Upstream reciprocity and the evolution of gratitude

If someone is nice to you, you feel good and may be inclined to be nice to somebody else. This every day experience is borne out by experimental games: the recipients of an act of kindness are more likely to help in turn, even if the person who benefits from their generosity is somebody else. This behaviour, which has been called ‘upstream reciprocity’, appears to be a misdirected act of gratitude: you help somebody because somebody else has helped you. Does this make any sense from an evolutionary or a game theoretic perspective? In this paper, we show that upstream reciprocity alone does not lead to the evolution of cooperation, but it can evolve and increase the level of cooperation if it is linked to either direct or spatial reciprocity. We calculate the random walks of altruistic acts that are induced by upstream reciprocity. Our analysis shows that gratitude and other positive emotions, which increase the willingness to help others, can evolve in the competitive world of natural selection.     

More 'altruistic' punishment in larger societies

If individuals will cooperate with cooperators, and punish non-cooperators even at a cost to themselves, then this strong reciprocity could minimize the cheating that undermines cooperation. Based upon numerous economic experiments, some have proposed that human cooperation is explained by strong reciprocity and norm enforcement. Second-party punishment is when you punish someone who defected on you; third-party punishment is when you punish someone who defected on someone else. Third-party punishment is an effective way to enforce the norms of strong reciprocity and promote cooperation. Here we present new results that expand on a previous report from a large cross-cultural project. This project has already shown that there is considerable cross-cultural variation in punishment and cooperation. Here we test the hypothesis that population size (and complexity) predicts the level of third-party punishment. Our results show that people in larger, more complex societies engage in significantly more third-party punishment than people in small-scale societies.     

Altruism among relatives and non-relatives

Hamilton's [Hamilton, W.D., 1964. The genetical evolution of social behavior, I, II. J. Theor. Biol. 7, 1-52] kin-selection theory predicts that altruism will be greater with greater genetic overlap (degree of kinship) between giver and receiver. Kin may be identified in terms of social distance-the closer you feel to someone else, (a) the greater your genetic overlap with them should be, and (b) the more altruistic you should be toward them. The present experiment determined the amount of their own (hypothetical) monetary reward undergraduates were willing to forgo in order to give $75 to other people at various social distances. We found that (a) genetic relationship and (b) altruism varied inversely with social distance; the closer you feel to someone else, the closer their relation to you is likely to be, and the more altruistic you are likely to be toward them. However, even at the same social distance, participants were willing to forgo significantly more money for the benefit of relatives than for the benefit of non-relatives. These results are consistent with kin-selection theory and imply that altruism is determined by factors in addition to social distance.     

Advance directives, dementia, and 'the someone else problem'

Advance directives permit competent adult patients to provide guidance regarding their care in the event that they lose the capacity to make medical decisions. One concern about the use of advance directives is the possibility that, in certain cases in which a patient undergoes massive psychological change, the individual who exists after such change is literally a (numerically) distinct individual from the person who completed the directive. If this is true, there is good reason to question the authority of the directive ‐ which is supposed to apply to the individual who completed it, not to someone else. This is 'the someone else problem'.
After briefly introducing advance directives as a basis for medical decision-making, this paper elaborates 'the someone else problem' in the context of severe dementia. The paper then reconstructs the reasoning that leads to this putative problem and exposes the important underlying assumption that we are essentially persons. An alternative view of what we are, one that regards personhood as inessential, is then considered, before several arguments are advanced in favor of that alternative view. The paper next explores implications for advance directives: 'The someone else problem' is effectively dissolved, while it is noted that a related problem (one beyond the paper's scope) may persist. A few implications beyond advance directives are also identified.     

Does nothing in evolution make sense except in the light of population genetics?

“The Origins of Genome Architecture” by Michael Lynch (2007) may not immediately sound like a book that someone interested in the philosophy of biology would grab off the shelf. But there are three important reasons why you should read this book. Firstly, if you want to understand biological evolution, you should have at least a passing familiarity with evolutionary change at the level of the genome. This is not to say that everyone interested in evolution should be a geneticist or a bioinformatician, but that a working knowledge of genetic change is an essential part of the intellectual toolkit of modern evolutionary biology, even if your primary focus is the evolution of behaviour or the diversity of communities. Secondly, this book provides excellent examples of another important tool in the biologist’s intellectual toolkit, but one that is rarely explained or illustrated to such an extent: null (or neutral) models. The role null models play in testing hypotheses in evolution is a central focus of this book. Thirdly, as an accomplished work of advocacy for a strictly microevolutionary view of evolution, this book provides grist for the mill for the important debate about whether population genetic processes are the sine qua non of evolutionary explanations.     

Reproductive investment patterns,sperm characteristics,and seminal plasma physiology in alternative reproductive tactics of Chinook salmon (Oncorhynchus tshawytscha)

Although alternative reproductive tactics (ARTs) are common across a range of taxa, little is known about whether the different tactics have adapted to sperm competition risk. Chinook salmon, Oncorhynchus tshawytscha, have two ARTs: large males that participate in dominance‐based hierarchies for access to spawning females, known as hooknoses, and small males that attempt to sneak fertilizations during spawning events from peripheral positions, known as jacks. Jacks continually face sperm competition risk because they always spawn in the presence of another male, whereas hooknoses face relatively low sperm competition risk because other males are not always present during spawning events. Based on the sneak‐guard model of sperm competition this asymmetry in sperm competition risk predicts that jacks ought to invest significantly more into sperm‐related traits important for sperm competition success relative to hooknoses. In the present study we report on reproductive investment patterns, sperm characteristics, and seminal plasma physiology of males that exhibit ARTs in Chinook salmon. We found that jacks invest significantly more of their somatic tissue into gonads compared with hooknoses. Sperm velocity also varied significantly between the ARTs, with jacks having significantly faster sperm than hooknoses. No significant differences in seminal plasma physiology metrics related to sperm quality were detected between the ARTs. We interpret these sperm investment patterns in light of the sneak‐guard model of sperm competition that is based on differences in sperm competition risk and alternative investment possibilities among ARTs. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

Biogenetic ties and parent‐child relationships: The misplaced critique

According to an almost axiomatic standard in bioethics, moral commitment should ground parents’ relationship with their children, rather than biogenetic relatedness. This standard has been used lately to express skepticism about extending existing assisted reproductive treatments (ARTs) to same‐sex couples and to research into novel fertility interventions for those couples, but this skepticism is misplaced on several grounds. As a matter of access and equity, same‐sex couples seem presumptively entitled to genetic relatedness to their children as far as possible both in regard to existing ARTs and to novel ARTs under investigation. For those worried about the effects of trying to secure biogenetic relatedness for same‐sex couples, it may be noted that same‐sex couples will only ever be a fraction of the parents implicated in propping up “biologism,” as the expectation of biogenetic relatedness it is sometimes called. The cultural force of biologism would survive almost intact even if no same‐sex couples were ever to have genetically related children. It is therefore hard to see why same‐sex couples should forfeit aspirations to biogenetic relationships with their children or enjoy less subsidy for ARTs than the subsidy given to different‐sex couples. As matter of moral consistency, the full implications of the biologism critique have yet to be evaluated relative to different‐sex couples.     

The emotion–valuation constellation: Multiple emotions are governed by a common grammar of social valuation

Social emotions are hypothesized to be adaptations designed by selection to solve adaptive problems pertaining to social valuation—the disposition to attend to, associate with, and aid a target individual based on her probable contributions to the fitness of the valuer. To steer between effectiveness and economy, social emotions need to activate in precise proportion to the local evaluations of the various acts and characteristics that dictate the social value of self and others. Supporting this hypothesis, experiments conducted in the United States and India indicate that five different social emotions all track a common set of valuations. The extent to which people value each of 25 positive characteristics in others predicts the intensities of: pride (if you had those characteristics), anger (if someone failed to acknowledge that you have those characteristics), gratitude (if someone convinced others that you have those characteristics), guilt (if you harmed someone who has those characteristics), and sadness (if someone died who had those characteristics). The five emotions track local valuations (mean r = +.72) and even foreign valuations (mean r = +.70). In addition, cultural differences in emotion are patterned: They follow cultural differences in valuation. These findings suggest that multiple social emotions are governed (in part) by a common architecture of social valuation, that the valuation architecture operates with a substantial degree of universality in its content, and that a unified theoretical framework may explain cross-cultural invariances and cultural differences in emotion.     

Benevolent Characteristics Promote Cooperative Behaviour among Humans

Cooperation is fundamental to the evolution of human society. We regularly observe cooperative behaviour in everyday life and in controlled experiments with anonymous people, even though standard economic models predict that they should deviate from the collective interest and act so as to maximise their own individual payoff. However, there is typically heterogeneity across subjects: some may cooperate, while others may not. Since individual factors promoting cooperation could be used by institutions to indirectly prime cooperation, this heterogeneity raises the important question of who these cooperators are. We have conducted a series of experiments to study whether benevolence, defined as a unilateral act of paying a cost to increase the welfare of someone else beyond one''s own, is related to cooperation in a subsequent one-shot anonymous Prisoner''s dilemma. Contrary to the predictions of the widely used inequity aversion models, we find that benevolence does exist and a large majority of people behave this way. We also find benevolence to be correlated with cooperative behaviour. Finally, we show a causal link between benevolence and cooperation: priming people to think positively about benevolent behaviour makes them significantly more cooperative than priming them to think malevolently. Thus benevolent people exist and cooperate more.     

Centris pallida (Hymenoptera: Apidae) male body size decreases across five decades

Historical data suggest that many bee species have declined in body size. Larger-bodied bees with narrow phenological and dietary breadth are most prone to declines in body size over time. This may be especially true in solitary, desert-adapted species that are vulnerable to climate change such as Centris pallida (Hymenoptera: Apidae). In addition, body size changes in species with size-linked behaviours could threaten the prevalence of certain behavioural phenotypes long-term. C. pallida solitary bees are found in the Sonoran Desert. Males use alternative reproductive tactics (ARTs) and are dimorphic in both morphology and behaviour. C. pallida male body size has been studied since the 1970s in the same population. The authors collected body size data in 2022 and combined it with published records from 1974–2022. The authors find a persistent decline in the mean head width of patrolling males, and shifts towards smaller body sizes in the populations of males found foraging and hovering. Both morphs declined in average body size, and the proportion of large-morph males in the population decreased by 8%. Mating males did not decline in mean body size over the last five decades. The authors discuss hypotheses related to the decline in C. pallida male head width. Finally, the authors advocate for C. pallida as an excellent study system for understanding the stability of ARTs with size-linked behavioural phenotypes.     

Transgenerational and developmental plasticity at the molecular level: Lessons from Daphnia

Listen to the news and you are bound to hear that researchers are increasingly interested in the biological manifestations of trauma that reverberate through the generations. Research in this area can be controversial in the public realm, provoking societal issues about personal responsibility (are we really born free or are we born with the burden of our ancestors’ experience?). It is also a touchy subject within evolutionary biology because it provokes concerns about Lamarckianism and general scepticism about the importance of extra‐genetic inheritance (Laland et al., 2014 ). Part of why the research in this area has been controversial is because it is difficult to study. For one, there is the problem of how long it takes to track changes across generations, making long‐term, multi‐generational studies especially tricky in long‐lived species. Moreover, there are presently very few (if any) known molecular mechanisms by which environmental effects can be incorporated into the genome and persist for multiple successive generations, casting doubt on their evolutionary repercussions. Fortunately, you only have to look in your local pond to find the creatures that are teaching us a great deal about how and why the experiences of parents are passed down to their offspring. In this issue of Molecular Ecology, Hales et al. (Hales et al., 2017 ) illustrate the power of Daphnia (“water fleas”) for making headway in this field.     

Age-specific survival of territorial and non-territorial male chamois

How alternative reproductive tactics (ARTs) are maintained in wildlife populations is one of the major questions in evolutionary biology. As a dominant status, territoriality is typically linked to increased mating opportunities, and one explanation why this behaviour coexists with other tactics is that dominance implies survival costs. Such a trade-off may occur in the Northern chamois Rupicapra rupicapra, as reproductive advantages of territorial males over non-territorial males could be counterbalanced by a reduction in survival mediated through energy expenditure, stress and parasitic infections, ultimately favouring ART coexistence. Here, we analysed age-dependent survival probabilities of territorial (n = 15) and non-territorial (n = 16) adult chamois using information collected over 12 years between 2010 and 2021 in the Gran Paradiso National Park (Western Italian Alps). Survival rates were estimated with a CMR approach using Burnham's joint modelling of live encounter and dead recovery data. The model selection procedure, based on AICc value minimisation, supported a linear decrease of survival with age but the results did not match our predictions, as territorial chamois did not have lower survival rates than non-territorial chamois. In contrast, territorial males appeared to enjoy reproductive success at lower survival costs. This, in turn, supports the role of other factors, such as snow-dependent environmental stochasticity, in the maintenance of ARTs in chamois populations. The limited sample size, however, calls for caution in interpretation, and long-term studies of lifetime reproductive success and survival are necessary to clarify the mechanisms underlying the expression and coexistence of different reproductive behaviours in this species.     

Culture, Speciation and the Genus Homo in Early Humans

Human behaviour, in addition to morphology, is essential to identify man. The characteristics of cultural behaviour are expressed by planning in tool making and territorial organization and by their meaning in the context of life. Cultural behaviour enriched the adaptive strategies of the human species and took on significance in the definition of the genus Homo since H. habilis/H. rudolfensis. Culture probably played a double role in the process of human speciation: (1) in isolation and differentiation from other groups of hominids that did not had such behaviour; and (2) in adaptation to the environment and in communication between groups that had the same cultural behaviour, thus slowing down or preventing the conditions of isolation that lead to new species.     

Complex adaptive traits between mating behaviour and post-copulatory sperm behaviour in squids

Emergence of male dimorphism within a species is the evolutionary process of disruptive selection. In squids, two types of male mating behaviour, known as alternative reproductive tactics (ARTs), are causally associated with adult body size. Males inseminate promiscuously with the same females; large “consort” males internally, and small “sneaker” males externally. Previously we found that in Heterololigo bleekeri, sneaker (but not consort) spermatozoa are able to swarm by sensing self-emitted CO₂. This suggests that a swarming trait might have arisen in sneakers as a “sperm cooperation” strategy among sibling sperm in order to compete with consort males, or as a consequence of adaptation to external fertilization. To address these possibilities, we examined six species where three patterns of insemination are present, namely, only internal, only external, or both ARTs. In three species that employ both ARTs (H. bleekeri, Loligo reynaudii and Uroteuthis edulis), sneaker spermatozoa always exhibited self-swarming capacity. In Idiosepius paradoxus and Todarodes pacificus, which use only external insemination, spermatozoa formed a swarm. However, in Euprymna morsei, which use only internal insemination, sperm were unable to swarm. These results suggest that the self-swarming trait is likely to be linked to the mode of insemination rather than the alternative strategy used by sneaker males. Thus we propose a new hypothesis in which cooperative sperm behaviour has evolved not only through kin selection against sperm competition risks, but also through adaptation to the insemination/fertilization environment.     

Allometry of a sexual trait in relation to diet experience and alternative mating tactics in two rubyspot damselflies (Calopterygidae: Hetaerina)

Several arguments have been put forward to explain how sexual selection drives the evolution of sexual trait allometry, especially hyperallometry. The ‘positive allometry theory’ suggests that hyperallometry is a rule in all‐secondary sexual traits, whereas the ‘display hypothesis’ suggests that only males in good condition will exhibit hyperallometric sexual display traits. In the present study, we investigated: (1) the condition‐dependence nature (by using two diet treatments that varied in the amount of food provided to the larvae) of a sexually selected trait (wing pigmentation; WP) in recently‐emerged adults of the American rubyspot damselfly, Hetaerina americana, and (2) the scaling relationship between WP and body size (wing and body length) in the rubyspot damselflies H. americana and Hetaerina vulnerata, according to alternative reproductive tactics (ARTs; territorial and nonterritorial males). First, we found support that indicated that diet positively affected WP length, although there was no significant WP allometric pattern in relation to diet regimes. Second, WP was hyperallometric in both Hetaerina species. WP size was similar between ARTs and, in H. americana (but not H. vulnerata), nonterritorial males showed steeper slopes than territorial males when wing length was used. The results obtained support the notion that sexual traits are hyperallometric, although there is no clear pattern in relation to ARTs. © 2013 The Linnean Society of London     

Embryo Donation in Iran: An Ethical Review

Iran is the only Muslim country that has legislation on embryo donation, adopted in 2003. With an estimated 10–15% of couples in the country that are infertile, there are not any legal or religious barriers that prohibit an infertile couple from taking advantage of Assisted Reproductive Technologies (ARTs). Although all forms of ARTs available in Iran have been legitimized by religious authorities, there is a lack of legislation in all ARTs except embryo donation. By highlighting ethical issues in embryo donation, the paper presents a critical review of the Act of Embryo Donation in Iran. The paper argues that the Act does not provide enough safeguards for the future child and assurance for the safety of the donated embryos. It also does not restrict embryo donation to surplus embryos from infertile couples and is silent about the number of embryos that could be donated by each couple as well as the number of recipients for donated embryos by a couple. The Act is also silent about the issues of genetic linkage (nasab) and heritage which are challenging issues, especially in a conservative Islamic society. As a result, the future child may not inherit from their birth parents, as it is not required by the Act, or from the genetically related parents under the anonymity policy. Finally there is no standard national protocol or guidelines to evaluate the safety of the donated embryos. The paper concludes that despite its benefits, the Act lacks clarity, and it is subject to misunderstanding and confusion.     

Parasitism and alternative reproductive tactics in Northern chamois

Alternative reproductive tactics (ARTs), discrete phenotypic variations evolved to maximize fitness, may entail different cost‐benefit trade‐offs. In large mammals, differences in costs associated with ARTs—including energy expenditure and parasite infection—are typically greatest during the breeding season. Nonetheless, physiological and behavioral differences between ARTs can manifest throughout the year, possibly involving costs that may contribute to maintain ARTs within populations. Using the number of nematode larvae per gram of feces (LPG) as a proxy, we explored the temporal changes in lung parasite infection in territorial and nonterritorial male chamois Rupicapra in the Gran Paradiso National Park (Italy), between 2011 and 2012. We aimed to identify which tactic‐specific physiological and behavioral features (including age, hormonal levels, inter‐ and intrasexual interactions, and space use) or climatic factors (temperature and precipitation) best explained yearly variation in parasite infection within and between ARTs. Generalized additive mixed models showed that the fecal larval counts of lung nematodes underwent strong temporal changes in both male types. Differences between ARTs (with higher LPG values in territorial than nonterritorial males) were greatest during the rut and—to a lesser extent—in spring, respectively, at the peak and at the onset of territoriality. The difference in LPG between tactics was largely explained by the greater levels of hormone metabolites in territorial males during the rut. The other variables did not contribute significantly to explain the different shedding of larvae within and between ARTs. Our analysis suggests that different values of LPG between territorial and nonterritorial males are largely a result of tactic‐specific differences in the secretion of hormone metabolites, but only during the rut. To clarify whether rut‐related parasitism contributes to the maintenance of ARTs, tactic‐specific life history trade‐offs, for example, between reproduction and parasite‐related mortality, must be investigated.     

Misusing uteruses? Childrearing capacity and access to transplantable wombs

In light of recent successful uterus transplantations, it is reasonable to expect that womb transplants will become more commonplace in the future. If this happens, important questions emerge about who should receive the donated wombs. Some arguments have been advanced that suggest that potential recipients should be screened for their anticipated childrearing capacity, as one component of a comprehensive process for determining eligibility. The main arguments provided in support of this position have to do with the presumed responsibility of the state to protect future children from harm, and with avoiding complicity for any resulting harm experienced by the child born through the transplanted uterus. The purpose of this paper is to reject this position, based on two main criticisms: (1) screening potential uterus recipients for anticipated childrearing ability, but not also screening other kinds of morally equal family builders, is unjustly discriminatory; and (2) with respect to actions performed in good faith (e.g. providing a transplantable uterus to someone for the purpose of having a child), one is not morally blameworthy for the consequences of those actions (a) that one did not intend, and (b) that were directly caused by someone else, and (c) where others are directly responsible for making sure that those consequences do not come about. These criticisms are sufficient for concluding that the state is not justified in assessing the anticipated childrearing capacity of potential uterus recipients, and this is so regardless of whether or not there is a scarcity of transplantable uteruses available.