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Teeth are good for chewing and biting, but they are also sensitive – and that may have been their original function hundreds of millions of years ago

After two decades of debate, research confirms that an odd binary star system has an equally odd planetary companion

The globe is criss-crossed by unused fibre-optic cables. Now, researchers are using them to defend against earthquakes and produce an unprecedented map of the underground world

Mars' oceans, lakes, and rivers are long gone. They've left behind evidence of their time here in river channels, deltas, paleolakes, and other features. The water's existence isn't a mystery, but its whereabouts is. Did it disappear into space, or did it retreat into underground aquifers?

In my first post of this series of two I maintained that First-Amendment-style freedom of speech, or something close to it, is necessary for the functioning of a democracy. But free speech is also touted not just as a prerequisite for having democracy, but a necessity for producing the “clash of ideas” that will give rise to the truth.  My contention in the first post is that while free speech is politically vital, it cannot by itself lead to finding the truth. For that you need what I call “expanded academic freedom”:  the right of individuals (usually academics or scholars) to think, write, and speak whatever they want. For this second endeavor is, unlike free speech, the one that allows people to look at the universe and see what is empirically true. (As I said earlier, the “truth” in my view, and that of the OED, is “something that conforms to fact or reality”, and knowledge, defined as “justified true belief”, is simply widely accepted truth.)

These are the two linchpins for finding and disseminating truth. Academic freedom guarantees the right to investigate reality and find out what is (provisionally) true, while freedom of speech guarantees the right to promulgate what you’ve found out. They work together to find the truth and (also important) make it publicly visible and publicly acknowledged: that is, they work together to produce knowledge.

I have construed academic freedom broadly and not limited it to academics. However, even on campus, academic freedom, just like freedom of speech, has its limits.  It is not true that I can teach creationism in an evolution class, or rail about Trump in a class about British history.  Academic freedom allows you to stay within the parameters of accepted knowledge and discourse within a field and, if you’re broaching new and heterodox ideas, they must be relevant to the class topic. If you violate this repeatedly, you’re likely to lose your academic job, and can have tenure revoked.

Similarly, academics are free to research anything they want, but that is no guarantee that their research will meet the standards of their field. If I was hired as a geneticist but spend my time studying the behavior of crickets, and not doing a good job of it, then yes, I could be disciplined or let go. You are free to do what you want within the parameters of your job, but that doesn’t guarantee career success.

(I won’t go into the the issue here of whether there is free speech in the classroom, though there clearly isn’t: again, professors can say what they want in class, but will be deep-sixed if it’s not relevant to the subject being taught. And classes also have is compelled speech: students are compelled to answer questions verbally or on exams, and are not free to give any answer they want.)

The separation of free speech and academic freedom is not a clean one. For example, a professor might say something in a didactic capacity that some students might consider harassment, like the professor at Hamline College who got into trouble for showing a picture of Muahmmad as a person, which offended some students. (The prof, who left, was ultimately vindicated.) However, there is a difference between freedom of speech adjudicated by the government, and freedom of thought, research, and teaching that is regulated by a professor’s field of work or department.

While freedom of speech assures professors at public universities of the right to promulgate their ideas, it is academic freedom, not freedom of speech, that allows them the latitude to study what they want and teach not only the gist of a subject, but promote a students’ ability to think.  It is academic freedom—the freedom of inquiry—that has:

• Made the American university system a huge draw for students and researchers throughout the world (the US has 80% of the world’s top 50 universities).
•  Led to 71% of all Nobel Prizes awarded having gone to Americans (29% of immigrants to America).  55% of the total are in science.
• Prompted many revolutionary discoveries, including polio and other vaccines, gene editing technology, MRI, lasers, and GPS. (note that academic freedom obtains in many other countries, where it’s also promoted discoveries, including the structure of DNA and, in part CRISPR editing).
• Led to the preeminence of American industry in creating scientific innovations, including microchip technology, vaccines for mumps, rubella, chickenpox, pneumonia, meningitis, hepatitis B, and hepatitis A, and various drugs.

While industry doesn’t have “academic freedom” in the sense that universities do, remember that most of the researchers in industry who create these innovations were trained in universities and absorbed their research ethos. But of course companies don’t have freedom of speech in the way that universities do; for example, they have the right to keep the technique behind their discoveries confidential for a time without publishing all the details.

You’ll notice that I have stayed away from humanities fields like literature, art, music, philosophy and law.  Why? Because, in my view, while these fields may produce interpretations or analyses of things like novels and paintings, they do not yield empirical truths. Literature, music, and painting, for example, are not “ways of knowing” but “ways of feeling or thinking”. (I discuss this in Chapter 4 of Faith Versus Fact).

This of course does not mean that such fields are without worth or merit; every reader here knows of my admiration for much of the humanities, particularly literature, art, and philosophy. It is simply that it’s not clear what we mean in such fields by the “pursuit of truth”.  What, for example is the “truth” in a Jackson Pollack painting or in Joyce’s Ulysses?  What is the (empirical) truth in John Rawls’s A Theory of Justice? The latter gives us a provocative way to look at and construct morality, but of course there are a gazillion other suggestions about how to do that. Which one is the “true” path to morality?

Granted, fields like sociology and economics do traffic in truth, but truth that can be ascertained only by using the scientific method construed broadly, which I see as confluent with academic freedom.  It is the toolkit of science, which developed under academic freedom, that allows us to reach real truths, and that toolkit includes implements like falsifiability, quantitative methods, pervasive doubt and criticality (a feature of academic freedom itself), replication and quality control, parsimony, collectivity, double-blind testing, and peer review. These are laid out in Chapter 2 of Faith Versus Fact.  And in that book I also define “science construed broadly” as any endeavor that uses some of these tools to ascertain what’s true. So, for example, plumbers, car mechanics, and others who solve empirical problems using a version of the scientific method can be considered practicing “science construed broadly”. Steve Gould realized this in his essay Genesis vs. Geology, recounting his testimony in the creationism trial of McLean v. Arkansas:

As I prepared to leave Little Rock last December, I went to my hotel room to gather my belongings and found a man sitting backward on my commode, pulling it apart with a plumber’s wrench. He explained to me that a leak in the room below had caused part of the ceiling to collapse and he was seeking the source of the water. My commode, located just above, was the obvious candidate, but his hypothesis had failed, for my equipment was working perfectly. The plumber then proceeded to give me a fascinating disquisition on how a professional traces the pathways of water through hotel pipes and walls. The account was perfectly logical and mechanistic: it can come only from here, here, or there, flow this way or that way, and end up there, there, or here. I then asked him what he thought of the trial across the street, and he confessed his staunch creationism, including his firm belief in the miracle of Noah’s flood.As a professional, this man never doubted that water has a physical source and a mechanically constrained path of motion — and that he could use the principles of his trade to identify causes. It would be a poor (and unemployed) plumber indeed who suspected that the laws of engineering had been suspended whenever a puddle and cracked plaster bewildered him. Why should we approach the physical history of our earth any differently?

I see I’ve digressed a bit, so let me summarize. What is this sweating professor trying to say? (And remember, this is simply a first draft of some nascent ideas.) My claim is that freedom of speech does not by itself lead to truth via the much-vaunted “clash of ideas”.  That clash is necessary to find the truth, but not sufficient. Atop it one must place academic freedom: the freedom of scholars to teach, think, and research what they want.

I also claim that much of the humanities, whatever they claims, is not capable of finding truth, since it doesn’t turn on empirical facts but on critical analyses, competing theories, and competing interpretations. That doesn’t make humanities lesser than science—unless scholars in fields like art, music, and literature claim that they are practicing “another way of knowing.” Some disciplines, notably philosophy are good at of pointing out errors of thinking and guiding rational thinking, but again (in my view) do not and cannot find truths about the universe in which we dwell.

Finally, academic freedom is separate but still intertwined with freedom of speech, but they differ in important ways. The practice of academic freedom does not assume that all ideas are equal or all people are equal in merit: academia is hierarchical and meritocratic, while the First Amendment assumes that all views when expressed are equal and nobody gets an extra say because of their merit. Freedom of speech promotes the emergence of competing truths, while academic freedom emphasizes the ascertainment of the “truest” of these competitors.

Today’s Jesus and Mo strip, called “conduit,” came with the caption, “To be fair, he did make that clear.” And once again we see two of the prime features of Mo’s character: hypocrisy and cluelessness.

In case you’ve forgotten your religious history, yes, the Qur’an was dictated to Muhammad, but through a primary conduit: an angel. As Wikipedia notes:

Muslims believe the Quran was orally revealed by God to the final Islamic prophet Muhammad through the angel Gabriel incrementally over a period of some 23 years, beginning on the Laylat al-Qadr, when Muhammad was 40, and concluding in 632, the year of his death. Muslims regard the Quran as Muhammad’s most important miracle, a proof of his prophethood, and the culmination of a series of divine messages starting with those revealed to the first Islamic prophet Adam, including the holy books of the Torah, Psalms, and Gospel in Islam.

And heeeere’s the Divine Duo:

As humanity heads back to the Moon, a silent danger lurks: exhaust plumes from multiple spacecraft will blast lunar dust into orbit, creating a potentially deadly obstacle course for future missions. The solution will be to build landing pads on the lunar surface out of the lunar regolith. Researchers simulated landing pads just like these and their tests showed they could handle the heat and force of the propellant exhaust from a landing spacecraft. The techniques they found will minimise erosion over multiple landings.

We’re running low on this feature, so please send in some good photos. I won’t beg again for a while.

Today we have photos from Africa by Loretta Michaels.  Her captions and IDs are indented, and you can enlarge the photos by clicking on them.

Brief Introduction: I used to do a lot of business in Africa and so I almost always tried to tack on a weekend safari of some sort while there.  Most of these times I had only my iphone to take pictures, unlike the bigger safari vacations my husband & I take with all our camera gear.

While in Dar es Salaam on business, I spent a weekend on Chumbe Island, just off the coast of Zanzibar.  One of the more bizarre sightings was a Coconut Crab (Birgus latro), the largest land crab in the world, which is able  to climb coconut palms and easily crack coconuts with its claws.  These crabs also eat fleshy fruit and even prey on smaller crabs. This species of crabs has evolved to live on land from the sea, returning to water only to lay their eggs. On land, they live in underground holes made with fibers from coconut husks, and are generally only spotted at night. An adult crab can reach one meter in length. It has a curled-under abdomen that makes it look like a lobster. Coconut crabs supposedly have very tasty meat, so, unfortunately, they are hunted:

Three nicely aligned bush elephants (Loxodonta africana) I saw during a trip to Zambia:

A nice female African lion (Panthera leo), spotted during a night drive in Zambia:

A Komodo Dragon (Varanus komodoensis) spotted during a drive:

Two white rhino (Ceratotherium simum) in Nairobi National Park, a 45 square mile wildlife sanctuary established in 1946 just outside Nairobi:

Lunchtime at the Lilayi Elephant Nursery just outside Lusaka, Zambia.  The baby elephants are just adorable to watch, especially as they come running in from the fields when they see it’s feeding time:

A Golden Monkey (Cercopithecus mitis kandti) spotted in Volcanoes National Park in Rwanda:

A mother and baby mountain gorilla (Gorilla beringei beringei) in Volcanoes National Park in Rwanda, just outside Kigali. It is one of two subspecies of the Eastern Gorilla.  The other population lives in the Congo. The park is one of the 3 homes of the endangered mountain gorillas within the Virunga Mountains:

Dominant male gorilla in Volcanoes National Park:

Variable Sunbird (Cinnyris venustus) in Rwanda. The sunbirds are a group of small Old World passerine birds which feed largely on nectar, although they will also take insects, especially when feeding young. Flight is fast and direct on their short wings. Most species can take nectar by hovering like a hummingbird, but usually perch to feed most of the time:

“Fragments” of West Nile virus have been detected in UK mosquitoes, suggesting that the virus is circulating in the country, probably as a result of the warming climate

While the medical world is melting down from the absolute apocalypse that is RFK Jr., it’s good to celebrate that (at least for now) medical progress continues to march on. Recently published in the NEJM is a case report of a breakthrough that we may look back on as a milestone in medicine. Patient-Specific In Vivo Gene Editing to Treat a Rare […]

The post Personalized CRISPR Gene Editing Therapy first appeared on Science-Based Medicine.

China's ambitious Tianwen-2 mission will soon be heading to two extremely different space rocks, and should provide vital data to help us understand the nature of asteroids and comets

A record 67,000 square kilometres of primary rainforest was lost from the tropics in 2024, with global warming and El Niño contributing to a massive jump in fire-driven damage

Jupiter and its powerful gravity have played a major role in sculpting the Solar System. A new study provides a glimpse into Jupiter's primordial state, which could have implications for our understanding of how the Solar System evolved.

A metamaterial is a composite material that exhibits unique properties due to its structure, and now researchers have used one featuring a small sawtooth pattern on its surface to move and position objects underwater without touching them directly. Adjacent speakers exert different forces on the material based on how the sound waves reflect off it, and by carefully targeting the floating or submerged metamaterial with precise sound waves, researchers can push and rotate the object attached to it.

In the intriguing realm of star-forming galaxies, the key factor isn't the total amount of gas but rather its strategic distribution within the galaxy.

When people think of fashion, they often picture runway shows, luxury brands, pricey handbags, or the latest trends among teens and young adults. Fashion can be elite and expensive or cheap and fleeting—a statement made through clothing, hairstyles, or even body modifications. Regardless of gender, fashion is frequently viewed as a way to signal income, social status, group affiliation, personal taste, or even to attract a partner. But why does fashion serve these purposes, and where do these associations come from? An evolutionary perspective offers surprising insights into the role of fashion in signaling status and sexual attraction.

The adaptive nature of ornamentation is something that has been long admired and studied in a wealth of nonhuman species. Most examples are ornaments the animals grow themselves.1 Consider the peacock’s tail, a sexually selected trait present only in males.2 Peahens are attracted to males with the largest and most symmetrical tails.

The ability of males to grow a large and symmetric tail is related to their overall fitness (the ability to pass their genes into the next generation), so that females that mate with them will have better quality offspring. Studies have shown that altering the length and symmetry of peacock tails influences mating success—shorter tails lead to less mating opportunities for the males. Antlers are primarily found on male members of the Cervidae family, which include elk, deer, moose, and caribou (the one species in which the females also grow antlers).3 Antlers, unlike horns, are shed and regrown every year. They are used as weapons, symbols of sexual prowess or status, and as tools to dig in the snow for food. Antlers increase in size until males reach maturity, and grow larger with better nutrition, higher testosterone levels, and better health or absence of disease during growth. The size of a male’s antlers is also influenced by genetics and females prefer to mate with males with larger antlers compared to smaller ones (much like in the peacocks).4, 5

In many species, exaggerated male structures like tails, antlers, bright coloration, and sheer size can serve as a weapon in intrasexual competition and as an ornament to signal genetic quality and thereby promote female choice. As a result, much attention has been focused on male ornamentation in nonhuman animals and what it indicates.6 Moreover, males of various species add outside materials to their bodies, nests, and environments specifically to attract mates. Consider the caddisfly, the bower bird, and even the decorator crab; all use decoration to attract females.7 Interestingly, in what are often referred to as sex role-reversed species, such as the pipefish,8 it is the females who are more competitive for mates and are more highly ornamented. But what about humans? Has ornamentation or fashion in humans also been shaped by sexual selection?

Humans do not have “natural” ornaments like tails or antlers to display their quality.

Humans have a fascination with fashion, as best summed up by the psychologist George Sproles:9 “Psychologists speak of fashion as the seeking of individuality; sociologists see class competition and social conformity to norms of dress; economists see a pursuit of the scarce; aestheticians view the artistic components and ideals of beauty; historians offer evolutionary explanations for changes in design. Literally hundreds of viewpoints unfold, from a literature more immense than for any phenomenon of consumer behavior.” To be fair, humans do not have “natural” ornaments like tails or antlers to display their quality. They also do not have much in the way of fur, armor, or feathers to protect their bodies or to regulate temperature, so “adornment” in the form of clothing was necessary for survival. However, humans have spent millennia fashioning and refashioning what they wear, not just according to climate or condition, but for status, sex, and aesthetics.

If fashion has been such a large part of human history with deep evolutionary roots, why do so many trends, preferences, and standards fluctuate across cultures and time? This is because fashion is a display of status as well as mating appeal. Many human preferences are influenced by context. For example, male preferences for women’s body size and weight shift with resource availability; in populations with significant history of food shortages, larger or obese women are prized. Larger women are displaying that they have, or can acquire, resources that others cannot and have sufficient bodily resources for reproduction.10 When resources are historically abundant, men prefer thinner women; in this context, these women display that they can acquire higher-quality nutrition and have time or resources to keep a fit, youthful figure. When tan bodies indicated working outside, and therefore lower standing, pale skin was preferred. When some societies shifted to tan bodies reflecting a life of resources and leisure, they gave tanning prestige, and it became “fashionable.”11

The shifts in what is fashionable can be attributed to these environmental changes, but one principle remains constant: if it displays status (social, financial, or sexual), it is preferred.12 A good example of this would be jewelry, which shifts with fashion trends—whether gold or silver is in this season, or whether rose gold is passé. However, if the appeal of jewelry was just aesthetic—to be shiny or pretty—people would not care whether the jewels were real and expensive or cheap “costume” jewelry. However, they do care, because expense indicates greater wealth and status. This is so much so that people often make comments regarding the authenticity or the size (and therefore cost) of jewels, such as the size of diamonds in engagement rings.13

Fashion for Sexual Display

It would be surprising if fashion and how humans choose to ornament themselves was not influenced by sexual selection. Humans show a number of traits associated across other species that are sexually selected, including dimorphism in physical size and aggression, delayed sexual maturity in males, and greater male variation in reproductive success (defined as the number of offspring).14 Men typically choose clothing that emphasizes the breadth of their shoulders and sometimes adds to their height through shoes with lifts or heels. In many modern western populations, men also spend significant time crafting their body shape by weight lifting to attain that triangle shaped upper body without the benefit of shoulder pads or other deceptive tailoring signals. These are all traits that females have been shown to value in terms of choosing a mate.15

Illustration by Marco Lawrence for SKEPTIC

Examining artistic depictions of bodies provides particular insights into human preferences, as these figures are not limited by biology and can be as exaggerated as the artist wants. We can also see how the population reacts to these figures in terms of popularity and artistic trends. The triangular masculine body shape has been historically exaggerated in art and among fictional heroes, and this feature continues today as comic books and graphic artists create extreme triangular torsos and film superhero costumes with tight waists and padded shoulders and arms. These costumes are not new and do not vary a great deal. They mimic the costume of warriors, soldiers, and other figures of authority or dominance. As cultural scholar Friedrich Weltzien writes, “The superhero costume is an imitation of the historical models of the warrior, the classic domain of heroic manhood.”16

If it displays status (social, financial, or sexual), it is preferred.

Indeed, military personnel and heroes share behaviors and purposes (detecting threats, fighting adversaries, protecting communities, and achieving status in hierarchies). These costumes act as physical markers and are used to display dominance in size, muscularity, and markers of testosterone. Research has found that comic book men have shoulder-to-waist ratios (the triangular torso) and upper body muscularity almost twice that of real-life young men, and that Marvel comic book heroes in particular are more triangular and muscular than championship body builders. What is remarkable is that even with imaginary bodies, male comic book hero “suits” have several features that, not coincidentally, exaggerate markers of testosterone and signal dominance and strength. Even more triangular torsos are created by padded shoulders and accents (capes, epaulets) and flat stomachs (tight costumes with belts, abdominal accents) with chest pieces that have triangular shapes or insignia, large legs and footwear (boots, holsters), and helmets and other face protection that create angular jawlines.17

Men’s choice of clothing and jewelry … convey information about status and resources that are valued by the opposite sex for what they may contribute to offspring success.

The appearance of a tall, strong, healthy masculine body shape is often weighted strongly by women in their judgments of men. There is also an interaction between sex appeal and status. Women choose these men in part because the men’s appearance affects how other men treat them. Men who appear more masculine and dominant elevate their status among men, which makes them more attractive to women.18 Men’s choice of clothing and jewelry or other methods of adornment can not only emphasize physical traits but also convey information about status and resources that are valued by the opposite sex for what they may contribute to offspring success. Some clothing brands (or jewelry) are more expensive and are associated with more wealth, and so are likely to attract the attention of the opposite sex; think of brand logos, expensive watches, or even the car logo on a keychain as indicators of wealth.19

Female fashion also shows indications of being influenced by its ability to signal mate value or enhance it, sometimes deceptively. In many mammals, female red ornamentation is a sexual signal designed to attract mates.20 Experimental studies of human females suggest that they are more likely to choose red clothing when interacting with an attractive man than an attractive woman;21 the suggestion being that red coloration can serve a sexual signaling function in humans as well as other primates. Red dyes in clothing and cosmetics have been extremely popular over centuries, notably cochineal, madder, and rubia. In fact, the earliest documented dyed thread was red.22

One of the primary attributes that women have accentuated throughout time is their waist-to-hip ratio, a result of estrogen directing fat deposition23—a signal of reproductive viability. The specific male preferences regarding waist to hip ratio have been documented for decades.24 But is this signal, and its amplification, really a global phenomenon? It is easy to give western examples of waist minimization and hip amplification—corsets, hoop skirts, bustles, and especially panniers,25 or fake hips that can make a woman as wide as a couch. Even before these, there was the “bum roll”—rolled up fabric attached to a belt to create a larger bulge over the buttocks.

Outside of Western cultures, one can find a variety of “wrappers” (le pagne in Francophone African cultures), yards of fabric wrapped around the hips and other parts of the body to accentuate and amplify the hips.26 Not surprisingly, these are also a show of status as the quality of the fabric is prioritized and displayed.

Just as with men, this specific attribute is wildly exaggerated in fictional depictions of women, from ancient statues to contemporary comic, film, and video game characters. One study concluded that “when limitations imposed by biology are removed, preferred waist sizes become impossibly small.”27 Comic book heroines are drawn with skintight costumes and exaggerated waist-to-hip ratios. They have smaller waists and wider hips than typical humans by far; the average waist-to-hip ratio of a comic book woman was smaller than the minimum waist-to-hip ratio of real women in the U.S. Heroine costumes further accentuate this already extreme curve by use of small belts or sashes, lines, and color changes. Costumes are either skintight or show skin (or both), with cutouts on the arms, thighs, midriff, and in particular, on the chest to show cleavage. The irony of battle uniforms that serve no protective purpose has been pointed out many times in cultural studies.28

Another feminine feature that plays a role in fashion is leg length. Various artistic depictions of the human body throughout history show that while the ideal leg length in women has increased over time, the preference for male leg length has not shifted. This increase appears to emerge during the Renaissance, which may be due to increases in food security and health during that time. As with many physical preferences in humans, leg length can be an indicator of health, particularly in cases of malnutrition or illness during development. This is another important reminder that preferences are shaped by resources, and consistently shift toward features that display status. What is the ideal leg length? One study found that if a woman’s height was 170 cm (5 foot 7 inches), the majority favored a leg length that was 6 cm (2.36 inches) longer, a difference that corresponds to the average height of high-heeled shoes.29 You can probably see where this is going: Sexual attractiveness ratings of legs correlate with perceived leg length, and legs are perceived as longer with high-heeled shoes. It should come as no surprise that women may accentuate or elongate their legs with high heels.

Photo by Ham Kris / Unsplash

High heeled shoes were not originally the domain of women, as they are thought to have originated in Western Asia prior to the 16th century in tandem with male military dress and equestrianism. The trend spread to Europe, with both sexes wearing heightened heels by the mid-17th century.30 They have remained present in men’s fashion in the form of shoes for rockstars and entertainers (e.g., Elton John), and boots worn by cowboys and motorcyclists. However, these heels are either short or hidden as lifts to make the men appear taller. By the 18th century, high heels became worn primarily by women, particularly as societies redefined fashion as frivolous and feminine.

As one might expect, high heels do more than elongate legs and increase height. High heels change the shape of the body and how it moves. Women wearing heels increase their lumbar curvature and exaggerate their hip rotation, breasts, and buttocks, making their body curvier. As supermodel Veronica Webb put it, “Heels put your ass on a pedestal.” When women walk in heels, they must take smaller steps, utilize greater pelvic rotation, and have greater pelvic tilt. All of these changes result in greater attractiveness ratings. Wearing high heels also denotes status—high heel shoes are typically more expensive than flat shoes, and women who wear them sustain serious damage if they have occupations that require a lot of labor. Therefore, women who wear heels appear to be in positions where they do less labor and have more resources. Research has asked this question directly, and both men and women view women in high heels as being of higher status than women wearing flat shoes.31

Fashion can also signify membership in powerful groups, such as the government, the military, or nobility.

At this point, it’s hardly surprising to learn that, compared to actual humans, comic book women are depicted with longer legs that align with peak preferences for leg length in several cultures, while men are shown with legs of average length. Women are also far more often drawn in heels or on tiptoe, regardless of context. Women are even drawn on tiptoe when barefoot, in costume stocking feet, and even when wearing other types of shoes or boots. This further elongates their already longer legs.32

Fashion as Status Signaling

Social status, as previously mentioned in terms of traits valued by the opposite sex, is also often displayed through fashion in ways relevant to within-sex status signaling, particularly when it comes to accessories. Men making fashion choices that indicate masculinity and dominance include preferences for expensive cars and watches—aspects of luxury consumption.33 Women not only emphasize their own beauty but also carry bags, for example, that are brand conscious, conveying information about their wealth and perhaps their preferences for specific causes, as in the popularity of animal welfare friendly high-end brands such as Stella McCartney.

Unlike high-end cars, however, which signal status to possible mates as well as status competitors, men are largely unaware of the signals sent from women to other women by such accessories. Women are highly attuned to brands and costs of women’s handbags, while most men do not seem to recognize the signaling value.34 While luxury products can boost self-esteem, express identity, and signal status, men tend to use conspicuous luxury products to attract mates, while women may use such products to deter female rivals. Some studies have shown that activating mate guarding motives prompts women to seek and display lavish possessions, such as clothes, handbags, and jewelry, and that women use pricey possessions to signal that their romantic partner is especially devoted to them.35

Fashion can also signify membership in powerful groups, such as the government, the military, or nobility. It can also signify the person’s role in society in other ways, for example, whether someone is married, engaged, or betrothed (by their own volition or by family). There are several changes in fashion that are specific to the various events surrounding a wedding, each with its own cultural differences and symbolism, and far too many to review here.36 Several researchers have explored the prominence and the symbolic value of a bride’s traditional dress in different societies.37 However, these signifiers are not just specific to the wedding rituals; what these women wear as wives (and widows) is culturally dictated for the rest of their lives.

These types of salient markers of female marital status are present in a number of societies. For example, not only are Latvian brides no longer allowed to wear a crown, but they may be given an apron and other displays (such as housekeeping tools) that indicate that they are now wives. In other cultures, girls will wear veils from puberty to their wedding day, and the removal of the veil is an obvious display of the change in status. Some cultures symbolically throw away the bride’s old clothes, as she is no longer that person; she is now the wife of her husband. In Turkey, married Pomak women cut locks of hair on either side of their head, and their clothing is much simpler in style than the highly decorated daily clothing of unmarried Pomak women. However, wives do wear more expensive necklaces—gold or pearls rather than beads.38 Notice that this is not only a signal of marital status, but also a signal of the groom’s wealth.

An evolutionary perspective suggests … people who choose to tattoo and pierce their bodies are doing so … because it serves as an advertisement or signal of their genetic quality.

Meanwhile, for men, the vast majority of cultures possess only one marker for married men—a wedding ring—which is also expected of women. Why are there more visible markers of marital status for women than for men? This seems likely to be a product of the elevated sexual jealousy and resulting proprietariness employed by men to prevent cuckoldry—what evolutionary psychologists call mate guarding. Salient markers of marital status for women show other men that she is attached to, or the property of, her husband. If the term “property” seems like an exaggeration, cultures have been documented to have rituals specifically for the purpose of transferring ownership of the bride from her parents to her husband, with the accompanying changes in appearance to declare that transfer to the public.39

Tattoos as Signals of Mate Quality, Social Status, and Group Membership

Body modifications, such as tattoos and piercings, have become increasingly prevalent in recent years in Western culture, with rates in the United States approaching 25 percent.40 Historically, tattooing and piercing were frequently used as an indicator of social status41 or group membership, for example, among criminals, gang members, sailors, and soldiers. While this corresponds with all of the other types of adornment we have reviewed, other researchers have suggested that these explanations don’t fully illuminate why individuals should engage in such costly and painful behavior when other methods of affiliation, such as team colors, clothing, or jewelry are less of a health risk. Tattoos and piercings are not only painful but entail health risks, including infections and disease transmission, such as hepatitis and HIV.42 One could suggest that the permanence of body modifications is a marker of commitment or significance, but an evolutionary perspective suggests an additional level of explanation: that people who choose to tattoo and pierce their bodies are doing so not only to show their bravery and toughness, but also because it serves as an advertisement or signal of their genetic quality. Good genetic quality and immunocompetence may be signaled by the presence and appearance of tattoos and piercings in much the same way as ornamentation, much as the peacock’s tail (in its size and symmetry), serves as a signal of male health and genetic quality.43

Photo by benjamin lehman / Unsplash

Even with tattoos, the same areas of the body are accentuated as we see in clothing.44 Researchers have reported sex differences in the placement of tattoos such that their respective secondary sexual characteristics were highlighted, with males concentrating on their upper bodies drawing attention to the shoulder-to-hip ratio. Females had more abdominal and backside tattoos, drawing attention to the waist-to-hip ratio. The emphasis seems to be on areas highlighting fertility in females and physical strength in males, essential features of physical attractiveness.45 In fact, female body modification in the abdominal region was most common in geographic regions with higher pathogen load, again suggesting that such practices may serve to signal physical and reproductive health.46 Recent work has also indicated social norms influence how tattoos affect perceptions of beauty such that younger people and ones who themselves are tattooed see them as enhancing attractiveness.47

Tattoos and piercings are not only painful but entail health risks, including infections and disease transmission, such as hepatitis and HIV.

Studies on humans and nonhuman animals have indicated that low fluctuating asymmetry (that is, greater overall symmetry in body parts) is related to developmental stability and is a likely indicator of genetic quality.48 Fluctuating asymmetry (FA), which is defined as deviation from perfect bilateral symmetry, is thought to reflect an organism’s relative inability to maintain stable morphological development in the face of environmental and genetic stressors. One study found49 FA to be lower (that is, the symmetry was greater) in those with tattoos or piercings. This effect was much stronger in males than in females, suggesting that those with greater developmental stability were able to tolerate the costs of tattoos or piercings, and that these serve as an honest signal of biological quality, at least in the men in this study.50 Researchers have also tested the “human canvas hypothesis,” which suggests that tattooing and piercing are hard to fake advertisements of fitness or social affiliations and the “upping the ante hypothesis,” which suggests tattooing is a costly honest signal of good genes in that injury to the body can demonstrate how well it heals. In short, tattoos and piercings not only display a group affiliation, but also that the owner possesses higher genetic quality and health, and these tattoos are placed on areas that accentuate “sexy” body parts. Thus, we have come full circle with humans: Just as other species like peacocks, people show off ornamentation to display their quality as mates and access to resources. Even taking into account cultural differences and generational shifts, the primary message remains.

Social Factors in Human Ornamentation

In addition to all of the evidence we have presented here, ornamentation is not just about mating or even signaling social status. Humans also signal group membership or allegiance through fashion. Modern sports fans show their allegiance to their sports teams by various shirts, hats, and other types of clothing—think the “cheese head” hats worn by Green Bay Packers fans at the team’s NFL home games. Fans of various musical performers, from Kid Rock to Taylor Swift, display their loyalty with concert shirts and other apparel. Typically, they also feel an automatic sense of connection when they encounter others sporting similar items. As discussed, tattoos can be seen as signals of genetic quality or health, and over the last twenty or so years tattoos have also increasingly become seen as statements of individuality. And yet, many serious sports fans, for example, have similar tattoos representing their favorite teams. Marvel fans sport Iron Man and Captain America illustrations on their skin, while fans of the television show Supernatural have the anti-possession symbol from the show tattooed on their torso. It may be that in many populations with weak social and family connections, individuals are seeking connection, and adornment is one way of indicating participation in a community or group. You can also see this in terms of political allegiance and the proliferation of Harris-Waltz and MAGA-MAHA merchandise during the 2024 election cycle in the United States.

While it is clear that an adaptationist approach to ornamentation can explain many aspects of fashion related to signaling social status (whether honest or not), group membership, or mate quality, much research remains to be done, including more work on what aspects are cross-culturally consistent and that are constrained more by unique cultural aspects or the local ecology. Not everything is the product of an adaptation; some aspects of fashion that seem less predictable or may be less enduring are unlikely to be explained by ornamentation and signaling theory because they are not rooted in mating or social motives. That being said, many fashion choices, including our own (for better or worse) make a lot of sense in the light of evolutionary processes. For all the small shifts from generation to generation and across cultures, the main themes remain the same. As Rachel Zoe noted: “Style is a way to say who you are without having to speak.”

What do your fashion choices have to say?

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