Human Muscles vs Other Mammals

[Starglider]

Wow. How does this continuous flow system work?

Mammal lungs consist of a tube branching out into a huge number of tiny pockets. Normally less than half of that air is exchanged on each breath (even during exercise), and the exchange itself isn't very efficient. Bird lungs consist of a huge number of tiny tubes. Air is pumped directly through the tubes on both the inhale and the exhale strokes, using a system of sacs and valves. Efficiency is further raised by using a countercurrent exchange system (blood flows in the opposite direction to the air - this is the only way to achieve better-than-equilibrium transfer in any passive gas or heat exchanger). Here's a detailed overview.

Does it work at rest at sea level, or only when the bird is in flight?

It works at rest, but the dedicated muscles are sized only for moderate exertion. In powered flight, contraction of the flight muscles greatly enhances the pumping effect, delivering the higher gas exchange rate needed to supply the muscles. Elegant, isn't it.

How do you get a high enough flow rate without any "in-out" pumping?

There is tidal flow in the trachea (of course) and the secondary air sacs, it's just the lungs that have near-continuous one-way flow.

That would look pretty weird in humans, wouldn't it? I can see these fat guys lining up for a 2000 km marathon, and crossing the finish line as skinny guys in really loose clothing.

I recall some crazy guys doing a polar (or was it antarctic?) trek over several weeks, pulling their sleds with human power only, in which they deliberately lost about a third of their body weight. There was a BBC program on it a few years back but I don't remember the specifics.

[Modax]

That's really interesting. The reason I asked if it worked at rest is because I was imagining the continuous flow to be like a sort of "ram-jet" effect that would only work when the bird was moving fast. Of course, now that I think of it, that wouldn't work very well, because all that air would need to have somewhere to go...

[Modax]

Mammal lungs consist of a tube branching out into a huge number of tiny pockets. Normally less than half of that air is exchanged on each breath (even during exercise), and the exchange itself isn't very efficient. Bird lungs consist of a huge number of tiny tubes. Air is pumped directly through the tubes on both the inhale and the exhale strokes, using a system of sacs and valves. Efficiency is further raised by using a countercurrent exchange system (blood flows in the opposite direction to the air - this is the only way to achieve better-than-equilibrium transfer in any passive gas or heat exchanger). Here's a detailed overview.

Come to think of it, that would solve a LOT of problems in Humans. If our tracheae were a series of tiny tubes, instead of one big monolithic tube, we would still be able to breathe through our mouths, (try exercising hard while breathing only through your nose) but we wouldn't be able to get food and crap stuck in the windpipe. That would be the best of both worlds, and that's not even taking into consideration the efficiency increase you mentioned.

[Starglider]

That's really interesting. The reason I asked if it worked at rest is because I was imagining the continuous flow to be like a sort of "ram-jet" effect that would only work when the bird was moving fast. Of course, now that I think of it, that wouldn't work very well, because all that air would need to have somewhere to go...

It would almost certainly be easier to simply have another orifice for expelling air. But evolution is a pretty awful design method; it can only follow incremental paths, and even then only when there's strong fitness pressure every step of the way. Frankly, almost all biology sucks from an absolute point of view; it only looks good because its been locally optimised to an insane degree and because it's had a billion years or so to accrete complexity. Yet supposedly-educated idiots still try to claim that nature is some kind of pinnacle of perfection - if birds didn't actually exist, those people would probably claim that they're impossible.

But yeah, birds still suck less than mammals.
Not that I ever managed to convince anyone on furry forums of that, in my possibly misspent teenage years

Come to think of it, that would solve a LOT of problems in Humans. If our tracheae were a series of tiny tubes, instead of one big monolithic tube, we would still be able to breathe through our mouths, (try exercising hard while breathing only through your nose) but we wouldn't be able to get food and crap stuck in the windpipe.

That doesn't sound practical. Lots of tiny tubes take more energy to pump air through than one big tube, are heavier and more fragile / difficult to keep open. In birds, only the lungs themselves are built like that, the rest of the respiratory system is large tubes and sacs. It would not be practical to make the whole airway out of tiny tubes; additionally it would make it more or less impossible to vocalise anything. Finally the benefit you propose - avoiding entry of large particles - is by far outweighed by the fact that small particles can now block the airway much more easily. A mesh or seive like structure over the top of the trachea would do the same job much more effectively - yet it hasn't evolved, probably because being able to cough up crap out of the lungs easily in an emergency is more useful than a little additional protection against solids getting in there in the first place.

[Modax]

A mesh or seive like structure over the top of the trachea would do the same job much more effectively - yet it hasn't evolved, probably because being able to cough up crap out of the lungs easily in an emergency is more useful than a little additional protection against solids getting in there in the first place.

How about a emergency "tracheotomy" orifice in the neck, held shut by a tight sphincter, that opens when the body senses that the trachea is blocked?

[Starglider]

How about a emergency "tracheotomy" orifice in the neck, held shut by a tight sphincter, that opens when the body senses that the trachea is blocked?

If we were in a transhumanist forum debating how to upgrade humans with genetic engineering, then that would be a worthwhile argument. There are lots of these little fixes you can do (see the classic Catalog Of Correctable Omnipresent Human Flaws for a detailed list), some of them have effectively no drawbacks, while some of them (like yours) have a minor cost (i.e. mass and associated pathologies such as new vector for infection) that may or may not be worth the benefit.

However evolution doesn't work like that. Choking to death is a rare problem. The amount of sustained fitness pressure that would be required for a species to evolve an 'anti-choke orifice' that is actually more of a benefit than a handicap is ridiculously high. In fact it's hard to imagine any incremental path for it at all, because any mutation that creates a hole in the windpipe (already a very, very unlikely event) isn't going to create a working sphincter, nerves or instincts for same. I can't think of any way such a thing could gradually evolve from our existing respiratory setup, and I highly doubt it's ever going to be in the top hundred list of most survival critical features for any animal, so I can't see it ever evolving (on earth at least).

[Modax]

Thank you for posting that link. This subject interests me immensely I will enjoy reading that list a great deal. Strangely, although I've visited a lot of transhumanist websites before, I had never come across that document.

[Count Chocula]

The avian efficiency comes with significant tradeoffs compared to mammals, as well. Their bone structures are necessarily lighter, they can not grow to significant sizes (at least enough to threaten any mammal over 20 lb.), and their metabolisms are much higher than mammals, reducing their endurance. Canadian geese, for example, have to eat for months to build up a reserve of fat that they burn for their biennial migrations. When you combine that with their inability to have claws for defense or fangs, avian species don't look like that great a deal. Those birds that did evolve to compete with mammals, ostriches and emus IIRC, lost their ability to fly. As did penguins, as an adaptation to their environment.

[Modax]

When you combine that with their inability to have claws for defense or fangs

birds do so have claws, they're called talons.

Also, criticizing the fact that birds need to eat for months to build up a sufficient energy supply for 11,000 km journey is a bit like saying the Boeing 747 is poorly designed because it burns a large amount of fuel.

[Count Chocula]

Talons are kinda hard to use for defense, especially against a predator with two sets of claws and a mouth full of fangs. They also travel "only" 650 miles or so (1,000km for you Great White Northers ) in a day. Impressive, no doubt, and birds in the air are unassailable, but they are very vulnerable on the ground.

[Modax]

I also wanted to suggest that Catalog of Correctable Omnipresent Human Flaws should be offered as REQUIRED READING for people (read: fundies) who praise "intelligent design". Of course, we can't force them to read it. Nor can we force them to think. But this doesn't get brought up in debates enough.

[Count Chocula]

Got through the first few paras on your link. I likey! Must read more.

[Modax]

Talons are kinda hard to use for defense, especially against a predator with two sets of claws and a mouth full of fangs. They also travel "only" 650 miles or so (1,000km for you Great White Northers ) in a day. Impressive, no doubt, and birds in the air are unassailable, but they are very vulnerable on the ground.

Yes, its true that birds are not perfect. Nor are they always the best adapted organisms in their environment. I think the point of the discussion though, is that humans (and mammals in general) are often held up as though they're the pinnacle of evolution, as though mammals are some kind of end-product of billions of years of evolutionary R&D, but that's simply not the case (as I'm sure almost everyone on this forum already knows, anyway)

[Molyneux]

I would like to add my thanks to everyone else, I have never seen that document before...or heard of metabolic water, for that matter.

I find the idea of a an organic ramjet intriguing. Perhaps it could augment its flightspeed with precisely timed bursts of avian flatulence?

[Starglider]

The avian efficiency comes with significant tradeoffs compared to mammals, as well. Their bone structures are necessarily lighter, they can not grow to significant sizes (at least enough to threaten any mammal over 20 lb.),

Wrong, moron. In recent (evolutionary) history there was a 20 kilo eagle that hunted 200 kilo prey.

and their metabolisms are much higher than mammals, reducing their endurance.

Are you even bothering to read this thread? Missed the whole 'nine days continuous flying' thing did you?

Canadian geese, for example, have to eat for months to build up a reserve of fat that they burn for their biennial migrations.

That's because pondweed isn't terribly nutritous. Rabbits take even longer to build fat, on a similar diet.

Talons are kinda hard to use for defense, especially against a predator with two sets of claws and a mouth full of fangs.

Have you ever actually seen an enraged raptor up close? They have razor beaks and are very good at using their talons, typically in ways that a quadruped would find very difficult (i.e. going for the eyes). Also almost no mammal uses rear claws for killing prey, for reasons that should be obvious. But then it's clear that you haven't bothered to either think through or research your statements.

Those birds that did evolve to compete with mammals, ostriches and emus IIRC, lost their ability to fly. As did penguins, as an adaptation to their environment.

Yes, and they still rock. I don't see any mammals thriving in the wastes of antarctica.

Impressive, no doubt, and birds in the air are unassailable, but they are very vulnerable on the ground.

Compared to what? Foxes generally will not attack geese, because they don't want their eyes pecked out and their bones broken by the goose's wings. Wolves will but they're much larger, what do you expect. For their size (and even moreso for their mass) birds are quite ferocious.

This reminds me of a cool bit in 'A Bug's Life' - the insect's view of the little songbird as a unstoppable killing machine.

[Dooey Jo]

Catalog of Correctable Omnipresent Human Flaws

That's hilarious. Oh noes, pubic hairs, involuntary erections and dreams! How disgusting! No, transhumanist wank should hardly be required reading for ID supporters, as that will only strengthen their idea that science is nuts. There are lots of books discussing evolution and jury-rigged design out there. Something by Gould would probably be best, as he could discuss these matters without necessarily pissing religious people off (which is good if you want to teach them something).

Those birds that did evolve to compete with mammals, ostriches and emus IIRC, lost their ability to fly. As did penguins, as an adaptation to their environment.

Yes, and they still rock. I don't see any mammals thriving in the wastes of antarctica.

You don't see penguins there either; they live by the coasts. As do seals. And there are plenty of whales in the waters there too. Polar bears would probably like it quite a bit in the Antarctic as well, if they could get there.

[Starglider]

That's hilarious. Oh noes, pubic hairs, involuntary erections and dreams! How disgusting!

I wouldn't take that stuff terribly seriously. I recall the tone of discussion when it was introduced was pretty much 'here's some annoying niggles we could fix even for people who insist on staying pretty much conventionally human'. All the actual transhumanists wanted to do things like this at the very least, mostly far more towards the 'brain-only cyborg' or 'just upload me damnit' end of the spectrum.

There are lots of books discussing evolution and jury-rigged design out there.

Certainly that transhumanist wish list is in no way suitable as material for a serious discussion of evolution.

[Molyneux]

Have you ever actually seen an enraged raptor up close? They have razor beaks and are very good at using their talons, typically in ways that a quadruped would find very difficult (i.e. going for the eyes). Also almost no mammal uses rear claws for killing prey, for reasons that should be obvious. But then it's clear that you haven't bothered to either think through or research your statements.

Uhh...have you ever seen a cat hunting anything close to its size? Or better yet, have a housecat play-attack your hand and start kicking madly at your forearm? That's because one of their hunting techniques (against, say, rabbits) if the initial neck-bite fails is to use those nice sharp back claws of theirs to disembowel the prey animal.

[Broomstick]

Ah, yes, the wannabe transhuman speaks...

Actually, I quite agree with you that this is an ideal goal of mine. Whether it could ever be realized in my lifetime however is another story. At the moment I rather doubt it.

WHY would we want to replace functional muscle?

Because 'functional' does not equate 'superior' or 'efficient', nor do I have the same attachment to frail human existence most other people seem to (which I gather you do?).

Personally, if I could safely discard my organic body for a superior artificial one surpassing all or even most the capabilities of my organic one, I'd do so without a second thought.

A lot of my skepticism comes in due to our current replacement technology. While LASIK, cochlear implants, and dentures sure as hell beat being blind, deaf, and toothless they all still have implementation problem. Even dental implants - usually a better alternative than dentures when you can afford them - still aren't the same as a mouth full of health teeth (a mouth full of diseased teeth are a different matter). So I'm skeptical about the "better than natural" idea. It's possible, but I am very skeptical about claims of that sort. Yeah, it shows in my posting.

And why with something "one hundred times stronger" when we don't need such strength? That makes no fucking sense at all.

Define 'need'. I doubt you 'need' to post on this board, yet you go out of your way to do so. I could compile an enormous list of things people do not 'need' but still desire and acquire nonetheless. Furthermore, enhanced personal strength, endurance and durability would certainly come in very useful in many situations, which presumeably I don't have to list for you.

Well, it might come in handy in some situations, but let's face it, for deskjockey jobs it's just not necessary. With time/expensive/pain involved a lot of people just might not view it as worth it, or not worth it until age causes deterioration.

Posting on this board is not terribly "out of my way", it's easy and cheap because I have a computer in my house, if I had to go several kilometers to library to read and post to this board (the most likely alternative) you'd see me very infrequently. Likewise, if this replacement is easy and cheap it's a lot more likely to be common, but I doubt "easy and cheap" will be a good description, particuarly when first developed.

Never minding the mental enhancements of integrating computers with our minds.

That is probably more likely to happen.

I suppose technically speaking it already has, just not as directly as I was implying.[/quote]
Well, if you want to get picky reading and writing are artificial memory enhancement and we've had that a long, long time.

[Broomstick]

The avian efficiency comes with significant tradeoffs compared to mammals, as well. Their bone structures are necessarily lighter, they can not grow to significant sizes (at least enough to threaten any mammal over 20 lb.), and their metabolisms are much higher than mammals, reducing their endurance.

Bullshit. Birds have enormous endurance. In addition to the aforementioned 9-day marathoner, Albatross can remain aloft for months - of course such things are made possible by mechanisms evolved to enable food storage and efficient flight. There's nothing mysterious about.

But you are wrong about "not threatening" to large mammals - adult geese and swans can and have severely injured or even killed adult humans. Eagles have been known to tear the throats out of falconers. And there is at least one instance of a pet macaw doing the same for a burgurler. Birds can be quite dangerous.

When you combine that with their inability to have claws for defense or fangs, avian species don't look like that great a deal.

Hyacinth macaws have a beak capable of peeling a Brazil nut like we peel an orange - they don't need fangs. Raptors and several other species have talons quite capable of causing severe damage.

Please go back and learn a little more about birds.

[Starglider]

A lot of my skepticism comes in due to our current replacement technology. While LASIK, cochlear implants, and dentures sure as hell beat being blind, deaf, and toothless they all still have implementation problem. Even dental implants - usually a better alternative than dentures when you can afford them - still aren't the same as a mouth full of health teeth (a mouth full of diseased teeth are a different matter).

The relevant supporting technologies are just now beginning to make some of these replacements (they don't really count as enhancements yet) possible. It's roughly equivalent to where aviation was in the mid 1800s; hydrogen balloons existed and have some limited utility, but powered flight was still decades away. Similarly I think we're decades away from radical human upgrading and probably a century from it being easy and cheap.*

* Actually I don't think that; this is what would be called a 'CRNS prediction' on a transhumanist forum, i.e. Current Rate No Singularity. I think we'll probably crack general AI first and that will invalidate all such predictions. But never mind that now.

[Junghalli]

Cool link Starglider, thanks.

That's hilarious. Oh noes, pubic hairs, involuntary erections and dreams! How disgusting! No, transhumanist wank should hardly be required reading for ID supporters, as that will only strengthen their idea that science is nuts.

Hey, I wouldn't mind having most of the mods on that list (though some of them are a bit too weird or silly for my tastes - for starters I'd rather keep my external appearance normal so no rearranging my nose please). But yeah, it wouldn't be a good discussion on evolution because some of the "defects" they want to correct aren't so much defects as areas where evolution had different ideas from us. Built-in birth control is one example. An even better one is reducing muscle atrophy; from a biological perspective muscle atrophy is a very sensible economy measure, and the way our bodies manage muscle tissue now makes vastly more sense than the way it would be managed in the "corrected state".

BTW about birds being a threat to mammals, back in prehistoric times there was a giant ostrich-sized flightless predatory bird that munched on the ancestors of horses. Yeah, they weren't the size of modern horses, but this thing was pretty formidable.

[Broomstick]

I forgot one major, major downside to avian respiration (I'm struggling with a slow connectionon an unfamilar computer during a family visit - pardon the coding errors). Yes, birds' lungs/airsacks/etc. are very efficient at extracting oxygen from the air, far more efficient than any mammalian system. They are are far more efficient at extracting toxins, too. That's why for a long, long time you could hear canaries singing deep inside coal mines - poison gases killed the birds much more quickly than the humans, often giving the miners time to flee before they (the humans) died.

Which, I suppose, is yet another example of "no free lunch".

[Starglider]

Which, I suppose, is yet another example of "no free lunch".

Well, kinda. Toxin vulnerability is something that can be fixed at the metabolic level, but like every other evolved feature it takes concentrated fitness pressure to make it happen. 99.99% of birds never encounter significant airborne toxins, so there has been no reason to fix the problem (because it isn't a problem under normal circumstances). If the whole atmosphere started getting toxic (but slowly enough not to just kill everything), I'm sure you'd see adaptation across all species to handle it.

[Broomstick]

Which, I suppose, is yet another example of "no free lunch".

Well, kinda. Toxin vulnerability is something that can be fixed at the metabolic level, but like every other evolved feature it takes concentrated fitness pressure to make it happen. 99.99% of birds never encounter significant airborne toxins, so there has been no reason to fix the problem (because it isn't a problem under normal circumstances).

I fail to see how you could metabolicaly guard against all possible toxins.

And, actually, birds DO encounter airborne toxins - anything airborne poisonous to us is usually more so to them, so smoke from a burning fire (as an example) will kill them much more quickly than us, and these things do occur in nature. Bird species typically compensate for both predation and environmental hazards by a high reproductive rate. While birds can potentially live very long lives for animals of their size and metabolism in real life the vast majority don't as they are killed off by one thing or another fairly early in life.

If the whole atmosphere started getting toxic (but slowly enough not to just kill everything), I'm sure you'd see adaptation across all species to handle it.

Yes and no. If, for example, carbond monoxide rates were to go up anything using hemoglobin is pretty much screwed, and I don't see any mechanism for an alternative oxygen transport molecule evolving in vertebrates. Ditto for certain cyanide compounds. There are life forms that can tolerate such things, but they aren't us or much of the animals we care about.