tag:blogger.com,1999:blog-227780861638767023.post7723245425629068887..comments2024-01-27T00:27:45.851+00:00Comments on race/history/evolution notes: Robert Axelrod on the evolution of ethnocentrismn/ahttp://www.blogger.com/profile/02378473351485233448noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-227780861638767023.post-47391792135315527192017-04-25T11:02:22.988+01:002017-04-25T11:02:22.988+01:00Dear all,
For dispersal in an agent-based model o...Dear all,<br /><br />For dispersal in an agent-based model of ethnocentrism, see:<br /><br />Tarik Hadzibeganovic & Cheng-yi Xia, Cooperation and strategy coexistence in a tag-based multi-agent system with contingent mobility. Knowledge-Based Systems 112 (2016) 1-13.<br /><br />http://www.sciencedirect.com/science/article/pii/S0950705116302994Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-227780861638767023.post-52052744808674732162015-06-14T20:06:32.547+01:002015-06-14T20:06:32.547+01:00Thanks.
Re: dispersal. In the Hammond and Axelro...Thanks. <br /><br />Re: dispersal. In the Hammond and Axelrod model (http://www.artisresearch.com/articles/Axelrod_Evolution_of_Ethnocentrism.pdf), there is no dispersal: offspring are born in a square adjacent to the parent, and they stay there indefinitely. This is not dispersal, unless you define dispersal as "not inhabiting the exact same physical space as your parent." If you add sexual reproduction, and assume that reproduction occurs among adjacent squares (as I did), then the result is that most matings occur with parents, siblings, and cousins. That's just not how it is. It also implies that virtually all social interactions occur among these very close kin, which again appears to be not true. (see links below.)<br /><br />I added dispersal by allowing that people "leave home" with some probability. If they do leave home, they randomly switch places with someone else on the board. Of course, in reality, short-distance dispersal should be more common than long, so there is room for improvement there. But this is only a 50x50 grid - even "long range" dispersal isn't that long (50 people away - like moving one or two villages away). And even a little bit of dispersal kills the results, it seems.<br /><br />Re: sexual reproduction: I checked with my model, and it does appears that sexual reproduction alone (without dispersal added) doesn't have a big effect. So it may be that dispersal is what really kills the results - or the combination of the two. (I am slightly bothered, btw, that the words "recombination" and "inbreeding" never show up in the Lima paper.)<br /><br />Overall, I'm not convinced that the 2D grid of individuals is a great way to model human groups. Probably a better structure would be a grid of groups (bands, tribes, whatever), rather than individuals, in which people can interact with every tag-carrying member of their group. Then have some dispersal between groups. With that model, you wouldn't get extremely small social/mating networks (like the 8 implied by Hammond + Axelrod), which are untenable for most human populations (papers below).<br /><br />Some useful recent research on the fluidity of extant hunter-gatherer populations.<br />http://anthro.vancouver.wsu.edu/media/PDF/Science_final.pdf<br />http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0102806RCBnoreply@blogger.comtag:blogger.com,1999:blog-227780861638767023.post-51677109043989450052015-06-14T18:15:06.498+01:002015-06-14T18:15:06.498+01:00RCB,
I'm not sure what sort of dispersal you ...RCB,<br /><br />I'm not sure what sort of dispersal you have in mind, but the model clearly does include dispersal in the simple meaning of the term. If you mean some sort of random, long-distance dispersal of lone individuals, a model of that sort would have little applicability to humans.<br /><br />Here's a group that added sexual reproduction to a similar model:<br /><br />Evolution of ethnocentrism on undirected and directed Barabási–Albert networks<br /><br />F.W.S. Lima 1 , Tarik Hadzibeganovic 2,3 and Dietrich Stauffer 4 <br /><br />Abstract. Using Monte Carlo simulations, we study the evolution of contigent co-<br />operation and ethnocentrism in the one-move game. Interactions and reproduction<br />among computational agents are simulated on undirected and directed Barabási-<br />Albert (BA) networks. We first replicate the Hammond-Axelrod model of in-<br />group favoritism on a square lattice and then generalize this model on undirected<br />and directed BA networks for both asexual and sexual reproduction cases. <b>Our<br />simulations demonstrate that irrespective of the mode of reproduction, ethnocentric strategy becomes common even though cooperation is individually costly and<br />mechanisms such as reciprocity or conformity are absent</b>. Moreover, our results<br />indicate that the spread of favoritism toward similar others highly depends on the<br />network topology and the associated heterogeneity of the studied population.<br /><br />http://arxiv.org/pdf/0905.2672<br />n/ahttp://racehist.blogspot.comnoreply@blogger.comtag:blogger.com,1999:blog-227780861638767023.post-87743945197679022012015-06-14T01:39:10.502+01:002015-06-14T01:39:10.502+01:00The first model (Hammond and Axelrod) has been stu...The first model (Hammond and Axelrod) has been stuck in the back of my head for a while. So I rebuilt it using R and C++. I was able to replicate the main results: that there is a wide range under which "tag-based" altruism evolves, under the model's particular assumptions.<br /><br />But adding two of realistic alterations (in my opinion) causes this result to break down.<br /><br />(1) The model assumes asexual reproduction. Adding sexual reproduction with recombination (as for humans) causes the tags to become much less associated with other loci. That means that tags become a much less reliable indicator of recent decent (and therefore loci at other genes), so tag-based altruism becomes untenable.<br />(2) The model apparently has no dispersal. That's obviously inaccurate. In fact, under sexual reproduction, no dispersal in this model implies extremely strong inbreeding (e.g., 2/8 chance of mating with your parent, since 2 of your 8 neighbors are parents!). Adding dispersal greatly reduces the scope for tag-based altruism.<br /><br />So, I'm much less swayed by this paper now.RCBnoreply@blogger.comtag:blogger.com,1999:blog-227780861638767023.post-13485284639873308092015-05-15T16:55:27.394+01:002015-05-15T16:55:27.394+01:00Pretty interesting. First paper would presumably s...Pretty interesting. First paper would presumably suggest that selection would favor ethnocentrism based on quickly evolving cultural, but not genetic, characteristics. (But maybe highly mutable genes - a mutation rate of .005 is pretty extreme.) <br /><br />One minor concern: I think the cultural transmission model could be explored here. Culture is modeled to behave like highly mutable genes, with parental transmission. But most gene-culture coevolution models allow for other kinds of transmission pathways. If you introduce horizontal cultural transmission (common in gene-culture coevolution models), for example, then these cultural tags will spread among non-kin, and then the system would break down, I imagine. But not entirely, perhaps. <br /><br />Anyway, cool simulation.RCBnoreply@blogger.com