Program
Tuesday 8 November
900 Registration (Social Room, Healey Family Student Center)
915 Arvid Ågren and Manus Patten - Welcome
930 Martijn Schenkel - Formalization of the paradox of the organism
1015 Walter Veit - Life history theory as the teleonomic theory of the organism
1035 coffee break
1105 Bryan Gitschlag - Multilevel selection analysis reveals diverse cheater strategies among mitochondrial mutations
1125 Guilhem Doulcier - Canalization and restraint of conflicting interactions through ecological scaffolding during evolutionary transition in individuality
1145 Israt Jahan - Revisiting Wolpert's hypothesis on the evolution of the egg
1230 lunch
1430 Pierrick Bourrat - In what sense can there be conflict between the levels of selection?
1515 Evgeny Brud - Mendel and maladaptation
1535 Zachary Compton - Comparative Phylogenetic Models of the Evolution of Cancer Risk
1555 coffee break
1625 Pedro Márquez-Zacarías - A compositional theory of life cycles
1645 Rodrigo Zorrilla González - Looking for leviathans: free riding on a multicellular yeast
1705 Nina Wedell - Selfish genetic elements and sexual selection
1750 drinks and hors d'oeuvres
1815 David Haig - Pax somatica
Wednesday 9 November
915 Arvid Ågren and Manus Patten - Welcome
930 Samir Okasha - Conflict within genomes, groups, and persons
1015 Robert Kōk - Host-Parasite Systems Are Holobionts
1035 coffee break
1055 Matthew Advent - On Purpose, By Chance: Teleology and the Parts of Animals After Darwin
1125 Michael Lachmann - Epigenetic inheritance and the evolution of the germline
1145 Laura Ross - Somatic genome elimination: why do many eukaryotes delete parts of their genomes from their soma?
1230 lunch
1430 Amy Boddy - We are multitudes: microchimerism, evolution and human health
1515 Augustin Chen - The response of somatic evolution to organismal selection
1535 Maja Sidzińska - Biological Individuality in Pregnancy: An Argument for the Evo-Devo Approach
1555 coffee break
1625 Cody McCoy - Evolutionary conflict in the coral-algae symbiosis
1645 Ellen Clarke - Organismal identity: how can organisms change over time without ceasing to exist?
1730 Arvid Ågren and Manus Patten - Closing
900 Registration (Social Room, Healey Family Student Center)
915 Arvid Ågren and Manus Patten - Welcome
930 Martijn Schenkel - Formalization of the paradox of the organism
1015 Walter Veit - Life history theory as the teleonomic theory of the organism
1035 coffee break
1105 Bryan Gitschlag - Multilevel selection analysis reveals diverse cheater strategies among mitochondrial mutations
1125 Guilhem Doulcier - Canalization and restraint of conflicting interactions through ecological scaffolding during evolutionary transition in individuality
1145 Israt Jahan - Revisiting Wolpert's hypothesis on the evolution of the egg
1230 lunch
1430 Pierrick Bourrat - In what sense can there be conflict between the levels of selection?
1515 Evgeny Brud - Mendel and maladaptation
1535 Zachary Compton - Comparative Phylogenetic Models of the Evolution of Cancer Risk
1555 coffee break
1625 Pedro Márquez-Zacarías - A compositional theory of life cycles
1645 Rodrigo Zorrilla González - Looking for leviathans: free riding on a multicellular yeast
1705 Nina Wedell - Selfish genetic elements and sexual selection
1750 drinks and hors d'oeuvres
1815 David Haig - Pax somatica
Wednesday 9 November
915 Arvid Ågren and Manus Patten - Welcome
930 Samir Okasha - Conflict within genomes, groups, and persons
1015 Robert Kōk - Host-Parasite Systems Are Holobionts
1035 coffee break
1055 Matthew Advent - On Purpose, By Chance: Teleology and the Parts of Animals After Darwin
1125 Michael Lachmann - Epigenetic inheritance and the evolution of the germline
1145 Laura Ross - Somatic genome elimination: why do many eukaryotes delete parts of their genomes from their soma?
1230 lunch
1430 Amy Boddy - We are multitudes: microchimerism, evolution and human health
1515 Augustin Chen - The response of somatic evolution to organismal selection
1535 Maja Sidzińska - Biological Individuality in Pregnancy: An Argument for the Evo-Devo Approach
1555 coffee break
1625 Cody McCoy - Evolutionary conflict in the coral-algae symbiosis
1645 Ellen Clarke - Organismal identity: how can organisms change over time without ceasing to exist?
1730 Arvid Ågren and Manus Patten - Closing
Contributed talks
Life History Theory as the Teleonomic Theory of the Organism
Walter Veit, University of Bristol and Oxford University
Philosophers of biology have spend much time thinking about the nature of organisms and their agential or goal-directed features. Yet, surprisingly little attention has been given to arguably the key theoretical tool evolutionary biologists have developed to think about the organism and the trade-offs inherent to biological design. This resource is modern state-based life history theory. In this talk, I will present an interdisciplinary project that I have undertaken during my postdoc at Samir Okasha's Representing Evolution project at the Department of Philosophy, University of Bristol and as a visitor at the Salgo-Team at the Department of Zoology, University of Oxford, to use life history theory in order to make sense of the unity and agency of organisms in spite of the apparent conflicts inside of them.
Multilevel selection analysis reveals diverse cheater strategies among mitochondrial mutations
Bryan Gitschlag, Cold Spring Harbor Laboratory
Owing to their evolutionary heritage as symbionts descended from free-living bacteria, mitochondria harbor their own genomes (mtDNA). These genomes exist at high intracellular copy-number and replicate semi-autonomously, enabling the occurrence of mutant variants that can fluctuate in frequency and compete for replication. Accordingly, mutant mitochondrial genomes can behave as selfish entities, parasitically propagating within organisms at the expense of host fitness. We previously designed experiments to quantitatively measure natural selection on selfish mtDNA at different levels of selection in isolation, namely at the intra-organismal and organismal levels. Building on this work, we developed a mathematical modeling approach that integrates these separate experimental measurements into a unified theoretical framework. Applied across a collection of mitochondrial genotypes, this approach revealed diverse cheating “strategies.” Specifically, mutant genomes with heavy fitness consequences can nevertheless persist by outcompeting cooperative (wildtype) mitochondrial genomes within hosts. Conversely, some mutant genomes fail to outcompete wildtype mtDNA but nevertheless persist by maintaining a frequency that elicits negligible organismal selection. Together, these findings suggest that the population dynamics of mitochondrial mutations strongly depend on the protein(s) affected. More broadly, we successfully integrate evolutionary theory with benchtop experimentation to uncover previously unrecognized diversity in the population dynamics of selfish mitochondrial genomes.
Canalization and restraint of conflicting interactions through ecological scaffolding during evolutionary transition in individuality
Guilhem Doulcier, Macquarie University and Max Planck Institute for Evolutionary Biology
Evolutionary transitions in individuality are events in the history of life where a collection of entities come together to form collectives that are recognized as Darwinian individuals. The emergence of the eukaryotic cell from procaryotic ancestors and the evolution of multicellular from unicellular organisms are two prime examples of such transitions. Ecological interactions between their components can threaten the continued existence of these newly evolved collectives. For instance, some lineages of entities can take over the ecosystem and cause the extinction of the higher-level entities before any propagule is sent out. In modern entities, conflict mediating mechanisms exist, from DNA copy-number control to cell-proliferation regulation. However, their emergence through natural selection seems to imply that higher-level entities are units of selection.
This is puzzling because higher-level entities are not units of selection at the beginning of a transition. The Ecological Scaffolding scenario of evolutionary transitions in individuality posits that a population structure, e.g., resource patches separated by boundaries with limited migration, could allow collectives that initially lack the Darwinian properties of variation, fitness difference and heritability to gradually acquire them and consequently explain the emergence of conflict mediation without initially positing collective-level selection. I will present a combination of mathematical, experimental and philosophical work that attempts to characterize better and understand the effect of scaffolding population structure in evolutionary transitions in individuality.
Mendel and maladaptation
Evgeny Brud, North Carolina State
Whatever the ultimate resolution to the paradox of the organism, the egalitarian nature of Mendelian segregation is likely to play a prominent explanatory role in discussions of sexual taxa. A curious feature of some recent evolutionary invasion analyses is that Mendelian segregation is expected to be replaced over long-term evolution by modifiers that enhance meiotic drive in opposite directions in the two sexes. In selfing organisms, the conditions for strong selection on unlinked drive-enhancers are unrestrictive: a locus has to exist at stable equilibrium due to heterozygote advantage. So far in panmictic context, the conditions for strong modifier selection correspond to a restrictive form of heterozygote advantage (asymmetric heterozygote fitnesses due to parent-of-origin effects). Here I expand the conditions for the repeal of Mendelian segregation to an additional scenario: a bivoltine population subject to seasonal selection and random mating. In light of the modifier theoretic results, I argue that the long-term survival of Mendelian segregation is a sub-paradox: why do Mendel-enforcing genes persist given the deleterious aspect of equal segregation ratios (i.e. the segregation load)? Or put another way, why did the parliament of genes settle on an apparently disadvantageous principle for inheritance? Clarity on the matter would benefit from a more biologically realistic treatment of modifier control than has so far been considered, and so lastly I present numerical iteration results under some more realistic assumptions.
Comparative Phylogenetic Models of the Evolution of Cancer Risk
Zachary Compton, Arizona State University
The pervasiveness of cancer across the tree of life has driven much research into detailing the scope and pathology of the disease in non-human species. Understanding cross-species cancer risk is fundamental in comparative biology, and highlights the importance of identifying uniquely cancer resistant species as well as stratifying risk across phylogeny. Comparative phylogenetics provides a robust modeling framework to understand how evolution has shaped the diversity of species' traits across the tree of life. Here we fit several models of trait evolution to the "cancer risk phenotype", which we assigned as the observed cancer prevalence for 47 mammalian species. In translating these models to the evolution of cancer susceptibility, we demonstrate how species-level shifts in cancer risk can mirror shifts in key traits such as longevity and body mass. We intend for this approach, and its expansion to other taxa, to add to our understanding of how evolution has shaped the diversity of disease risk and outcomes across the tree of life.
A compositional theory of life cycles
Pedro Márquez-Zacarías, Santa Fe Institute
Evolutionary change is not possible unless individuals reproduce. Thus, a central question in biology should be: how does reproduction itself occur, and how is reproduction organized across different lineages? The surprising answer is that we lack a general theory of reproduction, which is to say that we lack a general theory of life cycles. A central problem for developing a general theory is that life cycles are not processes that can be derived from existing theory. Life cycles are patterns of organization, and therefore they require a different way of theorizing. Here, we present a simple theory of life cycles based on category theory. We take individual organisms as constituents of reproductive paths, which we represent with a graphic algebra that allows for arbitrarily complex compositions of these paths. With our framework, we can express arbitrarily complex life cycles. As a case study, we present an analysis of the transition to multicellular life, and we show that aggregation seems to be a survival strategy of single-celled organisms, rather than a form of multicellular reproduction. We discuss the importance and implications of this distinction for multicellular research, but also for the more general problem of biological construction and evolutionary transitions.
Looking for leviathans: free riding on a multicellular yeast
Rodrigo Zorrilla González
Research into cooperation and collective action typically frames “free riding” behavior (benefiting from cooperation without bearing its cost) under the assumption that free riders will lead to the extinction of cooperative behavior. Experiments typically investigate how cooperating groups mitigate the damage that free riding incurs. I present a microbial model of cooperative and free riding Kluyveromyces lactis strains, which exhibit a stable equilibrium and co-exist over time. Cells are grown in liquid media, selected from the bottom of a glass test tube and transferred daily into fresh media. Under this selective pressure, collective action can rapidly evolve. The multicellular, cooperative strain benefits from a faster sinking speed, despite having a slower growth rate than the ancestor. Free riding behavior also readily evolves under this selective pressure. The unicellular, free rider cells attach to multicells, and benefit from increased sinking ability without the diminished growth rate of multicellularity. I propose that the costs and benefits of maintaining freeriding do not occur simultaneously - many of the continued problems associated with reconciling theoretical expectations with empirical results could be due to this temporal asynchronicity of costs and benefits. Historical assumptions constrain the questions scientists ask and the conclusions they make from their results. Interrogating the historical lineage of concepts used in scientific study is epistemologically valuable and has the potential to open up multidisciplinary discourse into the future.
Host-Parasite Systems Are Holobionts
Robert Kōk, University of Utah
Holobiont theories have provided scientists and philosophers a new conception of living things as interactive, interdependent systems involving the host organism and its symbiotic microbes. However, the perspective adopted in both scientific and philosophical analyses of holobionts has been entirely mutualistic: symmetrical part dependencies between hosts and symbionts that are necessary for the functioning and persistence of the whole biont entity. What would a holobiont look like from a parasitological perspective? Typically, parasites are treated as pathogenic agents exogenous to and, therefore, not parts of hosts. However, the opposite is not true: when infected with a parasite, hosts can become parts of parasites. This asymmetry in part dependency raises an interesting question: can host-parasite systems be considered as holobionts and how? I provide a positive answer to this question. To show this, I suggest that we move away from a mutualistic perspective to a parasitological one, with focus on parasite life cycles. Whether simple or complex, hosts are essential components of parasite life cycles and are necessary to advance important life stages, including growth, development, and reproduction. A striking feature of the parasitological perspective is that asymmetry in part dependency does not rule out host-parasite systems as holobionts, rather it expands our conception of what holobionts can be. Depending on the sort of symbiosis adopted, my analysis shows that what counts as a holobiont is relative to a perspective. Thus, from a parasitological perspective, host-parasite systems are holobionts.
On Purpose, By Chance: Teleology and the Parts of Animals After Darwin
Matthew Advent, The Catholic University of America
In this paper, I make an attempt to help clarify the profoundly confusing debates about teleology and evolution by articulating—without necessarily endorsing or arguing for–a broadly Aristotelian conception of teleology that is compatible with Darwinian evolution by natural selection. I do this by making two distinctions: The first between transient (other effecting) and imminent (self-perfective) causation and the second between why a class of animals engages in an activity and why this particular animal engages in that activity. By doing so, I argue that we can at least conceptually understand how it might be possible for this particular living thing to act for a purpose–sustaining its life–in developing its parts without contradicting the notion that those parts arose over time through the non-teleological processes of random mutation. If this view of teleology is true, it represents both a significant defeat and triumph for Aristotle’s conception of the organism. It is a defeat insofar as it means that the sort of purely mechanistic account of the parts of animals that Aristotle largely wants to reject is true, but it also represents a significant vindication for Aristotelianism to the degree that it is able to preserve the view that living things are teleologically oriented wholes that work to bring about an end.
Epigenetic inheritance and the evolution of the germline
Michael Lachmann, Santa Fe Institute
Differentiation within multicellular organisms is controlled by epigenetic markers transmitted across cell division. The process of differentiation will modify these epigenetic markers so that information that one cell type possesses can be lost in the transition to another. Many of the systems that encode these markers also exist in unicellular organisms but do not control differentiation. Thus, during the evolution of multicellularity, epigenetic inheritance systems were probably exapted for their current use in differentiation. The simultaneous use of an information carrier for differentiation and transmission across generations can cause conflict to transmit across generations even if the organism goes through a single cell stage. This shows that an intrinsic instability during a transition from unicellularity to multicellularity may contribute to widespread evolution of a germline and its maintenance, a phenomenon also relevant to the evolution of eusociality.
The response of somatic evolution to organismal selection
Augustin Chen, Collège de France
During multicellular development, different cell lineages do not contribute equally to the formation of the soma. Such asymmetries in the cellular phylogeny can be caused by diverse mechanisms, including differential division/death rates along the tree or competition between/within lineages. Interestingly, some organismal phenotypes like body or organ size are shaped by those somatic eco-evolutionary interactions, drawing a potential link between somatic and organismal evolution. However, little is known about how somatic evolution may respond to organismal selection. Here, we address this question using a model simulating both somatic evolution and organismal selection. In a first experiment, we find that when selecting for a specific number of cells at the end of development, somatic evolution first adjusts division and death rates to meet the target number, before engaging frequency-dependent interactions (e.g., competition) to reduce the variance around the target. In a second experiment, we observe that when organisms are given the possibility to generate cells with 2 different states, evolution favors only one of the 2 to dominate and establish the correct number of cells. Finally, when offered with the option to evolve a division of labor with 2 cell states and 2 functions, organisms evolve a single dominant cell state that takes care of both functions.
Biological Individuality in Pregnancy: An Argument for the Evo-Devo Approach
Maja Sidzińska, University of Pennsylvania
Is the pregnant eutherian one or two individuals? There are three recent approaches to resolving this question. The first is due to Elselijn Kingma, who showed that different criteria for biological individuality give different verdicts about whether pregnant eutherians are individuals; this result arises within a substance-ontological framework that attempts to provide necessary or sufficient conditions for biological individuality. But John Dupré claims that a process-ontological approach to biology defuses the problem of conflicting verdicts about the number of individuals present in a eutherian pregnancy; he and Anne Sophie Meincke endorse a process-ontological approach to theorizing pregnancy in eutherians. From the point of view of process ontology, the pregnant mammal is a bifurcating process. The third approach, called the evo-devo approach, developed by Laura Nuño de la Rosa, Mihaela Pavličev, and Arantza Etxeberria, provides a historical way to interpret biological individuality. From the evo-devo point of view, eutherian pregnancy reflects an evolutionarily novel and unique kind of individuality. In this talk, I criticize the first two approaches, and endorse the third. The evo-devo approach is better because it helps unify some criteria for biological individuality, and because it is more informative than the processual approach.
Evolutionary conflict in the coral-algae symbiosis
Cody McCoy, Stanford University
Global warming causes corals worldwide to “bleach”--expel their symbiotic algae, turn white, and die. Coral bleaching is an ecological catastrophe, and it can be viewed as a breakdown of the symbiosis between animal and microbe. But many other photosymbiotic animals, and some corals, are resistant to bleaching. Here, I argue for one possible driver of susceptibility to bleaching: conflicts of interest between host and symbiont. For example, about half of all reef-building corals do not reproduce together with their symbionts; larvae pick up symbionts from their environment (“horizontal transmission”) rather than from their parents (“vertical transmission”). Reproducing separately is one metric predicting evolutionary conflict, and many bleaching-resistant species reproduce together with their symbionts. Here, I compile data on transmission mode (and other metrics of evolutionary conflict) across corals, sponges, bivalves, and more. I investigate whether higher-conflict symbioses are more fragile and, therefore, more prone to bleaching.
Invited talks
Formalization of the paradox of the organism
Martijn Schenkel, Georgetown University and University of Groningen
The paradox of the organism refers to the observation that organisms persist as seemingly coherent entities with the singular agenda of maximizing fitness, despite the potential for intra-organismal elements such as genes and cells to hold and pursue conflicting agendas. Quantifying to what extent such intra-organismal conflict actually threatens the integrity of the organism and its ability to pursue fitness maximization requires the development of a mathematical framework that relates the agenda of the organism to the potentially-conflicting agendas of its constituent parts. Here, I will discuss which mechanisms contribute to intra-organismal entities having shared versus disparate agendas, and to which extent disparate agendas and the mechanisms of pursuing them represent a threat to organismal integrity. The resulting insights are used to discuss a preliminary framework for quantifying the paradox of the organism.
Revisiting Wolpert's hypothesis on the evolution of the egg
Israt Jahan, Washington University in St. Louis
High relatedness and low genetic conflict within multicellular organisms have been a longstanding explanation for the evolutionary success of organisms that develop from a single cell – an egg. However, Wolpert and Szathmary (2002) suggest an alternate explanation for the evolution of a single-celled life stage. They claim that the evolution of the egg is not a question of inclusive fitness but is driven by selective pressure for coordinated development. According to their hypothesis, organisms that develop from a group of non-clonal cells would be dysfunctional, causing their eventual elimination by natural selection. The problem of coordination is solved when a single cell is the unit of reproduction. We have empirically tested this developmental incompatibility hypothesis in the social amoeba Dictyostelium discoideum. We measure group function with slug mobility, an adaptive multicellular trait involving coordinated phototactic movement. In D. discoideum mixtures of unevolved and independently mutated lines, we observe intermediate slug mobility that is likely due to social dominance of the unevolved lines. Our results do not support Wolpert-Szathmary incompatibilities in the absence of strong within-organism conflict. We conclude that developmental incompatibilities alone, as suggested by Wolpert and Szathmary, are insufficient in explaining the evolution of multicellularity from a single-celled egg.
In what sense can there be conflict between the levels of selection?
Pierrick Bourrat, Macquarie University
The idea of evolutionary conflict is a staple of evolutionary biology. Naturally, it is often used in the context of multilevel selection and evolutionary transition in individuality or more generally in discussions involving more than one level (e.g., an organism and its genes). In this talk, I distinguish several possible meanings for the idea of evolutionary conflict in a multilevel context. I argue that one of these meanings is illegitimate or at best metaphorical
Selfish genetic elements and sexual selection
Nina Wedell, University of Melbourne
Selfish Genetic Elements (SGEs) are genes, organelles or microorganisms present within the genome or cell of an organism that spread by subverting normal patterns of inheritance to increase their representation in the next generation. SGEs such as endosymbionts, transposable elements, and segregation distorters are ubiquitous in living organisms and often associated with fitness costs to the bearer. In addition, several SGEs have sex-specific effects. For example, meiotic drivers often drive in only one sex, and endosymbionts are almost exclusively inherited from mother to offspring. This asymmetric impact and inheritance pattern have the potential to alter the strength of selection. I will discuss the potential for SGEs to impose sex-specific selection on males and females that in turn may alter the strength of sexual selection and sexual conflict with impact for a range of aspects such as mating systems, trait evolution, and sex determination.
Pax somatica and arena germinalis
David Haig, Harvard University
The sequestration of somatic cells from the germ line with most bodily functions performed in the soma is a remarkable device for the resolution of intragenomic conflicts. All genes in somatic nuclei have a common interest in the survival and reproduction of the associated germline. By contrast, conflicts are intense within cells of the inclusive germline (it includes embryonic cells before sequestration of the soma). Multicopy sequences in the germline are under selection to spread to new genomic locations. This competition is managed by the single-copy genome.
Conflict within genomes, groups, and persons
Samir Okasha, University of Bristol
Internal conflict within an organism (or genome) threatens to undermine the organism's "unity of purpose", in the sense that when the constituent genetic entities within the organism have non-identical evolutionary interests, there is no guarantee that they will all work together for the good of the whole. This is a well-known theme in evolutionary biology. The theme of internal conflict is also central in cognitive psychology, since people are often characterized by significant psychological conflict, e.g. when they have conflicting motivations or beliefs; and in extreme cases such as multiple personality disorder, the presumption that we have a single person, or agent, may be called into question. Authors including David Haig, Daniel Dennett and Robert Trivers have posited a link between intra-genomic and intra-personal conflict. I also see a link between these two phenomena, however it is quite different to the one that Haig, Trivers and Dennett see. I argue that the absence of internal conflict is a conceptual pre-condition for treating a biological organism as "agent like", and for describing its behaviour in intentional-psychological terms (whether intended literally or metaphorically).
Somatic genome elimination: why do many eukaryotes delete parts of their genomes from their soma?
Laura Ross, University of Edinburgh
We are multitudes: microchimerism, evolution and human health
Amy Boddy, University of California Santa Barbara
What is self? The strict definition distinguishes one individual from another, yet placental mammals contain genetic multitudes. In ancient Greece, the chimera was a mythical hybrid creature, yet a chimera is biological reality in the context of mammalian reproduction. Unlike our egg-laying cousins, placental mammals evolved the ability to exchange cells between the mother and offspring during gestation. This harboring of a small number of cells between two genetically distinct individuals is called microchimerism. Microchimeric cells are found across placental mammals, have the ability to differentiate and integrate into host tissues, and can last decades after birth. It has been hypothesized that these cellular transfers have an adaptive function within our bodies, boosting health, immune function and reproductive success. However, maternal-fetal conflict theory predicts negative consequences of microchimerism can emerge as a result of evolutionary trade-offs when two genetic interests diverge. I will summarize what is currently known and unknown in microchimerism research, address the current open questions in respect to human health and disease, and end the talk on the evolutionary consequences of being chimeric.
Organismal identity: how can organisms change over time without ceasing to exist?
Ellen Clarke, University of Leeds
Martijn Schenkel, Georgetown University and University of Groningen
The paradox of the organism refers to the observation that organisms persist as seemingly coherent entities with the singular agenda of maximizing fitness, despite the potential for intra-organismal elements such as genes and cells to hold and pursue conflicting agendas. Quantifying to what extent such intra-organismal conflict actually threatens the integrity of the organism and its ability to pursue fitness maximization requires the development of a mathematical framework that relates the agenda of the organism to the potentially-conflicting agendas of its constituent parts. Here, I will discuss which mechanisms contribute to intra-organismal entities having shared versus disparate agendas, and to which extent disparate agendas and the mechanisms of pursuing them represent a threat to organismal integrity. The resulting insights are used to discuss a preliminary framework for quantifying the paradox of the organism.
Revisiting Wolpert's hypothesis on the evolution of the egg
Israt Jahan, Washington University in St. Louis
High relatedness and low genetic conflict within multicellular organisms have been a longstanding explanation for the evolutionary success of organisms that develop from a single cell – an egg. However, Wolpert and Szathmary (2002) suggest an alternate explanation for the evolution of a single-celled life stage. They claim that the evolution of the egg is not a question of inclusive fitness but is driven by selective pressure for coordinated development. According to their hypothesis, organisms that develop from a group of non-clonal cells would be dysfunctional, causing their eventual elimination by natural selection. The problem of coordination is solved when a single cell is the unit of reproduction. We have empirically tested this developmental incompatibility hypothesis in the social amoeba Dictyostelium discoideum. We measure group function with slug mobility, an adaptive multicellular trait involving coordinated phototactic movement. In D. discoideum mixtures of unevolved and independently mutated lines, we observe intermediate slug mobility that is likely due to social dominance of the unevolved lines. Our results do not support Wolpert-Szathmary incompatibilities in the absence of strong within-organism conflict. We conclude that developmental incompatibilities alone, as suggested by Wolpert and Szathmary, are insufficient in explaining the evolution of multicellularity from a single-celled egg.
In what sense can there be conflict between the levels of selection?
Pierrick Bourrat, Macquarie University
The idea of evolutionary conflict is a staple of evolutionary biology. Naturally, it is often used in the context of multilevel selection and evolutionary transition in individuality or more generally in discussions involving more than one level (e.g., an organism and its genes). In this talk, I distinguish several possible meanings for the idea of evolutionary conflict in a multilevel context. I argue that one of these meanings is illegitimate or at best metaphorical
Selfish genetic elements and sexual selection
Nina Wedell, University of Melbourne
Selfish Genetic Elements (SGEs) are genes, organelles or microorganisms present within the genome or cell of an organism that spread by subverting normal patterns of inheritance to increase their representation in the next generation. SGEs such as endosymbionts, transposable elements, and segregation distorters are ubiquitous in living organisms and often associated with fitness costs to the bearer. In addition, several SGEs have sex-specific effects. For example, meiotic drivers often drive in only one sex, and endosymbionts are almost exclusively inherited from mother to offspring. This asymmetric impact and inheritance pattern have the potential to alter the strength of selection. I will discuss the potential for SGEs to impose sex-specific selection on males and females that in turn may alter the strength of sexual selection and sexual conflict with impact for a range of aspects such as mating systems, trait evolution, and sex determination.
Pax somatica and arena germinalis
David Haig, Harvard University
The sequestration of somatic cells from the germ line with most bodily functions performed in the soma is a remarkable device for the resolution of intragenomic conflicts. All genes in somatic nuclei have a common interest in the survival and reproduction of the associated germline. By contrast, conflicts are intense within cells of the inclusive germline (it includes embryonic cells before sequestration of the soma). Multicopy sequences in the germline are under selection to spread to new genomic locations. This competition is managed by the single-copy genome.
Conflict within genomes, groups, and persons
Samir Okasha, University of Bristol
Internal conflict within an organism (or genome) threatens to undermine the organism's "unity of purpose", in the sense that when the constituent genetic entities within the organism have non-identical evolutionary interests, there is no guarantee that they will all work together for the good of the whole. This is a well-known theme in evolutionary biology. The theme of internal conflict is also central in cognitive psychology, since people are often characterized by significant psychological conflict, e.g. when they have conflicting motivations or beliefs; and in extreme cases such as multiple personality disorder, the presumption that we have a single person, or agent, may be called into question. Authors including David Haig, Daniel Dennett and Robert Trivers have posited a link between intra-genomic and intra-personal conflict. I also see a link between these two phenomena, however it is quite different to the one that Haig, Trivers and Dennett see. I argue that the absence of internal conflict is a conceptual pre-condition for treating a biological organism as "agent like", and for describing its behaviour in intentional-psychological terms (whether intended literally or metaphorically).
Somatic genome elimination: why do many eukaryotes delete parts of their genomes from their soma?
Laura Ross, University of Edinburgh
We are multitudes: microchimerism, evolution and human health
Amy Boddy, University of California Santa Barbara
What is self? The strict definition distinguishes one individual from another, yet placental mammals contain genetic multitudes. In ancient Greece, the chimera was a mythical hybrid creature, yet a chimera is biological reality in the context of mammalian reproduction. Unlike our egg-laying cousins, placental mammals evolved the ability to exchange cells between the mother and offspring during gestation. This harboring of a small number of cells between two genetically distinct individuals is called microchimerism. Microchimeric cells are found across placental mammals, have the ability to differentiate and integrate into host tissues, and can last decades after birth. It has been hypothesized that these cellular transfers have an adaptive function within our bodies, boosting health, immune function and reproductive success. However, maternal-fetal conflict theory predicts negative consequences of microchimerism can emerge as a result of evolutionary trade-offs when two genetic interests diverge. I will summarize what is currently known and unknown in microchimerism research, address the current open questions in respect to human health and disease, and end the talk on the evolutionary consequences of being chimeric.
Organismal identity: how can organisms change over time without ceasing to exist?
Ellen Clarke, University of Leeds
