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The incredible complexity of anatomy is even more amazing considering * all the structures grow from a single cell * somehow it's all encoded in DNA (only 6 b
by roca 2y ago
The incredible complexity of anatomy is even more amazing considering
* all the structures grow from a single cell
* somehow it's all encoded in DNA (only 6 billion bits in humans, which has to also build cells and their ultracomplex machinery)
* this all had to evolve using only a very noisy objective function
- dotancohen 2y ago> only 6 billion bits in humans That's under 1 GB - it might all fit on a standard compact disc.
- lostlogin 2y ago> compact disc It’s probably not far off being easier to read DNA than a CD. And it’s surely less frustrating.
- semitones 2y agoI wonder if saying that "it's all encoded in DNA (which is only 6 billion bits)" is accurate. Every time life (considering only humans for now, to simplify) arises, in addition to the DNA (the "code"), you also have the rest of the first cell (the zygote), which already has an "expression" of that code (which may contain additional information beyond what is already in the code), + the entire environment of the mother (which obviously provides additional information). This makes me think that we need far more than just 6 billion bits to actually encode the entire process of new life formation (each instance always piggy-backs off the previous, and always provides processes/information).
- rolisz 2y agoMichael Levin has some awesome experiments where he screws around with the bioelectric fields of planetaria and he gets them to grow two heads and no tail, while being genetically identical to a normal one.
- elric 2y agoOne of my old classmates' area of research is applying electric stimuli to various types of cells. Apparently the right amount at the right time can briefly allow foreign material to pass through the cell wall unimpeded. The complexity of a single cell is insane, that of a complex organism is way beyond insane.
- dennis_jeeves2 2y agoI think you meant cell membrane rather than cell wall? (There is a contrarian theory that says that the cell membrane does not exist at all, look up Gilbert Ling. So it's no surprise that things can move in and out of the cell under certain conditions.)
- inglor_cz 2y agoPlanaria. (Yeah, I am a pedant sometimes.) Also, frogs, tadpoles, axolotls. Truly a wonderful mind. I admire him, not least for his ability to do really weird and important science outside the usual "don't do anything extraordinary" boundaries set by ossified grant committees.
- Gooblebrai 2y agoI thank you. I was looking for planetaria and I was confused
- rolisz 2y agofacepalm Thank you. That was not pedantic at all, I made an early morning mistake.
- dmd 2y agoAnd you keep them in the planetarium, right?
- wolpoli 2y agoYou are telling me that we do not have a way to clean build human from DNA source. That's a real continuity risk.
- heckelson 2y agoThe battle for reproducible builds continues
- Aerbil313 2y agoWe need purely functional nanomachinery to create every embrionic molecule from element atoms, and a declarative physical language to combine them in the right way to create a zygote.
- emptiestplace 2y agoWhat if, as human consciousness is an emergent property of complexity, so too are humans and DNA itself? Could it be that, just as consciousness arises from the intricate networks within the brain, life and its fundamental components—like DNA—emerge from an even deeper layer of complexity in the universe, suggesting that our very existence is a product of systems far beyond our current understanding?
- bgun 2y agoWe do, but it’s messy and usually involves a few years of courtship, followed by one to three decades of raising & educating the resulting human to anything resembling a useful model for comparison.
- admissionsguy 2y ago> you also have the rest of the first cell (the zygote), which already has an "expression" of that code It's called maternal effect (https://en.wikipedia.org/wiki/Maternal_effect https://en.wikipedia.org/wiki/Maternal_effect)
- tsimionescu 2y agoI think they meant something even more basic, and common to all cells: you can't make a new cell without an existing living functioning cell. We have no firm idea of how the first cells developed, but all of the cells we know of today come from the division of another cell, and we have never observed anything remotely like a new cell forming pit of a puddle of all the required substances and DNA.
- moi2388 2y agoYou might want to look up Dr.Michael Levin. He is studying exactly this. He found that when developing, cells move and grow in a particular direction. But when an obstacle is placed in their way, they move around it to somehow still end up where they’re supposed to. DNA is not all of the encoding. Even cells appear to have some form of navigation or space search capabilities.
- codesnik 2y agochemical gradients?
- fellowmartian 2y agoHis work is mind-blowing and completely upturned my perception of biology.
- doctorpangloss 2y agoWhy do miscarriages occur? They are frequent, so they seem to be an essential feature of pregnancy.
- cultofmetatron 2y agoI imagine from an evolutionary perspective, a false positive of the fetus bringing harm to the mother is preferable over the long term for increasing long term reproductive survival.
- candiddevmike 2y agoThe fetus's liveliness check failed
- im3w1l 2y agoMiscarriages must occur because our DNA is constantly mutating. Some of those mutations will be so harmful that the new organism cannot even survive until birth. In addition to those unavoidable ones, there can also be things going wrong by accident (e.g. the pregnant woman suffer physical injury which kills the fetus).
- 2y ago
- joshuahedlund 2y agoYes, I recently read the book The Master Builder by Alfonso Arias which gets into some of the detailed pre-requisites provided by existing cells. (it’s also why restoring extinct species may be harder than expected even knowing their full genetic sequence)
- thfuran 2y agoAt the very least, epigenetics are also partially heritable.
- dekhn 2y agohttps://en.wikipedia.org/wiki/Maternal_effect https://en.wikipedia.org/wiki/Maternal_effect The egg contains mRNA or protein created by the mother that affects the child's phentotype. It's unclear how much those non-genomic components affect organismal phenotypes; presumably, there is some minimal collection of factors that would suffice to allow us to construct an artificial egg cell that is viable for reproduction.
- TZubiri 2y agoDisclaimer. I'm not a great biologist. Couldn't this be proven by growing mammals in petri dishes? If the entire information is encoded in DNA, then the fetus would grow fine. If however, the fetus needs to be in a womb to develop, then there must be information (and resources) that need to be sent from the mother to the baby in a sort of quine fashion. Consider a Java compiler or python interpreter, they are themselves written in the target language, unless we are talking about early version. So you already need a java compiler to compile Java, the code for the compiler does not hold all of the necessary information, as you need a mother compiler to execute it. Which part of the target is in the code and which in the interpreter/compiler? A thought experiment would be a language where a built in statement compile() compiles code according to specifications. Thus the code for a compiler would simply be compile(). My best guess is that fetuses can only grow inside a functioning human, and that the information in DNA is not sufficient, you need a functioning specimen to grow another specimen.
- roca 2y agoThis is a very interesting observation. I wonder if there's a way to identify the contribution of that initial cellular environment to the phenotype. I guess you could do experiments where you tamper with the initial cellular environment or the DNA and see what happens.
- 9dev 2y agoI wonder if it's actually more similar to procedural generation, based on a seed value, that reliably recreates the same complex output that isn't entirely described by the seed alone. In this case, the DNA would just serve as input to a myriad of algorithms that yield a fully working cell. A single base pair change may lead to a mind-bogglingly long chain of side effects that result in a third arm, or really just nothing at all.
- tialaramex 2y ago> only 6 billion bits in humans A 27-state two value Busy Beaver can implement "Give a counter-example to Goldbach's Conjecture" - if there are none the program never halts. We can recognise that, and say "Oh dear" but it gets us no closer to an answer. Six billion isn't even in the right ballpark, our ability to understand the meaning of every self-acting machine extends maybe to six or seven bits if we're very smart.
- refurb 2y ago> somehow it's all encoded in DNA (only 6 billion bits in humans, which has to also build cells and their ultracomplex machinery) One has to be cautious to not assume that the only data DNA holds is in base pairs. We know that secondary factors like inter- and intra-strand interactions or DNA-histone interaction encodes information as well. A good analogy is a book. While it is made up of individual letters, the combinations build to words, which build to sentences, which build to ideas, which can interact with other ideas (sometimes in other chapters!) to create a complexity beyond just the combination of letters would suggest. That's not even getting into the temporal aspects of DNA expression.
- candiddevmike 2y agoI believe DNA is a compression algorithm beyond our current understanding, and the 6 billion bits is a post-compression size.
- thih9 2y ago> 6 billion bits in humans ~750 megabytes (unit conversion via google)
- BurningFrog 2y ago> all the structures grow from a single cell Two cells: Egg and sperm
- yjftsjthsd-h 2y ago...which merge into a single zygote cell.
- Metacelsus 2y agoA fertilized egg (zygote) is one cell.
- lubujackson 2y agoA crappy, self-improving function with a decent feedback loop (survival) can get pretty far given 100s of millions of years with hundreds of million (or trillions) of concurrent experiments running at the same time. The time scale of life is the hardest element to comprehend.
- wonnage 2y agoI don’t think it’s true that DNA actually encodes an entire organism. Leaving all discussion of epigenetics aside, the proteins produced from DNA can basically do anything, including modifying DNA. Maybe we could think of large portions of DNA as simply bindings to shared libraries (i.e, the proteins). Or like a package manifest and build script for life rather than the code itself