Novel Ritualized Motor Pattern Accompanying Human Ejaculation (CB Jones, 5/2011)

Case Study of a Novel Ritualized Motor Pattern, the "Neck-bite," Accompanying Human Ejaculation*

Clara B. Jones

5/27/2011 (posted to blog, 5/22/2020; slightly edited & revised, 5/23/2020)

Abstract

Communication forms the “glue” in all societies, and species-typical traits (e.g., morphology, behavior) have evolved by natural or sexual selection to enhance communication between a signaler and receiver(s). Over evolutionary time, the process of "ritualization" may simplify and exaggerate conserved morphological characters, modifying their original function(s), yielding stereotyped phenotypic features with signaling function(s) differing from those of the conserved traits. Employing analyses of photographs and videos as well as a modified version of phenetic methodology, the present case study dissects an apparently rare motor pattern of the human behavioral repertoire occurring at ejaculation during dorsal-ventral intercourse between consenting heterosexual partners. Dissection of the case material led to the diagnostic inference that this response, the “neck-bite”, represents a newly-described ritualized morphological feature for Homo sapiens with morphological and functional similarities to the "neck-bite" behaviors reported for other mammals.

Key Words: Communication; Ethology; Ritualization; Neck-Bite; Copulation; Carnivores; Primates; Qualitative Research, Ejaculation

Introduction

Communication is the “glue” of any society (Wilson, 1971). When “true communication” occurs, both Sender (Actor) and Receiver (Recipient) benefit from the exchange of information (Bradbury & Vehrencamp, 1998). For humans and many other taxa (e.g., birds and mammals), communication may be both auditory (e.g., Marler, 1976) and non-auditory (e.g., gestures: Morris, 1995). As discussed by Maynard Smith & Parker (2003; also see Enquist et al., 2010), elements of communication function as signals (traits modified by selection for communication function), and, in some species (e.g., many primates, including humans), these elements may be combined and recombined, producing complex, multimodal patterns (e.g., Jones & Van Cantfort, 2007), functionally referential communication (signals about external events: e.g., Seyfarth et al., 1980), and context-dependent meaning (e.g., Quattara et al., 2009).

Ritualized and Stereotyped Signals and Displays

Tinbergen (1952; also see Morris, 1957; Lorenz, 1981; Eibl-Eibesfeldt, 2007) describes the process of “ritualization” whereby features of the conserved (“primitive”) species-typical repertoire become “emancipated” or disassociated over evolutionary time from their previous function(s) leading to involuntary, exaggerated, simplified motor patterns known as “stereotyped” signals often termed postures, displays, or “fixed action patterns.” It is through the process of "emancipation" that stereotyped signals are said to be “derived” from earlier, conserved morphological elements. Stereotyped motor patterns are characterized by “typical intensity,” relatively invariant and relatively immobile morphological features characteristically similar across individuals of the same sex and species across space and time. Finally, ritualized behaviors may present as “intention movements” whereby the stereotyped action pattern is identifiable but appears truncated and incomplete in form.

Employing or not employing an exaggerated, stereotyped signal is not, by definition, an intentional or conscious and aware “decision” since the evolutionary process leading to ritualization of phenotypic characters yields “hard-wired,” involuntary responses that are "canalized," resistant to environmental modification or "plasticity" across time and space (Morris, 1957; Lorenz, 1981; Eibl-Eibesfeldt, 2007). As a caveat, although there are certain mechanistic similarities, stereotyped motor patterns should not be confused with "reflexes" which are not ritualized, derived signals but action patterns induced at the level of the spinal cord controlled by the autonomic nervous system. In ethological terms, "displays" have evolved in response to particular stimuli termed “releasers,” while reflexes have no particular communicative function and are not stimulus-specific (e.g., rapid jerking of a body part from an aversive stimulus may be exhibited in response to a wide range of different stimuli such as heat, electric shock, or physical disgust). Ritualization leading to stereotyped phenotypic elements yields discrete (digital), discontinuous signals rather than graded (analog) signals transmitted as a continuous sequence of information-transmission (e.g., Eibl-Eibesfeldt, 2007; Maynard Smith & Parker, 2003; Enquist et al., 2010).

Most motor patterns in the behavioral repertoire of humans are graded (Eibl-Eibesfeldt, 2007). Although discrete vocal signals may not be rare in Homo sapiens (Marler, 1976), this article addresses only stereotyped motor patterns or displays, not discrete auditory or other sensory signals. Stereotyped and ritualized behaviors in humans have been documented and discussed by Eibl-Eibesfeldt (2007), in particular, the “eye-flash” motor pattern (stereotyped lifting of the eyebrows). The same author conducted cross-cultural research including cryptic filming of the eye-flash, demonstrating that, in cultures throughout the world, the "eye-flash" occurs between males and females while flirting and in apparent courtship and other bonding contexts. Based on many years of research, Eibl-Eibesfeldt (2007) concluded that stereotyped and ritualized action patterns are rare in the human behavioral repertoire, and it seems reasonable to postulate that this observation obtains because, compared to other organisms, phenotypes of Homo sapiens are shaped to a large degree by learning. Learning mechanisms (e.g., "association," "social learning") are thought to have evolved in response to rapidly changing (“stochastic” or predictable relative to "generation time") environments permitting flexible, resilient, and “plastic” behavior, effects with the potential for rapid adjustment of the phenotype to environmental heterogeneity (e.g., Jones, 2005, 2012; Weber & Depew, 2003), possibly decreasing the selective advantage of some hard-wired responses such as those dedicated by the process of ritualization to stereotypy over time and space (e.g., as appears to have occurred in human evolution).

The present case study discusses a human motor pattern that is, based upon detailed analysis, inferred to be stereotyped. This response, the “neck bite,” is observed across numerous taxa, both invertebrate (e.g., Buskirk et al., 1984) and vertebrate (Saint-Girons, 2006). The behavior functions intraspecifically in a variety of modes as evolutionarily modified signals conditionally displayed in a range of contexts and states. To my knowledge, the stereotyped "neck-bite" as a component of the human sexual repertoire, has not previously been described in the technical literature.

Methods

Qualitative Research Design and Procedures

Information about the sexual encounter dissected in the present case study was availed to the author (hereafter, “the investigator”) by one of the participant-observers (hereafter, “the subject,” "receiver," or, "recipient"). On the basis of her training in Ethology emphasizing the study of sexual and aggressive behaviors, the investigator suspected that certain details of the described events deviated from patterns of behavior generally attributed to human dorsal-ventral intercourse, appearing, on the basis of the subject’s verbal report, to include action patterns often described as elements of non-human animal copulation and/or ejaculation. Motor patterns comprising the highly variable sequences of behavior observed for human sex (e.g., Roughgarden, 2009), generally appear intentional, fluid, and continuous unlike certain of the fixed and discrete responses described by the subject (Morris, 1957; Lorenz, 1981; Eibl-Eibesfeldt, 2007). Based on the subject’s report of one heterosexual experience with a long-term partner, the investigator decided, with permission of the subject but without knowledge of the subject’s partner (the "signaler" or "actor"), to further explore the described events on the condition that identities of both participants remain anonymous.

Rather than limit her behavioral analysis to narrative and interpretive methods, the investigator chose to employ "phenetic analysis," a standard procedure employed in systematic biology commonly applying diagnostic criteria to museum specimens to determine phylogenetic proximity among species (Schuh & Brower, 2009). This qualitative, descriptive method relies upon subjective assessments by an expert inspecting similarities of morphological traits, in the present case, behavioral characters, to construct "phylogenetic trees."  The construction of trees was not a goal of the present study; though comparative observations to other mammalian taxa, especially, felids and canids, were conducted and are discussed. Rather, phenetic methods were used to increase reliability of diagnosis by matching motor patterns described by the subject to a template of morphological features generally accepted by ethologists as diagnostic criteria for identification of ritualized motor patterns. Deviations from phenetic practice entailed, in particular, diagnosis based upon a sample size  of one (N= 1), constituting a Case Study, prohibiting application of descriptive statistics base upon, say, analysis of film or photographs yielding sequential responses, possibly, coordinated ones, by actor and recipient. Thus, case material employed for diagnosis deviated significantly from phenetic diagnoses because it was based upon the subject’s verbal, participant report rather than direct inspection of case material. Ethological methods often entail direct observation in laboratory or in nature using frame-by-frame analysis of images (Eibl-Eibesfeldt, 2007; Lehner, 1998; Jones, 1986) permitting calculation of “transition probabilities“ or assessment of results with descriptive and/or inferential statistical tests (Lehner, 1998; Jones, 1983).

Phenetic analysis, like all qualitative research, does not permit generalization beyond given case material, limited, instead, to subjective inferences by a trained investigator’s dissection of comparative morphological traits (in the biological literature, a "character" or "trait" is generally assumed to be genetically correlated, thus, a potential target of selection; this may apply to both "plastic" or "canalized" traits). Phenetic analysis, also, does not permit distinctions between traits derived from a common ancestor (plesiomorphies) and convergent traits evolved independently in one or more lineages (apomorphies). However, phenetic methods, like all scientific procedures, requires a description precise enough to permit other trained researchers to independently describe and replicate the investigator’s dissection and diagnosis. The specific research question posed in the present study was: Subsequent to dissection and prior to diagnosis, do the motor patterns described by the subject justify their classification as ritualized, stereotyped morphological traits similar in form but not, necessarily, in function to conserved (primitive) action patterns in the target species (in the present case, humans) or in other taxa?

To supplement the modified phenetic analysis, the investigator studied >250 photographs and videos of mammals [available on the internet, including, YouTube], including humans, in order to familiarize herself with the variable forms, contexts, and apparent motivations and functions of motor patterns targeting the neck. The diagnostic criteria used to infer stereotypy of the motor patterns displayed in the survey of images and the case material described herein are the same ones that would be employed by any other ethologist evaluating possible ritualization of morphological traits (Lehner, 1998) . A major difference was that this study’s case material consisted of subject report based upon memory of events rather than direct or indirect inspection by the investigator.

The dissection and diagnosis reported in this paper probably yielded inferences with a higher degree of confidence and a lower level of error than procedures frequently used by fieldworkers collecting narrative data from indigenous or other local individuals in habitat countries (e.g., to obtain information about rare or difficult to locate species or recalled events "in the world") since this study’s subject was a participant observer providing first-hand case material and because a unique sexual encounter is likely to be consolidated relative reliably in memory due to its intense emotional, associational, and cognitive effects. This investigator decided not to employ interview methods with the subject because this procedure has the potential to introduce additional error due to prompting, increasing the likelihood that a subject will embellish, exaggerate, or otherwise bias information (e.g., Berkowitz et al., 2008). Certain personal details are omitted from this case study to shield the identities of the subject and the subject’s partner.

Results

Mammalian Motor Patterns Targeting the Neck

The "neck-bite" is common to mammalian hunt and kill, and predators and their prey are presumed to have co-evolved (Franks & Nobel, 2004), with predator hunting strategies a function of prey defense responses (Sih, 1985; Alcock, 1998). Several sources note that selection will be particularly sensitive to the relative sizes of predator and prey, favoring flexible responses since hunting and defense are species- and condition-dependent and, frequently, opportunistic (Mc Coy et al., 2011). Documenting the history, likely origin(s), forms, distributions, and functions of the mammalian neck-bite motor pattern formed a critical component and first stage of this report’s results, permitting historical and comparative dissection and diagnosis. The following background assembles information on motor patterns targeting the neck in extant mammals, forming a body of evidence from the scientific literature (see, especially, Estes, 1992; Eisenberg, 1981). In the section on primates, Paleotropical non-human species are emphasized because of their systematic proximity to Homo sapiens and because, in general, these families are more completely described than Neotropical monkeys.

Information in the Results section was extracted from: Estes, 1992; Ewer., 1968; Morris, 1957; Moynihan, 1970; Napier, 1970; Poole, 1972; Klieman & Eisenberg, 1973; Eisenberg, 1981; Lorenz, 1981; Buskirk et al., 1984; Boesch & Boesch, 1989; Martin, 1989; Estes, 1992; McKenna & Bell, 1997; Smuts, 1998; Millon et al., 1999; American Psychiatric Association, 2000; Skinner & Chimimba, 2005; van der Dennen, 2005; Bauchot, 2006; Surbeck & Hohmann, 2008; Roughgarden, 2009; Swedell & Schrier, 2009; and, Enquist et al., 2010.

Carnivores

My literature search of mammalian motor patterns targeting the neck primarily discussed these responses as they function during the kill in carnivores. These morphological traits have been studied, particularly, in canids (e.g., wolf, fox, coyote) and felids (e.g., lion, tiger, leopard). Fossil Carnivores are dated to the Eocene, ~55 mbp, and their common ancestor can be traced to the early Paleocene, ~60 mbp. According to my sources, the felid-canid split was completed in the Oligocene-Miocene, ~20 mbp, with felids splitting from the common ancestor earlier than canids. These carnivore families, on whole, evolved different patterns of hunting and killing though both groups primarily target the neck. Canids generally hunt in groups, usually killing with a “death-shake” rather than the suffocating “neck-bite” employed by felids. Extant felids are solitary hunters generally larger than canids, character states likely to have favored a selfish and efficient, though individually riskier, kill tactic. Compared to group hunting, solitary hunting is probably more sensitive to relative size differences between predator and prey. It seems reasonable to suggest, additionally, solitary hunting and the neck-bite are almost certainly the derived state compared to group-hunting and the death-shake since the neck-bite is more energetically efficient than the death-shake. These propositions are consistent with reports that the felid line is older than that of canids since felids would have had a temporally wider opportunity for evolutionary changes to occur.

While characteristic hunting and killing strategies have been documented for carnivores, there are exceptions to observed patterns requiring analysis. For example, among felids, jaguars and cougars, both Neotropical taxa but not particularly closely related to each other, preferentially kill prey by using their teeth and jaws to crush the temporal lobes of their prey’s skulls, a method dispensing of prey virtually immediately compared to the methods of killing used by canids and felids. Again, based upon relatively increased energetic efficiency, killing prey with the method employed by jaguars and cougars suggests that it is a derived response. It has been suggested that this motor pattern is an adaptation favored during the Pleistocene’s great mammal extinctions when many available prey items were armored reptiles, a hypothesis seemingly supported by the observation that, while not a particularly large cat, cougars feed upon large, dangerous prey such as moose, elk, and bighorn sheep.

With the exception of humans and bonobos, the dorsal-ventral sexual posture is ubiquitous among mammals. Male canids and felids generally employ a stereotyped "neck-bite" during copulation interpreted as a character derived from a conserved action pattern. Though stereotyped, the neck-bite appears as an intention movement generally causing no harm to the female in copula because the force of biting to damage or to kill is inhibited. During sex, some mammalian males appear to use the "neck- bite" to maintain balance during intromission, and it is also likely that the motor pattern is employed multi-modally to communicate dominance and control over the female. This topic is discussed in greater detail below.

Other ritualized "neck-bite" responses, apparently derived from conserved motor patterns, occur in association with maternal “mouth transport” and play. Females in many mammalian families move their young from one location to another using a method of transport employing mouth and teeth with some force but inhibited sufficiently to prevent harming young (Fig. 1). The stereotyped "play-bite" most likely derived, also, from a conserved motor pattern and most often exhibited by immatures, is a common behavior, particularly among social mammals. A number of functions have been attributed to play, but most reports emphasize its role in social bonding, as an interaction permitting assessment of relative strength, communication of non-aggressive motivation, solicitation of non-aggressive response, and/or practice of behaviors characteristic of adult behavioral repertoires.

Primates

With the exception of three apes (bonobos, chimpanzees, and humans), coordinated hunting and killing of conspecifics and contraspecifics is rare or absent among primates. The three hominins are primarily terrestrial and widely acknowledged for their expert use of tools [Note added 5/23/2020: could this be related to frugivory?]. In the non-human apes and a few monkey species (e.g., capuchins), tools may be employed to break shells of nuts or crustaceans, to extract termites or ants from their colonies, and/or to extract marrow from bones and brains from skulls. Where killing has been observed in monkeys (e.g., Rhesus macaques, capuchins), an opportunistic capture and kill strategy was employed, and food items included both invertebrate and vertebrate taxa, including ants, spiders, birds, small mammals, as well as conspecific and/or contraspecific species of monkey. Bonobos, chimpanzees, and carnivorous monkeys generally kill prey by dismemberment and/or by disembowelment, using jaws and teeth, facilitated by hands, in both contexts. However, it has been communicated to the investigator anecdotally that chimpanzees sometimes kill in the manner of cougars and jaguars, by crushing the skulls of prey with the force of their mouths and teeth.

When primates kill, action patterns appear, ceteris paribus, intentional and graded rather than discrete and stereotyped as described for canids and felids. Humans are noteworthy for employing all manner of methods to kill conspecifics and contraspecifics, not only for food but, also, legitimately (e.g., policing, self-defense), by accident (e.g., vehicles, sports events), as well as for other reasons frequently classified as illegal acts (e.g., murder) or paraphilias (e.g., consensual or non-consensual practices leading to death exhibited for sexual gratification of one or more participants). These practices may be displayed independent of whether they are (e.g., attacks by formal street gangs, prison revolts, death resulting from impulsive aggression) or are not (e.g., offensive or defensive attacks by police, state warfare) considered illegal or pathological. Cultural rituals incorporating and/or leading to death (e.g., cannibalism, human sacrifice) are not uncommon practices in human societies and were not classified as paraphilias in the references inspected by this investigator.

In bi-sexual contexts among non-human primates, the stereotyped neck-bite or, similarly, a stereotyped shoulder-bite (Fig. 2), may or may not be displayed, even in species characterized by a detectable male dominance hierarchy. With the exception of bonobos and humans [Note added 5/23/2020: also, unless I am mistaken, gorillas in zoos] that frequently intromit in ventral-ventral orientation, primates copulate in the dorsal-ventral position with males typically restraining a female’s ankles with his feet in order to maintain balance. Both of these sexual postures, particularly dorsal-ventral, exhibit steoreotyped elements (e.g., "typical intensity" of bodies and arms during orgasm, often accompanied by vocalizations [signals?]). If a neck-bite occurs in combination with sexual egress, it is generally non-damaging. Despite the variety of patterns reported for class Mammalia, the non-human primate literature is dominated by studies of the "neck-bite" employed by males of a single species, Hamadryas baboons, to aggressively coordinate and control females in their harems. Although the teeth of these males may pierce the skin of females’ necks, the motor pattern is considered to be ritualized because the act of biting to kill is incomplete [Note added 5/23/2020: though, Hamadryas are among the few mammal species, the others being, humans, agouti, Northern elephant seals, walrus, chimpanzees, lions, domestic cats (Estes, 1992), in which adult males have been documented to kill mates or prospective mates]. 

Where it has been reported to occur, the neck-bite is “gentle” in prosimians (e.g., greater bushbabies), most of whom are solitary and nocturnal. In general, males of "conserved" or "primitive" primate species are reported to be “patient” with females in estrus (e.g., lesser bushbabies), not attempting to mount and intromit until the female communicates receptivity behaviorally (e.g., by approach and/or by presenting to the male with a stereotyped rear-present posture) and/or with other signals or displays (e.g., vocalizations). In humans, the stereotyped neck-bite has not, apparently, been reported, though “love bites” are common, particularly as components of flirting, play, foreplay, or other intimate contexts. "Love-bites," even those causing erythema (“hickies”) (Fig. 3) and, further, the infliction of mild pain including digging fingernails into a sexual partner’s back during foreplay or intercourse, are not considered pathological unless they are employed for sexual gratification in sado-masochistic or other contexts including, for example, humiliation, beating, restraint, cutting, hypoxia, and/or death, again, whether or not one or more participants act consensually.

Play focused on the neck is virtually ubiquitous among primates and other mammals, and, similar to carnivores, may occur as stereotyped play-bites, particularly in non-human species. Primate play bouts are often reciprocal, with interactants soliciting play by vocalization, exposure of neck or other areas of the body, or touch (e.g., tickling). My inspection of photographs and videos of play in simians suggested that play in anthropoids, especially among cercopithecines, frequently includes apparently stereotyped play-bites (Fig.4). The stereotyped play-bite was not, in general, apparent in the hominid images investigated. Stereotyped and non-stereotyped components of anthropoid and hominid play appeared primarily as solicitations or, possibly, appeasement, sometimes involving a "bared-neck" display, or vulnerable display of ventral region. These responses may function, also, to communicate subordinance or non-aggressive motivation or to solicit a non-aggressive response from the receiver. Bouts of play in hominids did not appear biased in favor of the neck region. My visual inspections of grooming, the most common social behavior among non-human primates, indicated that anthropoids groom most of the surface of the recipient’s body, though hand postures appeared to include stereotyped elements. If play bouts were skewed in favor of the neck region, it was not apparent during investigation of images of anthropoids. Non-human hominids (orangutans, gorillas, bonobos, and chimpanzees) frequently targeted the neck during grooming. However, though solicitations leading to grooming appeared to be stereotyped components of these interactions, grooming itself did not appear to be ritualized.

Human play directed at the neck and other bodily regions appeared primarily intentional, although certain of these action patterns exhibited during play, flirting, or in association with lovemaking may represent “intention movements” (Fig. 5), exhibiting elements of a stereotyped response (e.g., kissing, in the image depicted, or stroking, gentle scratching). All of these behaviors share similarities with both play and grooming in other primates. It seems possible that the phenotypes of many primate taxa, including humans, may incorporate both ritualized and non-ritualized action patterns for flexible, condition-dependent use. Intentional acts of play in the neck region are numerous in humans, including snuggling, mild nuzzling, and kissing, and all of these motor patterns appear to have some stereotyped elements (Fig. 6). Similarly, stereotyped elements in adult humans appear to occur as gentle biting in intimate contexts including mothers or other caretakers directing mild biting to infants or children, or nursing mothers stimulating an infant’s neck with fingers or mouth to induce sucking at the breast.

Most of the photographs and videos of human play that I reviewed were images of children. Many of these images depicted children playing in (apparent) solitary mode, standing side-by-side with one or more children at play [Note added 5/23/2020: see Piaget on this stage of so-called "parallel play"]. Quite a few images showed children playing face-to-face without threat display or other signs of negative arousal, and there seemed to be no bias in smiling which sometimes was exhibited and sometimes not. Considering the many images inspected depicting children at play, only one photograph employed features appearing to unambiguously fit diagnostic criteria for a ritualized action pattern. In this image (Fig. 7), a female child ~3 years old exposed and directed her bared-neck to her male playmate of about the same age whose head, oriented away from the girl, was, likewise, positioned with a bared-neck. Finally, the hypothesized functions of play in primates are similar to those advanced for social carnivores, although there is a strong predeliction in the primate literature to interpret human play and other behaviors as consequences of conscious and aware brain processing. Primates, like most mammalian species, employ similar behavior patterns during play or grooming.

Behavioral Observations

The subject’s description of the action pattern being dissected and diagnosed occurred in conditions not atypical for sexual encounters between human partners. In other words, copulation occurred in a known location on a comfortable surface (in this case, a bed), in this case, in dorsal-ventral posture. Description of the servicing partner’s (the Actor or Donor) sexual behavior was unremarkable up to the point of ejaculation. In other words, intromission was followed by thrusting increasing in intensity to the point of ejaculation. The servicing partner’s head was turned to the right above the receiving partner’s right clavicle. As commonly displayed, the servicing partner’s body became rigid during ejaculation, with hands and, partially, forelimbs pressed on surface of mattress on either side of the receiving partner’s (Subject, Recipient) trunk. The remarkable feature, and the motor pattern of note, concerned a response by the servicing partner accompanying the end-stage of ejaculation. During this phase of the sexual sequence, the servicing partner involuntarily, seemingly reflexively by subject report, head-turned further to the right and, with open mouth and bared teeth, bit the receiving partner’s epidermis between nape of neck and clavicle in “typical intensity,” exhibiting a “frozen” (immobile) open-mouth motor pattern. No element of the completed sexual sequence was reported to have been painful or discomforting to the receiving partner [subject], including the neck-bite that did not pierce the epidermal layer of skin. According to the subject, characteristics of the servicing partner’s end-stage ejaculation were observed in detail because the receiving participant’s head was already turned to the right, and, also, because, the response, unique in the receiving partner’s sexual history triggered (released?) a startle reflex directing receiving partner’s [subject] eyes to face of the servicing partner [actor], an action by receiving partner [subject] that did not deflect the attention of the servicing partner [actor].

Table 1 displays action patterns by the servicing partner as reported by the subject, matched to the diagnostic criteria conventionally accepted by ethologists to describe and define ritualized behaviors. The behavioral sequences detailed by the subject are consistent with most of the diagnostic criteria defining ritualized behavior by ethologists. The case material subsequently dissected was diagnosed. Another focus of the dissection was to demonstrate clear and precise differentiation between the case material and the intentional and graded “love-bite” commonly elemental to situations involving intimate human contact between two or more adults. Inspection of the results exhibited in Table 1 support the inference that the neck-bite detailed by the subject was stereotyped, classifiable as a discrete phenotypic character trait in the human behavioral repertoire.

It is submitted that the case material described by the subject and dissected by the investigator ranks with the “eye-flash” as another, previously undescribed, involuntary and, most likely, genetically-correlated ["hard-wired"] stereotyped action pattern [trait or character]. As reported, the receiving partner’s body was relatively stationary and rigid with head lying on the mattress and turned to the right. It seems of interest to note that, in this posture, the receptive partner’s neck would not be exposed to the servicing partner, the neck being at least partly sheltered by chin. Unfortunately insufficient material was provided by the subject to permit a diagnostic judgment regarding the likelihood that the receiving partner’s posture exhibited stereotypy.

Demographic Information

The subject and partner were both individuals of color in their early- to mid-thirties, one partner divorced and the other married and living with spouse. Both participants were parents of children born to a single mate. The partners were long-term, distant acquaintances, beginning a sexual relationship approximately six months prior to the events discussed in the present case study. The partners’ sexual relationship terminated approximately four months afterwards. The sexual relationship occurred in a major urban location in the United States, and encounters took place in either the home of one partner or a location associated with one partner’s profession. Partners met in public rarely and, in addition, had only occasional communication by phone. Based upon subject report, the sexual relationship was mutually satisfying, both physically and emotionally. Encounters were primarily sexual, rarely involving other activities (e.g., sharing meals, having extended conversations). At one point, the partners considered conceiving a child together; however, for practical, logistic, and other reasons this plan was rejected, a decision that was not mutual. Neither partner assumed primary financial responsibility in the relationship, although, one partner was significantly more secure than the other and provided transportation exclusively. The spouse of the married partner was reported to have had no knowledge of the extra-marital affair, and, according to the subject, both partners denied having conflict or guilt about the relationship. Per subject report, the relationship terminated by mutual agreement associated with but not limited to obligations and other restrictions and limitations imposed by one partner’s marital status and increasing anxiety and conflict about the relationship by the other partner. Apparently, no deception occurred concerning the married partner’s intent not to seek a divorce. Subsequent to ending their relationship, the partners maintained no contact with each other. Throughout the relationship, both partners lived in separate rented domiciles.

Developmental History

One partner’s developmental trajectory through high school took place in a stable, lower-middle-class home, with married, ostensibly monogamous, parents, siblings, and minimal conflict among family members. The maternal parent of this participant was a full-time homemaker. The family income did not permit home ownership, and the family inhabited an adequately-sized apartment in a depressed though relatively safe neighborhood in a major urban area. The second partner was raised in a middle-class family residing in their own home in a small city near a major metropolis. Although parents of this participant remained married and were ostensibly monogamous, the household was a zone of intra- and inter-individual conflict, including maternal neglect. The mother of this family unit worked outside the home, with a live-in housekeeper tending to children and household duties. Age of first sexual encounter for one partner was unknown to the subject whose first intercourse occurred after the age of sixteen. One partner married before the age of twenty, divorcing soon after the age of thirty. The other partner married after the age of twenty-five. When the relationship described in the present case study terminated, the divorced participant had more than one child while the other had one with one expected in ~7 months.

Cognitive and Mental Status Summary

Based upon subject report, both partners’ I.Q.s measured in the normal-high range though, as noted, one partner’s psychological trajectory was unstable relative to the other. No learning disabilities were reported for either partner or children.

Work and Academic Summary

Both partners were professionals with post-graduate training with one partner having work of significantly higher status, socially and financially, compared to the other. The professions of both partners were highly specialized.

Symptoms and Challenges

As reported by the subject, from childhood, the life trajectory of the unstable partner was single-mindedly focused on studies interrupted by episodes of serious mood disorders accompanied by anxiety (including bouts of agoraphobia). This partner’s status, compared to the other, was described as “unbalanced,” both psychologically, financially, socially, and energetically. The more stable partner apparently exhibited a noteworthy capacity for compassion and friendship; however, this partner’s sexual habits might be termed serially "polygamous." According to the subject, the cognitive, mental, and behavioral status of each partner’s children appeared to be within normal range.

Diagnostic Impressions

The investigator is not a psychological/psychiatric clinician; thus, the following interpretation is not supported by training or expertise using diagnostic criteria for psychopathologies. However, as noted above, the technical literature makes clear, gentle biting, focusing, in particular, on the "love-bite," is not classified as pathological behavior. The present case material was tentatively evaluated, further, with reference to the DSM-IV-PR Axes delineating relative degrees and levels of severity of presenting behaviors. According to these diagnostic criteria, the investigator concluded that the partner described as “unstable” would be classified in Axis I (severe presenting characteristics requiring immediate attention from a professional) and in Axis IV (significant work and interpersonal stress). The partner described as “stable”, was classified in Axis IV based on moderate to severe work stress and, despite this participant’s denial, likely multiple stressors associated with infidelity. Following the diagnostic criteria for Axis IV’s Global Assessment of Functioning Scale (GAS), the less stable partner received two ratings based on separate criteria detailed for the scale: 41-50 (difficulty with social and occupational symptoms) and 31-40 (some impairment in reality-testing, interpersonal relationships, judgment, and mood). The more stable partner also received two ratings: 41-50 (same criteria as above) and 61-70 (generally functioning, some meaningful interpersonal relationships).

Discussion

Using qualitative phenetic methods, this paper compiles evidence to test the hypothesis that a stereotyped "neck-bite" motor pattern is a component of the human behavioral repertoire. Employing ethological descriptions of the motor pattern by a participant observer matched to diagnostic criteria for ritualization and by inspecting scores of photographs of behavior targeting the neck in a variety of mammal species in diverse contexts, the investigator concluded that the described behavior exemplifies a stereotyped trait in the behavioral repertoire of humans. Comparing features of the present case material with structures and functions of the "neck-bite" postural response [action pattern, motor pattern] across mammals provided critical data for the present inferences. After Estes (1992), these comparisons revealed significant variability in structure and function of the neck-bite, not only between but also within Orders. For example, in carnivores, the neck-bite posture used during copulation is very similar when canids and felids are compared. However, modes of hunting and killing between these units have evolved differently, with canids, in general, hunting in groups and killing with the death-shake while felids are, on whole, solitary hunters killing with a ritualized neck-bite motor pattern.

Estes (1992) provides other examples of variability in the appearance of the neck-bite posture between the closely-related lesser and greater bushbabies. The "neck-bite" is absent from the behavioral repertoire of the first species but evident in the latter, more recently evolved, species. This pattern indicates that the "neck-bite" is a derived character state, evolved from solitary taxa lacking the morphological character. When studying this and other stereotyped traits, however, it is important to recall as a caveat that evolutionary biologists and behavioral ecologists conclude that "ritualized" motor patterns have the potential to evolve rapidly (Enquist et al., 2010), presumably in response to changing environmental conditions. Thus, systematic patterns of these derived signals over time are not necessarily expected to be linear or predictable within or between taxa. The latter issue should apply to investigations of both structure and function.

The ethological literature advances the idea that ritualized behaviors signal motivation in a variety of conditions, frequently functioning to decrease chances of direct confrontation between conspecifics and/or the likelihood of damaging aggression (Eibl-Eibesfeldt, 2007; Lorenz, 1981; Eisenberg, 1981; Morris, 1957). Researchers investigating signals and displays in non-human animals have generally followed the diagnostic criteria and conclusions by ethologists as well as treatments relying upon contemporary methods and theoretical treatments (Maynard Smith & Harper, 2003; Enquist et al., 2010). An extensive literature exists discussing and analyzing differential forms and functions of these morphological traits (Maynard Smith & Harper, 2003 and references; Enquist et al., 2010 and references). While thorough review of the ethology of mammals is beyond the scope of the present paper, Eibl-Eibesfeldt (2007), Eisenberg (1981), and Estes (1992) provide early, important summaries, with additional information located primarily in technical papers. Since, to my knowledge, no comprehensive evaluation exists of "ritualized" action patterns in mammals (but see, Eibl-Eibesfeldt, 2007; Ewer, 1968), this topic remains open for investigation.

Unfortunately, discussions of stereotyped responses by primatologists have been biased by early research on Hamadryas baboons (see Swedell & Schrier, 2009 and references therein). Because Hamadryas males employ the ritualized neck-bite aggressively for coordination and control of harem females in sexual and other contexts, the motor pattern has generally been interpreted in the framework of male coercion and force. Despite the aggressive behavior exhibited towards females by males of this species, it would be erroneous to generalize from this single case to all simian species displaying the neck-bite since most primate studies do not precisely discuss stereotyped and/or  ritualized features of sexual behavior. Furthermore, field experiments have not been conducted, and sex and aggression have not been studied systematically in many primate species.

According to Estes (1992), aggression (including rape) by adult mammalian males toward reproductive females is likely to be favored by selection in two conditions. First, females of harem species generally don’t copulate outside of their receptive periods. This state leads to a female-biased "operational sex ratio" if more than one female is in estrus at the same time and, also, if females breed seasonally (Emlen & Oring, 1977). Since a male will have difficulty monopolizing more than one female at a time (Emlen & Oring, 1977), this condition restricts a harem male’s temporal window for copulation and successful fertilization. Thus, in these conditions, coercion and force by males may be favored by selection, possibly representing a time-saving strategy benefiting a male’s “fitness budget” and minimizing mating investment. Estes (1992) points out, further, that "multimale-multifemale" ("polygynandrous") societies are primed, as well, for selection to favor male coercion and force toward females since females may mate with multiple males (sometimes referred to as “female promiscuity” or, less commonly in the mammalian literature, “polyandry," see elephant seals, "incitation of 'male-male competition'": Cox & LeBoeuf, 1977) during estrus and because females in these socio-sexual groups are pregnant or lactating for most of their lives. Both of these conditions lead to a male-biased "operational sex ratio" inducing intense male-male competition for cycling mates (e.g., chimpanzees).

On the other hand, Estes (1992) continues, when tactics of multiply-mating females successfully prohibit a single male from obtaining exclusive access to one or more females, aggressive behavior by males toward the opposite sex may be rare or absent. For example, female mantled howlers may rebuff male advances with a stereotyped, bared-teeth, open-mouth display (Jones, 1985), and female bonobos may form coalitions to overpower males (Vervaecke et al. 2000 [Note added 5/24/2020: bonobo females are dominant to males, uncommon among mammals]). Estes (1992) states further, that, as exemplified by bushbabies, solitary male primates rarely exhibit the neck-bite or aggression toward females in sexual contexts. Where the ritualized neck-bite is displayed in these species, however, it is generally expressed mildly and non-aggressively. Importantly, Estes (1992) shows that male to female aggression is, also, rare or absent where females are matrilocal (e.g., vervets), where females are dominant to males (e.g., bonobos), and where females exhibit strong "female-choice" of mates (e.g., mantled howlers, many cercopithecines). Following the criteria advanced by Emlen & Oring, 1977 who discuss “female emancipation,” it might also be suggested that male aggression toward females is not likely to be favored in heterogeneous regimes in which resources, especially food, are highly variable, making it energetically expensive for males to monopolize females (muruquis, mantled howlers, bonobos). It seems likely, as well, that male aggression towards females would be rare or absent in species characterized by female same-sex mate choice (e.g., Japanese macaques); however, to my knowledge, research has not been conducted or published on the use of stereotyped responses in species exhibiting same-sex mate choice or on coercion and force directed at females by males in these same societies.

Theoretical work advances the idea that males and females are in an evolutionary "arms race" to impose greater costs on the opposite sex than that sex imposes upon the other (Rice, 2000). The treatment by Rice (2000) assumes that males initiate the co-evolutionary race, a position that has been criticized in the animal behavior literature. Though Rice’s (2000) ideas are widely accepted by scientists studying the evolution and behavioral ecology of socio-sexual behavior, they have not often been applied by primatologists, or other social scientists, possibly because of the significant influence of feminists and humanists in this field. As the brief review in this paper indicates, sometimes males appear to have “won” this race (mantled howlers, Hamadryas baboons, chimpanzees), sometimes females appear to have won (lemurs, bonobos), and sometimes power relations between the sexes seem to vary by context (some capuchins, mantled howlers, gorillas, humans). Differential social influence between primate males and females is probably sensitive to limiting resource dispersion (distribution and abundance) over time and space; thus, it may be difficult to easily categorize these groups within and between taxa. Estes’ review (1992; also see Eisenberg, 1981; Martin, 1989; McKenna & Bell, 1997; Skinner & Chimimba, 2005) demonstrates noteworthy variability in male-female relationships within and between mammalian orders, dispensing with the prejudice that male to female behavior in sexual contexts can be generally characterized as coercion or force. Estes’ (1992) and Eisenberg’s (1981), among others’, important contributions to the literature on these topics in mammals require updating and comprehensive treatments, additional research programs in need of attention. As a final observation, it is likely that, when males direct a stereotyped "neck-bite" to females, the motor pattern expresses multiple motivations such as dominance, sexual intent, and/or coordination and control, motivations that may or may not be exhibited aggressively, other topics awaiting updates.

Limitations and Recommendations

Perhaps the primary criticism to be made of the present dissection and diagnosis of case material is the high probability that intraindividual and interindividual error within and between subject and investigator significantly impacted the study’s reliability and validity. Interview methodology was rejected in an attempt to minimize potentially biasing effects repeating case material solely to create a more vivid mental representation of events. Subject report was not sufficiently detailed to permit identification of possible "releasers" (a stimulus or stimulus pattern associated with the reported behaviors) inducing the ritualized neck-bite.

During a sexual encounter, it is likely that a mosaic of releasing stimuli arise from the physical (e.g., colors, shapes of objects, similarities and/or differences between familiar and less familiar contexts) and biotic, including social (e.g., mood, familiarity of sexual partners, general or specific anxiety or conflict about activities, number of concurrent sexual partners, olfactory and other perceptual stimuli) contexts. Precise delineation and identification of releasing stimuli would possibly pose an insurmountable challenge even under controlled conditions (e.g., by field experimentation or direct observation and measurement in the laboratory). However, it is clear that direct, sequential observation and measurement of the morphological and other characteristics of the sequence of behaviors comprising the sexual encounter and its context, possibly by video or related imaging techniques, would, at minimum, be required to permit informed speculation about releasing stimuli as well as precise delineation of morphological patterns. If these are idiosyncratic, specific to individuals, time, and space, the enterprise, even with a robust sample size, becomes much more challenging.

In this report, case material relied upon a single encounter (N= 1), obviating within-species comparative analysis and generalization. Thus, inferences made in the present study only achieve the status of propositions made by an expert investigator-observer. It is unclear whether the presumed absence of published reports describing the stereotyped "neck-bite" motor pattern delivered at ejaculation by the servicing partner to a receptive sexual partner represents the rarity of this response in Homo sapiens or reluctance to reveal such information (e.g., for reasons of reputation, embarrassment, shame, guilt). Another possibility would be failure to recognize details of a behavioral variant by one or more participants. A first step towards demonstrating the "neck-bite" as a component of the stereotyped behavioral repertoire of (most likely male) humans would require collection of anonymous questionnaire or other survey data using a large sample of sexually active adults. Stereotyped motor patterns appear to be rare elements of human phenotypes, and their proximate and evolutionary causation as well as their frequency, intensity, variability, forms, and functions are poorly understood. As suggested throughout this report, additional research is indicated.

Conclusions

The present case study used a modified phenetic methodology to dissect a participating subject’s verbal report detailing events occurring in one sexual context. Because certain features of the situation appeared to deviate from published reports of intercourse between heterosexual partners, elements of the events were scrutinized by an investigator with expertise in ethological theory, methods, and research. The morphological feature of note entailed co-occurring and post-ejaculation behavior by the servicing partner who was diagnosed to have exhibited a stereotyped "neck-bite," a posture observed to function in a broad range of mammalian taxa in a variety of conditions. In the ethological literature, the ritualized "neck-bite" motor pattern is generally advanced to function as a signal communicating motivation and/or intent, and numerous experts suggest, as well, that stereotyped patterns of behavior often function to decrease the likelihood of conflict or damaging aggression between conspecifics. Limitations of the program reported herein are discussed and recommendations are made to decrease error and refine procedures in future studies.

Stereotyped motor patterns targeting the neck reported for extant mammalian taxa, including the case study treated in the present report, display features most similar to the felid "neck-bite" rather than the "death-shake" of canids. Thus, the felid "neck-bite" may have been a generalized developmental template in mammals giving rise to a broad range of ritualized motor patterns targeting the neck. Another evolutionary scenario would advance the idea of convergence of motor patterns, possibly induced by a fundamental mammalian behavioral “toolbox”. Jaguars and cougars, for instance, may exemplify the relatively complete disinhibition, loss, and substitution of an ancestral feature, a topic studied by ethologists, particularly, Moynihan (1970), but awaiting a comprehensive comparative investigation. Importantly for topics of current interest to evolutionary biologists, these processes may pertain to the generation of behavioral novelty (West-Eberhard, 2003) and to evolvability (Kirschner & Gerhart, 1998). Also, as several sources have indicated, it would be significant to study relative predator-prey sizes and other characteristics within and across orders and families, including but not limited to, cranial anatomy, odontology, socio-sexual systems, ecology, climate, and other factors. Finally, biophysical and behavioral research, including, field experiments,  mathematical modeling, simulations, and other theoretical treatments, could compare the dorsal-ventral with other sexual postures (e.g., the “missionary” position) to assess whether these positions differ in their likelihoods of inducing the stereotyped "neck-bite" and/or whether the receiving partner is differentially vulnerable to harm by the servicing partner. Data such as these might provide insights into the evolution of mammalian and other vertebrate sexual postures, including reasons that ventral-ventral sex is so rare in nature [Note added 5/23/2020: the dorso-ventral sexual position would seem to benefit male interests if it benefits male coordination and control compared to the ventral-ventral posture]. It is hoped that the dissection and diagnosis exemplified by the present case study will generate intense scrutiny, probing questions, and future research on ritualized signals and displays in humans and other species.

Acknowledgments

I thank Jason Epperson for technical assistance and Dr. Kenneth J. Zucker for encouragement. Rick Murphy generously shared his photograph of a “shoulder-bite” displayed during copulation by a lowland gorilla silverback during ejaculation. I am very grateful for Murphy’s permission to publish this image. The accessibility and broad coverage of topics discussed in this report were significantly aided by the photographs available at Wikimedia Commons, by You Tube’s video collection, and on Google.

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Table 1. Table exhibits Ethological Features of ritualized motor patterns, Diagnostic Criteria as defined by ethologists for features of ritualized motor patterns, and investigator’s subjective diagnosis of this report’s case material matched to factors in the first two columns. This table provides a summary of the results employed for inferences, and, in the final analysis, the motor pattern described by the subject was diagnosed as a stereotyped neck-bite by the investigator. See text for greater detail, discussion, examples, and references.

ETHOLOGICAL FEATURES	DIAGNOSTIC CRITERIA	CASE MATERIAL MATCH
Ritualization	Process leading to discrete rather than graded morphological feature of a conserved character trait “derived” and “emancipated” from primitive form	Case report described discrete motor pattern comparatively similar to behaviors targeting the neck in other mammals, including primates
Stereotyped morphological feature	Character trait with signal function(s) exaggerated, simplified, and involuntary compared to conserved feature; stereotyped signals and displays appear “fixed” or “frozen” in time and space; “fixed action patterns” are condition-dependent, induced by “releasers” (subjective and/or environmental “releasing stimuli”)	Report of case material described motor pattern characteristic of stereotyped responses, including displays, and “fixed action patterns”; morphological features very similar to felid and other primate neck-bite displays; precise function(s) of case material and releasing stimuli could not be determined
Typical intensity	For given age and sex, stereotyped motor patterns, ceteris paribus, exhibit the same or similar morphological features within and across conditions	Unknown since N= 1; however, as described by subject, typical intensity exhibited for duration of event
Intention movement	A stereotyped motor pattern similar to other ones but failing to fully complete, carry out, or terminate a given ritualized morphological feature	As described by subject, motor pattern did not progress to uncomfortable biting nor did it puncture epidermal layer of skin of neck

Figure Legends

Figure 1. Felid “neck-transport” employed by females to move young from one location to another. Most canids, also, exhibit this motor pattern. Though not as incomplete or truncated as an intention movement, this response is inhibited or restrained compared to the neck-bite employed to kill. For this and following images, additional detail is provided in text of paper. Photo accessed from Wikimedia Commons.

Figure 2. A modified neck-bite, the “shoulder-bite”, displayed by a silverback lowland gorilla. According to the researcher providing this image, this display always occurs during ejaculation. The female in copula may respond with screams or may chase the servicing male; at other times, however, the female remains silent and passive. The shoulder-bite, in addition to the neck-bite, also occurs in sexual contexts in Hamadryas baboons, with varying responses by receiving females. ©Rick Murphy

Figure 3. Example of erythemas (“hickies”) resulting from human “love bites”. Love-bites appear to represent intentionally motivated behavior and not stereotyped motor patterns. Love-bites are not classified as paraphilias unless they escalate to sado-masochistic or other behavior harmful, physically or otherwise, to one or more sexual partner. Photo accessed from Wikimedia Commons.

Figure 4. An example of anthropoid (cercopithecene) “play-bite”, diagnosed as generally stereotyped based upon investigator inspection of photographs and videos. Similar analyses of hominid play did not reveal any apparent biases to target the neck. Photo accessed from Wikimedia Commons.

Figure 5. Movement by human male to female appearing to target female’s neck. Displays such as this one have been termed “impulsive” and may represent intentionally incompleted kiss or play. It is not possible from this image to determine whether the motor pattern includes stereotyped elements and whether it is classifiable as an intention movement by ethological criteria. Photo accessed from Wikimedia Commons.

Figure 6. The human kiss may have characteristics consistent with stereotypy, note, especially, tongue movement (the “French kiss”) that may at times be involuntary, thus, arguably, ritualized. Mouth motor patterns similar to the human kiss are displayed by bonobos, chimpanzees, and, possibly, other primates. Some other taxa (e.g., horse) exhibit similar behavior. Photo accessed from Wikimedia Commons.

Figure 7. The sole image of (human) children at play clearly depicting motor patterns oriented in the manner of stereotyped play postures employed by many mammalian species to solicit grooming or other behavior targeting the neck. These morphological features may also communicate subordinance and/or non-aggressive motivation in a broad range of vertebrate taxa. Despite appearance, it is not possible to confidently determine whether these motor patterns in this image conform to ethologists’ diagnostic criteria for stereotyped responses. Photo accessed from Google.

*This MS was submitted to journal, Archives of Sexual Behavior ~2011 but rejected on the basis of "ethical" concerns.