Darwinian Imperatives

In biology and evolutionary theory, the "Darwinian imperatives" broadly denote the fundamental biological requirements for individual survival and species propagation—or, more succinctly, survival and reproduction. Frequently, these imperatives are conceptualised at the population level, or reduced to fluctuating gene frequencies over time, abstracted entirely from the organism in which they reside. The primary concern here, however, is the central place of the individual animal, whether human or non-human.

Of these imperatives, individual survival appears straightforward, encompassing the acquisition of food, water, and shelter. Yet the concept expands naturally to include broader self-care routines, extending even to medical and pharmaceutical intervention—what clinical healthcare designates as activities of daily living. Ultimately, all such actions collapse into the single, essential category of personal survival.

Individual reproduction, by contrast, is far more complex. For higher animals, reproduction is never strictly an individual affair; it mandates a sexual partner, even if contact between the pair is fleeting or non-existent. Because the resulting offspring are genetically distinct from both parents, reproduction is accurately understood not as the replication of an individual, but as the transmission and copying of a recombined subset of genetic information.

Crucially, no animal—other than humankind—consciously sets out to reproduce or foresees the creation of offspring. The outcome is neither anticipated nor intended. Instead, what is biologically ingrained—or "programmed"—within the individual is the execution of a "reproductive act". A clear distinction must therefore be drawn between the evolutionary outcome of reproduction and the behavioural system driving the reproductive act.

This programmed impulse can express itself across diverse orientations. It may be directed towards members of the complementary sex, the same sex, or oneself, and occasionally towards other species or inanimate objects. While only the first orientation yields biological offspring, all these manifestations stem from the selfsame underlying neurological and hormonal drive.

This brings us to the status of the "reproductive system" within anatomical and physiological frameworks. Modern medical textbooks frequently isolate this system, often placing it at the very end as if it were an afterthought. This separation is instructive: unlike every other organ system, the reproductive system contributes nothing to individual homeostatic survival. Furthermore, it functions for only a fraction of the organism's lifespan—dormant throughout prepubescence, non-functional post-menopause in females, and subject to senescent decline in males. Thus, one of the two foundational Darwinian imperatives rests upon a physiological system active for only a limited segment of the individual's life.

Two Quotes

Here are two quotes that I consider worth mulling over:

“The greatest of all the accomplishments of twentieth-century science has been the discovery of human ignorance.”

    Lewis Thomas, physician and essayist, quoted in The Boston Globe, May 18, 1998

“For this, indeed, is the main source of our ignorance—the fact that our knowledge can only be finite, while our ignorance must necessarily be infinite.”

    Karl Popper, philosopher of science, in Conjectures and Refutations, 1960

A Growing Level of Respect

Numerous superlatives can be applied to the act of dissecting a human body. When one remains mindful that a cadaver represents the physical legacy of a living person, concepts such as honour, privilege, and responsibility immediately come to mind. In contemporary medical education, students are actively encouraged to humanise the donor to a far greater extent than was customary during my own formative career between the 1970s and 1990s. This transformation is entirely proper and represents the standard that ought to have prevailed historically. Because early anatomical dissections relied almost exclusively upon executed criminals—performed without consent as an extension of judicial punishment—reverence for the deceased was virtually non-existent. Consequently, when voluntary body donation eventually superseded execution, an ethos of formal respect was slow to take root in the dissecting room.

In my own experience, it was not until the early 1990s that tangible manifestations of deep respect towards the dissected dead began to emerge systematically. Initially, a university chaplain would visit the dissecting room—the place where staff, students and cadavers had met—to deliver a few carefully chosen remarks before work commenced. Within a few years, however, this role was transferred to a retired professor who had returned as an anatomy demonstrator. This transition was likely intended to establish a secular, non-religious atmosphere, accommodating a student body—and a donor cohort—comprising diverse faiths and secular worldviews that permit anatomical donation.

Today, the level of respect demonstrated within my former department is profound. Observing contemporary practices reveals an institutional ethic strikingly distinct from the environment of my earlier years. The institutional attitudes of my generation now feel exceedingly distant, leaving me with the distinct sense of being a product of a bygone era—a conclusion that is, in all likelihood, entirely accurate.

Desmond Morris (1928-2026)

Desmond Morris (1928–2026) died earlier this year. I have always admired his ability to view human beings through a purely biological and evolutionary lens. Such an undertaking required a degree of detachment from one’s own species that is by no means easy to achieve. It brings to mind a rather risqué anecdote regarding a Martian visiting Earth whose interests, without divulging too much, were not dissimilar to those of Masters and Johnson—who were themselves, perhaps, less scientifically detached than is commonly assumed. It is frequently the mythical Martian who is invoked in jokes and literary conceits whenever a profound sense of detachment from ourselves is called for; the Martian’s perspective forces us to pause and look afresh at human nature.

Morris, however, could not rely upon the device of a Martian perspective, but instead employed the rigorous framework of a serious scientist. When his landmark work, The Naked Ape: A Zoologist's Study of the Human Animal, was published in 1967, it met with predictable criticism from within the scientific establishment. Yet it was the reaction of the general public that proved particularly revealing—especially when viewed from a "Manwatching" perspective (to borrow the title of one of his subsequent works). Religious and moral commentators viewed The Naked Ape as a direct challenge to humanity’s position within a divinely instituted order. They judged its descriptions of reproductive physiology to be excessively explicit, even pornographic, prompting widespread demands for the book to be banned from school libraries. Naturally, such condemnation served only to fuel sales.

A distinct yet complementary methodology had previously been adopted by the American cultural anthropologist and sociologist Horace Miner (1912–1993). In 1956, he published an article in American Anthropologist entitled "Body Ritual among the Nacirema". The essay remains one of the most widely assigned texts in introductory sociology and anthropology courses, serving as a foundational instrument for introducing students to cultural relativism and the necessity of objective observation prior to undertaking fieldwork. Beyond this, however, I must refrain from further exposition, offering not even a spoiler alert.

What Morris achieved was a systematic interrogation of ordinary human behavior from a specific ethological perspective. This prompts consideration of a contemporary phenomenon that remains equally perplexing: how has the act of self-display—standing motionless in various artificial poses to be scrutinised or photographed—come to be regarded as a virtue? Why has it evolved into a lucrative profession, commanding extraordinary remuneration? What drives so many individuals to pursue the status of a model? Stated in more fundamental terms, why do people aspire to make a living by standing still, or to be photographed without clothing? These questions apply equally to male and female subjects, though male and female observers may well arrive at divergent conclusions. While one might propose answers along classic ethological lines, the questions are worth posing precisely because they are so rarely asked. Indeed, one wonders what Morris would have made of modern social media, saturated as it is with individuals uploading repetitive photographs of themselves. Why is a single image deemed insufficient? What impels the uploading of multiple, virtually indistinguishable iterations of the same pose? We routinely overlook these peculiarities despite—or perhaps because of—their omnipresence on our digital screens.

Consider, for instance, how many Instagram images are captured in public toilets. Such locations are frequently selected simply because they offer readily accessible full-length mirrors. Yet this raises a prior question: why the overwhelming impulse to capture and display full-length representations of oneself in the first place?

This impulse towards visibility exists in tension with the nature of modern digital observation. Cyberstalking is formally defined as the persistent use of digital communications to monitor, harass, or intimidate an individual, constituting a fixated and illegal pattern of behavior intended to induce fear or distress. But what of instances where harassment and intimidation are absent? What if the interaction consists solely of "following" or repeatedly visiting a specific profile in complete silence? Does this constitute a form of "silent cyberstalking"? And conversely, what psychological and behavioral effect does it have on an individual to know that they are being observed by thousands of unseen eyes?

One wonders what reaction would meet these "Desmond Morris-like" inquiries today. What impact might an updated version of The Naked Ape achieve if directed at the digital, social-media-saturated era?

The Antiquity of ‘Neo-’

I recently shared some reflections on the concept of the "layered brain." That piece began as a set of preliminary notes for this post, but my musings on the broader cerebral architecture took precedence. Here, I wish to return to my original subject: the neocortex. This specific focus was prompted by a compelling segment in the BBC series Secrets of the Brain, presented last year (2025) by Jim Al-Khalili. As Al-Khalili is a professor of physics, I found the choice of presenter for a neurological survey rather curious at first; however, I now realise that his extensive work in quantum biology provides a natural bridge to the study of complex biological systems. Indeed, viewing the brain through the lens of information theory and thermodynamics offers a perspective that a purely clinical approach might overlook.

As an identifiable structure within the fossil record, we learn that the neocortex is of a staggering age, likely emerging at least 200 million years ago. There is a distinct irony in this antiquity when one considers the term’s etymology. ‘Neocortex’ is a hybridism, grafting the Greek prefix neo- (‘new’) onto the Latin cortex (‘bark’ or ‘rind’). Despite its ancient roots, the name reflects its status as the phylogenetically "newest" or most recently evolved layer of the cerebral cortex. This creates a fascinating temporal paradox: while 200 million years is a vast expanse in the context of human history, it is relatively recent when measured against the three-and-a-half-billion-year odyssey of life on Earth.

The term entered the lexicographical record between 1905 and 1910. Although coined as a neutral descriptive label for the evolutionary age of the tissue, it arrived during a formative period in neuroscience. At the time, the marked expansion and complexity of this structure in humans were frequently interpreted as the biological mandate for human superiority. It was regarded not merely as a mammalian trait, but as the "crowning achievement of evolution," providing the physical basis for our unique capacity for cognition, language, and abstract thought.

However, Secrets of the Brain introduced a complication to this narrative in the form of Morganucodon. This mammaliaform creature first appeared approximately 205 million years ago. Its name, meaning "Glamorgan tooth," pays homage to the area of South Wales where its remains were first discovered. While the soft tissue of the cortex does not fossilise, the impressions left upon the interior of the cranium suggest the presence of a neocortex.

Significantly, Morganucodon preceded the "true" mammals of the modern sense, yet it seemingly possessed this defining feature. This raises a difficult question: is the neocortex truly unique to mammals? The standard academic response remains a hesitant "yes," yet the area is far more contested than the BBC series might suggest. The evidence for neocortical structures in early creatures, combined with the presence of functionally similar regions in birds and reptiles, necessitates a more nuanced evolutionary history. While non-mammals lack the specific six-layered architecture of the neocortex, many possess homologous structures—such as the dorsal ventricular ridge—that perform analogous higher-order functions.

A neutral path through this debate suggests that various ancestral lineages possessed the "mammalian blueprint" for a neocortex, regardless of the divergent evolutionary paths they subsequently followed. What remains certain is that any claims regarding human exceptionalism based solely on this physical structure should be approached with the utmost caution. As we peer into the fossilised echoes of Morganucodon, we find that our "new" brain is, in fact, an ancient inheritance.

Skipping Guts - Addendum 2

Beginning with the idea of expressing gut lengths as a proportion of height (Skipping Guts), I wandered into the idea of a standard (or reference) male and female (Skipping Guts - Addendum). While, to my knowledge, gut length is not mentioned in the reference tables to which I referred, the weights of different organs are.

Based on the International Commission on Radiological Protection (ICRP) standards, the physiological differences between the 70kg "Reference Man" and the 60kg "Reference Woman" are precisely defined to ensure consistency in medical and scientific research. Thus, they supply standardised organ weights (or perhaps I ought to say 'mass', as these values are no doubt applied to astronauts).

Organ Mass Comparisons
The Reference Man (170 cm, 70 kg) generally has larger organ masses than the Reference Woman (163 cm, 60 kg) due to overall body size, though the proportions relative to body weight vary.

Source: ICRP Publication 89

…and one could go on. There are other standards. For example, basal metabolic rate (BMR) also mentioned in ICRP Publication 89 but, having added two addenda to my original post, I will stop here.

A Thin Blue Thread

Human dissection can hardly be described as a dull or tedious pursuit. However, for many students, the encounter with the cadaver can prove onerous, even dispiriting. This is rarely a reflection of the subject matter itself, but rather the pedantry of its presentation. The requirement to memorise an exhaustive catalogue of nomenclature—frequently in an ancient, calcified tongue—can rapidly extinguish any innate curiosity. In contrast, a true study of anatomy should be synonymous with the fascinating and the intriguing.

Within this category of the intriguing, one must include the discovery of the unexpected. This requires a certain intellectual plasticity; one must be sufficiently open-minded to appreciate a find that deviates from the textbook norm. I recall a senior anatomist who, upon being shown a structure resembling a vein coursing along the internal aspect of the left abdominal wall—likely an aberrant epigastric vessel—simply dismissed it with a cursory flick of the forceps. It was a moment where dogma overrode discovery.

Perhaps the most compelling enigma I encountered was a fine, blue synthetic thread embedded within the wall of the right ventricle in the heart of an elderly male cadaver. The mystery lay in the absence of any thoracic intervention; the skin of the chest was entirely devoid of scarring. We were left at a loss. Utilising modern AI tools to review the possibilities, I have since identified a plausible explanation, even if the opportunity for physical verification has long since passed.

The filament was likely nylon or perhaps polypropylene—the latter notably introduced as the surgical monofilament Prolene by Ethicon in 1969. Designed to be inert and non-reactive, these materials can remain sequestered within bodily tissues for decades without eliciting symptoms. As for its presence in the myocardium, venous migration appears the most probable culprit. It seems likely that a fragment of suture material became liberated elsewhere in the body and entered the "highway" of the venous return. Carried through the vena cava to the right side of the heart, it eventually became permanently lodged in the ventricular wall.

Our failure to trace the thread to its source was ultimately a consequence of the rigid boundaries of the dental student syllabus. As their curriculum was strictly confined to the head, neck, and thorax, we never ventured into the abdomen or lower limbs where the point of origin—perhaps a forgotten inguinal or femoral repair—lay hidden. While we will never know for certain, a reasoned hypothesis for such a survival feels infinitely more satisfying than an unresolved mystery. There is, after all, a quiet and haunting poignancy in the find: a thin blue thread of plastic, indifferent to the passage of time, outlasting the very biological life it was designed to support.