Diving & Surfacing efficiently

[trux]

I am afraid, David, that you did not chose the best examples to support the aquatic ape theory. The mammalian diving reflex is present at practically all mammals, and despite its name, even at birds and other species. It really cannot be used for proving the AA theory. And the photic sneeze reflex being related to diving is a theory that was not proved at all. Besides it, it looks like the photic sneeze at diving is not as common as one would expect if it really originated in diving. There are other theories explaining the reflex - see for example Photic sneeze reflex - Wikipedia, the free encyclopedia

On the other hand, there is a lot of other indirect evidence supporting the AA theory, but I have to agree with Dave that none of it is sufficient for accepting it totally. For those who are curious, I really recommend studying the topic deeper (using links mentioned above in this thread).

[trux]

Originally Posted by turtle

very nice photo. that's one happy ape.

I admit I would look exactly as happy as him, were I in his place! And even much happier if my wife did not see it

[Mullins]

Originally Posted by wet

Do not be afraid, Ivo. I merely intended to show parallel convergence of human (ancestors) and blue whales and the ARC-MDR-PS link. That is what I did, no more, no less. Support AAT? I have no idea, I'll take your word on that.

You seem to be saying that because we share certain traits with whales, namely the MDR, our evolution must have been shaped by similar environmental pressures at least for a brief period. Trux pointed out that all mammals share this trait. So does this mean that all mammals spent time frolicking at the coast 1mya? Or is our human MDR a special case; did we get it at the coast while all the others hit upon it by accident and for no particular reason? I'd suggest this is not the case and that it is more likely to have been passed down from our common ancestor, which lived and died a lot further back than our flirtation with African beaches is said to have occurred. I'll have a read up on this however...

You also say that our lack of a laryngeal air sac indicates we have adapted for swimming and diving, unlike chimpanzees etc which have an air sac allowing them to float vertically. Yet on your page it points out that pygmy whales have these air-sacs. So Chimps share a trait with whales that we do not. Isn't that counter to your argument about parallel convergence? Do you consider a pharyngeal air-sac to be a swimming/diving adaptation or not?

Regarding swimming babies - if you consider 'swimming' to mean simply propelling oneself in water then yes, they seem able to do this to a limited extent. The points I was making were 1. they're hopeless (= very poor) at it when compared to other mammals and 2. this 'reflex' doesn't seem to include any strategy for breathing. This means it's a bit generous to call it 'swimming'. I'd expect that if we had inherited anything from these aquatic ancestors of ours it would be a good breathing technique. So what you (and doting mothers & fathers everywhere) call 'swimming' is more like mobile drowning and swift intervention is required as soon as the fun stops.

[turtle]

@ Mullins. To demand proof of the aquatic ape idea is understandable, but look at it another way - would you rather argue the case that human's genetic ancestors were 100% exclusively land-based?? I think that would be *much* harder to prove or argue convincingly.
I think it's an acceptable theory to put forward that humans have used relatively shallow waters to forage and hunt & that they have had some genetic predisposition to do this, just as most other animals do. Some animals have lost these predisposed faculties through lack of use, but by and large humans have had to stick near ready & plentiful sources of water. Therefore on the general scale of land-based animals, we're fairly close to the watery side of things in terms of what we can do without too much practice.

Some physical aspects don't make much sense otherwise - our bodily hair, our reliance on bodily fat for insulation, our relatively good aquatic streamlining compared to apes, the various diving reflexes etc.

f

[Mullins]

Turtle, if you come up with a theory, the onus is on you to prove it. Or at least provide a good line of reasoning that supports it. When your argument makes no sense, you can expect people to contest it.

No, It's NOT acceptable to put a theory forward unless you actually have evidence and sound reasoning backing it up. When what somebody says does not make sense, you don't need a counter-theory to replace it. You just need to show why it's wrong.

Having said that, yes it would be much easier to argue the contrary i.e. that we evolved to live in a terrestrial environment and not to dive underwater. For a start, you could probably demonstrate that plenty of mammals with no aquatic ancestry are still much better in the water than we are. Note that I'm not debating whether some humans lived near the coast and gathered seafood; of course they did. The question is whether we were physiologically adapted to diving. Those are two very different claims and it's the latter I take issue with.

If you do some research you'll find that the physical aspects you mention (lack of body hair, our body composition and our supposedly streamlined shape) actually support the 'dry ape' argument and have been sorely mis-interpreted in supporting the AA theory. Many aquatic mammals our size are very hairy (think seals). The fat of whales etc is distributed to give them a streamlined shape whereas ours is distributed very differently. Do female breasts or a male beer gut contribute to a streamlined form?? And do you really think we grew long and skinny in order to move better through the water? That claim would have any decent anthropologist rolling in the aisle.

[turtle]

I dunno! Jeez, i didn't suggest that we had wings and flew everywhere. Just that we probably have evolved to include the possibility of using watery environments, primarily for foraging. Why would humans evolve and specifically exclude a massive ready source of nutrients?

If you really want to roll around in the aisle, just think about the naked human condition - we have developed to be super skinny, useless in fighting or even escaping at any high speed, prone to burning from the sun, we die if we go without water for more than a hundred hours, we need clothing just to survive in 99% of the environment we have evolved into living in. The whole thing is faintly absurd, let alone the question of whether or not we used to swim.

I know you will disagree with me on some dialectic point, but it seems pretty obvious that on a planet with limited resources & multiple threats, humans have adapted to most environments therein in order to survive. There are tonnes of ancient engravings of people diving in the water to collect food, plenty of ethnological cultures based around the sea & diving (Amas, Badjos etc. etc.). I don't think humans started diving exclusively when these relatively modern cultures were around to produce engravings of them. Therefore, they were probably doing it sometime before then. What proof do you want? To my mind you can't prove it either way, at least not conclusively enough. Therefore there exists conjecture, which is exactly what we are both doing with our respective arguments - unless you have direct experiential proof of early human history that is.

Let me put forward a different (knockdown) theory for you - the earthbound ape - it goes like this: humans have never ever, not even once throughout their course of existence on this planet, collected food from the edges of the oceans, seas, rivers & lakes, nor have they waded, swam, or put their heads underwater. Sound pretty far-out no? Yet this is basically what you are claiming.

I like the word onus too. I hope you get to use it again in your next post.

cheers
f

[turtle]

OK, i see your distinction between people being able to dive & genetically evolved towards this purpose. But the fact that people are able to dive & have done throughout their history suggests that we are predisposed towards diving, through evolution, in much the same way that we are not predisposed to, say, flying.

In any case I would argue convincingly that we are considerably better at diving than tigers.

Give up, you win, well done.

Cheers
f

[wet]

Originally Posted by Mullins

Turtle, if you come up with a theory, the onus is on you to prove it. Or at least provide a good line of reasoning that supports it. When your argument makes no sense, you can expect people to contest it.

I hope to avoid arguing just for the sake of arguing.

No, It's NOT acceptable to put a theory forward unless you actually have evidence and sound reasoning backing it up. When what somebody says does not make sense, you don't need a counter-theory to replace it. You just need to show why it's wrong.

Perhaps. I don't think it is wrong, though the details are very fuzzy and much remains unknown.

Having said that, yes it would be much easier to argue the contrary i.e. that we evolved to live in a terrestrial environment and not to dive underwater. For a start, you could probably demonstrate that plenty of mammals with no aquatic ancestry are still much better in the water than we are.

Humans swim, dive and backfloat, name one other animal that does, beside the sea otter/marine otter and other (semi) aquatics. Humans have always been largely terrestrial, no argument on that.

Note that I'm not debating whether some humans lived near the coast and gathered seafood; of course they did. The question is whether we were physiologically adapted to diving. Those are two very different claims and it's the latter I take issue with.

Ok, indeed. Physiological adaption of a species to an ecological niche via natural selection of fittest mutations. COMPARED WITH OUR NEAREST GENETIC KIN, APES, even the "dry ape" supporters admit that we are more physiologically adapted to diving than any ape. Proof: go to any tropical seashore beach and count swimming/diving/backfloating humans vs apes.
Humans: millions
Gorillas: 0
Chimps: 0
Orangutans: 0

If you do some research you'll find that the physical aspects you mention (lack of body hair, our body composition and our supposedly streamlined shape) actually support the 'dry ape' argument and have been sorely mis-interpreted in supporting the AA theory. Many aquatic mammals our size are very hairy (think seals).

Only one: Sea Lions. All others have sparse (like humans) or extremely sparse body hair. Compare to inland apes.

The fat of whales etc is distributed to give them a streamlined shape whereas ours is distributed very differently. Do female breasts or a male beer gut contribute to a streamlined form?? And do you really think we grew long and skinny in order to move better through the water? That claim would have any decent anthropologist rolling in the aisle.

Compared to apes, humans are far more hydrodynamic and aquatically thermoinsulative.
Compared to deer, whales are far more hydrodynamic and aquatically thermoinsulative.

Human ancestors along shores were not fast swimmers, but slow divers, that spent much time ashore.

DD

[wet]

Originally Posted by Mullins

You seem to be saying that because we share certain traits with whales, namely the MDR, our evolution must have been shaped by similar environmental pressures at least for a brief period.

Yes, partially, however I'm always viewing it in comparison to our closest genetic kin, the inland apes. Whales (ancestors) have not slept ashore for at least 20 million years, and have not climbed trees for even longer. Human ancestors have always slept ashore and had the ability to climb trees, like the apes.

Trux pointed out that all mammals share this trait. So does this mean that all mammals spent time frolicking at the coast 1mya? Or is our human MDR a special case; did we get it at the coast while all the others hit upon it by accident and for no particular reason? I'd suggest this is not the case and that it is more likely to have been passed down from our common ancestor, which lived and died a lot further back than our flirtation with African beaches is said to have occurred. I'll have a read up on this however...

Yes, the origin of the MDR is much older, maybe 300,000,000 years ago or so. It likely developed when some ancient fish evolved air-sac-lungs to help respire in water with low oxygen (surface breathing supplemental O2), but spent time foraging in the water.

You also say that our lack of a laryngeal air sac indicates we have adapted for swimming and diving, unlike chimpanzees etc which have an air sac allowing them to float vertically. Yet on your page it points out that pygmy whales have these air-sacs. So Chimps share a trait with whales that we do not. Isn't that counter to your argument about parallel convergence? Do you consider a pharyngeal air-sac to be a swimming/diving adaptation or not?

A laryngeal air sac is used by surface foragers, like apes, pygmy right whales, bowhead whales.

A pharyngeal air sac is used by walruses, they inflate it and sleep on the water surface.

Regarding swimming babies - if you consider 'swimming' to mean simply propelling oneself in water then yes, they seem able to do this to a limited extent. The points I was making were 1. they're hopeless (= very poor) at it when compared to other mammals

AFAIK, sea otter infants cannot swim or dive, they just float on their backs, then climb aboard the mother's stomach after she dives for food. Human ancestral infants most likely did the same thing, just swimming when the mother was nearby, otherwise backfloating still. The father and grandmother may have assisted as well.

This is speculation, unsubstantiated so far: Ancestral Human infants consumed their mother's milk which contained lipids (fats) which are buoyant in salt water, combined with some air swallowed increased infant buoyancy while in a horizontal backfloat position. Humans cannot burp in that position, instead the air and lipids tend to migrate to the highest point of the belly, which then tilts back the face keeping the nose highest. (Human infants feed quite often compared to most mammals, this may be a selection for having consistently buoyant bellies.) Only when the infant was lifted vertically could it burp. Human infants are notorious for getting colic, which is correlated to this unusual selective situation, I've found no indication that any ape infants suffer from colic, even though their mother's milk is similar to human mother's milk. Notably, horses, which are close genetic cousins of semi-aquatic tapirs, suffer from colic, so possibly the last common ancestor of horses and tapirs also floated horizontally more than today, though not backfloating. Whereas ruminants like deer, cows, goats (closest living kin to whales) can burp all the time, so they have developed laryngeal air sacs to assist with surface floating, keeping the throat and head above the water. The water chevrotain instead dives under the surface to hide from eagles, I'd assume they have no laryngeal air sacs, no colic, no floating, and that their nursing infants hide in grass rather than enter the water (since their lungs are too small to hold breath long enough at water bottom).

and 2. this 'reflex' doesn't seem to include any strategy for breathing. This means it's a bit generous to call it 'swimming'. I'd expect that if we had inherited anything from these aquatic ancestors of ours it would be a good breathing technique. So what you (and doting mothers & fathers everywhere) call 'swimming' is more like mobile drowning and swift intervention is required as soon as the fun stops.

Today's swimming pools are quite unlike seashore lagoon sandy beaches, and today's mother's often don't know how to teach swimming & backfloating (or tree climbing or running) to infants, since they themselves were not raised at seashores. Technology has alleviated the need for daily forage diving, we've become far more terrestrial, we can get lots of seafood by buying it at a market far from the seashores, etc.

I do know that about 20% of newborns sneeze when they look at the sun after dark adaptation, nearly all will sneeze when parts of the face are tickled or lightly brushed (upper lip, nostrils, eyebrows, frontal scalp all sensitive to pressure changes), and the MDR is a common physiological reaction to face submersion in cool water. Humans sneeze at about the same speed as whales exhale, both exhale CO2 and inhale O2 instantly, far faster and deeper-breath than normal human aerobic breathing or anaerobic breathing. That provides a possible correlation, but still unproven, that ancient human divers respired this way during diving.

DDeden

[wet]

Highest numbers occurred on offshore shoals in the Red Sea proper... Overall, Tridacna stocks have plummeted to less than 5%
of their sizes in the 1980s and 1990s (0.1�"1.6 ind. m�'2) [21, 22] because of artisanal reef-top gathering for meat and shells
Current Biology -- Richter et al.

Giant clams may have fed early humans - LiveScience - MSNBC.com

New giant clam species offers window into human past

New giant clam species offers window into human past

Researchers report the discovery of the first new living species of giant clam in two decades, according to a report to be published online on August 28th in Current Biology, a Cell Press publication. While fossil evidence reveals that the new species, called Tridacna costata, once accounted for more than 80 percent of giant clams in the Red Sea, it now represents less than one percent of giant clams living there.

The researchers said they cannot say for sure which factors contributed to the loss of this giant clam species in favor of others, but the overall decline in giant clam stocks and the striking loss of large specimens is a "smoking gun" for overharvesting by humans many thousands of years ago, said Claudio Richter of the Alfred-Wegener-Institute for Polar and Marine Research in Germany. The new species appears to live only in the shallowest waters, making it particularly vulnerable to overfishing.

" These are all strong indications that T. costata may be the earliest example of marine overexploitation," he said.

Modern humans are believed to have coasted out of Africa during the last interglacial, some 125,000 years ago, Richter said. The Red Sea, a saltwater inlet between Africa and Asia, may have acted as a bottleneck, and its overall aridity may have driven the early hunter-gatherers to rely on shallow-water marine resources. Giant clams would have been a prime target, because of their sedentary nature, conspicuousness, and large size, he added.

The research team, including scientists from the Center of Tropical Marine Ecology in Germany and the University of Jordan, discovered the new species while attempting to develop a breeding program for another prized giant clam species. Study coauthor Hilly Roa-Quiaoit of Xavier University in the Philippines, known as the "mother of clams," recognized the new species, which can measure up to a foot long and has a shell with a distinctive zig-zag outline, as a new variety.

Analysis of those apparent differences in morphology confirmed that the species was in fact clearly distinct. To further resolve the relationship of this new variety to the other giant clams, Marc Kochzius at the University of Bremen led the molecular genetic analysis, which confirmed T. costata as a new species.

The new giant clam differs from others in the Red Sea in an early and brief reproductive period each spring, coinciding with the seasonal plankton bloom, they report. Underwater surveys carried out in the Gulf of Aqaba and northern Red Sea revealed that the long-overlooked clam must be considered critically endangered. Only six out of a thousand live specimens the researchers observed belonged to the new species.

Early shellfishing evidence in other areas has led to speculation that the dispersal of modern humans out of Africa into the Red Sea and adjacent regions 110,000 to 90,000 years ago was driven largely by competition for marine resources, the researchers said.

" Our discovery that T. costata was already on a trajectory of decline prior to this period corroborates this hypothesis, by providing the first circumstantial evidence that humans were not only using but also depleting reef resources, making T. costata the likely earliest victim of anthropogenic degradation of coral reefs," they wrote. "Declining marine and terrestrial resources, by human and climatic factors, respectively, may have acted in concert to thwart the precocious but short-lived colonization of the Near East by anatomically modern but technologically primitive humans at the end of the last interglacial."

(This clam species is just one of many many different seafoods available that were available to daily diving/beachcombing human ancestors along seashores.)

[wet]

Dive-Surface-Sneeze-Speak ARC

Speech, though completely dependent upon the mouth/larynx, is not particularly (externally) sensorial. Eating, breathing,
sniffing, sneezing are all face-sense-related, talking isn't. Talking is all about internal air valve control. One cannot talk sensibly underwater, yet if not for underwater air valve control, speech would not have happened.

What is the physiological alternative of the anaerobic O2 conserving MDR Mammalian Divers Reflex which occurs at depth? Instant exhalation (photic/pressure/thermal induced) & aerobic breathing at surface, with optional controlled exhaled vocalized speech. Has anyone immediately upon surfacing from a *long* dive, spoken during the first exhale? I think humans were selected not to, just like seals and sea otters. First exhale, then speak/bark.

I think that the LCA Hominoid/Hominid 20ma -5ma could not call while floating vertically, possibly due to external (water) pressure on the throat/lar. air sac/hyoid/thyroid cartilage. Only when external pressure was eased, could a vocal sound be produced (compare to having a "knot in ones throat" or feeling choked up). This allowed breathing clearly through the nose during vertical floating, then upon grasping tree branches/roots and lifting up or wading, the external air sac pressure is off, and oral breathing and calling can start.

This might have been a predecessor of being able to suction feed underwater, having the oral breathing disconnected during submersion, allowing the open pharynx for feeding and swallowing, then upon re-emergence to light/pressure change, the larynx reopens to the mouth and instantly exhales but with no vocalization, just a pure instant complete air exchange of the lungs, trachea, mouth.

DDeden

[wet]

Ear Popper -- Otolaryngologists Relieve Fluid-Filled Ear with Low-Tech Remedy

The Ear-Popper is a handheld, battery-powered device that delivers a constant, controlled stream of air pressure and flow into the nasal cavity, diverting air up the Eustachian tube when the patient swallows. This "pops" the ear so the fluid can drain, unblocking the ear and restoring hearing.

Trigeminal nerve - Wikipedia, the free encyclopedia
Facial nerve - Wikipedia, the free encyclopedia
Cranial nerves - Wikipedia, the free encyclopedia

Afarensis: Book Review: Your Inner Fish by Neil Shubin

Human anatomy article

Human anatomy is a formative experience in the training of future physicians -- it is the students' grand introduction to the body, when they memorize the names of bones, organs and nerves as they painstakingly dissect a real cadaver. That first year, as well as in years after, the medical students were curious about what kind of doctor I am. I am a fish paleontologist who studies finned creatures that have been extinct for more than 370 million years. Seeing the history inside our bodies is like peeling an onion: The first layers we see reveal the history we share with primates (large brains and opposable thumbs). Peel deeper and we find the layers of history shared with other mammals (hair and breasts), reptiles (our distinctive way of chewing food), fish (arms, legs, backbones and heads), worms (an anus on one side of the body and a mouth on the other), jellyfish (the DNA recipe that builds our bodies), sponges (our many celled bodies) and so on.

Chapter five, appropriately called "Getting Ahead", begins with Shubin studying cranial nerves several days before an anatomy test. Most cranial are easy because they have only one function and attach to one muscle or organ. Four, however, are a bit more difficult to trace. Shubin focuses on two of the four - the trigeminal and the facial. Each breaks up into a number of smaller branches that take a complex path through the head. The trigeminal nerves controls some of the muscles we use for chewing, innervate teeth, control some muscles in the inner ear, and is responsible for facial sensation. The facial nerve controls the muscles used in making facial expressions and like the trigeminal, it also controls some muscles in the inner ear. The question is why? As Shubin puts it: Nothing about them seems to make any sense. For example, both the trigeminal and the facial nerves send tiny branches to muscles inside our ears. Why do two different nerves, which innervate entirely different parts of the face and jaw, send branches to ear muscles that lie adjacent to one another? Even more confusing, the trigeminal and facial almost crisscross as they send branches to our face and jaw.

According to Human Physiology, Klinke, Silbernagel et al., 2006, we indeed have such a reflex, as every other mammal. To be more specific, trigeminal cranial afferent nerve (V) relays the information that the nasal and mouth cavities are submerged, which triggers the autonomus nervous system to 1* bradicardia, meaning a reduction of heart rate to about 4/5 of normal rate 2* blood "shift"(?) to the thorax to support the lung when under pressure to keep it from collapsing (which would be bad for numerous reasons) 3* vasoconstriction, first in the limbs to protect vital organs, and later of everything except the heart and the brain, which creates a heart-brain circuit [h/t Muchy]

[wet]

http://www.nytimes.com/2008/09/23/science/23obfish.html

Ancient coastal Hominins ate seafood regularly, had big brains

Two coastal sites in Gibraltar, Vanguard and Gorham's Caves, located
at Governor's Beach on the eastern side of the Rock, are especially
relevant to the study of Neanderthals. Vanguard Cave provides evidence
of marine food supply (mollusks, seal, dolphin, and fish). Further
evidence of marine mammal remains was also found in the occupation
levels at Gorham's Cave associated with Upper Paleolithic and
Mousterian technologies [Finlayson C, et al. (2006) Nature
443:850–853]. The stratigraphic sequence of Gibraltar sites allows us
to compare behaviors and subsistence strategies of Neanderthals during
the Middle Paleolithic observed at Vanguard and Gorham's Cave sites.
This evidence suggests that such use of marine resources was not a
rare behavior and represents focused visits to the coast and estuaries.

[Mullins]

Yikes. I'll avoid doing a point-by-point response as we'll only go round in circles. All I'll say is, if you're going to present this stuff to people it would be a good idea to learn how to present ideas with the appropriate academic caution. You're taking what's actually quite an interesting (if still frustratingly ill-defined) theory and wrecking what little credibility it has by mixing wild speculation and non-sequitur in together with the occasional good point.

Edit: the above caused some confusion in subsequent posts - it is a response to #23 and #24, not the post immediately above.

[wet]

Not sure what you're going on about. Do you still insist that human infants are the same as infant chimps in water?