This page is a work in progress.  I am thinking back over my encounter with non-human primates and my attempts to ask the question that was at the heart of anthropology in its own origins: "what is the most rudimentary form of human social organization, the most basic human kinship system.?"  I shall add to it as I go along and turn up more diagrams from the past, since I tend to think in diagrams when I can.

Bernard Chapais writes:

"Armed with a solid background in the anthropology of kinship,
Robin Fox tackled the literature on kinship and behavior in nonhuman
primates in a series of articles that appeared in the 1970s
and in a book The Red Lamp of Incest. His insights, thirty years
later, appear remarkable…Fox’s comparative studies constituted
a major leap toward an understanding of the origin of human
society…In the 1970s Fox, as a social anthropologist, was almost
alone and well ahead of his time in his efforts to understand
and extract the significance of the primate data for human society.
More than ten years were to elapse before Fox’s ideas were
taken up in a comprehensive manner and the decomposition of
exogamy significantly furthered." (Primeval Kinship HUP, 2008, p. 120)
The above diagrams appeared in "Primate Kin and Human Kinship" in Biosocial Anthropology, Robin Fox ed. Malaby Press/Halsted Press, 1975.

They were reproduced in Robin Fox, "Sister;s Sons and Monkey's Uncles: Six Theories in Search of an Avunculate" in Reproduction and Succession: Studies in Anthropology, Law and Society.  Transaction Publishers, 1993.

The whole chapter was reproduced in Robert Parkin and Linda Stone eds Kinship and Family: An Anthropological Reader (Blackwell, 2004.)

Below: Gelada Baboon Troop, Ethiopia. The males have long manes like lions.

The next diagrams appeared first in "Alliance and Constraint: Sexual Selection and the Evolution of Human Kinship Systems" in Bernard Campbell Ed. Sexual Selection and the Descent of Man 1871-1971 (1972) and later in The Red Lamp of Incest (1980/83).
Social Organization of Terrestrial Primates: The Baseline before the Transition

Social Organization of Genus Homo after the Transition to Humanity

Sister and/or Daughter Exchange resulting in double cross-cousin marriage

Below: the "Atom of Kinship" 4.1. according to Levi-Strauss; 4.6 according to Fox
 in Reproduction and Succession (Transaction 1993).  My argument is in essense that the avunculate which L-S sees as a product of the cultural invention of the incest taboo is in fact there in nature, as is permanent mating. (and for that matter incest avoidance). The human innovation is none of these, but the introduction of affinity and the creation of in-laws (affines) leading to the possibility of wife-exchange.  Thus diagram 4.6 easily morphs into the sister/daughter exchange systems between any two units as shown in the above diagram.
The Atom of Kinship according to Levi-Strauss and Fox

Originally I included Chimpanzees under "multi-male group" and Gorillas under "one-male group" and that is minimally correct but misleading.  Chimpanzees do not have matrilines for example.  They are in the jargon "male phylopatric" - the males tend to stay together and the females to move around.  If we are interested in the primeval precursors of the simplest human system, then this is a basic point.  For the latest work in this area see Bernard Chapais' book, and also Jonathan Turner and Alexandra Maryanski Incest:Origins of the Taboo (Paradigm, 2005.)

Below: Exchange of sister's daughters between matrilines
For the full text and all the diagrams see "Will The Real Murngin System Please Stand Up?" Chap. 12 in The Challenge of Anthropology (Transaction 1995.)
Exchange of Nieces (Sisters' Daughters) and Circulation of Sisters

Both the above appeared originally in Bernard Campbell ed., Sexual Selction and the Descent of Man (Aldine, 1972.)

Below: model of Cochiti preference for MFZDD marriage (MF Clan)
Below: marriage bettween the children of two brothers FBD/FZS marriage
Father's Brother's Daughter Marriage (patrilateral parallel cousin)

It is hard to diagram systematic marriage with the father’s brother’s daughter  (abbreviated FBD for convenience.)  Diagram 3.1 attempts this.  The man we have arbitrarily denoted our EGO (or reference point) can be seen to marry his FBD, and EGO’s son in turn marries EGO’s brother’s daughter.  But whom does EGO’s brother (B) marry?  The answer is that structurally he is the same as EGO and he too would marry a daughter of their common father’s brother.  We shall see how basic this form of marriage is to Semitic society generally in Chapter 6 when looking at the descendants of Adam in The Book of Jubilees
(from The Tribal Imagination p. 63)

When an American reporter asked the groom at an Iraqi wedding why he and so many of his compatriots, married their cousins, he was told "Of course we marry cousins.  Who would you have us marry, strangers?" (See "Kissing Cousins: On Mediogamy" in "Tribal Blogs") and the forthcoming "Marry In or Die Out: Optimal Inbreeding and the Meaning of Mediogamy" in J. Turner, R. Machalek and A. Maryanski eds. Handbook on Evolution and Society: Toward an Evolutionary Social Science. Boulder COParadigm Press, 2015

Below from The Red Lamp of Incest (1980, Rev.1983, Notre Dame Unv. Press)
Hominid Brain Size Increase over Past 2.5 Million Years

For almost four million years hominid brain size stuck at c. 486 ccms, not much bigger than a chimp.  Then over two-and- a-half  million years it shot up to its present  average of 1,330 ccms: a threefold increase.  Why?
Schematic Representation of the Human Memory Circuit

Based on Vernon Mark and Frank Ervin  (Violence and the Brain, 1971) who note that it shows how "many anatomical structures sub-serving memory are also important in controlling emotion."   From The Red Lamp of Incest (1980/3) And "The Passionate Mind: Brain, Dreams, Memory, Evolution and Social Categories." Chap. 8 in The Search for Society.

The Evolutionary Pendulum from the Upper Paleolithic to the Post-Historic Society

From. "Consciousness out of Context: Evolution, History, Progress and the Post-Post-Industrial Society." Chap.10 in The Search for Society: Quest for a Biosocial Science and Morality (Rutgers U.P. 1989.)
"One of the charms of kinship analysis is the challenge of rendering left-brain logical sequences into right-brain graphic diagrams."
The Challenge of Anthropology p. 209

Here then are some diagrams and illustrations: not from Kinship and Marriage, that would be too many, but from other sources often overlooked or ignored.

There is no room to reproduce the whole argument and the data here: no substitute for going back and reading the whole thing.  But the diagrams themselves are a kind of summary and may help to raise questions in your own mind about basic processes of our cognitive, behavioral and moral evolution.

Left is a sequence of diagrams from "Primate Kin and Human Kinship" in Biosocial Anthropology (1975).
Triangles are males, circles females
: "primates" is often used as a shorthand for what is correctly "non-human primates."  Although often a double meaning is intended since we are, of course, primates.  These are "models" - that is the point.  They formalize the untidy reality of group life so that we may compare and generalize.

This is a birds eye view of a "multi-male" group of non-human primates, with the dominant males in the center surrounded by the females with young and then the peripheral or junior males.  "Consort" mating pairs are temporarily outside the group.  The aim of juvenile males is to make it to the center,  become dominant, and hence breed.  

What is not seen in such a diagram are the connections of kinship between the animals, and in early studies of course these were not known.

Later studies showed that the animals (as in common baboons and macaques e.g.) were indeed grouped into ranked matrlines: descent groups of senior females, their daughters, daughters' daughters and dependent young. (The young males were ejected to the periphery at puberty.) I sometimes called this formation "Baboon 1" since it fits the common baboon.

The next diagram (3) then shows the same group but with the kinship relations inserted.

What we have is four ranked matrilines.  Not only do the males of line 1 outrank all the other senior males, the females of that line outrank the other females, and even the junior males of the dominant line outrank other males.

Thus the peripheral males of line 1 have a much better chance of reaching the center and dominance in their quest for power and breeding privilege. (Sometimes called "the Kennedy Principle.")

I also brought attention to the fact that there was a potential inbuilt avunculate: a relation between mother's brother and sister's son.  Thus male 2 is the sister's son of male 1: he is the descendant of the dominant male and female of the troop.  Similarly with 3 and 4.  The peripheral males of these matrilines will essentially succeed to their maternal uncles' positions.

In the next diagram (Figure 4) we have what I called the "one-male group" model: alternatively "Baboon 2" since it fit the Hamadryas and Gelada baboons.

This still has central dominant males, females with young and peripheral males, but the internal relationships are quite different.  

The dominant males do not form temporary "consort" relationships with females, but have permanent "harems" of females that they control and with whom they breed.  Juvenile males go to the periphery as in the first case, but they try to "kidnap" young females to form their own harems, or move in and be "tolerated" by a senior male as "apprentices" in the hope of taking over thei females at some time in the future.

At the time (early 1970s) I found, on a survey of all known primate kinship systems, that these two were exclusive systems; that is, there were no systems in  which  there existed both descent groups and permanent mating groups: you had one or the other.

My conclusion then was that kinship groups that had both "descent" and permanent mating units ("alliance") were  a human invention.  That this was THE human invention.  

If so, how had it come about?

Two things had to happen: (1) the two forms of organization had to come together in one system, and the relationships between individuals (in descent and mating) had to become relationships between groups.  For this to happen kinship had not only to relate individuals to each other in group membership, it had to become the basis of allocating them to groups in stable mating relationships.
(2) The ability to live according to rules, which (crucially) would determine such allocations, had to evolve.

There was an important discovery in the early 1990s by Lars Rodseth, Richard Wrangham, Alisa Harrigan and Barbara Smuts.  Their paper was called "The Human Community as a Primate Society" (Current Anthropology, 32: 221-54, 1991. They very kindly dedicated it to me saying "Robin Fox has always known the human community is a primate society.") They found that among Hamadryas and Gelada baboons there were relations of descent among the dominant males, thus forming "clans" - and that females tended to form mating bonds with males outside their clans.  Thus both descent and "exogamy/marriage" could indeed occur within a primate society.  What did not occur was the enduring relationships between affines (in-laws) that humans display and which set up relationships of alliance between groups.
To put it in more human terms,  while primates had evolved kinship connections and permanent mating, they had not evolved  in-laws.

The next two diagrams were an attempt to make graphic the essential shifts that took place in "the transition to humanity."

My way of phrasing the change noted above was to say that while in the baseline state kinship "linked" animals for various purposes, after the transition it both linked and "allocated" them.  The three "blocks" stayed the same, but the relations between them changed as the kinship system became a system of allocating women between males.  Thus the rules of kinship systems became rules of classifying women into "marriageable" and "unmarriageable."  Even more, it also laid down rules for who among the available women must be married: usually a close cousin.

Note this goes beyond the incest taboo which simply,as it were, has people leaving their natal families and bumping into possible mates. The original human system also laid down who the mates should be - what category of kin they should come from.

Primates could come close to this.  Japanese Macaque groups which had ranked matrilines often saw these segment into two groups: as though lines 1 and 2 in our diagram 3 above broke off from lines 3 and 4, each pair forming the nucleus of a new group.  The startling fact then emerged that over a period of years all the males of one group had moved to the other and vice versa.  On finding this I said that these Macaques were "only a naming system and one rule away" from a human system of two matrilineal moities with ranked matri- lineages and matrilocal residence: like the Tlingit and other Northwest Coast tribes, or the Mandan of the Plains etc.

Look at the right-hand diagram in the opposite column - 4.5 from Reproduction and Succession (1993).  The one rule the Macaques were away from being human was of course the rule of "marriage."  Their males simply went into the other "moiety" and mated with whomever they could get in "consort relationships" (as they had been doing in their moiety.)  In the human situation they "marry" -  which is more than just the permanent mating of the polygynous Baboons, but means setting up a relationship with a specific female (or females) and her kin (their kin).  This was the "allocation" step: the step to in-laws and a continuing affinal relationship between "A" and "B" whatever these groups were.  

The difference is huge because the primate system is stuck while the human system is systematically expandable.  The "sister exchange" or "daughter exchange" of these human systems was capable of binding groups together by marriage as well as by descent, and of logical progressions to a more expansive system until it too reached its limits: a phenomenon brilliantly explored by Claude Levi-Strauss in Les structures elementaires de la parente (1949).

The study of systems of kinship and marriage is then the study of what systems of descent and allocation are about and how they work, from the very simplest (that the primates are almost at ) to the most complex.  Some of those that look the most complicated are technically the most "elementary" to use L-S's term, especially those of the Australians, and these demand the most diagramatic ingenuity and hence challenge.

Start with the right-hand example on Diagram 4.5 above, with two matrilines exchanging sisters.  But what if the natives tell you that they are in fact exchanging their sisters' daughters (or even their sisters' daughters' daughters)?

Such cross-generational marriage gets hard to imagine, but I try to graph it in Diagram 12.7 opposite.  Note than in this system Ego marries his MBD (mother's brother's daughter) who is also his MMBDD (see 12.7)  Why is this odd?  Because societies in which men systematically marry their MBD are those in which women "circulate" between groups on an A -> B - > C -> A pattern, but the Australians where this happens - the Murngin - have two patrilineal moieties and appear to be exchanging women between them!
            Only a dedicated anthropologist (and that of an old-fashioned stripe) could find this fun and exciting.  But to me it is of the essence:the reconciliation of direct and indirect exchange in one system.  I tried in Diagram 12.8 opposite to sum up the impossible  in a simplified model (having repeatedly got it wrong in the past).
          You can take a pencil and trace out the relationships and you will see that if men systematically exchange sister's daughters with men of another clan of their own moiety, the result will be that clans A1 and A2 (and B1and B2) will directly exchange nieces, while the same women as "sisters" will "circulate" between A1 -> B1 -> A2 -> B2 -> A1.
          There is no way to go further with this here.  This is to give you an idea of the construction of diagrammatic models.  The same thing can, like all geometry, be reduced to mathematics and displayed as symbols.  But that is for another time. All the Murngin boy (in fact his elders) needs to do is obey a couple of easy rules and the "system" works.
          Just for sheer mischief I throw in the opposite diagram (13.8) from The Challenge of Anthropology, actually in a footnote to Chap. 13 "The Evolution of Kinship Systems and the Crow-Omaha Question."  I was discussing the preference the Cochiti Indians of New Mexico had for marriage into the mother's father's (matrilineal) clan.  This would entail marriage with a second cousin: a mother's father's sister's daughter's daughter (MFZDD) actual or classificatory. All the principals in a marriage needed to know however was that the girl should come from that clan, and be roughly the same generation as the boy.

What the diagram - a theoretical model, tried to show, was how this would work out if systematically practiced.  It would take four matrilineal clans and result in marriage with a MFZDD who was also a MMBDD but not a MBD (who would also be a FZD).  

And so on.  Again, all that is needed to know to "work" the system is one rule: "marry a woman of your own generation in your mother's father's clan." Easy.

Another mistake I made  early and have tried to make up for is to concentrate entirely on exogamic systems - marriage out of the kin group - since that was the logical thing that seemed to need explaining after the incest taboo.  It might be said to be the classic problem of anthropology. But of course the alternative is to marry into the kinship group (endogamy).  The most extreme of this would be the sibling marriage of royal families and nobility, but most common is the marriage between the children of the father and his brother - from the man's point of view: father's brother's daughter marriage (FBD).  This was a favored marriage of ancient Israel and the Semites generally, and is still common practice in Muslim countries.  It is difficult to diagram but I have tried it here (left).

Marriage can then go either way. Almost always avoiding sibling mating It can turn inward to the kin group keeping groups separate except by descent, or it can turn outward and seek to extend further and further the bounds of the affinal ties.  

One interesting point that doesn't get discussed is that endogamic marriage is always into the patrilineal group.   In other words there is no systematic rule of marriage with the mother's sister's daughter.  The mother's sister is most often called "mother" and her daughter "sister" and the marriage does not occur.

Playing By The Rules

We put aside the question of how we came to be an animal that could abide by rules in order to live in rule-governed societies.  Of course, rules are couched in language so that had to evolve, and they need a brain that could control emotions and impulses enough to make living by rules possible.  

The graph on the left (out of date - we have much more information now, but the pattern is the same) shows the remarkable increase in brain size that accompanied the transition to humanity.  In evolutionary terms quite rapid.  Something was happening.

For what was happening you have to go to the original and the mound of  material subsequent to these early speculations.  To us then it seemed obvious that the advent of group hunting with weapons was at the root of it, and it still must be involved, but it is not the whole story.  But in my scenario the free-for-all particularly in the mating competition between older and younger males of the primate system could not survive the hunting transition.  A major change was the invention of "initiation" of the young men and all it involves - often brutally unforgettable.  This is when they learn the rules, including the all-important rules of marriage.  What these rules do, I suggested, was to make the marriage choices of the young automatically dependent  on those of the old.  A major source of control and one that has pretty much disappeared in modern society.

Crucial to this whole development was the control of aggression.  Notice I say "control" not "elimination."  Lorenz (and common sense) told us that aggression was important as a component of behavior and its evolution.

 Diagram 6.1 (left - from The Challenge of Anthropology)  was meant to illustrate what components of, for example,  the digestive feedback system were "normal" and what were the result of some breakdown. The argument conlcuded that to say aggression was a "disease" was to equate it with diarhea, wheras it should be equated with digestion: a normal part of the organism's functioning that can go wrong.

The second diagram was to illustrate the complexity of "escalation sequences" in aggressive encounters which go through various stages of "ritualized fighting" before breaking down into real fighting.  I was interested in the idea of "circuit breakers" by which the action could be stopped short of its sanguinary conclusion.  The model was actually first developed to describe the behavior of pub fighters in England and Ireland. And note the various chemical components of the escalation behavior.

Crucial to the transition also was the ability to store categories in long term memory.  Memory becomes crucial to the argument.  The sum of the case was that only that which is processed through dreaming and REM sleep is retained in long-term memory, and that involves a "stamping in" process which is loaded with emotional content.  The route taken in the brain is illustrated in Mark and Ervin's diagram (left) which I have tweaked a bit but on which I cannot improve.  Go to Red Lamp of Incest, Chap. 7 "The Matter of Mind"  and follow out the argument and its expansion in Search for Society. The whole argument revolves around the classical anthropological debate about the meaning of Totemism and the nature of social categories.  I tried to reconcile Freud, Levi-Strauss and Durkheim through the mediation of Darwin.  Too rich a mix perhaps, but one tries.


One of my favorite diagrams and one that makes the basic point about the reality lying in the process not the substance (something that 21st Century evolutionary theory* including complexity theory is begining to recognize) was in The Search for Society chap 5 on the concept of the "Ethosystem").  Here organism and environment lived in a constant modification-feedback processI symbolized as: O = organism, > = "acts on", E = environment, m = modified


I summed up this in the passage and diagram on the left (Figure 3) as an addendum to the chapter.  It was impossible just to give the diagram without this explanation.  And note how the "discovery" of "niche creation" in evolutionary biology amounts to something very similar.  In this general view organisms and even societies of organisms (including unicellular organisms like bacteria) become not just the passive recipients of the forces of selection, but forces active in the creation of their own conditions of selection and adaptation.

*See James A. Shapiro, Evolution: A View from the 21st Century.  2011

Here is an interesting quote from Stanislaw Lem's SciFi masterpiece His Master's Voice. (All his books are masterpieces.  He may be the smartest writer alive.)

"It is impossible to commence anything without first making assumptions, and our awareness of this fact in no way diminishes its reality. Those assumptions inhere in the very biology of man, and the amalgam of civilization which serves as the interface between the organisms and the environment; and this amalgam is permitted because the actions that must be taken in order to survive  are not rendered unequivocal by the environment. The environment, rather, leaves the organisms a chink for freedom of choice, a chink spacious enough to include thousands of possible cultures."

Original in Polish (1968). Trans. Michael Kandel (1973)


The discussion and diagrams on the left are from the same chapter but moving onto the related issue of "universals" in human culture.  Here again the issue of process versus substance arises with my illustrations of two examples where universal processes can give rise to differing local substance's: the first following the lead of Ludwig Wittgenstein's "family resemblance" universals and the second the example of the "Guttman scale."

There is perhaps no substitute for reading the whole chapter, but for whatever reason it does not get read (except by Bernard Chapais op.cit. and in "Human Nature and Human Society: Why Anthropology Cannot Ignore Biological Constants." in Michael Egan Ed. The Character of Human Institutions: Robin Fox and the Rise of Biosocial Science.  Transaction 2014.)

It is a long leap from the earliest hominids to the post-industrial future, but in evolutionary terms it is a blip on the screen.  This diagram (5.1) attempts to sum it up as the ever widening swing of a pendulum away from the Upper-Paleolithic baseline which is our environment of evolutionary adaptedness (John Bowlby).  The pendulum swings through time of course (I drew this with an inverted saucer) and each swing takes it further away from the base which is its natural resting place. The great moving events in the world's history occur along the major swings.  They are concentrated on the West because  what was to influence the world-historical shifts took place there for better or worse.  You can pick your own major swings of course.  And World War III?  Perhaps it is already happening and we just haven't realized it, because it isn't like the previous world wars.

I presented  this first in a lecture at the University of Virginia (1987) with a very conscious reference to their alumnus Edgar Allen Poe's "The Pit and the Pendulum" and in the building that is the American monument to to the Age of Reason - the Rotunda, designed by the epitome of the Enlightenment, Thomas Jefferson. The wonderful audience did get the irony (I think.)


On the left is an example of where you can take kinship analysis.  These are from Reproduction and Succession Part two, Chapter 3 "The Virgin and the Godfather: Kinship Law versus State Law in Greek Tragedy and After."

The first diagram shows how Sophocles and those after him construed the kinship relationships of the relatives of Oedipus: it is taken from Robert Fagles and Bernard Knox (1984) Sophocles: The Three Theban Plays. This however hid what I, following anthropologist Phillip Bock, construed as essentially the conlict between two patrilines in Thebes: the clans of Cadmus and Echion, as shown in the second diagram.  This, I felt, explained Antigone's behavior much better than the usual "individualistic" interpretation.  It was not the Individual versus the State but the Kinship group versus the State that was the issue: back to Sir Henry Maine's great distinction between Laws of Status and Laws of Contract.  This was for me again epitomized in the struggle of Mary Beth Whitehead, the modern Antigone, in the famous "Baby M" trials.  For the playing out of that, see the book!

Also see how it challenges the Structuralist (Levi-Strauss) assignment of the the two poles of "contradictions" in human thought as being arbitrary, and how this analysis  makes more empirical sense - and more empirically testable sense. (To say nothing of more dramatic sense.)


This diagram - an attempt at a 3D picture rendered in 2D, has nothing directly to do with the others and is a simple product of my diagrammatic imagination,  intended as a summary of the argument in the chapter "Violence:Ritual::Power:Authority" in the section "Diary of a Superfluous Race" in The Violent Imagination (RUP 1989). It was not our innate violence that was our problem I argued, but our violent imaginations (coupled with the male-cultural-fantasy properties on the right side) that gave us perpetual and probably unavoidable trouble.
Below is my reconstruction of a diagram from the formidable sounding:    
Pathak, D.T., Wei X,, Dey A., Wall D.  2013.  “Molecular Recognition by a Polymorphic Cell Surface Receptor Governs Cooperative Behaviors in Bacteria.” PLoS Genet.  9(11): e1003891. doi:10.1371/journal.pgen.1003891.  
           This describes how a species of bacteria organizes its social life, and I would not have probably been reading it had not my colleague Dr Linton Herbert  called attention to how truly social these  mixobacteria (which live in soil) were.  See below the diagram for a longish quote from my "Marry In or Die Out" which gives the authors' own conclusions and my deductions.
 It is known that myxobacteria (which live in soil) have a lively social life, but recent extraordinary research (Pathak  et al. 2013) has shown that they have as remarkable a competitive life, and one as governed by kinship, as the evolutionarily more recent sperm.  Many of the elements of our story are already there.  Let Pathak and his colleagues explain:
"How individual cells recognize each other to cooperate and assemble functional tissues is a fundamental question in biology. Although multicellularity is a trait that is typically associated with eukaryotes, certain groups of bacteria also exhibit complex multicellular behaviors, which are perhaps best exemplified by the myxobacteria. For example, in response to starvation myxobacteria will assemble fruiting bodies, wherein thousands of cells function as a coherent unit in development and cell differentiation."

Now he comes to the guts of it:
"Here we describe a mechanism where myxobacteria distinguish sibling and cohort cells from other myxobacteria isolates. We show that molecular recognition is mediated by a cell surface receptor called TraA. Cell-cell specificity involves mutual recognition cells by partnering  and is mediated by proposed homotypic TraA interactions. The specificity for recognition is determined by variable sequences found within TraA alleles. Thus, simply swapping TraA alleles between isolates predictably changes partner recognition. TraA-TraA recognition in turn leads to the fusion and exchange of outer membrane (OM) components between cells. We suggest that OM exchange allows the cells to communicate and become homogenous with respect to their OM proteome. We further suggest these interactions build a cohesive cell population.

Swapping traA alleles also reprogrammed social interactions among strains, including the regulation of motility and conferred immunity from inter-strain killing. We suggest that TraA helps guide the transition of single cells into a coherent bacterial community…  In evolutionary terms, TraA functions as a rare greenbeard gene that recognizes others that bear the same allele to confer beneficial treatment."
          A “greenbeard gene” is a gene that allows one organism to cooperate with another even if they are not genetically closely related, and is a whole other fascinating story. Here with the mixobacteria are individual cells, produced from one mother-cell by simple division, trying for various reasons to combine into multi-cellular organisms.  They are in essence looking for their sisters, and they will know them by the TraA allele that they carry.  But then more amazingly, if they do not have enough siblings, they will transfer TraA to unrelated cells producing instant functional relatives to help build their “cohesive cell population” and win out in competition with other strains.
          As with the combative sperm, different strains of unrelated bacterial cells try to kill each other.  By transferring TraA the bacteria can grant immunity to strangers and recruit them essentially as pseudo kin.  Then they can cooperate in “the regulation of motility” – in causing “irruptions” of kindred bacteria that will swarm off with their propellers to find pastures new.  Astonishing. 

But the features of kin recognition, the bonding of close kin, the manipulation of kinship, and conflict between kinship groups, are all there in the most primitive organisms on earth. They were not a consequence of the evolution of sexual reproduction, and although that momentous shift did have a totally transforming result, it was built on mechanisms already present and active.

Copyright:© Robin Fox 2010

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