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Posts Tagged ‘Evolution’

Adaptation and Progress: Spencer’s Criticism of Lamarck

In Morganti on May 26, 2013 at 3:26 PM

Herbert Spencer’s conception of organic evolution is commonly interpreted as a form of Lamarckism (Peel 1971; Freeman 1974; Bowler 1996; Gissis 2005). To give an notable example, Moore (1981) once described Spencer as «Britain’s leading Lamarckian» of the last decades of the 19th century. Such a description is undoubtedly due to Spencer’s advocacy of the inheritance of acquired characters, against critics such as Wallace and Weismann. In this short notice I will briefly indicate two fundamental aspects of Spencer’s view of evolution that set him quite apart from Lamarck.

In the first place, while Lamarck considered evolution as a distinctly biological phenomenon, dependent on the properties which marked the division between the organic and the inorganic, Spencer regarded it as a special case of the basic physical transformations of matter, motion and forces. Secondly, while Lamarck had distinguished between a progressive (i.e. complexifying) and an adaptive factor of change, Spencer rather saw progress as dependent on the very process of adaptation.

It was the very bond between organic and physical evolution which in Spencer’s thought warranted the coincidence between progress and adaptation. According to the principle of the “instability of the homogeneous” (Spencer 1857), given the universe as a field of forces, the parts of any homogeneous aggregate would be necessarily exposed to the actions of different forces (both quantitatively and qualitatively), which would then produce different effects on each of those parts. The resulting heterogeneous parts would then be  exposed to forces as differentiated as the first, thus producing further heterogeneity. In other words, the production of more heterogeneous and complex phenomena is the predictable result of the interaction between matter and forces, a principle which in Spencer’s eyes held its validity at all levels of reality.

Such principle had also another important consequence, insofar as the heterogeneity of environmental forces was critically dependent on the complexity of the organism on which they acted: the more complex was the latter, the more diversified were the formers. Evolutionary progress, in other words, was embedded in the very encounter between organism and environments, thus being a direct consequence of adaptation.

Therefore, Spencer could reject Lamarck’s hypothesis of an intrinsic complexifying tendency of life, which he regarded – quite incorrectly, in my opinion – as a remnant of supernaturalism (i.e. an explanation in terms of God’s will rather than natural laws). At the same time, he could consider Lamarck’s failure to explain organic evolution in physical terms as a serious weakness of his theory (Spencer 1864-67).

Federico Morganti

Bibliography

Bowler P. J. (1996), Charles Darwin: The Man and His Influence, Cambridge University Press: Cambridge.

Freeman D. (1974). The Evolutionary Theories of Charles Darwin and Herbert Spencer. Current Anthropology 15: 211-37.

Gissis S. (2005). Herbert Spencer’s two editions of the Principles of Psychology: 1855 and 1870/72. Biological heredity and cultural inheritance. S. Müller-Wille, H. G. Rheinberger (eds.), A Cultural History of Heredity II: 19th and Early 20th Centuries, Max Planck Institute for the History of Science: Berlin, 137-51.

Moore J. R. (1981), Post-Darwinian Controversies: A Study of the Protestant Struggle to Come to Terms with Darwin in Great Britain and America, 1870-1900, Cambridge University Press: Cambridge.

Peel J. D. Y. (1971), Herbert Spencer: The Evolution of a Sociologist, Heinemann: London.

Spencer H. (1857). Progress: Its Law and Cause. Westminster Review 11: 445-85.

Spencer H. (1864-67), The Principles of Biology, 2 vols., Williams and Norgate: London.

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Giuliana Pulvirenti: Review of Farine R. D. “Social network analysis of mixed-species flocks: exploring the structure and evolution of interspecific social behavior”.

In Philosophy of Biology, Pulvirenti, Review on March 29, 2013 at 1:20 PM

Functional explanations advocated for mixed-species groups (mainly foraging and anti-predator advantages) are based on top-down approaches that implicitly assume the species as fixed and static social structures and shift the analysis of fitness benefits and costs from the level of individuals to the one of the groups/species. According to Farine, this operation of over-simplification leads to cursory inferences. On the contrary, a bottom-up approach, usually used to study intraspecific sociality, could provide an insight and a better understanding of the emergent and dynamic properties at each level of the social system. In this perspective, the author proposes Social Network Analysis (SNA) as a tool to measure inter-individual interaction within mixed species flocks. His aim is to explore the different roles within the flocks and the individual variations of sociality, as well as the fitness consequences that such variations leads to both individual and community structure. SNA main strength is the possibility to graphically represent and quantify, at any scale between dyads and groups, specific aspects of social relationships, such as number, intensity, frequency of direct and indirect interactions and individual roles, centrality (i.e. “keystone” individuals). As an istance, Loussou & Newman (2004) found a “keystone” individual in a bottlenose dolphin community in Scotland that acted as a bridge between two subgroups, therefore playing a critical role in keeping the connection between them. However, SNA current applications raise some issues concerning spatial and temporal constraints (Wey et al. 2008). On one hand, pattern of associations vary on a case by case basis depending on habitat topology and distribution of resources, while on the other hand, it’s important to distinguish genuine social network structures from relationships explained solely by shared space use. Furthermore, traditional graph models are limited in addressing temporal questions regarding changes that may occur over a given time period. Future work must also go beyond simple description, beginning to link network structure to biological and evolutionary consequences, in order to answer the “why” questions in sociobiological and ethological studies (Hock & Fefferman 2011).

Bibliography

Farine Damien R., Garroway Colin J., Sheldon Ben C. (2012), Social network analysis of mixed-species flocks: exploring the structure and evolution of interspecific social behavior, in Animal Behaviour 84: 1271-1277.

Hock C. & Fefferman N. (2011), Extending the role of social networks to study social organization and interation structure of animal groups, in Ann. Zool. Fennici 48: 365-370.  http://www.bioone.org/doi/abs/10.5735/086.048.0604

Lusseau D. & Newman M. E. J. (2004), Identifying the role that animals play in their social networks, in Proceedings of the Royal Society B (suppl): Biological Sciences 271: 477- 481. http://rspb.royalsocietypublishing.org/content/271/Suppl_6/S477.short

Sih A., Hanser S. F. & McHugh K. A. (2009), Social network theory: new insights and issues for behavioral ecologists, in Behav. Ecol. Sociobiol. 63: 975-988. http://link.springer.com/article/10.1007%2Fs00265-009-0725-6?LI=true

Sueur C., Jacobs A., Amblard F., Petit O., King A. J. (2011), How can social network analysis improve the study of primate behavior?, in American Journal of Primatology 73: 703-719. http://onlinelibrary.wiley.com/doi/10.1002/ajp.20915/abstract

Wey T., Blumstein D. T., Shen W. & Jordan F. (2008), Social network analysis of animal behaviour: a promising tool for the study of sociality, in Animal Behaviour 75: 333-344. http://www.colbud.hu/apc-aa/img_upload/4d11dfd490c468ca39fcefabae592944/JordanAniBe2008.pdf

Ivan D’Annibale: Review of Marshall, R.A.J., “Group selection and kin selection: formally equivalent approaches.”

In D'Annibale, Philosophy of Biology, Review on March 28, 2013 at 8:47 AM

The level at which natural selection “acts” has been a much debated issue in evolutionary biology (Okasha 2006), especially in connection with the evolution of altruism. Two major kinds of explanations have been proposed: group selection theory (GST) and inclusive fitness theory (IFT). Marshall (2011) surveys the most common objections to the latter, claiming that the two approaches are in fact formally equivalent. We discuss exclusively his claim of equivalence. Rewriting of the Price equation (Price 1970) yields: 1) a version of Hamilton’s rule (a basic tool in IFT); 2) a partition of selection in between-group and within-group selection (typical of GST explanations). Thus, 1) and 2) are formally equivalent. If we assume that 1) holds, then also 2) holds, and conversely. Is this the same as saying that IFT and GST are formally equivalent? The author concedes that IFT cannot be identified with Hamilton’s rule. Thus the claim of formal equivalence must be, at least as far as this article goes, re-evaluated. On the other hand, to prove formal equivalence it requires an explicit set of axioms to be given. This request seems honestly unreasonable. Even in the case where such a formal model could be described, it remains dubious that many, or any, would agree on it. The word “theory”, as in “inclusive fitness theory” and “group selection theory”, should be better understood as a set of different but related explanations (for IFT alone, in addition to Hamilton’s rule and the Price equation, population genetics and evolutionary game theory have been useful approaches, among others). In particular, formal models are currently being used with a more modest goal: to describe more limited and well defined (agreed upon) aspects of the world, in order to produce testable predictions. On a final note, even if any two of these models will be found to be formally equivalent, we may have gained a more thorough “understanding” in the process. Mathematics also, after all, is more than the axioms that we put into it.

Bibliography

Okasha, S. (2006), Evolution and the Levels of Selection, Oxford: Oxford University Press.

Marshall, J.A.R. (2011), Group selection and kin selection: formally equivalent approaches, Trends in Ecology and Evolution, 26 (7): 325-332.

Price, G.R. (1970), Selection and covariance, Nature, 227 (5257): 520-521.
(I thank all the participants in our last reading group for discussing and sharing ideas).