http://news.bbc.co.uk/2/hi/health/4067039.stm The parathyroid gland used to be our gills. All we need to do is a little gene therapy, and we could have gills once again. I think that gills would be a valuable asset to have. Better than a tail, but not as good as wings. This article says we will have gill implants in 2043. http://www.enigmata.org/writing/fut-his/2031-2049.html I think it will be much earlier, as the demand for gills will rise sharply as the oceans rise due to global warming.
I dont belive we had gills but yea, even if we get gills what kind of clean fresh water are we going to swim into??. You mean that water with the crap from my tolet and yours with some poisen lab chemical stuff in it. If we wanted fresh water to sim in with less chance of being eaten by predators our best bet would be near north america but we cant live in that cold. And were not genitically fit to fight under water.
Yes, we once did have gills, but welcome to the wonderful world of evolution. That was over 500 million years ago during the Cambrian when our gill structure was used for feeding and some for respiration. Gill slits have now developed into parts of our ears, cranium bones, and jaws - and yes, a portion of where are parathyroid gland is too. But don't start whimsically saying that all we have to do is ..... and then we can instantaneously reverse 500 million years of evolution! If you are intrigued by this, then why don't you consider studying evolution as a career? It is very rewarding and enjoyable. But you have to be strictly scientific about it, and not just make fantisizing statements.
Technically, we still do have gills - but only while we are still in the womb as a small embryo. As Valich correctly noted, as we continue to grow and develop in the womb, our gills are transformed and used for other functions. Artificial/mechanical 'gills' would be an interesting device that perhaps might be developed for extracting oxygen from water so we could breathe underwater without the use of a SCUBA. That should prove to be an interesting engineering challenge - but one with a potentially HUGE payback, as they would be extremely popular.
That would require water flowing over the artificial gill at the rate of about one gallon per second, with near 100% oxygen extraction efficiency, to obtain sufficient breathable oxygen for a human. Tough engineering challenge. The Israeli company's design apparently uses a centrifuge to force the oxygen out; but there are likely other methodologies that should work. It might be more important for replenishing the oxygen suppley of an underwater habitat, rather than for swimmable gills.
I was wondering how efficient gills would be on mammals, as we have much higher metabolisms than our distant aquatic relatives. You guys ever hear of a rebreather? It's like SCUBA, but with less gear. I'd really like to get my hands on one, one day.
Technically humans no longer have gills, although they are present in embryology. And during that developmental stage you can at best consider them as transient vestigial parts or organs that all animals have in their development (similar/vestigial organs - DNA sequences in the genome). So lets not feed the flames to think otherwise, i.e., that this phase of development can now be haulted to produce.... this-and-that-and-this..... Whales and dolphins are also mammals. Some fish, such as Lungfish, can breath in or our of water. Bony fishes evolved lungs first but they are usually only used to give the fish buoyancy so it doesn't go belly-up, and they are especially important in South American fish (sturgeons and many teleosts have dorsal lungs - on top). Most fish acquire oxygen through filtration from their gills and the lungs that evolved are used as accesory respiratory devices, as in Coelacanths, or as a gas bladder. Jaws in jawed fish developed from the anterior gill slits (anterior gill arches), then there was the evolution of the semicircular canal with phosphate crystals called otoliths. Lampreys have two semicircular canals that serve as nerve coordination for movements. Some fish used gills for respiration while others used gills strictly for filter feeding. Human embryos initially develop with gill slits and pharyngeal gill slits that partially develop the pharynx. Welcome to the wonderful world of evolution.
What the hell are you guys smoking? Humans do NOT have gills at ANY stage during embyrological development. I repeat, humans do not have gills at ANY stage during embryological development.
Gee - - I guess all the textbooks are wrong when they show comparisons of emryonic development of various animals - fish, amphibians, reptiles, mammals - - all showing gill slits at an early stage of embryonic development. I believe Valich has the best description - - gill slits in mammals that never develop into functioning gills, but derived from the same tissue types and morphology (actual slits) as develop into the gills in fish. It's interesting that the more advanced jawed fishes developed the lower jaw from gill-slit tissue. It seems that the gill slit tissue develops into many portions of the head in the higher animals, and to try to 'tamper' with it in the embryo would likely be fatal.
I think that Mountainhare was simply saying that human embroyos never actually have gills. They do have gill slits at some stage, and perhaps some other portions of the gill structure (I'm not entirely sure), but they don't have gills. Just the slits wherein the gills would develop if development continued in such a direction (which it doesn't.) In fact, aren't some people born with their gill slits still open? I seem to remember there being some type of condition like this... Hmm. Tried googling it. Kept coming up with Christian bullshit... Even with -christian thrown in the mix. Bah! Google should add an option to categorize its searches so as to categorically remove such idiot nonsense. Stupid creationists anyway. What the hell are they even doing on the internet? Shouldn't they be off somewhere burning witches or driving around in horse and buggies? Stinking Luddites.
I was in bio the other day, and my prof said something to the extent of "whales and dolphins don't have gills because they lost them. Once you lose something evolutionarily, it doesn't come back." Whihc got me thinking; given enough time, would cetaceans evolve gills? Then I recalled a thread about killer whales vs. great white sharks, with Doc and Fraggle making some great posts. Doc confirmed that orcas are badass mothas, and routinely beat the shit out of sharks. Fraggle explained that mammals are extremely good competitors with cold-blooded animals, since our metabolism allows us to use more energy, more efficiently. So perhaps cetaceans would never evolve gills because there would be a disadvantage to it, as they wouldn't be able to respirate as efficiently.
I was thinking the exact same thing, Roman. Then noticed you'd already brought it up earlier. Thus stealing my fire and limelight you piece of dog crap!!!! Hee. Yeah. I doubt that gills are capable of providing enough oxygen to feed warm-blooded metabolism. It's hard to say without direct experimentation and physical data however. Perhaps if we had huge gills? I mean freakishly enormous? Would it be feasible (even if unwieldy)? Perhaps gills might not re-emerge in mammals going back to the sea, but monster sized gills could be incorporated into a submarine with little difficulty. The question is if it is feasible or not. There was a series of books based on some Arthur C Clarke story that featured in one of them a submarine with gills. It also had a locomation system like a manta ray. Interesting proposition. The sub had to stop at certain depths to allow the system to recalibrate itself to the new depth, however.
Invert, Walter has this to say about artificial gills: I don't know where he got his data from, but with a name like Walter L. Wagner, I'm going to say I believe him. Submarines go fast, though, so supplying oxygen at a rate of 1 gallon/second may not be so difficult, especially with humungous gills. But then, when using nuclear subs, why bother? You've got jillions of years of energy you can use to extract oxygen from seawater without developing new (and ludicrous) technologies.
Invert is absolutely correct that humans never have "gills" per se, but in the embryology stages of development of the fetus we do have "gill slits." This is an undisputable fact known to all biologists and to anyone who has studied evolutionary biology beyond a beginning level course. Almost all of the posts above refer to the fact that humans "used to have gills," and this is correct. We evolved from animals that used to have gills, and the gill slits that we still have in our embrological stage is a living testament to this fact of evolution and a fact that clearly supports the theory (fact) of evolution itself. Actually, it is not very accurate for me to say that they are "vestigial organs" because they do not remain with us but evolve into other physical features. Pharyngeal "gill slits" are clearly visible in the human embryo. Through DNA conservation in our genome we still code for gill slits - and possibly even for gills? - but I don't know enough to state this as fact. If this thread continues, it would not be much trouble for me to review my past course notes and post what each individual gill slit now develops into when we are born. I think there are five pharyngeal gill slits in the human embryo. Another example is the neck region of a human embryo. These are the branchial arches containing the blood vessels - aortic arches. They develop into gill circulation and gill arch supports in fish, but eventually close in the human embryo. http://home.earthlink.net/~dayvdanls/biology1_2/branchial_arches.htm These traits are called "shared primitive characteristics," as opposed to "derived characteristics." Of equal interest to this subject, the following are all shared primitive characteristics that all vertebrate animals have: 1. a dorsal hollow nerve chord that develops into the brain and spinal cord 2. a notochord that exists in all chordate embryos that provides back skeletal support 3. a post-anal tail (present in the embryo, absent in the adult) 4. pharyngeal gills (gill slits) - present in human embryos 5. cephalization (brain, head...) 5. bilateral symmetry Adult Tunicate: Please Register or Log in to view the hidden image! Human Embryo at One Month: Please Register or Log in to view the hidden image! Source: http://embryology.med.unsw.edu.au/wwwhuman/Stages/stage12.htm In this view you can see 3 pharyngeal arches, heart prominence, forebrain, notochord neural tube developing the spinal cord, and an extensive tail See also embryo view at: http://www.visembryo.com/baby/11.html Also, I do not think that Walter was incorrect in any of his posts. A forum will start out with a general topic and then get more deeper and require more accuracy in terminology as it progresses. Walter was responding to Zephyr's reply that referenced a Wikipedia article called "Like-A-Fish" that describes a system to extract breathable air from water by developing an "artificial" gill. But this drifts away from the subject matter of the original post.
Evolution of fish jaws, and in mammals, came from the anterior (frontal) gill slits/arches. Wow! I just came across an article on the web the equates the notochord as being the same thing as the dorsal hollow nerve cord. This is a big mistake. The notochord is a long rod that develops into the spine as a skeletal structure for support in both fish and humans. The dorsal hollow nerve cord is the nerve chord - a key element of the chordate nervous system. In all vertebrate embryos it develops into the spinal cord and the brain. At least this is how I learned it. http://instruct1.cit.cornell.edu/courses/biog105/labs/deuts/chordates.html Vertebrae have two main parts. One, the main bony disk-shaped or spool-shaped portion of the vertebra that forms around, and usually replaces, the notochord. On the dorsal side of the centrum is the neural arch, through which the nerve cord or spinal cord passes. The neural arch is often elongated into a neural spine, which may be very long in the case of "sail-backed" synapsids such as Dimetrodon. In tetrapods and a few bony fishes, the neural arches bear processes, the zygapophyses, that link the vertebrae together. Two: Probably the most important vertebrate feature is the presence of neural crest cells. In early development, as the nerve cord [dorsal hollow nerve chord] is forming, neural crest cells leave the nerve cord and move through the body. These cells form, or cause to form, many important nerves, neural ganglia, and many head and facial features. Other features that separate vertebrates from other chordates include: a relatively well-developed brain, paired complex eyes, a muscularized mouth and pharynx, and a well-developed circulatory system with a heart. http://www.ucmp.berkeley.edu/vertebrates/vertmm.html
Invert_Nexus: Precisely. Gill SLITS are a far cry from GILLS. Reading the comment that humans have gills during embryological development (which was made by MULTIPLE POSTERS!) made me want to punch a baby. This is sciforums, for goodness sakes! And technically, the gill slits are known as pharyngeal slits.
Yes, I agree with you 100%. I did not mean to mix this up - only to add understanding to the thread. However, I can cite you many paleontological articles that refer to pharyngeal slits as "pharyngeal gill slits." Perhaps they do this to emphasize the origin.
