[Fis] Emergence of Human Sexual Behaviour

[Rainer Feistel (IOW)]

Dear Steve,

Thank you for your quick response, your careful reading, and encouraging 
comments with which, including the more critical ones, I may fully 
agree. You raised a number of non-trivial points. However, I cannot 
provide any rigorous proofs you are asking for, but merely a 
“scaffolding” working hypothesis. In the Spanish film “Jamon, jamon” the 
girl is asking her boyfriends why they do what they do with her body. In 
fact, the boys had no idea except that they just enjoyed doing that. I 
guess that most men all over the world instinctively share their kind of 
behaviour, suggesting that this is commonly inherited from a distant 
past. In my narrative and related paper, I just speculate from where 
such courtship habits may have originated, apparently being encoded in 
our genes. It is habit of use that specifies the meaning of arbitrary 
symbols, as already Charles Peirce had emphasised.

(i)It is correct that my suggested scenario is a succession of critical 
turnarounds, so that the entire staircase will break down as soon as a 
single step underway is missed. No step appears plausible without the 
preceding one, each step does not solve the problem but urgently 
requires the next step until some final one. This is intentionally so 
rather than representing a deficiency of the model. Fossils have shown 
that hominin evolution in the past several million years was a tree with 
numerous branches of which virtually all disappeared except our direct 
ancestors. Low reproduction rate is a crucial selective value; hominins 
that failed to find the next step of the staircase suffered from 
subcritical reproduction rates and got extinct. Likely, only one line 
successfully managed the entire risky parcours, starting at challenging 
bipedalism and ending at safe surplus multiplication with emigration 
pressure: our ancestors. No stagnant survival possible in between, so 
the idea that violent selective pressure enforced the (necessarily 
speedy) evident hominin sexual revolution (rather than gradual sexual 
selection).

(ii)I prefer to argue that any kind of information may be classified 
into either “structural information” or “symbolic information”. Any form 
of physical interaction necessarily transfers structural information 
between the interacting objects, without purpose, predictive intention 
or the need of symbols. Looking into the sky, the light of a star 
carries structural information that arrives at our eye. Our sensor cells 
convert this structural information into symbolic information in a 
“symbolisation” process: representative standard nerve pulses as symbols 
are generated, communicated, stored and processed with purpose and 
intention. By natural evolution, symbolic information emerged from the 
structural one by “ritualisation” transitions. Shannon entropy refers to 
symbolic information, Pauling entropy to structural information. More 
details at, say, “Self-Organisation of Prediction Models”, 
https://urldefense.com/v3/__https://doi.org/10.3390/e25121596__;!!D9dNQwwGXtA!TmF4lJQQcFFNFN9zh1E5coecSZrIeYlSi0nPgVRsMtY7svqlLkADN-38MGVEnqQa51pmrPf0HrdeEvbVgQLKtE9nyB4$  , and “Emergence of Symbolic 
Information by the Ritualisation Transition”, 
https://urldefense.com/v3/__https://doi.org/10.1142/9789813109001_0004__;!!D9dNQwwGXtA!TmF4lJQQcFFNFN9zh1E5coecSZrIeYlSi0nPgVRsMtY7svqlLkADN-38MGVEnqQa51pmrPf0HrdeEvbVgQLKQYbCZQU$ 

(iii)“Alternative hypotheses—fat storage byproduct, honest signal of 
reproductive value, sexual selection, pair-bond reinforcement”: May or 
may not be so. Common but vague and unspecific arguments. If so, why do 
not chimp females exploit sexy breasts? By contrast, my argument applies 
specifically to coercive mating of hominins. And to mammary glands only. 
And supports contraception in order to protect toddlers after weaning. 
It even explains, in the subsequent step, the mysterious, cumbersome 
sexual interest of men in female nipples.

(iv)“deceptive signals are often evolutionarily unstable”, and so also 
here, as all the steps of the chain of transitions are unstable and are 
dynamically replaced by their particular following step. The lactation 
fake by adipose breast will sooner or later be revealed by the next move 
of male behaviour: inspecting breast and nipples visually, manually or 
orally.

(v)There is little doubt that contraception implies futile ovulation and 
menstruation instead of pregnancy. For the menopause, I have borrowed 
the ovary exhaustion argument from Wallace and Kelsey (2010), 
https://urldefense.com/v3/__https://doi.org/10.1371/journal.pone.0008772__;!!D9dNQwwGXtA!TmF4lJQQcFFNFN9zh1E5coecSZrIeYlSi0nPgVRsMtY7svqlLkADN-38MGVEnqQa51pmrPf0HrdeEvbVgQLKgdLs5yc$  . It does not only support 
the grandmother hypothesis, it may also explain why humans find young 
females sexy, quite in contrast to chimps who typically ignore young 
females. As far as I know, chimps have post-reproductive lives typically 
in captivity.

(vi)Subcritical reproduction rates result from early weaning of mothers 
with their sole responsibility for the helpless offspring during 
childhood. To overcome this, other group members (preferably females 
such as sisters or mothers) must assist in childcare when the mother 
gives another birth too early. I prefer menopause and infertile 
grandmothers as plausible candidates, produced by preceding 
contraception and regular menstruation. I do not believe that male 
chimps, as had elsewhere been suggested, which neither know about their 
paternity nor are involved in any childcare, suddenly turn into caring 
fathers who even voluntarily refrain from sex with the fertile 
attractive mother after weaning.

(vii)Proper investigation of human sexual behaviour is far beyond my 
expertise. I merely review the published sex life of chimps from a 
special perspective. I just imagine a fictitious scenario of the effect 
of bipedalism on the reproduction behaviour of earliest hominins, and 
the hypothetical emergence of novel sex symbols as a consequence. Even 
this seems to appear, though, already as politically provocative to 
radical feminists.

(viii)I believe that my narrative is rather distinct from the typical 
approaches in the anthropogenic literature, such as sexual selection 
that gently transformed wild chimp hordes into harmonic 
mother-father-child families. I am convinced that hominins were often at 
the brink of extinction. Radical changes of reproduction (and other) 
behaviour went along with frequent population bottlenecks and enforced 
evolutionary progress at high speed. In order to support or disprove my 
model, it may hopefully inspire experts of the various fields involved 
to take a different look at their facts and models.

Rainer

-------- Weitergeleitete Nachricht --------

*Betreff: *

	

Re: [Fis] Emergence of Human Sexual Behaviour

*Datum: *

	

Thu, 12 Feb 2026 11:40:27 +0000

*Von: *

	

Steve Watson <sw10014 at cam.ac.uk>

*An: *

	

Rainer Feistel (IOW) <rainer.feistel at iow.de>, fis at listas.unizar.es 
<fis at listas.unizar.es>

Dear Rainer

Thank you for initiating this stimulating discussion. Your narrative on 
the emergence of human sexual behaviour is ambitious in scope and 
admirable in its integrative intent. By placing ritualisation at the 
centre of symbolic emergence and embedding human sexuality within a 
biosemiotic framework, you invite precisely the kind of 
cross-disciplinary dialogue that Foundations of Information Science aims 
to foster.

I would like to offer several reflections, structured around (1) the 
conceptual strength of your approach, (2) empirical considerations, and 
(3) theoretical implications concerning information and symbol formation.

First, regarding ritualisation as a mechanism of symbol emergence: your 
use of ritualisation—following Julian Huxley’s ethological work—as a 
transition from use-activity to signal-activity is theoretically 
compelling. This move situates symbolic forms not as sudden inventions, 
but as emergent transformations of already functional behaviours. 
Symbols, in this view, crystallise from repeated behavioural 
coordinations under selective pressures. That conceptual continuity 
between biological function and informational form is one of the 
strongest elements of your argument.

Applying this mechanism to human courtship behaviour—especially the 
proposal that inspection behaviours could have undergone 
ritualisation—represents an interesting and creative extension of 
ethological theory into anthropogenesis.

However, several elements of the specific evolutionary narrative raise 
questions concerning evidentiary robustness.

One issue concerns the adaptationist chain structure of the argument. 
The scenario is constructed as a sequential causal series: bipedalism 
leads to earlier weaning; earlier weaning increases infant risk; this 
selects for suppression of fertility swelling; persistent male interest 
follows; coercion dynamics emerge; permanent adipose breasts function as 
deceptive lactation signals; inspection behaviours are ritualised; 
contraception produces futile ovulation and menstruation; ovarian 
depletion lowers menopause age; grandmothering increases reproductive 
success; demographic expansion follows.

Each link may be plausible in isolation. Yet when combined into a single 
linear chain, the explanatory burden becomes very high. If one step is 
weakened, the dependent steps become unstable. Evolutionary history is 
often more reticulate and multi-causal than such linear reconstructions 
suggest. Clarifying which steps are essential to the thesis and which 
are heuristic would strengthen the model.

A particularly delicate component is the hypothesis that permanent 
adipose breasts evolved primarily as anti-coercion deceptive signals. 
Signalling theory suggests that deceptive signals are often 
evolutionarily unstable unless constrained by costs or enforcement 
mechanisms. Alternative hypotheses—fat storage byproduct, honest signal 
of reproductive value, sexual selection, pair-bond reinforcement—remain 
active and empirically viable. At present, the evidence does not 
decisively privilege the anti-coercion account. The proposal would 
benefit from explicit, discriminating predictions that could in 
principle falsify it.

Similarly, the suggestion that successful contraception led to futile 
ovulation and regular menstruation is innovative but currently lacks 
strong mechanistic support. Evolutionary explanations of menstruation 
remain contested and diverse. A clearer account of physiological 
pathways would be necessary to substantiate this connection.

With respect to menopause and the grandmother effect, while there is 
meaningful support for grandmothering hypotheses, the topic remains 
debated. Moreover, recent primate research complicates sharp contrasts 
between humans and chimpanzees regarding post-reproductive lifespan. 
Thus, integrating menopause into the scenario is conceptually elegant 
but empirically provisional.

 From an information-scientific perspective, further clarification may 
also be helpful. When describing breasts or swellings as “sex symbols” 
or “information tools,” it is important to specify what is meant by 
information. Is it conceived in a Shannon-type transmission sense, a 
functional selection sense, or a relational coordination sense? The 
narrative occasionally risks reifying symbols as objects that carry 
information, rather than describing them as stabilised patterns of 
interaction within coupled organisms. Emphasising the relational 
dimension of signalling may strengthen theoretical coherence within the 
Foundations of Information Science context.

Finally, the text connects deep evolutionary dynamics to contemporary 
phenomena such as sexual harassment, divorce rates, and declining birth 
numbers. While exploring long-term behavioural legacies is legitimate, 
caution is warranted. Contemporary sexual behaviour is deeply shaped by 
cultural, economic, institutional, and technological factors. Any 
evolutionary inheritance operates within these higher-order symbolic 
systems. Distinguishing between speculative evolutionary predispositions 
and modern socio-cultural dynamics would enhance explanatory precision 
and avoid unintended normative implications.

In conclusion, your scenario is bold, integrative, and intellectually 
generative. Its strength lies in provoking dialogue and in foregrounding 
ritualisation as a mechanism for the emergence of symbolic coordination. 
At present, however, the evidentiary scaffolding appears insufficient to 
support the full sequential model as more than a plausible 
reconstruction. Clarifying empirical commitments, alternative 
hypotheses, and falsifiable predictions would significantly strengthen 
the contribution.

I look forward to further discussion.

With collegial regards,

Steve Watson


-- 
Note: New Email Address:rainer.feistel at iow.de
Dr. rer. nat. habil. Rainer Feistel
Physicist (emeritus)
PS Gustav Hertz Prize, Berlin 1981
CITAC Best Paper Award, Paris 2011
IAPWS Honorary Fellow, London 2013
BIPM Metrologia Highlight Articles, Paris 2016
EGU Fridtjof Nansen Medal, Vienna 2018
LS Daniel Ernst Jablonski Medal, Berlin 2021
IAPWS Gibbs Award, Boulder, Co., 2024
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