Finding a Mate with Eusocial Skills

Finding a Mate With Eusocial Skills Chris Marriott1 and Jobran Chebib2 1University of Washington, Tacoma, WA, USA 98402 2University of Zurich,¨ Zurich,¨ Switzerland 8057 [email protected] Downloaded from http://direct.mit.edu/isal/proceedings-pdf/alif2016/28/298/1904330/978-0-262-33936-0-ch052.pdf by guest on 30 September 2021 Abstract mutual response of the individuals in the herd with no need for social awareness or exchange of information. Sexual reproductive behavior has a necessary social coordina- Prior work (from now on when we reference the prior tion component as willing and capable partners must both be work we mean the work in Marriott and Chebib (2015a,b)) in the right place at the right time. It has recently been demon- strated that many social organizations that support sexual re- showed that herding, philopatry, and assortative mating production can evolve in the absence of social coordination arose through non-social mechanisms of convergence and between agents (e.g. herding, assortative mating, and natal common descent. This work raised a few questions regard- philopatry). In this paper we explore these results by including the role that social interaction plays in many of these ob- ing social transfer mechanisms to our agents and contrasting served behaviors. These mating behaviors can be explained their reproductive behavior with a control group without social transfer mechanisms. We conclude that similar behaviors by both non-social and social mechanisms. In many cases emerge in our social learning agents as those that emerged in the non-social solution is the simpler one, though it is likely the non-social learning agents. Social learners were more in- that certain instances of these behaviors indeed rely on un- clined towards natal philopatry. Social learners also evolved derlying social mechanisms. Further, it is not clear how a culture of eusociality including reproductive division of la- these behaviors vary relative to the nature of the underlying bor. mechanisms. We have augmented the non-social agents from the prior Introduction work with both individual learning and social learning capa- bilities. Our null hypothesis is that the same breeding struc- Sexual reproduction is a social behavior as two able partic- tures and organizations will be observed as before. How- ipants must coordinate their behaviors as well as their posi- ever, we expect that the new adaptive mechanisms will im- tions in time and space. This social coordination problem pact these organizations quantitatively and may lead to other is solved by sexually reproducing species in many different organizations. Our current work can be compared directly ways. to the prior work but because of implementation differences Some of the behaviors that enhance finding and attract- between the models we have also conducted control tests of ing a mate include herding (Reynolds, 1987), philopa- our own. These control tests involve the same agents but try (Clutton-Brock and Lukas, 2012), assortative mating under conditions in which social learning and/or individual (Jiang et al., 2013) and eusociality. These behaviors can learning is unavailable. arise through social mechanisms or non-social mechanisms (Whiten and Ham, 1992). Social Animals For instance, consider witnessing a herd of animals cross- ing a plane to drink water from the river. A well known Animals display different levels of social behavior (Mich- explanation of the herd is that the animals in the herd follow ener, 1969). Social behavior often is centered on repro- simple social rules of cohesion, alignment and separation ductive activities and caring for the young (Trivers, 1972). (Reynolds, 1987; Grunbaum¨ and Okubo, 1994; Parrish and Some social animals can extend this social behavior to other Edelstein-Keshet, 1999). These are social rules and social activities like hunting, foraging, and grooming (Lovegrove mechanisms because to follow these rules the agents must be and Wissel, 1988; Boesch, 1994; Creel and Creel, 1995; aware of each other and make decisions based on informa- Nakamura, 2003). The highest categorization of social be- tion about others’ states. However, a non-social explanation havior in animals is eusocial (Crespi and Yanega, 1995). might be that all the animals were getting thirsty in the sun Ants, bees, termites, and some mole rats are categorized as and independently navigated around obstacles to the river. eusocial (Wilson and Holldobler,¨ 2005). Humans, of course, With this second explanation, the herd is maintained by the are also very social and loosely fit under the eusocial definition (Nowak et al., 2010). On the opposite side of the spectrum are non-social animals. Non-social animals engage in the minimal amount of social activity required of a sexual reproductive species, which is to mate. After mating the mother lays her eggs or gives birth to her young and leaves them to fend on their own (Starck, 1998). All parental investment in child rearing comes prior to birth. To be classified as eusocial, animals must satisfy three conditions. Eusocial animals share responsibility for caring for their young, have reproductive division of labor, and have multi-generational communal cohabitation (and also philopatry in some definitions (Burda et al., 2000)). This Downloaded from http://direct.mit.edu/isal/proceedings-pdf/alif2016/28/298/1904330/978-0-262-33936-0-ch052.pdf by guest on 30 September 2021 means that parents live with adult children and older generations help to care for their grandchildren and others. This, in particular, allows for sharing of learned information across generations. We can see that humans loosely fit into this definition. We certainly share responsibility for child rearing, and we certainly have multi-generational communal cohabitation. However, we do not have reproductive division of labor in the sense we normally think of. That is, we don’t have a single “queen” that births us all after breeding with a few Figure 1: Dual Inheritance Model privileged, male courtiers. However, many still like to apply the label eusocial to humans while some prefer to keep humans in a category of their own. This debate is not critical birth and to be replicated in reproductive events. When an to our discussion. agent is born its memome is created by copying segments of the genome. This is a process of development that results in Model the agents initial cultural information. Our simulation consists of agents in a random geometric Memomes are active in behavior selection over the life- network of resource sites. Each day the agents in a popu- time of an agent and they can also be altered through in- lation expend energy to move from site to site, forage for dividual learning and social learning events. The memome resources, and engage in mating, learning and social learn- selects behaviors through interaction with the environment ing. Energy in the simulation normally corresponds to the and these choices shape the phenotype of the agent. The time an agent can spend doing activities during a day but ex- phenotype is used for selection and thus an agent’s repro- cess stored energy is also used to reproduce. The resources ductive success and survival is dependent upon its memome, gathered during a day determines the energy an agent has its genome, and its environment. for activities in the next day. The net daily energy gain or The cognitive model of our agents is inspired by the pan- loss determines whether an agent lives or dies (if the energy demonium model (Jackson, 1987; Franklin, 1997). The is depleted) and whether an agent is capable of reproduction mind of a single agent in our simulation consists of many (if stored energy exceeds a threshold). specialized sub-agents, or daemons, that compete for con- Agents in our simulation implement the dual inheritance trol of the agent. In our model we call these sub-agents model (Marriott and Chebib, 2014, 2016b). The dual inher- memeplexes and this internal competition is an evolutionary itance model is a model incorporating three modes of adap- competition. tation: phylogenetic, ontogenetic, and sociogenetic. That is, agents engage in genetic evolution, individual learning and Genome social leaning. Figure 1 shows how genetic and cultural in- The possible behaviors of agents are encoded in their formation are stored and transferred in the dual inheritance genomes as a path of resource sites in the network (our model. model extends the model from (Marriott and Chebib, Genetic and cultural information are stored in separate 2015a,b)). We consider each site in the path a gene in the information stores called genomes and memomes, respec- genome. A gene has three components: gathering, non- tively. Genomes are inert within the lifetime of an agent gathering, and travel. At each site an agent has an opportu- meaning they remain static and are not active in behavior nity to gather resources, perform non-gathering actions like selection. Their only purpose is to create memomes upon breed, learn, and/or socialize, and finally must travel to the next site. a single memeplex. Notice that since every site in the en- In our current model an agent always gathers resources vironment is not necessarily represented in a genome there when it visits a site. When not depleted a site will always may be sites that do not have corresponding memeplexes. return a fixed number of resources to an agent gathering at that site. The energy that an agent spends on gathering is Memome determined by an agent’s strategy which is encoded in a gene As mentioned above memeplexes in a memome are arranged corresponding to a site. The energy expended in gathering is by starting site. The model bears similarities to the MAP- always at least the number of resources gathered (one, two elites strategy of multi-objective evolutionary optimization or three) and at most five.

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