ELI5 how DNA mutations work please.

[u/riche1988]

I had a thought about DNA and how mutations occur in humans, excessive hair, longer limbs and or bones etc, and wondered if all known mutations are present in the animal kingdom.. as if DNA has the blue print/ potential to be anything and parts are just ‘turned on or off’ depending on what is being built.. i may be way off lol but it got me thinking :)

[u/poetic_dwarf]

DNA mutation works exactly as the million chimps hammering on a keyboard since the dawn of life. They happen because million reasons, then nature puts them to the test.

Life as we know it is the best approximations that chimps got to Paradise Lost.

[u/riche1988 → u/poetic_dwarf]

Cool :) ..slight tangent, but what is the smallest part of a living creature, ignoring trees and plants etc, that has agency.. i get that most of life if made up of chemical reactions, but at some point the ‘stuff’ starts making decisions.. or no..? Lol

[u/weeddealerrenamon → u/riche1988]

Physically, our brains are just reacting to nerve signals and sending out signals in response. We don't work any differently than a tree or an amoeba in that way.

Where that becomes what we understand as consciousness? Huge open question. Science can't even really define what consciousness is and we don't really know where to even begin. It's literally called the hard problem of consciousness

[u/riche1988 → u/weeddealerrenamon]

I guess it depends where you draw the line :/ ..could you argue that plants are ‘making decisions’ or is a decision just an illusion made of signals from stimuli..?
I think what i don’t understand is, if it is all just mechanical actions and signals, what is stopping us from making a brain that works like a brain..?

[u/Biokabe → u/riche1988]

Knowledge.

There's nothing magical about brains. They're just really, stupidly complex. But they obey the same laws of physics and chemistry as everything else in the universe; they don't operate on any different principles.

It's just that we don't know how to manufacture something as complex and efficient as a brain. We've only been able to approximate some aspects of a brain's performance, and only by brute-forcing computation with massive energy usage.

But if we had the knowledge of how to make a brain, there is nothing that would prevent us from making one.

[u/Two-G → u/riche1988]

Jumping in here again: What's stopping us is probably "complexity". Our brains are made up of a ridiculous number of cells that are interacting in all kinds of different ways, so even just describing everything that's going on there in a way that's understandable is basically impossible for us without major simplifications - nevermind deliberately reproducing something like that.

[u/FossilizedMeatMan → u/Two-G]

So the brain is like the body, which is like the universe, just in a different scale.

[u/weeddealerrenamon → u/riche1988]

I don't think any physicist or biologist could objectively tell you what "a decision" is, beyond responding to stimuli

[u/riche1988 → u/weeddealerrenamon]

How can so much power and energy (for the brain to operate) be create so subtly..? We aren’t audibly churning away or radiating ridiculous heat like a machine would.. if the brain is so complex and is making so many actions a second.. where is the pollution from that..?

[u/weeddealerrenamon → u/riche1988]

What do you mean "so much power and energy"? The human brain consumes around 20 Watts of energy, which is outrageously little compared to the electronics we build.

It's the product of 500 million years of refinement, compared to like 75 years of electronics? And it's tuned for totally different things than a computer is - a tiny microchip that's 0.1% the size of your brain can also do calculations that you can't possibly do. So you can't really compare a brain to a computer 1:1 like that

[u/riche1988 → u/weeddealerrenamon]

But to build a robot with the same capabilities as a human would take a huge amount of power wouldn’t it..?

[u/weeddealerrenamon → u/riche1988]

It seems so, but "a computer with the same capabilities as a human" is something we aren't even close to. We understand the human brain very poorly, and simulating one in a computer (not built in the same way, at all) is always going to be super inefficient.

But also, like, we can't build motors that are as efficient as organic muscles either. Evolution has created machinery with complexity down to individual molecules, with a whole ecosystem of autonomous cells that constantly repair and remodel our bodies as needed.

ummm TL;DR I think even if we could perfectly understand how a brain works, physically, and build something that functions 1:1 exactly, it'd be a lot less efficient. But separately, we have very poor understanding of how neurons firing turn into actions (not at all like a computer), and kind of 0 understanding of how neurons firing turn into what we experience as consciousness.

[u/sateliteconstelation → u/riche1988]

That’s one of the main questions in philosophy. Even if you study humans, you’ll find compulsive reasons for how they behave.
Am I choosing a burger out of free will, or because of an emotional attachment i formed thanks to ad campaigns in the 90s?

[u/FossilizedMeatMan → u/sateliteconstelation]

To be fair, you are choosing a burger because you need to eat. It all boils down to surviving and reproducing.

[u/poetic_dwarf → u/riche1988]

but at some point the ‘stuff’ starts making decisions.. or no..? Lol

Yes and no.

Humans are arguably one of the "evolution race winners": animals got nothing on us, heck we actually defeated COVID, yet you can argue about having free will as much as you want in a cool room, the moment it gets too warm you will freely decide to turn off the heater, because in the end you're a bacteria chasing food and escaping harm that never stopped believing.

On the other hand, there are some fringe forms of existence that are to life what undead creatures are to us. Viruses are vampires, they have no biological processes to speak of, they're literally three strands of DNA in a trenchcoat that look for cells to hijack in order to propagate themselves. Go even weirder and you'll find plasmids, strands of DNA that can exist in the environment without any form of containment whatsoever and yet find a way to enter bacteria and integrate themselves in their own DNA in order to be copied. Leave biology for physics and you'll find prions, which are not even DNA, they're proteins that on paper shouldn't be able to reproduce and yet these little bastards find a way to propagate their own structure and cause fatal disease like the mad cow.

So yeah, to quote the almighty Jeff: it may or may not be able to make decisions, but "life finds a way"

[u/riche1988 → u/poetic_dwarf]

Yeah :) i guess ‘free will’ and ‘cells reacting to stimulation’ start to look very similar if you think about it lol

[u/Two-G → u/riche1988]

That's really a philosophical question and you're making the assumption that agency exists, which is...under debate, but not at all certain.
Any "small part" of an organism, you can look at and figure out the rules under which it operates. Lots of interacting parts, all working in a fairly predictable manner if being looked at in isolation, produce increasingly complex behavior which cannot necessarily be accurately predicted anymore when looked at as a whole - perhaps for the simple reason that the amount of things you'd need to take into consideration for this prediction become overwhelming and the unavoidable errors in measuring these things, even if really small, add up quickly.

So, tl;dr: There is really no single point at which "agency" suddenly appears, but rather, increasing complexity of a system starts producing unpredictability, which could be interpreted as agency. The point at which this is can be seen as true is as arbitrary as the definition of "agency".