Almost all of the responses here putting this down as "not that big a deal" are completely missing the point. It's extremely easy to say that evolution should do a thing, but if you cannot provide a mechanism to explain how such a thing is passively selected for, then evolution doesn't care. Evolution has no intelligence. There is no designer. This is probably the most important aspect of evolution to understand and the one hardest to grasp intuitively.
For example: say you had a savannah with grass and tall trees populated by 4-legged horse-like animals that survive by grazing on the grass. We can look at such a scenario and say that it would be advantageous for some sub-population of those horse-like animals to grow longer and longer necks until they were capable of also grazing on the trees (doubling their available food supply, relative to their neighbors), but it will never happen! In each generation there will be a distribution of neck lengths, and as there is no advantage to those with slightly longer (but not long enough to reach the trees) necks, the distribution will remain unchanged. This is the basic Hardy-Weinberg principle.
The only way you get giraffes is if the trees start out much shorter, so that the horse-like animals are capable of grazing on them. Then the trees that are slightly taller will have an advantage, and the distribution of tree heights in the population will shift. This will give an advantage to the horse-like animals with longer necks, causing their distribution to shift, and on, and on. This is the basic Red Queen hypothesis.
So saying that an organism that has an inherent capacity for adaptation, or one that knows to cooperate with neighbors, would be better able to survive than the alternatives doesn't mean crap. If you cannot provide a mechanism (backed by a mathematical model) of how such traits arise, then evolution doesn't care.
That is what makes this work so particularly interesting. The authors are providing a model to explain how a mechanism for the selection of cooperation could occur.
>But evolution is a random process based on the short-term advantages that emerge in each generation.
This idea is easily discredited, even "disadvantageous-but-viable" mutations are prized possessions among my offspring. Environments change, and whether or not my lineage goes unbroken is a result of its ability to survive those changes.
Those environmental changes are unpredictable. phenotypes that benefit me now do not necessarily benefit me in the future. If it is my goal to extend my lineage as long as possible, then my optimal strategy must give extra value to diversity.
Since every organism possesses a lineage that goes back to the origin of life, it's fair to say that cooperation for the goal of increasing diversity is a pretty heavily selected for trait.
>it's fair to say that cooperation for the goal of increasing diversity is a pretty heavily selected for trait.
It seems like you're making the mistake of thinking that traits we see were necessarily being actively selected for. It's like saying that because we see an increase in complexity in organisms over time, that evolution is selecting for complexity (its not).
It's true that more diverse populations can withstand changes to the environment better. But to then say that the trait of diversity is selected for is a huge stretch. If diversity has no current value then it won't be selected for, and will be selected against in competitive environments. Evolution doesn't have a way to see into the future in that way. Diversity might be selected for in cooperative populations, but only when diverse behavior provides an immediate benefit to the population.
> Evolution doesn't have a way to see into the future in that way.
Model A: Let's say there is an environmental change every 100 years, and if a population is not diverse enough, then it dies. After 1000 years, we would expect the only populations to be around would be those that are diverse.
Yes, it is true that if there there is a short-term advantage to nondiversity in a population, then it will evolve to be nondiverse, and it will die - in this sense you're right that evolution does not see into the future. However, given the existence of diverse populations assuming the Model A, we can conclude that these populations have found a local minimum of fitness in which diversity is advantageous. Further, there might be "genetic guards" to nondiversity, such that fixation of a gene promoting nondiversity is rare (because this would resilt in extinction!), either through social sexual selection or by such a mutation being a rare event.
>However, given the existence of diverse populations assuming the Model A, we can conclude that these populations have found a local minimum of fitness in which diversity is advantageous.
But any mechanism in which "diversity" is advantageous will be advantageous for more specific reasons. Diversity is just too unspecific. Perhaps you're speaking in terms of group selection, so in a sense evolution evolves diversity in populations. But I don't think this works either. Aside from group selection itself being highly questionable, every environmental event in your Model A would reduce the diversity of the remaining populations. Remaining populations were more diverse in the past (owing to their ability to survive abrupt environmental shifts), so any trend in diversity is in fact downward on large timescales. On short timescales, diversity only grows when there are no selective pressures at work on a given gene. There just is no pro-diversity selection going on.
It's not a huge stretch. The two statements are logically equivalent.
The only organisms which can be said to have been successful are the ones who are either alive today, or were the n-grandparents of the organisms alive today. Zero organisms alive today have n-grandparents whose reproductive strategy did not encourage diverse offspring. Not all diversity is adaptive, but exactly no anti-diversity is adaptive. Therefore diversity is selected for.
>Zero organisms alive today have n-grandparents whose reproductive strategy did not encourage diverse offspring
An obvious counter example seems to be species that reproduce through cloning.
>Therefore diversity is selected for.
"Selected for" has a precise meaning. You guys are using it way too loosely. Selected for simply means the differential survival of one trait over another. There is no time where "diversity" (that isn't really a more specific adaptation) is selected for.
diversity is selected for as a heritable trait when big, unpredictable changes to the environment end lineages which do not have sufficient heritable tendency towards diversification.
At some point you guys have to start putting this into a mathematical model or it devolves into wordplay.
(For example, I could easily say that versatility is selected for rather than diversity. But who cares? We're not saying anything scientific if it doesn't have a formal definition.
I just don't see this as being meaningful. There is no heritable "diversity" trait. You can apply these concepts at the population level, but only very loosely.
The other problem I have is that any metric of diversity decreases over time for a population. Normally when we say evolution selects for trait X, your metric for X increases over time. Instead of diversity being selected for, its more like the gas that drives the engine of evolution. Without diversity in a population, natural selection can't happen. But the diversity comes first.
That seems like too big a statement to be true. You're saying there is no structure which controls the variability of any phenotype? No gene that decides how much butterfly wing splotches vary? No gene that decides the difference between the shortest and longest legs in a family of mountain goats? No heritable diversity traits across the entirety of life?
Putting aside how unlikely that seems to me, if it was true... How could you possibly know such a thing? You can't prove a negative.
>No gene that decides how much butterfly wing splotches vary?
I think you're reading diversity to mean something different than the previous responses intended. Surely there are genes to control a phenotype. The issue under discussion is whether evolution selects specifically for genetic variation within a population (diversity of a population), without a more basic selection going on. My argument is that selection happens at the level of an individual and so it makes no sense to say that evolution selects for population diversity; there is no organism level selection mechanism that is the proxy for diversity at the population level, as there is in other purported population/species level selection events.
Are you saying you think selection happens only at the organism level?
I disagree with that, it happens at every level, from the continental down to the molecular.
Here's a question: are humans individuals, or are we colonies? What about an ant? Is it an organism, or is it an organ? I am not aware of a clear answer to these questions, so I would be excited to hear from you if you know of one.
>I disagree with that, it happens at every level, from the continental down to the molecular.
The problem is that evidence for this has been extremely hard to come by.
> I am not aware of a clear answer to these questions, so I would be excited to hear from you if you know of one.
Richard Dawkins' The Selfish Gene very elegantly explains the evolution of cooperative/altruistic behavior through analyzing the dynamics of gene selection. It's a great read for anyone interested in the finer details of evolution. The main takeaway is that cooperative behavior in organisms can be understood as genes encouraging their own proliferation by increasing the fitness of its copies in other organisms; a gene to help my brother is really a gene helping itself.
You seem to be contradicting yourself. On the one hand, you say molecules can't be selected for because they're not organisms. Then you say genes encourage their own proliferation, but genes aren't organisms, they're molecules.
You also never responded to the fact that humans are colonies, not single organisms, and yet I assume you believe humans are subject to selective pressure?
>you say molecules can't be selected for because they're not organisms
You misunderstand. My point about organisms was that selection happens at the level of organism, which was an imprecise way of saying organisms are what either procreates or dies, and so this is the level at which selection events occur. So any purported selection at a different level must have some organism-level proxy.
The statistics of what survives and what doesn't can still show effects happening at different levels. So when I speak of gene selection, I'm speaking from a statistical perspective. When I said that diversity isn't itself selected for, I meant that there is no strictly "diversity" selection happening at the level of organism.
>You also never responded to the fact that humans are colonies
Yes, humans are "colonies", meaning that we show cooperative behavior. But I don't see how that's relevant, at least in light of ways to understand the evolution of cooperative behavior at the gene level.
Try to find a reputable scientist who will tell you there is an unambiguous distinction between an organism and an ecology. You won't find one, because there is no line. Nature doesn't care if you're a hive or a molecule.
How about viruses? Those aren't organisms, they can't reproduce at all. Just like an organ, or a gene, they need a host to replicate them.
Is it your opinion that viruses aren't subject to selective pressure?
>How about viruses? Those aren't organisms, they can't reproduce at all.
You seem to have trouble comprehending what's being said in context. Try to stop taking things out of context and then nitpicking them. If you came away from anything I've said thinking that I don't think viruses are subject to selective pressures, then you just didn't understand any of it.
Mutation as in the random copy errors in DNA, aren't heritable in the sense that we're not inheriting the mechanism for mutation.
Recombination is a trait that increases diversity of a population, but its also a trait that increases the fitness of the individual organism's lineage as it allows greater diversity of genetic material and interactions between genes in its offspring. So there is an organism level effect that promotes the selection of recombination.
I originally granted that there are traits that can be seen to promote population diversity, but that they would be selected for by the increased fitness at the organism level, not because populations with more diversity better survive random black swan events.
Right, so we inherit the mechanism for replication, which has an intrinsic error rate. But the machinery isn't being selected for its ability to create random errors, that's just a byproduct.
You're basically arguing for a species-level (or at least a deme-level) view of selection. That's something that we've tried to find for many decades, and there just isn't a lot of evidence for it. Selection happens at the level of the individual animal, not any higher grouping.
I've taught evolutionary biology to non-biology majors and the way I would explain natural selection is as follows.
First, to clarify the last sentence above, selection does not happen at the level of an individual. Selection is a statistical process that requires a population of individuals.
For evolution by selection to occur, there has to be 1) variation in traits (i.e. "Phenotypes"), 2) the variation in these traits has to be in part heritible (i.e. Have a genetic basis), and 3) there have to be average differences in success of leaving offspring that themseves go on to reproduce, etc, etc, based on the trait differences amongst individuas.
I'm not sure what you think selection is. Organisms which do not have diverse offspring are very unlikely to maintain a lineage through big changes to the environment. Big changes to the environment are frequent. Therefore diversity of offspring, as a trait, is selected for.
Unless big changes to the environment happen at least once every generation, then there is no way that diversity of offspring will be selected for. Say you have a population of 100,000 organisms and 1 randomly mutates to produce more diverse offspring. That gives the gene a 0.001% occurrence in the population. Hardy-Weinberg principle says that gene will remain at about that percent of the population unless it is selected for. So if a generation passes without selection for that trait, there is a very high probability that gene's occurrence drops back to 0%.
In other words, without a constant source of selection, there is no way for a trait to become fixed in a population.
Why doesn't Hamilton's rule or evolutionary game theory in general justify a social-network aware view of evolution? What evidence or theoretical argument would constitute a species level view of selection?
Cause in the opposite direction may be more fundamental, though in evolution all cause is circular. Because the world is variable a necessary adaptation in every lineage is a corresponding variability in each of its systems, subject to homeostasis. Combinations of this variability may then happen to offer survival of new challenges. So yes specific diversity is selected but it's because general diversity has been there from the beginning.
The article doesn't address this second-order effect of innovation. Instead it seems to take a basic result of evolutionary game theory and cast it in a model from physics.
You should read up on cryptic mutations. I don't think it is that popular in the evolutionary biology field though, mainly because it can be a very vague mechanism.
Cool take on things, but not really fundamentally new as an explanation of evolution of cooperative traits. Models involving reputation and punishment have been around for awhile. Basically, once you introduce reputation and memory, together with punishment, cooperation becomes more viable as a strategy. It's even led to models of higher-order cooperation, of enforcing the enforcers, etc.
To me it seems like the paper isn't really offering a fundamentally new explanation of how these traits arise, it's just providing a sophisticated analysis of the dynamics.
That cooperation is eventually selected for has been known for decades, but we didn't know how. Yes, there have been many speculative models describing how cooperation might arise, kin selection being among the earliest of these. Each of these mechanisms has some applicability and some predictive power (for example, kin selection is pretty good at describing cooperation in everything up to and including eusocial insects), but we've been missing the general mechanism that has predictive power across all domains.
In other words, the field of evolutionary biology today has its Newton's laws and Maxwell equations, but we're missing anything like the Standard Model. The authors of this work have been at this for a number of years. A sophisticated analysis of the dynamics is a key and very important step in beginning to develop a "grand unified theory" of evolution.
>To me it seems like the paper isn't really offering a fundamentally new explanation of how these traits arise, it's just providing a sophisticated analysis of the dynamics.
MIT Tech Review has often news about fascinating research, but one has to adjust for some amount of unnecessary hype.
>a crucial factor turns out to be the process of punishment. “Punishment acts like a magnetic field that leads to an 'alignment' between players, thus encouraging cooperation,” say Adami and Hintze.
either you're a team player or else. Collective punishment comes to mind too as a very effective way to induce cooperation/alignment inside the collective which is going to be or threatened to be punished.
Yes, they start out with game theory, which is only about rewards, and then add in punishment.
Game theory is enormously insightful, but It leaves out a great many factors that are very important in the real world, such as communication between the parties,uncertain rules, and reputation.
All the factors you mention are accounted for by researchers that use game theory as the basis for evolutionary modeling (for a primer, check out "Evolutionary games on graphs" - https://arxiv.org/abs/cond-mat/0607344).
Society already includes many forms of punishment, and there is no way that would ever change. The question is which forms of punishment are helpful and which not, and the social scientists can answer that question only if they include it in their studies.
Dear science journalists, please quit saying that papers "solve" problems ("By treating evolution as a thermodynamic process, theorists have solved one the great problems in biology."). Also, as much as I love Arxiv, I wish journalists would note that articles posted are not subject to peer review.
That would be a neat derivative of poker. Same as regular poker where everyone antes but if everyone folds they get 1.1 X their ante. if one person doesn't fold, you play it like regular poker.
Cooperation is related to a family (or a clan/pack) life. It is the "most natural" survival strategy. Expanding it to a non-keen is not a big deal. Nothing to see here.
White blood cells are clearly altruistic. To the extent a species or even an ecosystem functions like an organism, there is an evolutionary advantage to evolving altruism. To quote Spock, "where the good of the many outweigh the good of the few, or the one."
There have been models that pretty convincingly show altruism arising without any special prerequisites. It's basically a balance between propagating directly versus ensuring propagation of enough of your kin. They may even be very distant kin, not sharing that many genes with you - but if your altruism helps sufficiently many by sufficiently much, you end up propagating those shared genes more successfully, in a sense of having more carriers of them in the follow-up generations. And if those shared genes include the ones that affected your altruistic behavior - again, in at least some of those you helped, not necessarily all - then it becomes a selectable trait.
Remember this article for the next time somebody complains about how perfect an Ayn Randian world would be. Remember that free cooperation helped humanity get this far, not Rugged, Individualism.
For example: say you had a savannah with grass and tall trees populated by 4-legged horse-like animals that survive by grazing on the grass. We can look at such a scenario and say that it would be advantageous for some sub-population of those horse-like animals to grow longer and longer necks until they were capable of also grazing on the trees (doubling their available food supply, relative to their neighbors), but it will never happen! In each generation there will be a distribution of neck lengths, and as there is no advantage to those with slightly longer (but not long enough to reach the trees) necks, the distribution will remain unchanged. This is the basic Hardy-Weinberg principle.
The only way you get giraffes is if the trees start out much shorter, so that the horse-like animals are capable of grazing on them. Then the trees that are slightly taller will have an advantage, and the distribution of tree heights in the population will shift. This will give an advantage to the horse-like animals with longer necks, causing their distribution to shift, and on, and on. This is the basic Red Queen hypothesis.
So saying that an organism that has an inherent capacity for adaptation, or one that knows to cooperate with neighbors, would be better able to survive than the alternatives doesn't mean crap. If you cannot provide a mechanism (backed by a mathematical model) of how such traits arise, then evolution doesn't care.
That is what makes this work so particularly interesting. The authors are providing a model to explain how a mechanism for the selection of cooperation could occur.