Commentaries

Pinker redux: We need data

By Michael Hochberg July 18, 2012 5 Comments

The Pinker essay has generated a lot of commentary on different websites. This can only be a good thing, insofar as channels for reactions remain open.  The Social Evolution Forum is committed to this.

Needless to say, there is a tinge of hegemony in various essays on the Edge website.  How can two individuals, who are diametrically opposed in their views, both be correct?  One way, obviously, is if there are semantic issues permeating one or both commentaries, and that once these are ironed-out, one or both perspectives will be found to have elements of truth and/or falsehoods.  We are likely never to know the outcome on semantic issues, since decades of discussion have not resolved these.  What is the next step beyond these disagreements?

Anecdotal evidence, developed narratives, and comparative analyses are very good starts to organizing ideas and predictions about individual and group effects (be they traits or scales of selection).  We are however generally lacking rigorous scientific approaches, and I am not very optimistic that we will go very far on human populations.  However, group selection, group traits, inclusive fitness, etc. can be measured and manipulated in microbes, and in particular, in bacteria. Examples of possible traits include quorum sensing, siderophore production, and biofilm structures.  I include a few references at the end of this commentary.

Briefly, we need to measure the following:

1. The traits elicited specifically when individuals interact with their(non-social) environment.

2. The traits elicited specifically when individuals are in small-scale social situations (e.g., dyads).

3. Traits elicited when individuals are in larger groups.

4. Traits that cross one or more of the boundaries in points 1-3.

An example of an experimental evolution study on microbes that investigates levels of selection is Kummerli and colleagues (2009).  We need to identify and catalog these traits, explain their origins and understand their current contexts and effects. Are they adaptive, maladaptive, or neutral?  When does the scale concern the individual, sub-ensembles of groups or whole groups?

This simple plan of action could be done to some extent for humans, but as I mention above, bacteria are our best bet for scientific approaches (proper controls, determination of cause and effect, possibility of phylogenetic approaches, etc.).

More than one level of selection may be acting simultaneously in any given system. The big challenge is to measure what very may well be very subtle effects and to apportion them to the level(s) of selection that they affect. Surely, some systems will be dominated by individual selection and traits; others will have an integration of individual and large-scale effects.  It is frankly hard to see that group effects will not play a significant role in explaining for example, multicellularity, transitions in individuality and eusocial insect societies. Once we have data on a range of situations to describe, substantiate and refute, we can revisit the question of individual and/or group selection.

Brockhurst M.A. et al. 2006. Character displacement promotes cooperation in bacterial biofilms. Current Biology 16:2030-2034

Buckling A. et al. 2007. Siderophore-mediated cooperation and virulence in Pseudomonas aeruginosa.FEMS MicrobiolEcol 62: 135-141

Hochberg M.E. et al. 2008.The coevolution of cooperation and dispersal in social groups and its implications for the emergence of multicellularity.BMC Evolutionary Biology 8:238

Kümmerli, R. et al. 2009.Limited dispersal, budding dispersal, and cooperation: an experimental study. Evolution63: 939-949

Nadell C.D. et al. 2009.The sociobiology of biofilms.FEMS Microbio Rev 33: 206-224.

Rainey P.B. & Kerr B. 2010.Cheats as first propagules: A new hypothesis for the evolution of individuality during the transition from single cells to multicellularity. Bioessays 32:872-880

Ratcliff W.C. et al. 2012.Experimental evolution of multicellularity.PNAS 109: 1595-1600

Velicer G.J. 2003. Social strife in the microbial world.Trends in Microbio 11:330-337

Published On: July 18, 2012

Michael Hochberg

Michael Hochberg

Dr. Hochberg’s research focuses on interdisciplinary applications of the evolutionary process. he is interested in how environmental conditions impact the genetics and expression of virulence, and what the implications are in areas ranging from cooperation in social groups, to the management of virulent pathogens, to population diversification and speciation. His laboratory uses a combination of mathematical modeling and experimental evolution with the system Pseduomonas fluorescens SBW25 – lytic bacteriophage PHI2.

5 Comments

  • Tim Tyler says:

    I don’t see much point in wondering how Pinker and his opponents can both be correct. I’m all for sympathetic readings where these are possible – but Pinker is flat wrong about a number of things: he’s wrong about group selection and he’s wrong about cultural evolution – two of the main things his article discussed.

    Group selection and kin selection are equally well supported by the data – since they turned out to be different descriptions of the same process. See my article “Group selection and kin selection are formally equivalent” for references.

    • Fernanda says:

      After reading Steven Pinker’s artlice, The Tower of Babel, I have learned a lot about languages that I did not know before. For instance, in Lauren16, one subject that really shocked me was that there is a universal grammar that all languages share. As Pinker puts it, “if a linguist examining a language for the first time calls a phrase a ‘subject’ using one criterion based on English subjects, the linguist soon discovers that other criteria, like agreeing with the verb in person and number, and occurring before the object, will be true of that phrase as well,”(Pinker 239). These correlations show a foundation for language which then gives way to various dialects that use a specific arrangement of verbs, subjects, nouns and inflection. Variation is yet another part of language. An example of this is how we are continuously borrowing and reusing words from other languages, and then make them our own, (Pinker 245). Even though Pinker explains that this does not excite him, it makes me feel a bit ‘more cultured’ (even as I say that with a smile)! All too often we try to categorize people into “us and them,” but there is so much more that we all share. I’ve come to understand that the English language was influenced by French, German, Latin and even the Norsemen. Because language is constantly changing, I feel it is important to teach children how we have all helped each other grow into the modern languages in use today. Perhaps if we teach students how languages came to be, there will be more acceptances of people who speak differently than we do – and who knows where that lesson of tolerance and cooperation will lead!

  • Peter Turchin says:

    Mike, I agree with you. But we need to go further. We need to design what are essentially ‘critical experiments’. In other words, we need to identify a potentially observable quantity for which MLS and its rivals make different predictions. Then we actually measure the quantity and determine whether it is consistent with the MLS prediction or with an alternative theory. Ideally, we want to publish our predictions ahead of time, and do it many times.

    • Tim Tyler says:

      Or, alternatively join what D. S. Wilson calls the “Consensus of the Many” on the topic,
      ackowledge that MLS and its main rival make identical predictions, and then see what productive ways forwards there are from there.

      Seeking differences has been going on for ages. It seems to be an unproductive way of finding the selling points of MLS – because it doesn’t work. Surely it is better to join all the other scientists that acknowledge equivalence, and work on the idea that MLS still offers a valuable perspective, and an interesting way of visualising the situation.

  • Michael Hochberg says:

    If you have not done so already, I suggest reading the recent PNAS paper by Travisano’s group. A lucid account + experimental evolution that shows how levels of selection and traits either merge or not towards groups of different sizes, and how this may be mediated by adaptations to commit suicide (apoptosis). Brilliant stuff.

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