What is life? Its vast diversity defies easy definition
quantamagazine.org
quantamagazine.org
This definition is a rubric of several qualities:
1. Metabolizes energy
2. Stores Information
3. Self-replicates
#1 rules out crystals; they are formed by outside forces, they don't metabolize themselves. It also rules out viruses and prions; they don't ingest any "food" to perform metabolic activity. #2 rules out fire; it doesn't store information in a DNA-like molecule or anything simliar. It's purely a chemical reaction. #3 is the obvious thing that differentiates non-living things like rocks from plants and animals.
In humans, the haploid phase of the lifecycle is single-celled, while the diploid phase is multicellular. In contrast, in mosses and fungi the haploid phase is multicellular while the diploid phase (sporophytes/zygote) is single-celled.
Red blood cells are discussed in the article.
The unfertilized eggs of bees become drones, so they must be alive. As a side effect, this indirectly make bee-like insects evolve a lifestyle with a big colony with a queen.
In fungus, most of the life is as haploid (i.e. a single copy of the chromosomes, like sperm and eggs) instead of diploids (i.e. two copies of each chromosomes, like most of our cells.)
In some ¿unicellular organism? [I can't find a good link now] the haploid and diploid versions are almost equal.
[And plants are also weird, some have 4 or 6 copies of the chromosomes instead of 2.]
I think in reality like most things its not black and white, there is a continuum of life and some things are more alive than others.
Edit: perhaps adapting to environment through mutation/evolution or learning or both might be better.
Simple historic example: change of oxygen level, change of temparature is another likely event
Interestingly this definition would encompass countries and probably any social group as long as they have a name, an identity and processes to maintain it. I think life doesn’t need integrated intelligence to be life, though intelligence could probably be defined as a predictive kind of self-preservation process. Essentially devising a chain of actions for moving from state A to state B with a limited set of possible operations and minimized energy consumption. An efficient way to return to initial state, or to another state that increases likelyhood of identity preservation.
As someone else said in a comment, life may be seen as a continuum where these characteristics are more or less developed and integrated, for instance making coutries or viruses living organisms while still distinguishing the unique character of humans or animals.
I think it's a thin pro-argument. Viruses are completely dependant on the host cell and the host cell's metabolism. The host cell's protein unwraps the jacket, and the host cells' proteins replicate the viral DNA/RNA payload. The virus does not reproduce itself, and it does not metabolize anything. There are no inputs to a virus.
Whereas living cells, give them the proper inputs, and they metabolize energy, catalyze reactions, and create copies of themselves.
IMO, self-replication is the most fundamental characteristic, and the ability to mutate/evolve is key as well. The rest is all details.
I'm asking this question because the aforementioned definition of "life" is flawed in my opinion. Evolution has nothing to do with it.
1. Unless you have some way to stop time, it is impossible to stop humans from mutating/evolving.
2. I would argue it is part of being human, and being alive, to evolve and adapt to your environment. Humans have multiple ways of doing this. Beyond our ability to genetically evolve, our intelligence is a mechanism we use to adapt to your environment much faster than genetics permit.
They don't metabolize energy.
1. metabolic cycle
2. ~~stores information~~
2. membrane/boundary
3. template replication
1. periodicity/cycles
2. compartmentalization/boundaries
3. microdiversity/entropy
But that such a thing as AI life forms will exist and be accepted as such by scientific consensus is not a given, at all.
The question seems to be to be "what exact criteria categorises what is commonly meant when people talk about what is alive". I think you could interpret OP as claiming that there is an idea of artificial or alien life as presented in science fiction which people would commonly describe as life but may not replicate.
You cannot say "this definition of life fails to account for an uncertain future phenomenon not everyone is convinced will count as life, therefore your definition of life is incomplete".
Fictional life is not real life. Authors, especially fiction authors, are not bound by the rules of nature. Sometimes they guess right, sometimes they don't, sometimes they simply provide thought experiments or parables.
That is, again, begging the question.
Bees and Humans fit the definition. Therefor, aggregations of bees and humans, like hives and countries, also fit the definition.
"Countries" seem more of a stretch, as replicating would technically mean creating other countries like itself. Not just sustaining itself into the future.
Do hives seed other hives? I suppose they would, so they better fit the definition.
But with bees it's much worse -- in each hive, only the queen and some drones reproduce, most bees are worker bees that can't. So this definition fits bee hives better than it does individual bees.
Seems the definition would need to say something about the species as a whole reproducing. But that leads to the species definition problem. And what about that tortoise that was the last of its species?
The world is full of countries, nations and so forth. At some time in the distant past there was no nations. After that there was one. Now there is over a hundred, with the corpses of many more lying in our past.
All usable land on Earth has been claimed now so they have no space to grow in number without cannabilising one another. Their walls have grown hard and inflexible with the passage of time and laws and agreements, and the evolutionary pressures of conflict have subsided of late, as they cannot move against one another without incurring the wrath of alpha predators, and the alpha predators cannot attack one another without the assurity of mutual destruction.
But countries live a long time, and their frame of reference is different from our own. Their moods encompass entire generations of the lives of mankind. They will eventually again fight among themselves unless ordered into cells within a higher organism. They will fight and devour one another, birthing new border states or vassal states. To any greater being it would appear like an almost peaceful dance, the ebb and flow of lines on a map, the respiration of civilisation.
To us it would be every bit as savage and chaotic as it must be for the cells and bacteria which comprise us.
Not sure how often or even if countries self-reproduce.
Colonialism and independence.
OTOH, not all human populations are states, as in countries, and arguable that is the "organism" said to be reproducing itself....
People self-replicate. People are alive. Societies are composed of people. Therefore, societies are alive.
(may or may not be a hole in your argument depending on whether you think a society is "alive")
The thing I've always loved about pure science is that the best work is approached with much humility. We do not know what something is or why something is. We have a lot of data, may be able to predict a secondary behavior or predict a primary behavior fairly consistently, but that's a bandaid at best--we know it (hehe) and try to dig deeper. Outside of science, we tend to just "know" and brush off deviations from what we know as mysticism or something else.
Sometimes I wish I wasn't aware of how little I really know compared to what I'd like to know. When you peel away the facade of certainty in a lot of aspects of life, it's a bit disheartening to see how people treat each other based on the assumptions they often make of such falsely placed certainty.
There are so many phenomena that are beyond human intellect, intuition, and language that the best we can do is to observe and marvel. It doesn’t mean that we should give up trying to seek explanation or modeling of observed reality, just that don’t be dogmatic about it.
The concepts behind words in human languages are extremely fuzzy and ambiguous. That is why progress on computational linguistics was stuck for a long time, until researchers started using statistical models.
This fuzzy and ambiguous way of modeling the world seems to better fit whatever it is our brains do. The definition of what is or isn't "life" is fuzzy and ambiguous, because however the concept is encoded in our brains is fuzzy and ambiguous.
For example, mathematics is not mystical. Philosophy is also well argued.
And secondly, not everything might be definable with data. For example, how should one treat others is not a purely scientific question.
Having said that, what would you like to know?
We could make up any definition. The problem is that we instantly think "well, that's stupid, let's define it again". But I'll say it again, that wasn't ever the problem. The problem was when we thought we were talking about one thing, but we were really talking about something else - our own personal heuristic.
And nature doesn't care about your heuristic. Hueristics make terrible definitions.
Virus's are alive by a lot of heuristics. They act alive-ish. They're not alive by a lot of definitions. Bacteria are one species by definition. But since that's not useful, we make up heuristics that separate them into all sorts of species. Go through every situation, every time we are disappointed with the definition of life, and we find that the reason is that we just don't like it. We WANT something else to be called life, because it feels that way.
Humans need to categorize things; it is how we are able to navigate our complex world, by recognizing patterns and acting on them. We get in trouble when we think our categorizations are objective fact, or that we can ever cleanly categorize things in a way that will satisfy all our categorizing needs.
Well said. E.g., for almost any definition of life, we end up with superorganisms like ant colonies and bee hives being live things--not to mention cities and human societies being superorganisms too.
Sounds like a simple inductive problem to me.
Simply put, every thing (and grouping of things up and down the scale of size) is more or less alive depending on the order / configuration within itself and in relation to the things surrounding it. So a door can be more or less alive, taken by itself or taken in context of the wall, floor, and ceiling around it (and so on). Or compare a city with no sidewalks, completely paved with concrete, all buildings identical, square grid streets, no plant life whatsoever to some of the great cities in Europe which organically grew according to the needs of the populace over time. Can't you say one is literally more alive than the other, both the physical city itself as well as its inhabitants?
Since adopting this perspective, I've been able to make great strides in improving the order of my home which has resulted in an increase in well-being and mental health. The house is more alive and so I'm more alive for it, and vice versa, and so the positive feedback cycle continues.
He goes into great depth identifying principles we see occurring in nature to help define this gradient of liveliness and analyzes countless examples of great works of art from human history. He also shows how to bring such life to the world around you and in the things you make. Check it out. :)
I think the consequence of this is that quite a few systems can be considered alive that traditionally wouldn't, like crystals or DNA itself but I don't think that's that big of a deal.
Might the definition change, as biologists encounter new stuff and develop an interest? Sure. Does that make the old definition wrong? No.
Dividing the world into life / non-life boxes is a purely human distinction. The universe totally doesn't care. Who does? People. Who cares most? Biologists.
It's true that life can't really be defined by some essentialist statement (i.e. it has properties that neatly divide X from not-X), and the family resemblance approach works better (things like rabbits and viruses and oaks and cyanobacteria), even though it's not as satisfying. Mind, it's OK to just tell kids in biology classes a more convenient definition.
That is where you get conflict. Too simple? Too inclusive? Too not? But it's the only place where you need one that doesn't mention biologists.
"Life is a process that uses energy obtained from outside a boundary to reduce entropy inside it."
You have define entropy, then, which kids might not like much.
> 1. Reproduces itself/making things similar to itself (sort of; viruses are on the periphery, prions...).
> 2. Metabolizes chemicals for energy
> 3. to grow, and as a result,
> 4. produces waste.
> 5. Reacts to stimuli in the environment.
> 6. Maintains homeostasis (reacts to stimuli in itself and keeps 1-5 going).
I really like these, because while they are wrong on some level, they are pedagogically useful: they orient students to what life does, what we can learn about it, and what sorts of data we can collect. Plus, it points towards both ecology and evolution.
Your definition is more encompassing in a way, so it better describes any life-form, but so encompassing that it also describes crystalization! (The parallels between life and crystals are admittedly interesting, especially when thinking about abiogenesis.)
Just from a practical perspective, I would rather start from those criteria than from physical chemistry and physics. Then, come exceptions and complications, which are great! Even when learning physics, I recall every other lecture beginning with, "Those assumptions we made were wrong. Instead, ..."
Is that at all okay???
Note, I say 'self', since just as a cloud is transitory, so too, we live on food and can't divide us from it
Please note, I'm not saying this is right, I'm just having fun stabbing in the dark
From memory: 1. Reproduces itself/making things similar to itself (sort of; viruses are on the periphery, prions...). 2. Metabolizes chemicals for energy 3. to grow, and as a result, 4. produces waste. 5. Reacts to stimuli in the environment. 6. Maintains homeostasis (reacts to stimuli in itself and keeps 1-5 going).
I'm probably forgetting some and there are exceptions to all of these. Notably, in interesting cases like at the inception of life, or at the periphery of life: viruses, parasites, potential extraterrestrial chemical systems, and arguably cultural systems. But those criteria are still convenient.
- They both reproduce - They both eat - They both have some sort of a nervous system - They both breath - They both live and die
Many plants, and some animals such as birds, can produce fertile hybrids after being separated for millions of years. Especially true for organisms that have reproductive barriers besides genetic and physical incompatibility (different pollinators, geographic separation, birdsong differences, etc).
No doubt there are edge cases.
Actually they probably aren't because I guess otherwise all different planets would have them (but hey we are also only here so far).
There's interesting question what would god-like(unlimited power over mater and limitless knowledge) entity do? I guess killing oneself and recreating with sprinkle of rng makes some sense after such event as you probably get bored thus I'm speculating that universe could be god itself (if it's bound by same laws of physics - if not then IDK). Don't ask me what I'm smoking :p
Eugene Spafford got an article published in 1994 arguing just the opposite: https://www.mitpressjournals.org/doi/abs/10.1162/artl.1994.1...
There is another related idea I stumbled on called the "constructal law," [3] which seems related.
Where I think they are related to the question of what life can be defined as is that you could express this constructal force in terms of that information theory idea by summarizing it with a slight extension - as a bounded system is living based on its ability to dynamically cohere information forward in time. The limits of this constructal theory will be defined in using information theory terms.
When we discover stuff in the universe and ask, "is/was this life?" there might be some criteria in these ideas in terms of asking, does this thing take feedback from its environment and produce coherent information? Or, is this thing a source of neg-entropy in its environment? If we look at life as a temporary, dynamic whorl of neg-entropy, it might yield some useful criteria. Half-baked, but measuring information-in, information-out could tell us whether something other than classical physics is processing it. It suggests we could figure out whether something was created by life as well, since the internet is not "alive," but it is evidence of life. Sorting things based on whether it is evidence of life, seems testable.
[1] https://news.ycombinator.com/item?id=22825048 [2] https://alexdanco.com/2020/04/09/life-is-made-of-unfair-coin... [3] https://mems.duke.edu/research/energy/bejan-constructal-law
> if you want to understand the laws of gravitation, then you go and study black holes because you have a very intense gravitational field there. And you can understand and probe gravity very well there.
> If you want to understand the laws of information and how information operates in the physical world, then you should go and study a living thing. Because that's where information actually is at its most dense or most intense.
I'd personally define it more widely, as I think that's more aligned with reality. It's much more of a gradient than we usually take it for, imho
disclaimer: biochemist in a past life
A forkbomb implemented in hardware.