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Comment by pfannkuchen | Hacker News Reader

Should genetic engineering on humans ever become feasible to the point where you can make large changes to the body plan, I wonder if reverting bipedalism would be easier than fixing all of the problems it causes (such as, I assume, knees, due to taking all of the load on half of the limb joints, but, also, back problems, etc). With human computer interaction technology advancements, we may eventually move beyond needing hands at all, anyway.

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This comment is peak HN. Like it's so absurd that it feels like it must be satire.

When predictable genetic engineering of animals will become possible, there will be no difficulty in growing both two hands and four legs, like in the mythical Centaurs.

Not necessarily. That is like saying “when predictable engineering of bridges becomes possible, there will be no difficulty in creating a floating-in-air bridge”. Engineering challenges still exist. My point is whether going to a more standard body plan is an easier engineering problem than fixing the design flaws in the nonstandard human one.

Your counterexample is not valid. There are reasons why a "floating bridge" would not be easy to make, but the fact that all the vertebrates with jaws that exist today have no more than four paired limbs is just a historical accident and only small changes in their body plan would be necessary to make one with six paired limbs or even with much more.

In some vertebrates, i.e. amphibians, it is very easy to generate supernumerary limbs without any genetic engineering, but just by manipulating the embryos.

Due to defects in the development of the embryo, birds or mammals and even humans are sometimes born with polymelia, i.e. with extra legs, and some of them succeed to have a relatively normal life.

https://en.wikipedia.org/wiki/Polymelia

The purpose of predictable genetic engineering would be to ensure the development of a body precisely into a form optimized for a certain purpose. Obtaining random monstrous forms is easy even today, by using various mutagen agents and/or embryo manipulations.

The problem isn’t generating something with a certain body plan, I agree that is easy. The problem is achieving a design without common or significant mechanical problems over the lifespan of the organism. Can we assert that, in your example, animals with extra limbs don’t have problems on par with the back or knee problems of bipeds? I don’t think we can?

It is very unlikely that predictable genetic engineering for animals will become possible earlier than twenty years from now and a time between 50 years and 100 years from now seems most likely.

We are still very far from completely understanding how a single nucleated (eukaryotic) cell works. After understanding a cell we should first be able to completely understand simpler multi-cellular living beings like fungi and plants. The animals are the most complex and there is no doubt that they will be the last for which it will become possible to change some genes and then predict with certainty what kind of animal will develop from such a modified cell.

In any case, when that will happen it will be possible to design the body of an animal, within certain constraints, like we design now any complex machine. Bad designs will always remain possible, but good designs should easy avoid mechanical problems in the legs. By that time the simulation possibilities should be much better than today.

Bipedalism doesn't cause problems. Sitting on your ass all day and then occasionally doing stuff that overstresses your now-weakened joints causes problems.

You only get knee and back problems when you're old, which is because the body just stops repairing itself as effectively as it does when you're young.

It's going to be far easier to re-enable the ability to self-repair our bodies as we do in youth than to completely change the function of two of our limbs.

Completely false. Lots of people in their 20s have knee and back problems. Torn ACLs are common in athletes and people who participate in sports. I had a coworker a few years ago who had his ACL replaced; he was in his mid-to-late 20s.

Please re-read and reconsider the context of my post. This reddit-tier "must seek to contradict and attack others" behavior doesn't do anyone any good.

Ok, fine. I re-read it, and it says: "You only get knee and back problems when you're old, which is because..."

Your statement is blatantly false. It says, literally, you only get knee and back problems when you're old. This is wrong, and stupid.

Why are you arguing this?

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