Tag Archives: diagrams

Depictions of human genetic relationships: Exploration 1

Exploration 1: Rearranging the horizontal sequence of a tree diagram

(Continuing from the previous post, we consider alternative depictions of human genetic variation keeping in mind the question, “Can any depiction of genetic relationships among humans allow simultaneously for similarity, diversity, ancestry, and admixture?”)

The diagram of human ancestry from Tishkoff and collaborators branches out like an upside-down tree from a common ancestral group into 18 groups today.  (The diagram shows some cross-links that indicate gene-flow between populations, but we will ignore these for the time being.)

(Source: Michael C. Campbell1 and Sarah A. Tishkoff, 2010, “The Evolution of Human Genetic and Phenotypic Variation in Africa,” Current Biology 20, R166–R173.  Letters at the bottom added for the purposes of referring to the groups in this series of blog posts.)

Below we see the tree for the first three forks, where AR is short for a group that includes all the ancestors of groups A through R; NR for all the ancestors of groups N through R; etc.

Now, the branches at any fork can be flipped so the next diagram conveys the same information about ancestry and branching.

Notice that the second variant does not convey the impression that the branch that in ancestral to the non-Africans, i.e., NR, is more different from the branches ancestral to the African groups, i.e., AB, CC, DM, than these branches are from each other.  Although the lineage that ended up at CC (the ancestor of group C) branched off earlier than the lineage leading to NR, there is nothing in the ancestry diagram that says it should be more similar genetically to AB than to NR.

If we exclude diagrams with crossing over of branches, such as the one below, there are four distinct reorderings of the four branches that preserve the sequence of the branchings.  There are 2 to the power 16 = 65536 reorderings of the full set of the 18 current groups.  The point is not that we need to find one correct ordering from among such a large set.  The lesson is that no lessons should be drawn from the order along the bottom of a branching diagram that is not already contained in the sequence of branches above.  (In this light, diagrams with crossing over should be excluded because they suggest that the two branches at a fork are further away from each other than to one of the earlier branches, which goes against the information contained in the sequence of branches.)

It is not easy, however, to convince one’s brain not to give significance to these horizontal positions.  This cognitive weakness gives rise to the explorations in the next posts.

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Diagrams of society and nature: A simple, but profound, contrast

Cultural anthropologists Schwarz and Thompson (1990, 4-6) use diagrams to illustrate four worldviews concerning nature and the effect society can have on it (Fig. 1).  This classification and the cultural (“grid-group”) theory that underlies it have been widely invoked in analyses of responses to environmental issues (e.g., Thompson 1984, Rayner 1990, Harrison and Burgess 1994), but in this post I want only to draw attention to the basic character of the diagrammatic representation of society-nature relations.

Figure 1.  Four views of nature (from Schwarz and Thompson 1990).

These diagrams share certain features:  The society-nature system has a point of balance, represented by the position of the balls in the diagrams.  Although this is not shown, it is implied that different forces stimulate the society to exploit its resources and push the system out of its basic condition of balance—the ball would be moved sideways in the diagram.  If the forces diminish, the system may return to its point of balance—as the displaced ball would do under the force of gravity.

The diagrams differ on the return to the point of balance.  Moving clockwise from the bottom left in Fig. 1, the return happens either: a) readily and reliably; b) slowly, perhaps so slowly that the system appears to have no preferred state; c) contingently, provided the system has not been disturbed beyond some threshold; or d) rarely, because almost any disturbance pushes the system over the threshold.  These differences notwithstanding, the common formulation of society-nature relations depicted in these diagrams is of society disturbing a system whose basic dynamics are set by biological and physical conditions, not by society, that is, Nature is something external to society, and the nature of this nature determines the range of acceptable human “disturbances.”

A contrast between this formulation and another view of society-nature relations is represented in a diagram by resource economist Raúl García-Barrios (pers. comm..; Fig. 2).  García-Barrios wants to highlight that in many places the environment or natural resources, for example, topsoils, rainforests, bodies of water, have already been deeply transformed by people.  A local threshold has been reached and surpassed, but this socially conditioned environment (ball 1) is prevented from “rolling down the hill” into a situation of degradation by various social conservative forces (e.g., when agricultural terraces are maintained by well disciplined labour; see the next section).  If this social-natural system degrades, the reason is not that a natural balance has been disturbed by social forces beyond nature’s basin of resilience (ball 2).  Instead, one has to inquire into how the social conservative forces have been eroded (see Taylor and García-Barrios 1997).  Even in the case of extreme temperature and rainfall or drought (i.e., situations where it might seem that nature has become less benign or tolerant), the timing and form of environmental degradation must depend on the character of the socially conditioned environment.  This contrasting formulation motivates a contrasting theme: Natural and social are inseparable in social and environmental dynamics.

Figure 2.  Environmental degradation prevented by social forces (1) vs. Society as a disruption of nature’s balance (2) (after García-Barrios, pers. comm.).

García-Barrios’s diagram is simple.  It points only to the existence of processes that are simultaneously social and natural; it leaves undeveloped how one engages with particular cases and how to analyze the “forces” pictured in Fig. 2’s arrow.  Nevertheless, the simple contrast motivates an important question:  What are people doing when they represent nature and society as separate, albeit interacting, realms?

Extracted from Taylor, P. J.,  “Exploring themes about social agency through interpretation of diagrams of nature and society,” pp. 235-260 in How Nature Speaks: The Dynamics of the Human Ecological Condition , ed. Y. Haila and C. Dyke. Durham, NC, Duke University Press, 2006.

References

Harrison, Carolyn M. and Jacquelin Burgess.  (1994). Social constructions of nature: A case study of conflicts over the development of Rainham Marshes. Transactions of the Institute of British Geographers, 19, 291-310.

Rayner, Steve. (1990). A Cultural Perspective on the Structure and Implementation of Global Environmental Agreements.  Oak Ridge, TN: Oak Ridge National Laboratory.

Schwarz, Michiel and Michael Thompson. (1990). Divided We Stand: Redefining Politics, Technology, and Social Choice. London: Harvester Wheatsheaf.

Taylor, Peter J. and Raúl García-Barrios. (1997). The dynamics and rhetorics of socio-environmental change: Critical perspectives on the limits of neo-Malthusian environmentalism. In Advances in Human Ecology, ed. L. Freese, pp. 257-292.  Greenwich, CT: JAI.

Thompson, Michael.  (1984). Among the energy tribes:  A cultural framework for the analysis and design of energy policy. Policy Sciences, 17, 321-339.

Intersecting processes combined with Historical scan to generate enactable, group-specific praxis

This post describes an activity that addresses the shortcomings and potentialities of i. Intersecting process accounts, ii. Mapping by researchers of “connections” that motivated, facilitated, or constrained their inquiry and action; and iii. Historical Scan to set the scene in which a project is to be undertaken.
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Diagramming of Intersecting Processes (a teaching activity)

I want more people to think in terms of intersecting processes, which means being able to read the diagrams I present, appreciate the theoretical implications of the concept, start to make their own accounts and diagrammatic depictions, and teach others to do the same.  Thus this teaching activity.

Goals for students
1. to understand the development of biomedical and social phenomena in terms of linkages among processes of different kinds and scales that build up over time—genetics, treatment, family and immediate social context, social welfare systems and economics, wider cultural shifts, ….
2. to use graphic organizers to help them visualize such “intersecting processes” and to identify places where detail is missing and where further inquiry is needed.
3. [depending on level of students and prior preparation] to contrast the implications of thinking in terms of direct causation (like spokes going to a hub) with “heterogeneous construction.”

Instructions
Pre-session reading:
Paul, D. (1997). Appendix 5. The history of newborn phenylketonuria screening in the U.S. Promoting Safe and Effective Genetic Testing in the United States. N. A. Holtzman and M. S. Watson. Washington, DC, NIH-DOE Working Group on the Ethical, Legal, and Social Implications of Human Genome Research: 137-159. http://biotech.law.lsu.edu/research/fed/tfgt/appendix5.htm

Excerpt from Taylor, P. J. (2001). Distributed agency within intersecting ecological, social, and scientific processes. Cycles of Contingency: Developmental Systems and Evolution. S. Oyama, P. Griffiths and R. Gray. Cambridge, MA, MIT Press: 313-332 on The development of severe depression in a sample of working class women.

Phase A: Mini-lecture to introduce the ideas under goals 1 and 2 and the use of diagrams to identify missing detail (goal 2). Followed by Question & Answer.

Phase B: Following the procedure below, diagram Paul (1997) article with respect to either a) the life-course of a female with PKU detected by neo-natal screening for PKU; or b) the routinization of neo-natal screening for PKU in the United States. Followed by discussion of potential and limitations of the diagramming activity (for discussion among colleagues or for teaching).

a) the life-course of a female with PKU detected by neo-natal screening:
1. Identify important connections mentioned in the article (from p. 7ff) between things in the following categories or strands (open to adaptation): Condition of person with PKU; Diagnosis and care; Social support; and Wider social context.
2. Arrange the things as well as you can given the information available on parallel strands according to age of the person.

b) the routinization of neo-natal screening for PKU in the United States:
1. Identify important connections mentioned in the article between things in the following categories or strands (open to adaptation): Experience of persons with PKU (condition, care, social support); Advocacy (pro + con); State mandates & regulation; Research; and Wider social context.
2. Arrange the things as well as you can given the information available on parallel strands according to year (from 1930s to 1990s allowing more space for 1960 through 1980).

For both a) and b):
3. Draw dotted lines to show connections between things.
4. Identify connections about which you want to know more. Use the ideas under goal 3 as a checklist.
5. Note where these instructions were hard to put into practice.

Example of connection for a): mandated test (social support) and neo-natal initiation of special diet (diagnosis & care)
Example of connection for b): enthusiasm for biomedical prevention of mental retardation over education/social support/rehabilitation of retarded persons (wider social context) and promotion of PKU screening in advance of research on effects of diet (state mandates & regulation/ research)

Acknowledgement: This unit draws inspiration and some ideas from Matthew Puma’s adaptation of my teaching about intersecting processes in CrCrTh 640 during Spring 2002.

Draft 8 Feb 2004; revised 17 April 2005

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Reflections on teaching activity

This activity is still under development. Some issues that have arisen:
1. What do arrows mean? Mechanisms, material connections; Increase in probability; Makes possible; or Makes significant
2. Some participants wanted to focus on explaining a specific outcome.
3. Technologies of representation, e.g., colors for countervailing processes
4. Are we representing an individual or a population or a generic individual + variation