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Here's something I've been wondering that maybe some smart hackernews-ian can explain to me. I watched a spider build a web last night. A ton of extremely compl

Here's something I've been wondering that maybe some smart hackernews-ian can explain to me. I watched a spider build a web last night. A ton of extremely complicated engineering went into it, all driven by pure instinct, presumably coded in DNA somewhere. If you gave me enough time I could lay out how a semi-conducting material turns into a T-gate transistor, which can be chained with other transistors to create AND, OR, NOT and NOR gates, which are executed in the CPU by machine language code, which is created by compiling down from higher-level C code, which is executed by Javascript code running in the browser, which uses React to power the Facebook front end. Maybe I missed a step in there, but you get the idea. Is that how DNA tells a spider how to build a web? Or tells me I should drink water when I feel thirsty? Does it all boil down to ones and zeros stored in protein sequences? And if so, are there layers of abstraction like in computer code? Or is there some other fundamental mechanism?

jxramos 3y ago
biology and physics operate at more dimensions where physical forces conspire to be leveraged by some neat tricks. Chemical gradients, various pressures, mechanical forces, electrostatic gradients, all sorts of differences out there to ride--some are passive, some are actively produced and take energy.
- dekhn 3y ago
  See also "Life at Low Reynolds Number" - viscosity becomes exdtremely important at the small scale. https://www.damtp.cam.ac.uk/user/gold/pdfs/purcell.pdf https://www.damtp.cam.ac.uk/user/gold/pdfs/purcell.pdf
reginaldo 3y ago
Also interested in the answer, and I thought a bit about this and have a hypothesis that DNA does not encode everything, instead it depends on implicit assumptions about the environment. To give an example, gravity is likely not encoded in the DNA, but instead, there are many encoded behaviors that would make sense only on an environment where gravity is present. The same for the presence of predators, wind, solar radiation, etc., i.e. many of the things that we take for granted. That's how you would get more than 750MB of behavior on 750MB of DNA data [1] [1] https://en.wikipedia.org/wiki/Human_genome#Information_content https://en.wikipedia.org/wiki/Human_genome#Information_conte...
- captainclam 3y ago
  Interesting! I like that thought. I enjoy thinking about how surprisingly good we are at predicting trajectories, good enough that we can throw, catch, and dodge small objects with remarkable accuracy. I wonder if our internal calculations of acceleration due to gravity is purely learned, or future space-faring infants will be surprised by how their block castles react when they knock them over.
  - mensetmanusman 3y ago
    When we duck away from low flying birds, it’s probably because they used to hunt us a million years ago.
    - taskforcegemini 3y ago
      or because in our past we got hit by low flying things often enough (conditioning)
    - stubish 3y ago
      Come to Australia during magpie breeding season, where we are still hunted by low flying birds.
ertgbnm 3y ago
Here is not a very good answer to your question, but think about how you know how to walk. It's something that is not entirely conscious. You legs just move between places that you desire to go without any thought to the angle of your knee or tension in your gluts. You feel unbalanced when you center of gravity is too far forward despite having no conscious understanding of where exactly your center of gravity is in the first place. Spiders likely have a similar feeling but even further refined. They don't know how to build a truss, but they do end up building analogous structures because in their tiny bug brains it just feels right. This is the same way a human knows they are more stable with their legs spread apart and knees slightly bent. Part of that certainly comes from learning but a lot of it is built into our biology too.
- tibbydudeza 3y ago
  Also by falling a lot until your brain figures out how to handle the various sensor input to get it right - can't remember but our kid took a month to get it right waling short distances after figuring out how to stand upright with support of the furniture. A newly born antelope calf has 3 minutes to figure this all out before it becomes prey.
adr1an 3y ago
You are looking to emergent properties of biological systems from a reductionist philosophical perspective. It's pretty common to have that view. I believe the nature-nurture debate of the 80s (iirc) will be of your interest.
mensetmanusman 3y ago
An analogy captures some of it, but probably not everything, unless you believe the universe is already determined for all time.
bglazer 3y ago
Honestly, I don’t think we have metaphors or figurative language that really captures how biological systems work. That said, I think the most faithful description is something like a dynamical system with incredibly structured and robust emergent behavior. This means that the underlying rules of biology are simple, just physics, but life/biology maintains very complex states. So there’s this bug difference between how much information it takes to describe a biological system’s state and how much information it takes to describe the underlying rules. Like to describe myself, I would have to know the state of quadrillions of proteins and molecules across about 30 trillion cells, down to atomic precision. To describe how that state changes, I only need to know a few physics equations. For most software the situation is more or less reversed. To describe a program, there’s a few state variables, and a ton of rules describing how the program manipulates those variables. The consequence of this for biology is that there’s no true abstraction between the spatial or time scales. Like, a few atoms in the wrong place can often lead to effects across the whole organism. Think genetic mutations leading to cancer: a single DNA base change drastically changes the whole organism. But, the arrow can also point the other way. Large scale changes like deciding to smoke or take chemotherapy causes molecular changes that then filter up to whole organism changes. Like I said, it’s hard to describe because some of these properties are also true for human engineered systems so it’s tempting to use our existing engineering abstractions to describe life. But, they’re woefully insufficient for capturing some of the most important characteristics of life. My opinion on the matter is that we just don’t have good ways of deciding how life works because we don’t really understand it; there are fundamental laws at work that we haven’t captured mathematically or even conceptually.
kylebenzle 3y ago
I'm not a programmer but can any one tell me, like how does a computer know stuff? Is it like how I know stuff, I have to read it, do computer read like that?

jxramos 3y ago

biology and physics operate at more dimensions where physical forces conspire to be leveraged by some neat tricks. Chemical gradients, various pressures, mechanical forces, electrostatic gradients, all sorts of differences out there to ride--some are passive, some are actively produced and take energy.

dekhn 3y ago
See also "Life at Low Reynolds Number" - viscosity becomes exdtremely important at the small scale. https://www.damtp.cam.ac.uk/user/gold/pdfs/purcell.pdf https://www.damtp.cam.ac.uk/user/gold/pdfs/purcell.pdf

reginaldo 3y ago

Also interested in the answer, and I thought a bit about this and have a hypothesis that DNA does not encode everything, instead it depends on implicit assumptions about the environment. To give an example, gravity is likely not encoded in the DNA, but instead, there are many encoded behaviors that would make sense only on an environment where gravity is present. The same for the presence of predators, wind, solar radiation, etc., i.e. many of the things that we take for granted. That's how you would get more than 750MB of behavior on 750MB of DNA data [1] [1] https://en.wikipedia.org/wiki/Human_genome#Information_content https://en.wikipedia.org/wiki/Human_genome#Information_conte...

captainclam 3y ago
Interesting! I like that thought. I enjoy thinking about how surprisingly good we are at predicting trajectories, good enough that we can throw, catch, and dodge small objects with remarkable accuracy. I wonder if our internal calculations of acceleration due to gravity is purely learned, or future space-faring infants will be surprised by how their block castles react when they knock them over.
- mensetmanusman 3y ago
  When we duck away from low flying birds, it’s probably because they used to hunt us a million years ago.
  - taskforcegemini 3y ago
    or because in our past we got hit by low flying things often enough (conditioning)
  - stubish 3y ago
    Come to Australia during magpie breeding season, where we are still hunted by low flying birds.

ertgbnm 3y ago

Here is not a very good answer to your question, but think about how you know how to walk. It's something that is not entirely conscious. You legs just move between places that you desire to go without any thought to the angle of your knee or tension in your gluts. You feel unbalanced when you center of gravity is too far forward despite having no conscious understanding of where exactly your center of gravity is in the first place. Spiders likely have a similar feeling but even further refined. They don't know how to build a truss, but they do end up building analogous structures because in their tiny bug brains it just feels right. This is the same way a human knows they are more stable with their legs spread apart and knees slightly bent. Part of that certainly comes from learning but a lot of it is built into our biology too.

tibbydudeza 3y ago
Also by falling a lot until your brain figures out how to handle the various sensor input to get it right - can't remember but our kid took a month to get it right waling short distances after figuring out how to stand upright with support of the furniture. A newly born antelope calf has 3 minutes to figure this all out before it becomes prey.

adr1an 3y ago

You are looking to emergent properties of biological systems from a reductionist philosophical perspective. It's pretty common to have that view. I believe the nature-nurture debate of the 80s (iirc) will be of your interest.

mensetmanusman 3y ago

An analogy captures some of it, but probably not everything, unless you believe the universe is already determined for all time.

bglazer 3y ago

Honestly, I don’t think we have metaphors or figurative language that really captures how biological systems work. That said, I think the most faithful description is something like a dynamical system with incredibly structured and robust emergent behavior. This means that the underlying rules of biology are simple, just physics, but life/biology maintains very complex states. So there’s this bug difference between how much information it takes to describe a biological system’s state and how much information it takes to describe the underlying rules. Like to describe myself, I would have to know the state of quadrillions of proteins and molecules across about 30 trillion cells, down to atomic precision. To describe how that state changes, I only need to know a few physics equations. For most software the situation is more or less reversed. To describe a program, there’s a few state variables, and a ton of rules describing how the program manipulates those variables. The consequence of this for biology is that there’s no true abstraction between the spatial or time scales. Like, a few atoms in the wrong place can often lead to effects across the whole organism. Think genetic mutations leading to cancer: a single DNA base change drastically changes the whole organism. But, the arrow can also point the other way. Large scale changes like deciding to smoke or take chemotherapy causes molecular changes that then filter up to whole organism changes. Like I said, it’s hard to describe because some of these properties are also true for human engineered systems so it’s tempting to use our existing engineering abstractions to describe life. But, they’re woefully insufficient for capturing some of the most important characteristics of life. My opinion on the matter is that we just don’t have good ways of deciding how life works because we don’t really understand it; there are fundamental laws at work that we haven’t captured mathematically or even conceptually.

kylebenzle 3y ago

I'm not a programmer but can any one tell me, like how does a computer know stuff? Is it like how I know stuff, I have to read it, do computer read like that?