterns, it's even kind of neat. But it still might be completely wrong. That's science. Still looking for contradictory evidence. (And a tropical lagoon. And a female dive buddy. And $eriou$ funding.) Ce la vie.

DD

 

[laminar]

Cool thread.

Sorry, just getting into it now. Where's the source of the speculation about the photic sneeze having a role in clearing C02? And it being a reflex (or would these prehistoric people try to consciously induce a sneeze)?

I guess it all depends on the dive style of these early people. If they are pushing each dive and hoping to stay alive and avoid blackout, that's one scenario.

The other scenario would be a less taxing method for shallower waters that they could do over and over again until they got tired or cold.

In the less demanding scenario, why bother sneezing? Just go with an instinctive exhale/inhale combination. That's what most mammals do when they surface, AFAIK.

In the more demanding scenario, I'm still not clear how clearing C02 from the lungs would help you (vs. getting fresh 02 as a priority). Wouldn't your bp in your head drop significantly after a sneeze? (Any data on bp during and after sneezes?) Or is a sneeze optimal because it is so fast and is immediately countered with a quick inhale, thereby keeping bp high?

I just think it's unlikely that a sneeze could be initiated on every surfacing and on every dive.

Also, the danger of an involuntary sneeze when a wave hits you (each sneeze is initiated by a sharp inhalation) would be significant, I think.

Wet, if I've missed some vital part of your reasoning, let me know.

My guess is that forgaging for food underwater would evolve into a practice that would be fairly easy on the body (ie low intensity shallow diving) and with few fatalities, but of course that didn't stop the Polynesians from suffering from taravana.

Pete

 

[trux]

I think explosive exhales are typical for mammals that habitually dive lengthily, though only whales do so in such spectacular fashion.

That's not really a good example supporting your theory of surfacing related photic sneeze. Although it may sound impressive when a whale exhales, just because of their lung volume, it is nowhere close to sneezing. Whales do not explosively exhale by their mouths. Their exhaust hole is relatively small, and does not allow one-shot clearing of the lungs. Their exhale is relatively long. And additionally and most importantly, they actually exhale prior the dive.

I've never heard of anyone fainting, blacking out or having a samba during or after a sneeze,

I am not surprised, nobody would be fool enough doing it after a pushed breath-hold. But try explosively exhaling when you are already in hypoxia after a long breath-hold. The sudden drop of both PaCO2 and PaO2 plus the energetically billing sneeze may well bring you into unconsciousness.

To clarify, I'm not suggesting anyone try this type of diving, rather, to consider it as a possible vestige of past seashore foraging.

I do not really believe that photic sneeze has anything to do with diving. These are my reasons:

1. I saw no supporting evidence showing it could
2. It brings no advantage
3. You do not want to get rid of CO2 too fast after surfacing
4. It increases risk of blackout / samba
5. It increases risk of choking (as Laminar correctly pointed out)
6. The diver might drop his prey when sneezing
7. A sneeze underwater would likely kill the diver if he looked upwards into the light during surfacing
8. Sneezing divers would likely extinct fast because of 3, 4, 5, 6, and 7
9. It does not help cutting surface time as suggested, because getting rid fast of the CO2 is not what decides about the needed surface time
10. To my best knowledge other aquatic animals do not have any photic sneeze reflex (except of horses, who are not aquatic - they have a similar photo sensitive syndrome)
11. The photic sneeze might not work when surfacing in cloudy days, in shadow, or in clear water.
12. Photic sneeze is much more common at Caucasians than at others human races, showing it probably appeared later in the evolution

And on another, lighter note, there is also this funny video of sneezing (though I'd tell it is apparently not a photic sneeze in this case):

 

[azapa]

great panda sneeze trux, video of the day award!

ever so slightly on tipic: neanderthal mans size and structure demanded about 5000 kcals a day (about twice "us") that would make ocean foraging very tempting

 

[wet]

Alternative energy source found ? for the brain - More health news - MSNBC.com

Study: Lactate, a byproduct of the muscle, can be used as back-up fuel

The body breaks carbohydrates from food into glucose, the primary fuel of muscles and the mind. When muscles work hard, they produce lactate as a byproduct. Though recent studies have shown that muscles can re-use the lactate as fuel, conventional wisdom holds that it can also build up in the form of lactic acid, reducing performance and causing pain. The new research shows that the brain can switch to lactate during strenuous exercise, using the muscles' byproduct as backup fuel.

The researchers, in Denmark and The Netherlands, looked at existing studies that had compared the blood running to and from the heads of volunteers engaged in strenuous exercise. The blood on its way to the brain was found to contain considerably more lactate than blood flowing from the brain. Further investigation showed that the brain was not storing the lactate which had come from the muscles during exercise, but rather using it as fuel. In fact, the brain helped to clear lactate from the circulation, thereby leaving glucose to the muscles that need it for the hard work they were performing.

The finding helps explain why the brain is able to work properly when the body's demands for fuel and oxygen are highest, and it shows that the brain actually shifts into a higher gear in terms of activity. This opens doors to entirely new areas of brain research related to understanding lactate's specific neurological effects that could lead to new treatments for common brain ailments, the researchers said in a statement today.

Anthropologist John Hawks: http://johnhawks.net/weblog/
Note: this has nothing to do with lactose metabolism. There's actually a substantial literature on the role of lactate in brain metabolism -- it seems to be very important for times when the brain must recover from hypoxic conditions, so there has been a lot of research. So there probably is a deeper story to be written here -- the "backup energy source" hypothesis is a little simplistic.

[I'm curious about the globins (neuro, cyto, hemo, myo) in relation to lactate in hypoxia]

Neuroglobins protect against anoxia in the freshwater (and sea) turtle
http://www.springerlink.com/content/g5jvt66337521503/

Globins in the zebra fish
http://jeb.biologists.org/cgi/content/abstract/209/11/2129

Globins and lactate
The role of Neuroglobin (Ngb) as a terminal oxidase for sustaining glycolysis under hypoxia (scenario c) has not yet been investigated. According to the "lactate shuttle" hypothesis, it is currently believed that in normoxia and even under functional activation of a brain region, glycolysis occurs predominantly in the astroglia, which produces substantial amounts of lactate [63]. This lactate is taken up by neurons, which appear to have a preference to oxidize imported lactate instead of producing lactate/pyruvate by their own glycolysis. Under this scenario, Ngb as a purely neuronal protein should not play a substantial role in glycolytic energy production. Energy depletion under hypoxia, however, may stimulate enhanced glucose oxidation in neurons, compensating for a reduction in lactate supply by astroglia. http://209.85.173.104/search?q=cach...ate&hl=en&ct=clnk&cd=9&gl=us&client=firefox-a

 

[Mullins]

AFAIK no food gathering is allowed in any AIDA or other official sanctioned event. DD

I think the rules need to be clarified lest we end up with a bunch of hirsute, sagittal-crested genetic throwbacks dominating our competitions for the purpose of bottom-foraging: CNFNC (Constant No Fish No Clams).

 

[wet]

Cool thread.

Sorry, just getting into it now. Where's the source of the speculation about the photic sneeze having a role in clearing C02? And it being a reflex (or would these prehistoric people try to consciously induce a sneeze)?

(depth) Dark adaptation -> (surface) sunlight -> sneeze -> lung gas exchange instantly (100mph, about same as dolphin)

One note I hadn't thought of before, what about a photic sneezer that is dark adapted and oxygen supplied (low CO2 in lungs) that then gets sunlit? Does the sneeze occur both when lungs are oxygenated and deoxygenated? If it had evolved in diving, then only high CO2 should be expelled.

Consciously induced sneezing might be if a bit of seawater is allowed into the nose just at surfacing. That would work night or day presumably, a possible advantage. I'm still trying to figure if seawater was normally allowed into the naso-sinuses and middle ears, perhaps only at puberty (infants couldn't). (per Seb Murat's equalizing).

I think a million years ago, both male and female adults had very sensitive eyebrows, eyelashes, nose hair, and mustaches (only males had beards) that combined with the photo-sensitivity of the eyes for very very good water surface detection. The same with the skin of the forehead, nose tip and beneath, and lips, all pressure sensitive.

I guess it all depends on the dive style of these early people. If they are pushing each dive and hoping to stay alive and avoid blackout, that's one scenario.

The other scenario would be a less taxing method for shallower waters that they could do over and over again until they got tired or cold.

In the less demanding scenario, why bother sneezing? Just go with an instinctive exhale/inhale combination. That's what most mammals do when they surface, AFAIK.

Shallow short dives have quiet exhalations, and don't have dark adaptation, so no photic sneeze anyway (a photic sneeze can't be induced except when leaving a dark area). The deeper & darker & longer at depth, the more explosive the exhalation, true for all marine mammals AFAIK. Perhaps 'expulsive' rather than explosive is better?

In the more demanding scenario, I'm still not clear how clearing C02 from the lungs would help you (vs. getting fresh 02 as a priority).

It's essentially the same thing, the faster the exhale, the faster the inhale. If they dove on empty lung or partly filled, the first sneeze would be small, the first inhale would be small, followed by a bigger sneeze and a bigger inhale, then perhaps dive on exhale. (Guessing of course)

Wouldn't your bp in your head drop significantly after a sneeze? (Any data on bp during and after sneezes?) Or is a sneeze optimal because it is so fast and is immediately countered with a quick inhale, thereby keeping bp high?

Unknown. AFAIK sneezing does not change body blood pressure significantly, I've never heard of anyone fainting or stroke from a sneeze, although a pre-existing aneurism or so might be affected.

I just think it's unlikely that a sneeze could be initiated on every surfacing and on every dive.

Only on mid to deep dives on sunlit conditions in warm water, I'd think. Shallow dives may have been mild expulions, more voluntary, deeper dives more stronger and faster and more reflex-driven.

Also, the danger of an involuntary sneeze when a wave hits you (each sneeze is initiated by a sharp inhalation) would be significant, I think.

Photic sneezing requires dark adaptation, then bright light. A wave would have to hit right at the moment of sneeze inhalation to be a problem, and even then, the face has baro-receptors (pressure sensors) to stop a sneeze (put your index finger across the base of the nose to stop a sneeze). Humans have everted lips (unlike apes) that can press against the base of the nose, some people can even block their nostrils that way.

I doubt they dove in wavy surf waters, lagoon reefs tend to reduce waves, unlike open ocean beaches where low tide beachcombing was more practical.

Wet, if I've missed some vital part of your reasoning, let me know.

My guess is that forgaging for food underwater would evolve into a practice that would be fairly easy on the body (ie low intensity shallow diving) and with few fatalities, but of course that didn't stop the Polynesians from suffering from taravana.

Pete

The pearl divers were working for money not foraging, hyperventilated quite a bit and used boats. Very different. Boats really changed the dynamics and allowed transit into freshwater areas of crocs and hippos, which had been avoided previously (neither live on reefs). Shallow diving yes, but then wading too. I'm sure it was a mix, whatever got the food. Deeper dives and backfloating gave advantages not available to very shallow divers.

DDeden

 

[wet]

That's not really a good example supporting your theory of surfacing related photic sneeze. Although it may sound impressive when a whale exhales, just because of their lung volume, it is nowhere close to sneezing. Whales do not explosively exhale by their mouths. Their exhaust hole is relatively small, and does not allow one-shot clearing of the lungs. Their exhale is relatively long. And additionally and most importantly, they actually exhale prior the dive.

I think there needs some flexibility here, in interpreting whale spouts, as biologists are still trying to figure out what happens. Whales have proportionately small lungs, compared to most ground animals. Whale don't sneeze, yet they exhale at about 100mph, so very likely it's the same physiological thing. It's true that whales can spout slowly, but this depends on their foraging patterns and depth/length, the majority do exhale very quickly and deeply compared to terrestrials, when volume is compared. One reason that they spout somewhat slowly may be the need to retain/recycle (non-salt)water in their bodies. Whales don't exhale at all from the mouth. Human ancestors may have partly-exhaled prior to the dive as well, though not to the extent that whales do. Also, you really can't compare the largest animal that has ever lived (blue whale, sperm whale) to humans in proper context. Remember, I'm always comparing human and arboreal apes, we are a lot more whale-like than any of them, but obviously we aren't cetaceans. And neither cetaceans nor apes backfloat, but sea otters do. And sea otters exhale explosively after deep dives, and I think they only forage during daylight, unlike echolocating odontocetes that don't need light to hunt.

I am not surprised, nobody would be fool enough doing it after a pushed breath-hold. But try explosively exhaling when you are already in hypoxia after a long breath-hold. The sudden drop of both PaCO2 and PaO2 plus the energetically billing sneeze may well bring you into unconsciousness.

Conjecture? Any evidence of this? (Not disagreeing, just not known)

I do not really believe that photic sneeze has anything to do with diving. These are my reasons:

1. I saw no supporting evidence showing it could
2. It brings no advantage
3. You do not want to get rid of CO2 too fast after surfacing
4. It increases risk of blackout / samba
5. It increases risk of choking (as Laminar correctly pointed out)
6. The diver might drop his prey when sneezing
7. A sneeze underwater would likely kill the diver if he looked upwards into the light during surfacing
8. Sneezing divers would likely extinct fast because of 3, 4, 5, 6, and 7
9. It does not help cutting surface time as suggested, because getting rid fast of the CO2 is not what decides about the needed surface time
10. To my best knowledge other aquatic animals do not have any photic sneeze reflex (except of horses, who are not aquatic - they have a similar photo sensitive syndrome)
11. The photic sneeze might not work when surfacing in cloudy days, in shadow, or in clear water.
12. Photic sneeze is much more common at Caucasians than at others human races, showing it probably appeared later in the evolution

And on another, lighter note, there is also this funny video of sneezing (though I'd tell it is apparently not a photic sneeze in this case):

Thanks for considering it Ivo, I know you put some focus on it. I'll answer your statements later, as it's time for a cheeseburger. That lil panda is a champ!

 

[wet]

ever so slightly on tipic: neanderthal mans size and structure demanded about 5000 kcals a day (about twice "us") that would make ocean foraging very tempting

Yeah, I figure benthic diving and backfloating, but also ambushing with spears bigger animals that came for water or salt. I just don't think they were running around chasing big game too much, being so stocky.

Maybe some hid around a waterhole or shore, and one or two backfloated under a mat of reeds, holding jabbing spears, at sundown a herd of deer coming down for a drink could be attacked from all sides. Based on fossils, they seem to have been often injured in the upper body, maybe the ones in the water got stomped occasionally.

But then, neandertals had fire for cooking meat. Older hominins like Java Man probably didn't have fire. Raw oysters and clams are a lot easier to eat than raw venison, and a lot tastier too. I think they stayed pretty close to shores, but I'm sure they went looking for flint, basalt, ochre up in the hills too, maybe during the rainier times.

 

[wet]

I think the rules need to be clarified lest we end up with a bunch of hirsute, sagittal-crested genetic throwbacks dominating our competitions for the purpose of bottom-foraging: CNFNC (Constant No Fish No Clams).

What a concept!
=========================
Added in October:

"hirsute, sagittal-crested" = Gorilla and their ancestors, fur coat & bony 'mohawk'.

sagittal crest: Human Ancestors Hall: KNM WT 17000 (not actually human ancestor) Compare side profiles: Note lower face prognathic, jaws jut forward.
sagittal keel: Human Ancestors Hall: Weidenreich Reconstruction (human ancestor morphology) Note mid-face prognathic, large nose juts forward.

Our ancestors about a million years ago, dive-foraging and backfloating at sunlit tropical seashores, were probably as hirsute as many people today, but nothing at all like a forest ape (which never dives or backfloats and lacks skin fat).

Sagittal crests are found among apes which mostly chew tough fiberous foods, they are bony attachments for thick chewing muscles on the top of the head, like those on vegetarian gorillas in inland rainforests. We and our ancestors didn't have these, instead having relatively weak jaws. A gorilla could chomp a piece of bamboo that we couldn't even dent with our teeth.

Our human ancestors ate softer raw foods, like oysters & fruits, and used tools to cut tougher foods (hand axes, razor-shell blades, nut pounding stones) and did not develop sagittal crests.

Instead they had sagittal keeling, which is hydrodynamic smoothing of the rear of the crania, similar to modern aerodynamic bicycle helmets.

After the development of simple boats (hollow logs, dugouts, rafts), harpoons, nets, baskets, between 50,000 and 200,000 years ago, dive-foraging became less habitual, since fish and game could be harvested en masse, rather than individually. Boats and nets allowed access to areas dangerous for forage diving (cold/rough water, hippo/croc/shark infested waters), with beach combing at low tide, shore net wading, and boating at high tide, hydrodynamic cranial profile gave no advantage in these foraging activities and was no longer selected for, and as a result, rounder skulls resulted (structurally stronger than flat long skulls).

DDeden

==========================

You work on the clarification of regulations,

I'll work on the photic exhalatory sternutations...