Link to video interview given at and posted by the International Summer School on Evolution, University of Lisbon, Summer 2013.
Before going to Portugal to teach I attended the semi-annual meeting of the International Society for the history, philosophy and social studies of biology which was held this year in Montpellier, France. Along with Alejandro Rosas of the National University of Colombia, I organized and took part in a round table on the major transitions in evolution. Here are five questions I asked and what I had to say about them.
1) Should the topic be understood as “transitions” or additions i.e. as a change from one level of selection to another or as an addition of another level of selection?
I would argue for additions i.e. there is an evolving metapopulation of mitochondria in an evolving population of eukaryotic cells, an evolving metapopulation of cells in an evolving population of multicellular animals, an evolving metapopulation of modules in an evolving population of modular organisms and an evolving metapopulation of multicellular individuals in an evolving population of eusocial colonies etc. To employ a metaphor that has been used, such a point of view is neither deflationary nor inflationary but both simultaneously.
2) What is required for the emergence of an (additional) aggregate level of Darwinian individuals?
I agree with Godfrey-Smith that it is the emergence of entities subject to evolution by natural selection. However, rather than B, G and I (i.e. bottleneck, germ line and integration) I would argue that what is required is an additional aggregate developmental cycle, including but not restricted to a life cycle. That in turn requires a minimum of a complementary pair of life history strategies, each of which constructs the ecological conditions that favour, and in the transition or addition, come to induce (or whatever predicts them comes to induce) the other. So niche construction or eco-evolutionary dynamics are central. For example in a renewable environment, a cycle of plentiful resources which favour (and come to induce) growth, which constructs scarce resources, which favour (and come to induce) maintenance in the form of diapause for example, which constructs plentiful resources again – is a developmental cycle subject to selection, albeit not a life cycle, i.e. not progeneration in Griesemer’s sense.
3) Queller’s “fraternal” or what Nowak’s group has called the “staying together” case: is it attributable to kinship or ecology?
Staying together is better described as kin facilitated, because it most fundamentally requires an ecological explanation. If it’s hot and you need to lose heat it is better to be apart, but if it’s cold and you need to retain heat it is better to be together; if parasites are the greatest threat it is probably better to be apart, but if predators are the greatest threat it is probably better to be together; and so on. Such advantages of being small or large and there are many others, pertain to the advantages of having a proportionately greater ratio of surface area to volume for the small relative to the large or volume to surface area for the large relative to the small. The point is that kinship can facilitate either staying together or going apart depending upon ecological conditions. This implies that in the recent great debate between E. O. Wilson and (almost) everyone else in which he emphasizes the importance of ecology over kinship (defensible nests for eusociality for example), I have concluded that he is more right than wrong, including his 2012 description of genomes as chimeric (selected for at different levels) albeit not about some of the more fanciful extensions e.g. that humans are a eusocial species.
On the “staying together” case too, it is worth noting that a new life cycle it is not typically just a “staying together” but a cyclical staying together and going apart. For example cells in a multicellular organism reproducing asexually by multicellular propagules do not just “stay together” – they cyclically stay together and go apart – the propagules go apart from each other and if there are distinct reproductive and somatic cells, the reproductive ones go apart from the somatic.
4) Queller’s “egalitarian” or what Nowak’s group has called the “coming together” case: are sexual families additional Darwinian individuals and if so, what role do cooperation and conflict play in them?
Like Michod, I think sexual families likely are additional Darwinian individuals i.e. there is an evolving metapopulation of individuals in an evolving population of sexual families. However, sexual families too are not just a coming together but a cyclical coming together (fertilization) and going apart (meiosis) in haploids with a zygotic meiosis, or a going apart and coming together in diploids with a gametic meiosis. On the role of cooperation and conflict in these comings and goings, assuming an equal allocation to both at equilibrium, the simplest possibilities would be that in haploids for example, they either come together in conflict and go apart in cooperation, or come together in cooperation and go apart in conflict. The former (conflict then cooperation case) is implied by the traditional PBS theory of the evolution of anisogamy in which at fertilization, microgametes are viewed as reproductive parasites of macrogametes, but then recombination at meiosis is assumed, as it traditionally has been, to be mutually advantageous for whatever reason. The latter (cooperation then conflict case) is implied by the “market” or “trade” theory which Noë and Hammerstein originally suggested and I more recently have revived, and which might then be taken to imply that meiosis is a matter of conflict with genetic recombination a side effect of the mechanics of gene conversion rather than gene conversion a side effect of the mechanics of recombination. In a stunning recent paper, Laurence Hurst and some colleagues from China (Yang et. al. 2012) employed next generation sequencing techniques to determine that the great majority of recombination events in Arabidopsis (over 90% and probably nearer 99%) are gene conversion events. On the other hand, whether they come together in conflict or in cooperation, it is still possible that they go apart in cooperation – sexual families having discovered the advantages of risk reduction under uncertainty (like investing in index funds or dollar cost averaging rather than trying to pick stocks or time markets). What is unlikely I think is that both are a matter of conflict which would not pay back the two-fold cost of sex and would hence be unlikely to out compete asexuals.
5) Can it be said, as Bourke (2011) believes for example, that egalitarian or coming together transitions (or additions) require a “shared reproductive fate.”?
I doubt it. Assuming he means being confined inside the same ‘skin’ as say a vertically-transmitted symbiont, then I doubt it is necessary. I don’t know a lot about multispecies communities but occasional casual mutually positive interactions rather than regular cyclical ones between members of different species for example would not be sufficient. Nor do I think that “differential persistence” is sufficient – a slab of a hardwood persists longer than one of a softwood but are hardly Darwinian individuals (unless viewed as cultural ones). But I think it likely that theorists like Watson and Bouchard are still generally right. Some interspecific “coming togethers and going aparts” without remaining confined in the same ‘skin’ are likely systematic enough to indeed constitute additional Darwinian individuals. Positively non-additive fitness interactions at some stage at least sufficiently large enough to compensate for any negatively non-additive ones which may obtain at another would be a key requirement.
Instructors at the International Summer School on Evolution, at the Applied Evolutionary Epistemology Lab in the Faculty of Science, University of Lisbon. Left to to right, Derek Turner, Michael Ruse, Frédéric Bouchard, , Fiona Jordan, Nathalie Gontier, Marion Blute, Ilya Tëmkin, Luis Villarreal, Frietson Galis, Emanuele Serrelli.
Thanks to Nathalie and her staff for their hospitality and the pics!
I have not been a very faithful blogger the last few months – whether that will change in the new year remains to be seen. I travelled more in November than usual and then spent December getting caught up on some book reviews, referees reports etc. that I had been asked for and had agreed to do. Among other things, I have been left with a pile of reading to catch up on. One thing that caught my attention as I began to do so was three related front-of-the-magazine pieces in Nature on December 1st, the first of which here was called “the new cell anatomy”.
Apparently a mixture of biophysicists, cell biologists and biochemists in recent years have been discovering all kinds of previously unknown structures inside of cells. The phenomena and terminology are bewilderingly diverse – various “tubes, sacs, clumps, strands and capsules” including filaments, nanotubes, purinosomes, microcompartments, carboxysomes, exosomes, cytoophidia (cell serpents) – some of which concepts undoubtedly will last, others of which undoubtedly will not. A lot of the discussion has been about the development of new methods as well as of applying old methods to single cells accompanied by a fair amount of arm waving about possible medical and industrial applications.
My point is that I hope in all of this, at least some of the researchers will keep their eye on a different question. As the late Lynn Margulis among others showed – there is a lot of knowledge to be gained about evolution working between the cell and the molecule, including by microscopy, newer fancier versions of which play a role in some of the new work. Since nobody thinks that life began de novo with prokaryotic cells fully formed, and since evolution always, always leaves marks of its history, there surely is a lot to be learned about the origin and early evolution of life by peering into, prodding and manipulating existing cells. So I very much look forward to eventually hearing more about the implications of the new work for that subject.
Like many cities in the developed world these days I suppose, mine has a recycling programme. Basically, organic (kitchen) waste is put out in one can once a week for composting; cans, bottles and paper in another every two weeks for recycling; garbage in a third every two weeks as well for disposal; and garden waste seasonally in paper bags. In our household, the first two are accumulated in similar sized plastic bags in containers in the kitchen and put out in the cans every once in a while, while the third is put out bagless in the third can more frequently as it accumulates. Now here is the puzzle. Whenever I happen to put out the first two at the same time, always in similarly sized bags and therefore similar in volume, the organics for composting are always, always heavier than the garbage for disposal, and by quite a lot. Every time I wonder why that is. Some possibilities might be:
- it’s just idiosyncratic to our household. I suppose if we were repairing cars and disposing of scrap metal (not that anybody would be, scrap metal is valuable these days) but if for the sake of argument we were, it would be different. But I doubt if our experience is unique (otherwise I would not be wondering about it here!)
- biological organisms need protection against antagonists, parasites and predators, hence the denser (from our point of view, waste) – thick skins, peels etc. as well as needing to reproduce – seeds etc. I doubt if that is the answer either. After all, a lot of our garbage is in fact protective – various kinds of non-recyclable packaging like the tissue thin plastic bags that bulk foods and produce are put in and some heavier packaging which have properties designed to persuade you to purchase it, i.e. to serve its reproduction.
-culturally-evolved processes have become more efficient than biologically-evolved ones. Now that is an intriguing possibility.
- finally my (originally an engineer) husband’s suggested answer is that the organic material is wet and water is heavy. Hmm – this possibility admits of an experimental answer, if we dried out a bag of organics would the weights be similar? I have never been much of an experimenter but . . .
I was invited by Chris Kortright and Jaime Yard to take part in a session at the annual American Anthropological Association here meeting held last week in Montreal, a session which was titled “The Conceptual Work of ‘Ecology’”. The word that stuck out for me in the abstract provided for the session was “entanglements”. So I gave my talk the title above and here is the abstract of what I talked about.
“Not long ago it was thought that causal relationships between ecology and evolution were unidirectional – ecological environments (including physical environments and other species) structure evolving populations. We now know that the unidirectional view was false. Evolving populations also construct ecological environments (commonly called niche construction).
Similarly it was thought that causal relationships between genes and culture were unidirectional. The sociobiological/human behavioural ecological/evolutionary psychological revolution(s) revealed how the propensities of human nature, including our cultural nature, had been shaped by genetic evolution. But we now know that unidirectional view to have also been false. Anthropologists like William H. Durham played a significant role in showing how much our genetic evolution has been shaped by culture. A count (by Laland et. al. blogged about here on Dec. 8, 2010) includes 8 categories, some including as many as 30 genes, whose evolution can plausibly be linked to culturally-transmitted selection pressures. Thus came the era of not only gene-culture but also of culture-gene coevolution.
However, this theory and research remains anthropocentric. Genes and culture in the human species are viewed as coevolving in interaction with each other – i.e. excluding other species. However, the evidence that has been accumulating for decades now showing the ubiquity of culture and its evolution in other species implies that we are on the cusp of yet another revolution – interspecific gene-culture and culture-gene coevolution. And this revolution will not only be about our culture shaping their genes, but also about their genes shaping our culture.”
I enjoyed the annual 4S meeting (Society for Social Studies of Science) in Cleveland this week. I gave a talk with the above title which flowed from a paper titled “The Reinvention of Grand Theories of the Scientific/Scholarly Process” published with a graduate student, Paul Armstrong, in the current issue of Perspectives on Science (a paper which MIT press seems to have unusually made available for free here). That paper dealt with the work of ten contemporary sociologists and sociologically-minded philosophers of science who have presented general theories of the scientific/scholarly process on eleven issues. Methodologically it was done by means of an analysis of texts as well as interviews with the majority and was designed to assess the compatibility or lack thereof of their theories with each other and whether a new general theory is emerging. It ultimately concluded that it is a powerful argument in its favour that a Darwinian-style sociocultural evolutionary theory (of the general kind pioneered by Stephen Toulmin and David Hull) “can incorporate both all of the common and all of the useful unique features of contemporary grand theories of the scientific/scholarly process”.
The talk however was about four empirical generalizations not discussed in the paper that an evolutionary theory of science/scholarship can explain – the first from David Hull’s book Science as a Process, the second from my book, the third blogged about here on June 14, 2010, and the last from an article by Jonah Lehrer in The New Yorker on December 13, 2010 here.
i) Fraud and plagiarism. It is well known that the scientific community treats fraud (such as falsifying data) more harshly than it does plagiarism (although journal editors have begun to crack down more on the latter recently – perhaps because the availability of electronic data bases makes it easier to do so). According to Hull the reason for the traditional attitude is that plagiarism hurts only the ‘ancestor’ upstream i.e. the author or authors of the paper plagiarized while fraud hurts all those ‘descendants’ downstream – those whose time and energy spent building on falsified results has been wasted. You may have noticed that this has been one of the major complaints about the recent scandal involving Andrew Wakefield’s claims about the relationship between the MMR vaccine and autism and bowel disease. It resulted not only in damage to some of the children whose parents avoided having them vaccinated, but also in effort wasted on subsequently testing the theory – effort which could have gone into other better approaches to the causes of and treatments for these diseases.
ii) Citations to long papers. I was once puzzled to learn that longer papers gain more citations than shorter ones because the evolutionary ecology of life histories would predict the reverse. Without getting technical, the reason for that prediction is that under low density (plentiful resources) selection favours ‘productivity’ – eating a lot and producing a lot of (hence necessarily small) offspring. Under high density (scarce resources), it favours ‘efficiency’ – deriving more breakdown products from each unit of resources acquired and deriving more grand-offspring from each offspring produced (hence necessarily few, large offspring). In the light of this expectation that short papers would garner more citations but long ones would garner more citations to the papers that cite them, I was subsequently relieved to find out that studies have shown that many citations are not taken from original papers at all but from the citations of others to them. In short, many of the apparent “offspring” of long papers are likely not offspring at all, but grand-offspring. However, the necessary definitive study, comparing the “copied” citation rates of long and short papers has not to my knowledge been done.
iii) Mentors, students and their students. A study of roughly a century and a half of the lineages of mathematicians published in Nature last year showed a similar life history phenomena with respect to students rather than papers. The students of those who produce few students go on to produce about a third more students themselves than expected – i.e. less prolific teachers produce higher quality students who yield more grand-students.
iv) The truth wears off. The last example came to my attention from an article by Jonah Lehrer published in the New Yorker titled “The truth wears off.” It has long been known that there is a bias in science in favour of the publication of positive results. In the 1950′s for example, a statistician found that ninety-seven per cent of psychology papers found positive results. Perhaps authors themselves, and certainly referees and editors are loathe to publish results that say, “Nope I didn’t find what I was looking for, sorry”. What seems to happen is that if a novel, interesting result is found, a rash of confirmatory studies follow. What has not been so well known (and certainly not to me) is that such a trend is often followed by a trend in the opposite direction! What seems to happen is that by that time, the opposite result is the novel and interesting one and is therefore published, after which a rash of confirmatory studies of that follow. A cultural fad in science in one direction is followed by one in the opposite direction. Other observers of science have noticed more or less the same phenomena. Both continuity and innovation are valued in science but according to Hull, there is a tension between them. Citations claiming one’s work follows from that of others gains support but detracts from its apparent innovativeness, while originality is admired but detracts from the support that showing continuity provides.
The point I would like to make about this is that evolutionary theory has long been familiar with the phenomenon and has basically explained the reason for it. Evolutionists call it “negative frequency-dependent selection” – it being commonly adaptive to do the opposite of what the majority are doing because that reduces competition. So for example if most members of a population of birds are eating small seeds, an innovation (mutant) that eats large seeds could be favoured and spread until it becomes most common, upon which small seed eaters would again be favoured and so on. Actually, I suspect that avoiding competition may not be precisely the actual proximate explanation. The reason why large seed eaters are favoured when small seed eaters are common is because not only are the two kinds of seed eaters dependent on the exogenous availability of the two kinds of seeds, but because eating small seeds alters the ecological environment (depleting small seeds but permitting the population of large seeds to recover) thus favouring large seed eaters and of course vice-versa. Effects like these have recently come to be called “niche construction” i.e. the ecological environment not only structures populations but populations also construct their ecological environment. In science, both continuity and originality matter but not always simultaneously apparently.
Lehrer briefly discusses a number of other reasons for the truth “wearing off” – plain poor science, regression towards the mean in subsequent studies, data mining of studies with a large number of variables and comes to a more radical conclusion that I think justified – that “when the experiments are done, we still have to choose what to believe”. It is worth noting however that the sociological phenomena of negative frequency-dependent selection – cultural fads or social movements in one direction being followed by those in the opposite direction – does not readily explain the truth wearing off in a sequence of studies done by the same individual unless negative frequency-dependent selection works psychologically as well as socioculturally – at least one example of which Lehrer highlights. Maybe the story there is that we just get bored!