Biology subjects

Szamado, S.

Publications and source records attributed to Szamado, S..

14 recordsLinked to original sources

bioRxiv2024

A Darwinian model of cultural replication over the continuum of Weismannian and Lamarckian inheritance

Universal Darwinism argues that entities capable of multiplication, variation and inheritance evolve by natural selection. Besides genetic reproduction implementing Weismannian inheritance, other adaptive systems were proposed to support Darwinian evolution, most notably culture, assuming autonomous cultural replicators akin to genes. Culture, on one hand, lacks direct template copying and inherits acquired changes, while on the other its overall behaviour is Darwinian as languages attest. The properties of culture setting it apart from biological evolution suggests a Lamarckian, while its overall behaviour a Weismannian interpretation, which is often coined as "the duality of cultural replication". According to canonical Darwinism, Lamarckian and Weismannian inheritance are disjunct mechanisms and only the latter is sufficient to maintain cumulative evolution. We resolve this apparent contradiction via a mathematical model of cultural information replication. We model the inheritance of information, cultural or genetic, as a successive set of template-based transformations of digital information between generations. We demonstrate that Lamarckian and Weismannian inheritance form a continuum and that both can reconstruct information stably for an indefinite time. Our formalism naturally unifies Lamarckian and Weismannian inheritance, proving that cultural replication, in theory, can approximate the fidelity of genetic replication. We claim that (well-defined) Lamarckian inheritance is an adequate low-level model of culture and can support population-level Darwinian evolution. We discuss the implications of our results to bridge the gap between the Lamarckian and Darwinian explanations of cultural evolution. Significance statementMuch of the standstill of cultural evolution theory stems from under-defined concepts that lack rigorous mathematical formalism. We provide a strict application of established concepts of biological evolution to the replication of cultural information. According to our analogy, cultural replication corresponds to Lamarckian inheritance (inheriting acquired changes), genetic replication to Weismannian inheritance, both being part of the same continuum of informational replication. We prove in our model, that despite a lack of template copying in Lamarckian replication, overall copying fidelity can approximate that of Weismannian replication, i.e. culture can approximate genetic copying fidelity. Cultural inheritance may be Lamarckian at the level of inheritance (microevolution) while it can still lead to Darwinian evolution at the population level (macroevolution).

evolutionary biology↗

bioRxiv2023

Moderate Diversity of activation thresholds promotes cooperation in the Threshold Public Good Games

Societies face various collective actions which posits social dilemmas, in which a certain number of group members must act cooperatively in order to reach a collective goal. Such social dilemmas are often modelled as Threshold Public Good Games, in which the collective goal is reached successfully if the number of cooperative decisions reaches a threshold. Because cooperation is often a costly act, to coordinate such actions actors can attempt to communicate, to ensure that cooperative decisions are only made once the chances of reaching the goal, thus meeting the threshold is secured. Here we focus on the distribution of activation thresholds in societies, which captures the dynamics of peer pressure and the interaction between different levels of selfish and cooperative behaviours. Here we show that moderate diversity of activation thresholds favours cooperation under wide range of parameters.

ecology↗

bioRxiv2023

Cue-driven microbial cooperation and communication: evolving quorum sensing with honest signalling.

BackgroundQuorum sensing (QS) is the ability of microorganisms to assess local clonal density by measuring the extracellular concentration of signal molecules that they produce and excrete. QS is also the only known way of bacterial communication that supports the coordination of within-clone cooperative actions requiring a certain threshold density of cooperating cells. Cooperation aided by QS communication is sensitive to cheating in two different ways: laggards may benefit from not investing in cooperation but enjoying the benefit provided by their cooperating neighbors, whereas Liars explicitly promise cooperation but fail to do so, thereby convincing potential cooperating neighbors to help them, for almost free. Given this double vulnerability to cheats, it is not trivial why QS-supported cooperation is so widespread among prokaryotes. ResultsWe investigated the evolutionary dynamics of QS in populations of cooperators for whom the QS signal is an inevitable side effect of producing the public good itself (cue-based QS). Using spatially explicit agent-based lattice simulations of QS-aided threshold cooperation (whereby cooperation is effective only above a critical cumulative level of contributions) and three different (analytical and numerical) approximations of the lattice model we explored the dynamics of QS-aided threshold cooperation under a feasible range of parameter values. We demonstrate three major advantages of cue-driven cooperation. First, laggards cannot wipe out cooperation under a wide range of reasonable environmental conditions, in spite of an unconstrained possibility to mutate to cheating; in fact, cooperators may even exclude laggards at high cooperation thresholds. Second, lying almost never pays off, if the signal is an inevitable byproduct (i.e., the cue) of cooperation; even very cheap fake signals are selected against. And thirdly, QS is most useful if local cooperator densities are the least predictable, i.e., if their lattice-wise mean is close to the cooperation threshold with a substantial variance. ConclusionsComparing the results of the four different modelling approaches indicates that cue-driven threshold cooperation may be a viable evolutionary strategy for microbes that cannot keep track of past behavior of their potential cooperating partners, in spatially viscous and in well-mixed environments alike.

ecology↗

bioRxiv2022

General solution to biological signalling games: costly signalling and beyond

Explaining signal reliability poses a central problem in animal communication. According to Zahavis Handicap Principle (HP), signals are honest only when they are costly at the evolutionary equilibrium - hence the term handicap; otherwise, deception evolves, and communication breaks down. The HP has no theoretical or empirical support, despite claims to the contrary, and yet this idea remains immensely popular. Theoretical evaluations of the HP are difficult, however, because finding the equilibrium cost function in signalling games is notoriously complicated. Here we show how cost functions can be calculated for any arbitrary pairwise asymmetric signalling game at the evolutionary equilibrium. We clarify the relationship between signalling costs at equilibrium and the conditions for reliable signalling. We show that these two terms are independent and the costs of signalling at honest equilibrium have no effect on the stability of communication. We show that honest signals can take any cost value, even negative, being beneficial for the signaller independently of the receivers response at equilibrium, without requiring further constraints. Our results are general, and apply to seminal signalling models, including Grafens model of sexual selection and Godfrays model of parent-offspring communication. Our results refute the claim that signals must be costly at the evolutionary equilibrium to be reliable, as predicted by the HP and so-called "costly signalling" theory. The handicap paradigm can thus be fully rejected. We provide testable predictions to help advance the field and establish a better explanation for honest signals.

evolutionary biology↗

bioRxiv2019

Condition-dependent trade-offs maintain honest signaling: A laboratory experiment

How and why animals and humans signal reliably is a key issue in biology and social sciences. For many years the dominant paradigm in biology was the Handicap Principle. It claims a causal relationship between honesty and signal cost and thus predicts that honest signals have to be costly to produce. However, contrary to the Handicap Principle, game theoretical models predict that honest signaling is maintained by condition dependent signaling trade-offs and honest signals need not be costly at the equilibrium. Due to the difficulties of manipulating signal cost and signal trade-offs there is surprisingly little evidence to test these predictions either from biology or from social sciences. Here we conduct a human laboratory experiment with a two-factorial design to test the role of equilibrium signal cost vs. signalling trade-offs in the maintenance of honest communication. We have found that the trade-off condition has much higher influence on the reliability of communication than the equilibrium cost condition. The highest level of honesty was observed in the condition dependent trade-off condition as predicted by recent models. Negative production cost, i.e. fix benefit-contrary to the prediction of the Handicap Principle-promoted even higher level of honesty than the other type of costs under this condition.

evolutionary biology↗

bioRxiv2019

Scarce and directly beneficial reputations support cooperation

A human solution to the problem of cooperation is the construction and maintenance of informal reputation hierarchies. Reputational information contributes to cooperation by providing guidelines about previous group-beneficial or free-rider behavior of opponents in social dilemma interactions. How reputation information could be credible, however, when outcomes of interactions are not publicly known, remains a puzzle. In this study, we propose that credibility could be ensured if reputation is a scarce resource and it is not believed to be earned for direct benefits. We tested these propositions in a laboratory experiment in which participants played two-person Prisoners Dilemma games without partner selection, could observe some other interactions and could communicate reputational information about possible prospective opponents to each other. We found that scarcity is a necessary condition for reputation scores to be informative. While cooperation has not been sustained at a high level in any of the conditions, reputational information clearly influenced cooperation decisions. The possibility of exchanging third-party information was able to increase the level of cooperation the most if reputation was a scarce resource and contrary to our expectations, when reputational scores have been directly translated into monetary benefits.

evolutionary biology↗

bioRxiv2018

Attention seeking in a spatially explicit game of mate choice and the evolution of dimorphic ornaments

The evolution of conspicuous signals fascinated biologist ever since Darwin. The Handicap Principle was dominant explanation in the last decades; it proposed that exaggerated and conspicuous signals are costly signals of quality. There are other less popular explanations however, one them is that conspicuous signals function to call the attention of potential receivers. These attention seeking displays need not reveal the quality of the signaller. There are many empirical examples and recently the idea was modelled in terms of a simple action-response game. However, action-response games model an interaction of a pair of signaller and receiver, thus they omit potential competition between signallers, which could be a crucial force behind the evolution of attention-seeking displays. Here I model this competition in a spatially explicit model of mate choice where males can give a continuous signal to call the attention of potential mates. The results show that attention-seeking displays readily evolve to the allowed maximum when the cost of signalling is low. However, dimorphism evolves when the cost of signalling is high. The population consist of two types of males at this dimorphic state: males that do not give a signals and males that give the highest intensity signal possible. The results show that variation in quality is not a necessary requirement for the evolution of dimorphic traits.

evolutionary biology↗

bioRxiv2018

Honest and cheating strategies in a simple model of aggressive communication: the role of spatial correlations

The evolution and maintenance of communication in terms of aggressive interactions is a long-debated issue. Several game theoretical models and individual based computer simulations investigated this problem in terms of a simple game of aggressive communication. So far all of these investigations focused on well mixed population of individuals. However, spatial correlations can emerge in nature where individuals or group of individuals defend resources. The extensive literature on cooperative games show that these spatial correlations can be vital in the maintenance and evolution of cooperative strategies, thus it is reasonable to expect that such correlations could play an important role in the evolution of honest communication as well. Here we investigate a traditional game of aggressive communication in a spatially explicit context. We investigate the role of spatial correlations by comparing results of evolvability in well mixed populations with results from spatially explicit populations. Spatial correlations seem to inhibit the evolution of communication in the spatially explicit version of this game. This result is unexpected, and it requires further investigation to understand.

evolutionary biology↗

bioRxiv2018

Honesty needs no cost: beneficial signals can be honest and evolutionarily stable

How and why animals communicate honestly is a key issue in biology. The role of signal cost is strongly entrenched in the maintenance in honest signalling. The handicap principle claims that honest signals have to be costly at the equilibrium and this cost is a theoretical necessity. The handicap principle further claims that signalling is fundamentally different from any other adaptation because honest signalling would collapse in the absence of cost. Here I investigate this claim in simple action-response game where signals do not have any cost, instead they have benefits. I show that such beneficial signals can be honest and evolutionarily stable. These signals can be beneficial to both high and low-quality signallers independently of the receivers response, yet they can maintain honest signalling just as much as costly signals. Signal cost-at or out of equilibrium-is not a necessary condition of honesty. Benefit functions can maintain honest signalling as long as the marginal cost-loss of benefit-is high enough for potential cheaters.

evolutionary biology↗

bioRxiv2018

The role of equilibrium cost in the evolution of honest signalling: waste or optimal investment?

The relationship between signal cost and honesty is a controversial and unresolved issue. The handicap principle assumes that signals must be costly at equilibrium to be honest, and the greater the cost, the more reliable the signal. However, theoretical models and simulations question the necessity of equilibrium cost for the evolution of honest signalling. Honest signals can evolve without costs, and they can evolve through differential benefits with no need for differential costs. Here we investigate the role of equilibrium signal cost in the evolution of honest signals in both differential benefit and differential cost models using an agent-based simulation. We found that there is an optimal investment paid by honest individual that allows for the highest level of honesty when there is correlation between signal cost paid by low and high-quality individuals. This holds for both differential benefit and differential cost models as long there is a correlation between signal cost paid by low and high quality individuals. However, increasing equilibrium signal cost poses an obstacle and hinders the evolution of honest signalling when there is no correlation between the cost paid by low and high-quality individuals. Last but not least, we found that the potential cost of cheating is a much better predictor of honesty than the equilibrium cost paid by honest signallers.

evolutionary biology↗

bioRxiv2018

Soft song: help thine enemy!

The proximity risk model offers one possible explanation of honest signalling of aggressive intent in biology. This model assumes that the probability of successful attack is a function of the distance between the contestants and that this distance can be correctly estimated. This later assumption may not hold in nature where contestants have to estimate this distance under noisy conditions. Here I investigate with the help of a game theoretical model whether short-range ranging signals can be evolutionarily stable under such conditions. These signals can help the opponent to estimate the correct distance, thus they can promote honest signalling of intentions. Here I show that ranging signals that help the estimation of distance between opponents can be evolutionarily stable. However, such help only benefits those individuals who are able and willing to attack. As a result, ranging signals in themselves are an honest cue of proximity and in turn they are honest cues of aggressive intent. I give an example: \"soft-song\" in birds, and I discuss the predictions of the model.

evolutionary biology↗

bioRxiv2017

Juvenile honest food solicitation and parental investment as a life history strategy: a kin demographic selection model

Parent-offspring communication remains an unresolved challenge for biologist. The difficulty of the challenge comes from the fact that it is a multifaceted problem with connections to life-history evolution, parent-offspring conflict, kin selection and signalling. Previous efforts mainly focused on modelling resource allocation at the expense of the dynamic interaction during a reproductive season. Here we present a two-stage model of begging where the first stage models the interaction between nestlings and parents within a nest and the second stage models the life-history trade-offs. We show in an asexual population that honest begging results in decreased variance of collected food between siblings, which leads to mean number of surviving offspring. Thus, honest begging can be seen as a special bet-hedging against informational uncertainty, which not just decreases the variance of fitness but also increases the arithmetic mean.\n\nAuthor SummaryParent-offspring communication is a fascinating problem that captures the attention of scientist and layman alike. Parent-offspring interaction is the first interaction with non-self in the life of most young birds and mammals. The future life success of such young animals crucially depends on how successful they are in interacting and communicating with their parents. This communication has different functions: it is important for the offspring to solicit food from the parent and it is important for the parent to be informed about the state (hunger level) of the offspring. There is an optimization problem on top of this level: the parent has to decide what part of the available resources should be allocated to the offspring and what part should she keep for herself. Here we show in a probabilistic model that the honest phenotype -where offspring beg only if they are hungry-has a greater growth rate than a selfish type - which begs regardless of its hunger level. This result holds in asexual populations; here honesty serves as a reduction uncertainty for the parents. The improved decision making of the parents -in turn-increases the survival of the offspring as well.

evolutionary biology↗

bioRxiv2017

One problem, too many solutions: How costly is honest signalling of need?

The \"cost of begging\" is a prominent prediction of costly signalling theory, suggesting that offspring begging has to be costly in order to be honest. More specifically, it predicts that there is a single cost function for the offspring (depending on e.g. offspring quality) that maintains honesty and it must be proportional to parents fitness loss. Here we show another interpretation of the cost. We demonstrate that cost, proportional to the fitness gain of the offspring, also results in honest signalling. Since the loss of the parent does not necessarily coincide with the gain of the offspring, it is provable that any linear combination of the two cost functions (one proportional to parents loss, one to offsprings gain) also leads to honest signalling. Our results, applied for a specific model, support the previous general conclusion that signalling games have different cost functions for different equilibria. Consequently, costly signalling theory cannot predict a unique equilibrium cost in signalling games especially in case of parent-offspring conflicts. As an important consequence, any measured equilibrium cost in real cases has to be compared both to the parents fitness loss and to the offsprings fitness gain in order to provide meaningfully interpretation.

evolutionary biology↗

bioRxiv2017

Caring for parents: an evolutionary rationale

The evolutionary roots of human moral behavior are a key precondition to understand human nature. Here we investigate whether a biological version of Fifth Commandment (\"Honor your father and your mother, that your days may be long\"), respected in different variants across cultures, can spread through Darwinian competition. We show by a novel demographic model that a corresponding Fifth Rule (\"During your reproductive period, give away from your resources to your post-fertile parents\") will spread even if the cost of support to post-fertile grandmothers considerably decreases the demographic parameters of fertile parents but radically increases the survival rate of grandchildren. Teaching vital cultural content is likely to have been critical for the value of grandparental service. Selection on such behavior may have produced an innate moral tendency to honor parents even in situations, such as experienced today, when the quantitative conditions would not necessarily favor the maintenance of this trait.

evolutionary biology↗