Dominance Hierarchies in General

Although I made a thorough search, I was not able to find any indication that the amphioxus forms dominance hierarchies. 

Cross references: 
Lamprey Dominance Hierarchies         
Shark Dominance Hierarchies  
Teleost Dominance Hierarchies          
Lungfish Dominance Hierarchies   
Salamander Dominance Hierarchies 
Monotreme Dominance Hierarchies    
Marsupial Dominance Hierarchies      
Rodent Dominance Hierarchies    
Primate Dominance Hierarchies         
Human Dominance Hierarchies     

Endocrinology of Dominance 

Testosterone Receptor                  Testosterone Transcription Factor 
Testosterone Serotonin Interaction  

 
Glucocorticoids          Lamprey Cortisol, etc.     Shark Hormones  
Teleost Cortisol, etc.            Human Cortisol, etc.    

Vasopressin, Serotonin & Aggression              


NOTE:  The references, below, consider the male dominance hierarchy in general.  For discussion of its manifestation at a specific evolutionary level, click on the appropriate link, above. 



Dominance hierarchy (Wiki) 
http://en.wikipedia.org/wiki/Dominance_hierarchy#Humans 
"A dominance hierarchy (in humans: social hierarchy) is the organization of individuals in a group that occurs when competition for resources leads to aggression.  Schjelderup-Ebbe, who studied the often-cited example of the pecking order in chickens, found that such social structures lead to more stable flocks with reduced aggression among individuals.
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Dominance hierarchies occur in most social animal species that normally live in groups, including primates. Dominance hierarchies have been extensively studied in fish, birds, and mammals. Dominance hierarchies can be simple linear structures, which often arise from the physical differences among individuals in a group in relation to their access to resources. They are also influenced by the complex social interactions among individuals in the group.

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The most basic interaction that establishes a Dominance Hierarchy is the dyad, or paired interaction among individuals. To study the formation of hierarchies, scientists have often used the dyadic method, in which two individuals are forced to interact isolated from others.
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Individuals with greater hierarchical status tend to displace those ranked lower from access to space, to food and to mating opportunities. Thus, individuals with higher social status tend to have greater reproductive success by mating more often and having more resources to invest in the survival of offspring. Hence it serves as an intrinsic factor for population control, insuring adequate resources for the dominant individuals and thus preventing widespread starvation. Territorial behavior enhances this effect.[1] [2]

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These hierarchies are not fixed and depend on any number of changing factors, among them are age, gender, body size, intelligence, and aggressiveness.

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The suppression of reproduction by dominant individuals is the most common mechanism that maintains the hierarchy.
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Dominance hierarchies, though often more subtle, can be observed in human societies and are important for understanding the organization of family, tribe or clan, work organizations, politics, etc. in normal and abnormal social situations. It is not clear how much of dominance hierarchy in humans is due to the intrinsic biology of our brains, derived from evolution, and how much is due to cultural factors.
"    
My comment
This article does not mention the endocrine system specifically, so we will have to make that connection ourselves.  However, the statement that "
... suppression of reproduction by dominant individuals is the most common mechanism that maintains the hierarchy", gives us our first clue.   


Dominance hierarchy as integral to reproductive suppression; an adaptation  consequent to the evolution of the male (Goog) 
Full length PDF available online for free.  Download to copy-and-paste.    


Dominance, Status, and Social Hierarchies (Goog) 
Full length PDF available online for free.  Download to copy-and-paste.  
    "The direct connection between status effects and neuroendocrine response is plainly evident in research based on animal models, particularly research on individuals living in naturalistic ecologies in intact social groups. Hormones play a large role in the development and expression of social status. Status correlates with androgen and serotonin levels in many species of primates in that those with higher levels are also higher-ranking. This relationship is also bidirectional: Changes in social status produce marked changes in levels of these hormones. Following contests of rank, defeated males exhibit a drop in androgen levels while winners' levels rises..."    

    "Subordinates who receive frequent beatings from dominants suffer persistently elevated cortisol (stress hormone) levels, and impaired endocrine feedback responses to stress. And cortisol levels of all members of a social group soar during periods of social instability resulting from upheavals in the dominance hierarchy, such as when unfamiliar individuals are introduced into a group or an alpha male is ousted."  
    "Are these effects seen in humans? The answer appears to be decidedly, yes. ...  Changes in status produce large changes in hormone levels. For example, following competitive games, male winners typically show elevated testosterone levels relative to losers. This is true even when the competition involves little physical action, as in chess competitions"    
My comment
Note that dominance hierarchies
are particularly evident among "individuals living in naturalistic ecologies in intact social groups"     


Territory (Wiki) 
    "In ethology the term territory refers to any sociographical area that an animal of a particular species consistently defends against conspecifics (and, occasionally, animals of other species). Animals that defend territories in this way are referred to as territorial.  Territorial animals defend areas that contain a nest, den or mating site and sufficient food resources for themselves and their young. Defense rarely takes the form of overt fights: more usually there is a highly noticeable display, which may be visual (as in the red breast of the robin), auditory (as in much bird song, or the calls of gibbons) or olfactory, through the deposit of scent marks."  
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Territories may be held by an individual, a mated pair, or a group. Territoriality is not a fixed property of a species: for example, robins defend territories as pairs during the breeding season and as individuals during the winter, while some nectarivores defend territories only during the mornings (when plants are richest in nectar).



The Territorial Imperative (Goog) 
Full length online book by one of my early influences.   
    "When two or more fish are in the same tank there will always be a struggle for dominance. When the struggle is resolved, a fairly stable relationship will be formed in which one fish usually or always gives way to the other, usually or  always retreats when attacked, usually or always in the end will allow the other priority in feeding or females or favorite resting places."     

Alpha - ethology (Wiki)  
    "In social animals, the alpha is the individual in the community with the highest rank. ... Other animals in the same social group may exhibit deference or other symbolic signs of respect particular to their species towards the alpha. The alpha animals are given preference to be the first to eat and the first to mate; among some species they are the only animals in the pack allowed to mate.
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The social group usually follows the alpha to the hunt and to new breeding or resting grounds. The alpha is thus sometimes seen as deciding the fate of the group.



Robert Ardrey, The Social Contract (Goog) 
Ardrey's other online book. 
    "Out of all these early studies two generalizations appeared which the multitude of recent studies confirm: In any society of monkeys or apes, a degree of dominance among males will be evident, and there will always be one or more individuals with greater influence than others. And in such societies adults will always be dominant over juveniles... "   
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In the organization of any society of unequal beings to act as one, evolution has favored the mechanism of hierarchy. 
,,, To the successful organization of unequal beings in confrontation with common needs, hierarchy makes many a contribution.
    It reduces fighting. Once the order of dominance is established, serious aggression becomes rare, since each member knows too well his own capacities in relation to the next fellow's.  Rank order sorts through competition the unequals, placing in positions of influence those with superior assets for the group as a whole.
    Then, through social learning and the following response, it makes their achievements available to become individual assets of every last member. 
   There are genetic consequences as well, since in most species the sexual attractiveness of high rank and unattractiveness of low favors a disproportionate contribution to the gene pool on the part of the highly endowed. ,,, but perhaps the most significant contribution to the species as a whole, and to evolution in its long upward sweep, has been the demand placed by status on intelligence.

    "The Japanese monkey ... lives in some of the largest organized societies achieved by any primate, human or subhuman, before man began to gather in towns. In these colonies, males sort themselves out in rank orders of dominance, a state of affairs common in monkeys.

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All juveniles are omegas, since all adults are dominant over all young.
... the adolescent bears only the low rank of youth. It is a deserved omeganess, since if his society is to survive, then he must have reached a fullness of development guaranteeing his responsibility when he enters the ruling ranks. ... .
My comments
1.  "...
adults will always be dominant over juveniles ...".  
2.  "
Once the order of dominance is established, serious aggression becomes rare ..." 
3.  
"All juveniles are omegas, since all adults are dominant over all young. ... the adolescent bears only the low rank of youth. It is a deserved omeganess, since if his society is to survive, then he must have reached a fullness of development guaranteeing his responsibility when he enters the ruling ranks. ... .  
    The three comments, above, are key concepts in my explanation of why boys who try to grow up without a father have so many problems.   
4.  I've been very selective in quoting from these full length books.  Ardrey raises many issues that I have not addressed.  Most striking were  Sugiyama's langurs
.  You can read about them by searching Space and the Citizen for the researcher's name.  



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