‹ BackHN Continuity

Thread

Why is the liver so weirdly regenerative?

576 points · 293 comments · jbotz

  1. schnuri · · focus · HN ↗
    I am in awe about how wonderfully engineered by evolution the body is. E.g., what we are able to do with it and how it heals itself when we have an injury. Sure, many people would not live long without external intervention, but many others would. I still want to see the robot that can survive 80 active years without maintenance.
    1. chistev · · focus · HN ↗
      The human body can't survive 80 active years without maintainance. They take drugs, they see the doctor, etc.
      1. CookieCrisp · · focus · HN ↗
        What did people do 500 years ago?
        1. EduardoBautista · · focus · HN ↗
          Die as a child at alarming rates
          1. lukan · · focus · HN ↗
            But those who did not, got quite old without ever seeing a doctor.

            (If we are talking about hunter gatherers, not poor exploited peasants)

            1. 1attice · · focus · HN ↗
              Citation required
              1. Fezzik · · focus · HN ↗
                Gurven, Michael & Hillard Kaplan (2007). “Longevity Among Hunter-Gatherers: A Cross-Cultural Examination.” Population and Development Review, 33(2), 321–365

                If you made it past age 5 as a hunter-gatherer you’d likely live to 50-60 years of age.

                1. 1attice · · focus · HN ↗
                  Interesting. Yet as someone approaching the first of those two last numbers, I would say that that isn't very old at all
                  1. Fezzik · · focus · HN ↗
                    It’s also worth noting that, while this is (I think) likely the most cited paper on the topic, all the observed societies are from the 20th century. So we can’t necessarily extrapolate from that that hunter-gatherers 300,000 years ago fared the same.
                  2. exe34 · · focus · HN ↗
                    Old people are at least 20-30 years older than I am.
            2. steve_adams_86 · · focus · HN ↗
              Humans have assisted each other medically, supported injured and disabled tribe members, and sought out medicinal herbs since long before history was written. I'm not sure how you'd delineate between modern health care and when humans never had some notion of health care and/or support when bodies enter failure modes. We don't survive well without a lot of assistance and care, and living long lives required plenty of bodily maintenance regardless of how fortunate and healthy we were.
              1. b112 · · focus · HN ↗
                I think, if you add clarity, such as how aspirin alone is a wonder, how iodine to clean wounds is a life saver, how soap is a miracle, and all the parasites we don't have, yet all this we take for granted.

                We are certainly much healthier, with the little trinkets we keep in our houses.

                1. lukan · · focus · HN ↗
                  Willow bark was used like aspirin. Soap is a old concept (ash is desinfectant as is vinegar ). Alcohol for cleaning wounds is a very old concept alike. As was jumping into clean water every day (also in winter).
                  1. b112 · · focus · HN ↗
                    Yes, and all of those solutions are suboptimal compared to the modern variants, were not always available, and making alcohol required technology (just as fire usage was technology).

                    The real point here, is a lot of people today don't realize how supported they are, with medicine and the trappings of modern life. The simple things I've listed are quite literally a wonder, but to the modern human, often it's not even considered a big deal.

                    Even in a rural remote areas of Canada or the US, you can just get in your vehicle, drive for half an hour, and then suddenly be surrounded by tens of thousands of products to make you healthier. A city dweller can walk for five minutes, and have the same.

                    1. lukan · · focus · HN ↗
                      "The real point here, is a lot of people today don't realize how supported they are, with medicine and the trappings of modern life. "

                      No doubt. But I like to spend time in remote wilderness, so I do know what I have and do not have there. I definitely feel healthier if I am outside more often and can take care of various injuries myself, but if I would really need one, I surely would call for a modern medical helicopter and not go find some plants.

                    2. TheOtherHobbes · · focus · HN ↗
                      One of the problems with modern life is that we've forgotten how many things will try to kill you given half a chance. So we grow up complacent with normalcy bias and end up inventing imaginary personal threats - like being scared of vaccines - instead of dealing with real collective threats like climate catastrophe.
                      1. b112 · · focus · HN ↗
                        The entire species is designed to deal with 'far off' threats and ignore them. Think of any animal, let's take a squirrel. It has to be afraid of cats, canines, bird of prey, and at the same time leave the burrow every day, and all day long look for food.

                        If the predator is not breathing down your neck? You are watchful but ignore it.

                        Similarly, our ancestors and ourselves? We are social animals. We live in a pack. We share defense with our tribe. You and your neighbour will stand back to back, to fight off barbarians. Meanwhile, in parallel, we need to defend ourselves from members of our tribe. The very person who fights back to back with you, to save your community, may be your tribal competitor. Whether for dominance or breeding, we fight amongst ourselves. We know there is risk of our neighbour, our fellow community member attacking and killing us, meanwhile? We lay our head down and sleep.

                        We're designed to take low probability threats, and cast them off, and nothing is more low-probability than 'it will happen in the mysterious future'.

                        Global warming is as 'far off' thing. You may say "But this and this is happening!", and I agree! But I still live in my house, I still have grass and trees, I still have food, and so for most people "far off in the mysterious future" is a valid response.

                        If you can't see the enemy before you, it is easy to shrug away. If you cannot see the threat as impending, it is easy to ignore.

                        It's in our very nature. It's a requirement to sleep soundly at night.

                        At least, this is my take on 'far off' threats.

            3. fhn · · focus · HN ↗
              quite old as in 50 because the avg lifespan back then is certainly lower than it is now.
              1. LorenPechtel · · focus · HN ↗
                There was no "average" lifespan back then. It is a bimodal curve, one peak young, one peak old. "Life expectancy" is far more about the size of the two peaks than an average. In modern society the old peak very much dominates, but even then "life expectancy at birth" is still substantially influenced by the size of the two peaks. Much of the difference across the developed world actually comes down to what doctors classify as a live birth. (Big negative correlation between infant mortality and stillbirth.)
    2. markyc · · focus · HN ↗
      no you don't
      1. arcanemachiner · · focus · HN ↗
        Well, so much for that discussion.
        1. [deleted] · · focus · HN ↗

          [deleted]

    3. dgunay · · focus · HN ↗
      Well, we do at least have to eat enough food and sleep ~1/3rd of our lives. That's kinda maintenance
      1. micromacrofoot · · focus · HN ↗
        that's absolutely maintenance, without it you have a total system failure in a week
      2. yhjc2692 · · focus · HN ↗
        quite the delightful maintenance too
      3. vconnor · · focus · HN ↗
        Compared to most animals that spend their entire day foraging for food, it's not too bad. Adapting to eating dense and very nutritious animal flesh is a great time-saver, and as we didn't evolve long fangs, we had to learn to use tools instead, and the rest is history. (mixing cause and effect here for dramatic purposes)
        1. nerdralph · · focus · HN ↗
          I think learning to cook food was likely a greater benefit. It's like we externally expanded our means of digestion.

          I watched a Ted talk where the speaker suggested our large brains with their high energy consumption would not have been possible were it not for cooking.

          1. NetMageSCW · · focus · HN ↗
            Which came first, steak or intelligence?
            1. jamiek88 · · focus · HN ↗
              Bone marrow came first. We were scavengers for the longest time. We invented tools to break the bones hyenas would leave. Skulking little scavengers.. until spears were invented then hoo boy - shit went exponential.
            2. vconnor · · focus · HN ↗
              Steak I’d imagine, which is a prerequisite to growing a very energy-intensive organ such as our brain. Couldn’t have supported such a brain if we had been ruminants.
          2. hobo123 · · focus · HN ↗
            Indeed, carbs, and cooking to make those carbs available (from grasses, tubers, etc).
    4. RobotToaster · · focus · HN ↗
      Humans don't last long without topping up their fluids and consumables.
    5. ericmay · · focus · HN ↗
      When you watch those sci-fi shows and folks have nanobots implanted in them that heal wounds really fast or do other cool things I can't help but think in many ways we already have that technology we just need it to do more, faster as our brains and ability to create things have outpaced the rate of evolutionary change.
    6. onlypassingthru · · focus · HN ↗
      The human machine doesn't just survive without external intervention, it actually gets better at being a machine. Speed, endurance, power, coordination... all improve with usage.
      1. fhn · · focus · HN ↗
        until you get old and goes the opposite direction
Open on Hacker News to reply ↗

Unofficial Hacker News client; not affiliated with Y Combinator.