Monday, 6 January 2014

A "Questionable Analogy" paper

My last post referred to a paper which referenced:

I have some comments on that paper as well. I think it is a bad paper. The authors claim to have found:

key differences between the two domains that compromise, we think, the attempt to understand cultural evolution on par with genetic evolution.
The paper concludes:

This suggests that in each domain, specific cognitive mechanisms lead to the emergence of domain-specific cultural dynamics. There is therefore no particular reason to build models of cultural evolution based on an analogy with population genetics (Daly 1982).
It is true that there are domain-specific cultural dynamics. However, there are also domain-specific dynamics in the organic realm. That doesn't prevent models from population genetics being useful there. It seems to me that the merit of models based on techniques from population genetics in cultural evolution has been well established empirically over the last four decades. The authors don't really present a case which counters this large body of work.

Instead they focus on the issue of "Transmission Modes" - which they define as follows:

A central feature of population genetics is the reliance on the concept of transmission modes (TMs). A TM is a way in which genetic material is transmitted between individuals.

The authors claim in the abstract:

Modes of cultural transmission are, by analogy with modes of genetic transmission, ways in which cultural information is transmitted between individuals. Despite its importance across the behavioral sciences and for theories of cultural evolution, no attempts have been made, to our knowledge, to critically analyze this analogy. We here aim at such detailed comparison and show that the fundamental role of modes of transmission in biology results mainly from two properties of genetic transmission: (1) what is transmitted generally does not influence the way in which it is transmitted; (2) there is a limited number of simple and stable modes.

However to my mind they fail to establish either of these points.

There are an enormous number of methods of transmission in the organic realm. Genes may be transmitted between individuals by sneezes, by sexual intercourse, by contaminated water, by blood transfusions, by biting insects - and so on and so forth. If you are classifying transmission methods into discrete "modes" and arguing that these differ in number in cultural and organic evolution, the you should present a classification scheme, and argue for its utility in both domains. However, the authors present no methodology for doing that. Also, few other authors do that: "transmission method" is a much more common phrase in genetics than "transmission mode" is - as can easily be seen by performing some searches.

Saying that a transmission mode is "a way in which genetic material is transmitted between individuals seems vague. Are mosquito bites and tick bites different "ways" of transmitting genetic material between individuals? Or is it one "way" - on the grounds that both are biting insects? Are coughing and sneezing different transmission modes? - or one mode? - on the grounds that both involve airborne particles. The authors don't say - and don't provide any way of answering such questions.

Since they don't defend a classification scheme for transmission methods, it seems to me that they have failed to substantiate their case that the organic realm features a limited number of simple and stable transmission modes. Looking at the range and diversity of transmission methods in the organic realm, this claim seems implausible to me.

Also in the organic realm, what is transmitted very often does influence the way in which it is transmitted. When a cold virus is transmitted, it makes the host sneeze. When a warts virus is transmitted it makes the host itch. When a stomach bug is transmitted, the host gets diarrhoea - and so on and so forth. Where there are multiple tranmission methods, mutations may alter the balance between them - showing that genetic control over the transmission method exists.

For me, these simple observations cause the whole thesis of the paper to collapse.

Interestingly, the paper describes itself in grandiose terms, saying:

This article therefore specifies the fundamental properties upon which the analogy between cultural and genetic transmission modes rest, suggests different interpretations of previous data, raises challenging modeling opportunities and develops a new hypothesis regarding the origin of the difference between biological and cultural transmission.

I think this captures some of the excitement of those who seek to characterize the differences between the cultural and organic realms. These explorers are seeking out new laws and new principles. However, step one for scientists is to familiarize yourself with the existing literature. Often, once you have done that, not everything looks quite so new and shiny. To me, many of the supposed innovations associated with cultural evolution fit into the category of phenomena that have already been characterized by evolutionists.

No comments:

Post a Comment