39 thoughts on “Lungs”

  1. Lungs were present in the ancestors of all bony vertebrates. They didn’t evolve “for” life on land–they served very well in the water for fish. In some lineages they became swim bladders or were just lost. See this book chapter for a great overview: http://bit.ly/1VNK4MQ

    1. I thought they were derived from swim bladders. Still useful for fish with gills, taking a gulp of air in low oxygen waters. Some fish still do that.

    2. I was going to reference Carl Zimmer’s At the Water’s Edge to explain that lungs came first, only to see that Mr. Zimmer himself beat me to it.

      To add just a bit, quoting myself from a personal blog entry, “Only teleosts have true swim bladders… there are other groups of fish that have lungs. And there exist other groups with structures intermediate between lungs and swim bladders. The most parsimonious explanation is that lungs evolved first, and only developed into bladders in one lineage. And just for reference, sharks and rays, which diverged from other fish around 450 millions years ago, don’t have any type of lung or swim bladder at all.”

      The benefits of air breathing for fish is also clear from the teleosts that have independently evolved new structures for air breathing, such as the labyrinth organ in bettas.

    3. Carl beat me to it! Every year in vertebrate zoology, one of the exam questions is “What evidence indicates that lungs and gas bladders are homologous structures? Consider their embryological origin, connection to the gut, and distribution and nature in living and fossil forms.” An essential part of the answer is showing that lungs came first.

      This is one of the great triumphs of comparative morphology. It was not known in Darwin’s time; he like most people today, thought bladders became lungs, rather than vice versa.

        1. I don’t know when it was first known, but it was certainly known by the late 1970s. Romer and Parsons condensed Vertebrate Paleontology, published in 1977, discusses it.

          One of the problems with textbooks, particularly High School textbooks, is that once they get hold of a good “Just So” story they won’t let it go. My mother in law had a ~1950 vintage High School science text that asserted that atoms were indivisible and unchangeable. You’d think Hiroshima and Nagasaki might have given them a clue that wasn’t quite the case.

          1. Oh, I have no illusions about the quality of textbooks, particularly high school ones (as you say) but was curious whether I had missed the consensus building. After all, biosciences aren’t my speciality. (One of the reason I come to this site is to learn!)

            Speaking of atoms, many textbooks even get the translation of “atomos” wrong, which is simply “not to be cut”. (The further twist is that we actually don’t know for 100% certain that Democritus meant that the atoms were indivisible, either. He was certainly taken that way later, but …)

    5. A plague on the House of Zimmer. That reference was so interesting I was compelled to buy the book. Do you know how much backlog reading material I have waiting for me??

      (Maybe they should put you on a commission!)

  2. I contemplate the asymmetrical 3-lobe/2-lobe arrangement in humans. Is that true of all or most mammals? Is that to accommodate the heart? Even so, why 3-2? Why not 2-1, 4-3, 5-3? (The more lobes, the more redundancy/increased chance of survival should a lobe be damaged, eh?)

    1. Why asymmetric lungs in humans? This appears to be a packaging solution. The mammalian heart takes up a lot of room in the thoracic cavity, is already asymmetric with separate pulmonary and systemic circulation, so it’s going to be offset –just happens to be on the left. The amount of heart offset looks to be just right to allow five roughly equal lobes: 2 left 2 right.

      It’s at least possible that the separation into lobes has some benefit in recovering from illness or injury. My mother survived TB[for 4 decades, but ultimately succumbing to congestive heart failure]. As I recall, pre-antibiotic treatment included selective collapsing of affected lobes. In any case she had to live with only 2 right-side lobes that were really functional.

      And as an often-winded senior athlete,don’t tell me that the God who made us in his image didn’t give himself the good stuff like avian flow-through lungs and internal genitalia!

      1. I’ve read that snapping turtles can exchange oxygen through the lining of their rectums when underwater….

        2. You can do that too.
          The standard “Oh Shit I’m Gonna Die” emergency medical pack for placement in the more isolated bits of cave in the UK includes equipment for perfusing drugs into the victim through the rectum. The intention is for people who are quite seriously injured and possibly don’t have good circulation to the periphery of their crushed and mangled limbs.
          By the time you’ve lost circulation to the colon, you’re in a really bad way and religion isn’t going to help you.
          Something worth filing in the back of the mind, in case you wake up after a major car crash wondering “What the hell happened … and what is that stranger doing to me with a length of hose and rubber gloves?????”
          (The mountain rescue teams just include strong painkillers and suturing equipment. On a mountain, you’re rarely more than a couple of hours from the trauma team ; down a cave you can be days from a trauma team.)

  3. I have only tumbled onto a view papers on the deep origins of it in my #TIP research (as origins of organs are naturally part of antievolutionist apologetics). The salient ones on the developmental biology & genetic side (they spread over quite a long time period, so I’m sure I’m missing much):

    Cieri et al 2014. “New insight into the evolution of the vertebrate respiratory system and the discovery of unidirectional airflow in iguana lungs.” Proceedings of the National Academy of Sciences 111 (2 December): 17218-17223.

    Liem 1988. “Form and Function of Lungs: The Evolution of Air Breathing Mechanisms.” Integrative and Comparative Biology (AKA American Zoologist) 28 (April): 739-759.

    Shu et al. 2007. “Foxp2 and Foxp1 cooperatively regulate lung and esophagus development.” Development (AKA Journal of Embryology and Experimental Morphology) 134 (15 May): 1991-2000.

    Torday 2004. “Deconvoluting Lung Evolution Using Functional/Comparative Genomics.” American Journal of Cell and Molecular Biology 31 (July): 8-12.
    ________. 2007. “The evolutionary continuum from lung development to homeostasis and repair.” American Journal of Physiology –Lung Cellular and Molecular Physiology 292 (September): L608-L611.
    ________. 2009. “Lung evolution as a cipher for physiology.” Physiological Genomics 38 (June): 1-6.

    I’ll be looking forward to seeing what else is brought forward, to add to the #TIP dataset.

    1. Did a second pass of the bibliography refs, this time for respiratory, and caught a few more relevant papers (bigger picture and deeper insights, moe broadly than just the tetrapod split):

      Carvalho & Gonçalves. 2011. “Comparative Physiology of the Respiratory System in the Animal Kingdom.” The Open Biology Journal (online @ benthamopen.com) 4 (10 January): 35-46.

      Castresana & Moreira. 1999. “Respiratory Chains in the Last Common Ancestor of Living Organisms.” Journal of Molecular Evolution 49 (October): 453-460.

      This topic prompted me to do a fresh google search, which turned up another older paper on tetrapod issue (which I’ll be adding to the #TIP set as I hadn’t spotted it previously):

      Perry & Sander. 2004. “Reconstructing the evolution of the respiratory apparatus in tetrapods.” Respiratory Physiology & Neurobiology 144 (15 December): 125-139.

      Only have the abstract of it, extract: “The air-breathing apparatus of tetrapods has its origin in gill breathing. The lungs of the first tetrapods were probably long and consisted of a single series of parenchyma-filled chambers, arranged along an intrapulmonary duct. The duct gave rise to a broad central lumen in anurans. In amniotes a cartilaginous reinforcement evolved. The septate nature of the gas-exchange tissue (parenchyma) is recognizable in all tetrapods except birds. Active expiration began with the origin of transverse body wall musculature in amphibians, whereas active, negative-pressure inspiration is seen only in amniotes. The functional transition of trunk musculature from locomotor to respiratory is most complete in birds.”

      That diapsid/dinosaur/bird split deserves a section of its own, of course, and haven’t included any of the #TIP refs on that here.

      I suspect the evo-devo genetic work still ongoing, and that will have to kick in to resolve the blips that are showing up on the fossil scope.

    2. One or other (or both?) of the FOXp genes was implicated in larynx development a few years back, and touted as “the gene that let us speak”.
      (RE : the Shu et al. 2007 paper.)

      1. It’s always unwise to get bogged down on popular media coverage of any scientific or technical subject. FOXP2 has in fact been coopted in language usage, along with a host of other components. It is not a language gene itself, though (indeed, few genes appear to be “for” specialized functions like that), and none of the technical work claimed that as far as I can recall, but quite a body of work has documented the wide exaptation of this old gene in language related areas (and not just people), beyond that Shut et al 2007 you note that relate to lungs and esophagus. The track of the work may be seen in just the limited collection I had put together for the topic in #TIP, in order of publication:

        Zhang et al. “Accelerated Protein Evolution and Origins of Human-Specific Features: FOXP2 as an Example.” Genetics 162 (Dec 2002): 1825-1835.

        Enard et al. “Molecular evolution of FOXP2, a gene involved in speech and language.” Nature 418 (22 Aug 2002): 869-872.

        Marcus & Fisher. “FOXP2 in focus: what can genes tell us about speech and language?” Trends in Cognitive Sciences 7 (June 2003): 257-262.

        Haesler et al. “FoxP2 Expression in Avian Vocal Learners and Non-Learners.” The Journal of Neuroscience 24 (31 March 2004): 3164-3175.

        Vargha-Khadem et al. 2005. “FOXP2 and the neuroanatomy of speech and language.” Nature Reviews Neuroscience 6 (Feb 2005): 131-138.

        Shu et al. “Altered ultrasonic vocalization in mice with a disruption in the Foxp2 gene.” Proceedings of the National Academy of Sciences 102 (5 July 2005): 9643-9648.

        Teramitsu & White. “FoxP2 Regulation during Undirected Singing in Adult Songbirds.” The Journal of Neuroscience 26 (12 July 2006): 7390-7394.

        White et al. “Singing Mice, Songbirds, and More: Models for FOXP2 Function and Dysfunction in Human Speech and Language.” The Journal of Neuroscience 26 (11 Oct 2006): 10376-10379.

        Shu et al. “Foxp2 and Foxp1 cooperatively regulate lung and esophagus development.” Development (AKA Journal of Embryology and Experimental Morphology) 134 (15 May 2007): 1991-2000.

        Li et al. “Accelerated FoxP2 Evolution in Echolocating Bats.” PLoS ONE (online @ plosone.org) 2 (Sep 2007): e900.

        Coop et al. “The Timing of Selection at the Human FOXP2 Gene.” Molecular Biology and Evolution 25 (July 2008): 1257-1259.

        Miller et al. “Birdsong Decreases Protein Level of FoxP2, a Molecule Required for Human Speech.” Journal of Neurophysiology 100 (Oct 2008): 2015-2025.

        Enard et al. “A Humanized Version of Foxp2 Affects Cortico-Basal Ganglia Circuits in Mice.” Cell 137 (29 May 2009): 961-971. Commentary by Lieberman “FOXP2 and Human Cognition.” Cell 137 (29 May 2009): 800-802.

        Konopka et al. “Human-specific transcriptional regulation of CNS development genes by FOXP2.” Nature 462 (12 Nov 2009): 213-217.

        Schreiweis et al. “Humanized Foxp2 accelerates learning by enhancing transitions from declarative to procedural performance.” Proceedings of the National Academy of Sciences 111 (30 Sep 2014): 14253-14258.

        Adegbola et al. “Monoallelic expression of the human FOXP2 speech gene.” Proceedings of the National Academy of Sciences 112 (2 June 2015): 6848-6854.

          2. Jim Downard has a project called “Troubles in Paradise” (TIP) where he exposes the lack of attention that anti-evolution activists give to the relevant scientific literature.

            http://tortucan.wordpress.com

            The scope of Downard’s work is rather daunting, and many evolutionary scientists might see his work as unnecessary because we recognize that the anti-evolution activists are pursuing an agenda that is inherently unscientific.

            Still, I for one think that what Downard does is worthwhile. I’d add that he’s an independent researcher, not a salaried academic, and he solicits donations for his work via gofundme (http://www.gofundme.com/dseego), which grates on some people. I’ve supported his work via that channel, and I’d encourage others to explore his work and consider supporting it, too.

          3. Sounds a challenging project indeed.
            Actually, I’ve just dropped a comment on Troy Britain’s “Playing Chess with Pigeon’s” blog in response to his “help with access to academic journals” thread, which may be relevant here.

            I’ve just signed up for Science’s $50-for-a-year taster deal. Don’t waste your money. You don’t get access to the PDFs or any other storable version of an article (as far as I can tell. You can only store single-page images. No searchable text or anything.

            If it sounds as if I’m publically urinating on AAAS’s advertising scheme, you’re right. I am.

  4. There is a separate but intriguing theory re ‘aquatic man’. Explains brain development?

    1. Are you thinking of the “aquatic ape” concept (promoted by … my memory fails me, Welsh woman … it’ll come back to me) that proposes that human ancestors at some point had a significant period of time living and developing in a very wet marshy or coastal environment. Elaine Morgan, that was here name (there have been many other promoters over the years).
      The evidence needed to support such a hypothesis is severely lacking. For sure humans have been able to adapt well to littoral and costal environments, but they do so by developing cultural artefacts (e.g. boats) rather than the far slower pace of physical evolution.

  5. This is a cool post. (Lungs: what amazing organs!!) Got me googling swim bladder. Wikipedia says there are no animals with both lungs and a swim bladder, some people eat swim bladders, and swim bladders were once used to make condoms.

    1. At the Asian market it’s called Fish Maw. It’s used to make a poor man’s version of birds nest soup. Doesn’t taste like much but it adds texture to soup.

      1. It makes a great duck soup, but what you say is true – it’s used largely for its interesting texture, and it does take on the flavours of whatever is in the soup.

    2. Also, as for their use as condoms they could be costly since you had to change them every time you came up for air.

    3. I think the thinking is that swim bladders are evolved from the lungs of early fishes. Fish lungs were pretty widespread.

  6. I did this when I was a kid! I dissected racoon road kill, and among other things I took out the lungs, stuck a soda straw into the trachea, and blew. I was amazed.

    1. Ah.. roadkill anatomy

      Did a little of that. I mostly remember showing my little sister the insides of a garter snake. Was surprised to find just one lung!

    2. Interesting. As a kid, an uncle of mine discovered that I’d found a dead bird (killed by one of our dogs, I think) and had placed it in a protected covering on the large outside satellite dish to prevent insects from nomming it. He was so horrified that I’d kept a dead bird that he went out and bought me a parakeet. He missed the point entirely. I didn’t want a pet. I was saddened by death and wanted to prevent suffering. Interesting foreshadowing toward a career in epidemiology and disease prevention. It would not have occurred to me to dissect the bird. I wanted to prevent future birds from dying in the yard.

      Later in my life, I witnessed a human head autopsy and brain removal. The person had just died, so the body wasn’t preserved and was full of blood. The brain steamed when extracted, as this was the Bay Area and it was a typically cool San Fran winter day. I saw the severing of the optic nerves.

      Despite having seen that, I still feel like vomiting when I see someone fishing with a worm. I can’t imagine dissecting roadkill. I could never be a vet!!

      1. The brain would be cool, but I am afraid I would pass out.

        Photons and electrons, I can kill and/or dissect those without mercy, but the stuff of us is better inside than out.

    3. Oh, thanks for the reminder … I need to send in a road-kill report to the county recorder. It’s all part of head-counting the badger population. Before the local farmers try to exterminate them because they catch TB from infected cattle.

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