For the terms of this debate, I’m not debating what the purpose of life is (ie various religious philosophies, the purpose is to be happy, etc). I’m going off of evolution via natural selection. The ‘purpose’ is to possess traits that increase the likelihood that you will survive and procreate.
But I feel like words like purpose or meaning do not properly convey this principle. For example, in some environmental niches it is better for survival/procreation to be fast. In another niche its better to be slow. In some its better to be big, in others its better to be small. But nobody says the ‘purpose’ of life is to be big, or small, or fast, or slow. These are just traits. The purpose of life isn’t to be as big as possible, and the purpose isn’t to survive. Its just that the ones that are good at surviving are the only ones that survived.
Even ‘possess traits that increase survival odds’ isn’t really the purpose. Artificial selections by humans proves that. We breed dogs and livestock that have major health problems. We create dog breeds that can barely breathe and we create chickens who are so large their legs can’t carry them. Neither one leads to an increase in survival.
So what I’m wondering is, what perspective, term, description, etc what have you is better than ones like ‘meaning’ or ‘purpose’ to describe what life is from an evolutionary POV? Its not that the purpose of life is to survive and procreate, its just that the life forms that are good at that tend to have more offspring.
I don’t think life has a purpose deep down. Its just random chemistry. But linguistically, terms like purpose and meaning to describe the trajectory of biological life don’t seem like the proper terms to describe what the ‘goal’ of life is, and I don’t know what term is better.
Optimization (the effect of evolutionary mechanisms is to increase the fitness of organisms). There are related words like fitness, selection, genes, but there need not be any natural teleology behind these processes or to be able to discuss them.
The problem with “purpose” is that it’s a priori, whereas the actual outcome (that being well-fitted produces more offspring) is an outcome.
So I’d turn this around. You said
and I’d say
When it comes to evolution, there is no “purpose” or any other word or concept close to “purpose”. Instead, there is a set of external environmental & statistical facts that lead, in the presence of individual variation, to differential reproduction. Nothing more. If that individual variation is heritable, then whatever changes over generational timespans is labeled “evolution”.
Speaking of the “purpose” of evolution is a bit like saying the purpose of mass is to make things accelerate in the presence of a gravitational field. That description correctly captures that gravity + mass = a predictable change in velocity over time, but it utterly confuses cause and effect.
I was also thinking of ‘nature’ or ‘essence’ when I wrote my post, but the outcome of life makes more sense than the purpose of life. The outcome is whatever traits lead to survival and reproduction are passed on more than traits that do not.
I think 'nature" works, or ‘trajectory’, or ‘course’, as a shorthand for ‘observed outcomes’, maybe?
I prefer course to trajectory, because trajectories tend to be simpler things, whereas a course (e.g. of a river) can be a much more complicated system, even though it’s following exactly the same physical constraints as a trajectory.
I’ve always thought the most useful statements of “purpose” was that life’s purpose is to hydrogenate carbon dioxide.
The universe “wants” to be in a higher entropy state, and life increases entropy more than non-biological processes can.
So, simply stated, the purpose of life is to innovate and propagate chemical and other processes that will hasten the heat death of the universe.
All the emergent phenomena of things like cells, multicellular life, animals, vertebrates, mammals, and humans are all in service of this one fundamental drive.
Life exists because of, and is in service to, the second law of thermodynamics.
So, the word purpose is fine, it’s just that the purpose is much deeper than the motivations of individual living entities.
What’s interesting to me about that formulation is that life is an active process to locally and temporarily push back against entropy. The opposite of the direction you mention.
When things are getting more ordered, getting pushed “uphill” against an energy gradient or order gradient, that’s when life is involved. Not all such changes are life-driven, but life always drives such changes.
To be sure the long-term net result of that temporary improvement is the opposite: the order it extracted and used is gone for good.
Maybe,”function”, depending on the context. The function of life is to possess traits that increase the likelihood of survival, procreation, and survival of offspring.
Yes, entropy is decreased within an organism, within its cells and body. It may even decrease the entropy of its immediate surroundings in creating nests or dens or houses.
But that always comes at a price, usually a steep price as everything involved is pretty inefficient, of the overall entropy.
Other way around, life increases the rate of increase of overall entropy. A rock that will sit there happily for a billion years can be dissolved in mere centuries by lichen. A low entropy photon from the sun will be at much lower entropy if it reflects off of a lifeless planet, than if it is absorbed by photosynthesis, turned into sugar, then burned in our bodies, then emitted as hundreds of high entropy photons in the infrared spectrum.
Since lifeforms live and evolve at near-about constant temperature and pressure, a much more useful way of understanding Entropy in this context is Gibbs Free Energy
Gibbs free energy is more useful in understanding equilibrium conditions too.
Depends entirely on the timeline and locality. IMO we’re all saying the same thing, just focusing on different timescales and definitions of locality.
Life locally and temporarily within itself, slows the rate of entropy of the stuff it’s made of or ingests. And when it dies or excretes that same stuff, the rest of the universe is worse off forever to “pay for” the temporary local benefit life gained from having been alive and having successfully pushed back against relentless entropy for a while within the small space of itself and its sphere of influence.
But then we get into emergent behavior, that of above mere chemistry. A spider web is lower entropy than the atoms that make it up being dispersed in the environment, a bird’s nest is lower entropy than a bunch of twigs laying on the ground, and a house is lower entropy than the trees and ore that went into making it. But all that comes at the cost of increasing the entropy of the universe far more than the local entropy decreased.
Intelligence is a force multiplier there. We can use our intelligence to increase the entropy of the universe far more than our bodies do naturally. We can even use our intelligence to spread this entropy increasing self perpetuating chemical reaction we call life across the solar system, galaxy, and reachable universe.
But the odds are that it doesn’t reflect off that lifeless planet. It just gets absorbed and immediately converted to low-grade heat. The albedo of the moon is about that of asphalt, after all. It gets re-emitted, as you say, as hundreds of infrared photons.
If a plant absorbs it, it can use that photon to drive chemical reactions against their natural gradient. Sugars are formed, which drive other processes, perhaps gets eaten by an animal, and so on. During this time the stored energy is only being gradually released. For some of the energy, it may even get stored underground as coal and not be released for hundreds of millions of years.
The net result is the same; the low entropy photon got converted to a bunch of high entropy ones. But in the case where life intercepted it, it took longer for that to happen, and it also used the gradient for useful activity.
Except that it is emitting at a much higher temperature (250F, 120C) than your skin is (98F, ~37C). The photons coming from the moon are lower entropy than the photons emitted by your body.
For every joule of chemical energy that is stored, several joules were released as heat.
The inside of a cell is an exercise in entropy itself. Everything is constantly falling apart, proteins are denaturing, lipids are delaminating, and the chemical gradient is leaking out. It takes energy to constantly be repairing all these structures and to pump ions in and out of the cell to maintain the chemical environment conducive for cell life.
I’m not really up for doing the math, but I very strongly suspect that if you did so, the overall entropy of the universe would come out well ahead by having the photons reflect off a lifeless moon than going through all the processes requires to having the energy stored as carbon.
I don’t think the effect is the same, I think that where life intercepted it, it increased entropy more than if it had been just reflected. The second law of thermodynamics guarantees that it is going to be more, but my “semi-educated gut instinct” tells me that it’s going to be a whole lot more.
I wonder if this is the sort of question that Sean Carroll would enjoy answering on his monthly AMA.
That’s only true on the hot side. On the cold (i.e., dark) side, the temperature is far lower–but it’s still radiating, since the background is ~3 K. I’m not sure what it comes to on average. Regardless, these photons are so low energy that they’re essentially useless for anything aside from heat. The 6000 K photons from the Sun are high quality and can be used for all kinds of things. Once you get down to the hundreds of degrees, they’re pretty much used up.
True, but that’s just because life isn’t all that efficient. It’s better than releasing all of the energy as heat.
Again, I’m not sure why you’re focusing on reflection. Most bodies in the universe are not very reflective. Green leaves are more reflective than the Moon, asteroids, etc. Although plants definitely want to absorb some frequencies efficiently, they reject other ones. So even focused purely on reflection, life is sending more high-energy photons back out into space than dark rock would have. (That said, it’s hard to predict what Earth would be life without life–maybe atmospheric sulfur compounds in the atmosphere would have made it more reflective than the Moon)
How can it be more? It has to be exactly equal. The source photons are the same. The final state is the temperature of the cosmic background radiation. Even those photons that were perfectly reflected, and never hit anything, eventually get stretched way out into the infrared.
