Category: human behavior

Beauty is in the (evolved) eye of the beholder

May 18, 2026 • 9:45 am

Right now I’m reading Steve Stewart-Williams’s new book: A Billion Years of Sex Differences: How Evolution Shaped the Minds of Men and Women. It is neither a pure blank-slate social-constructivist book nor a hereditarian, genetic-deterministic book, but takes an evidence-based middle ground, asking to what extent behaviors and mindset are molded by evolution and to what extent social conditioning plays a role.  I won’t give a take on the book as I’m not yet finished, but it does make many arguments I’m familiar with.  One of these is the familiar and well-documented claim that, based on different degrees of parental investment, men concentrate more than women on beauty when looking for a mate, while women are less interested in appearance than are men but more interested in paternal behavior, status, and wealth of a prospective mate. These are not absolute differences, of course: many men want women who will invest a lot in their offspring (we are, after all, generally monogamous), and many women want men who are pleasing to the eye. This is a difference in average preferences, not absolute ones characterizing all individuals.

Although some of this average sex difference in behavior may reflect social conditioning, its evolutionary background is likely based in part on the differential investment between the sexes in offspring: although many societies are polyandrous and monogamous, on average males still have a potentially larger number of offspring than do females. This appears to be true in many societies, as well as in our closest relatives, the apes and in most species of animals. Women, who by virtue of their reproduction (as well as by both the evolutionary and social impetus to do most of the childcare) need fathers who will do their share of parental duties and provide for the offspring.  And of course men do share some of those duties, but are also more interested in casual sex and adultery—a way to spread more of their genes when they don’t invest as much in offspring.

If you want the evidence for this, read Stewart-Williams’s book or the references he cites.

Why am I pondering this? Because when I went to the library the other day, I caught a glimpse of myself in the entry door and thought, “Geez, look at that ugly old man!”  Whatever attractive physical features I once had—and I was never close to being a Robert Redford—have vanished, carried away by time’s wingéd chariot.  Women, too, worry about ageing, and are even more concerned about it because of a key difference between men and women: as women get older and become unable to reproduce, they become less desirable faster than do men.  A man can have offspring even in his eighties, while in their early fifties most women hit menopause, which means no more kids. Since men have largely evolved to be physically attracted to women who can give them children, women try harder than do men to retain the signs of youth: hair color, plastic surgery, botox, and the like. On average, they try harder to retain physical attractiveness because it is that rather than status that is a dominant way of attracting partners—and most people want a partner.

Which brings up a tangential point: what about gay men and women?  I don’t know their preferences but it would be interesting to study (and I’m sure people have) whether men attracted to other men for lasting partnerships are less concerned with looks than are women attracted to other women for partnerships.

Back to the point, which is this. It is my theory, which is mine (and likely many other people’s) that there is really no objective difference in physical attractiveness with age, in either men or women.  Old men and women look different from their younger selves (I now refrain from looking in mirrors), but the beauty associated with youth and the loss in attractiveness associated with age are not anything objective (beauty never is, of course).  We are simply evolved to think that those features associated with having more offspring on us are more “beautiful”, as those mindsets are the ones promoted by natural selection. This explains why women are more concerned with the physical ravages of time then are men, for their physical attractiveness to the other sex wanes faster with time. I’ve often heard older actresses say that by the time they hit forty, Hollywood no longer wants them, while that doesn’t happen so much with male actors.  Why is this difference retained past the age of reproduction in women? I suppose it’s because it’s largely innate and most women didn’t live past menopause during most of our evolution.

Thus beauty is in the eye of the beholder: it is subjective, like all standards of beauty, but the subjectivity is molded in certain directions by natural selection.

I am not, of course, saying that this is good—only that much of it is natural. I do not want to commit the naturalistic fallacy here, but simply consider what aspects of our minds and behaviors might be based on genes, to what extent, and whether those evolutionary bits have been molded by natural selection.

This parallels a point I’ve made before: other aspects of our senses, like tastes, are clearly molded by natural selection.  I have said, for example, that to a vulture rotten meat tastes as good as an ice-cream sundae does to us.  Animals have evolved to search for food that tastes good because, over time, our senses evolve to find the food we need to grow and reproduce to be tasty. In other words, natural selextion has molded our taste buds and our brains so we prefer what is nutritious and fosters reproduction.  This can be hijacked: we now eat too many fats and sweets because those substances were desirable to our ancestors as they were rare but promoted reproduction.  Now they no longer do so because of the surfeit of “bad” food on tap.  But our taste buds haven’t yet caught up to our health.

Why do feces and vomit repel us, smelling foul? It’s very likely that these substances were evolutionarily associated with the spread of disease, and so we evolved smell-detectors that find them repugnant. After all, dung beetles love the odor of feces!

I’ll draw one more parallel here. Anybody who thinks about it seriously must admit that male orgasms, intricate and immensely pleasurable physiological mechanisms associated with ejaculation, have evolved as a way of promoting reproduction (the evolutionary basis of female orgasms is more speculative, but there is no shortage of adaptive hypotheses).  Orgasms are a way of getting men to produce offspring, just as sweetness is a way of getting us to eat sugar. And, like eating too many sweets, orgasms can be hijacked—severed from their reproductive function by condoms, chemicals, or medication. Organizations like the Catholic Church have tried mightily to try to reconnect sex and reproduction, but it is largely in vain.

I have undoubtedly written this too fast, as I just had some thoughts and wanted to get them down on paper before I forget them. I’ve considered that I’m trying to dispel my idea that I’m unattractive, and in so doing thought about physical attraction in general. And yes, I’m also reading Stewart-Williams’s book, which considers in detail this and other aspects of human (and animal) mentation and behavior.

Once you get an evolutionary mindset, all sorts of behaviors now become more interesting. That doesn’t mean we should make up adaptive stories and consider those stories to be true, but neither should we ignore possible evolutionary explanations. To explain the evolutionary basis of human behaviors and minds will be hard, as most of them evolved in the unrecoverable distant past—in our ancestors.  But some of the explanations are testable, and here I must stop.

Readers’ wildlife photos

February 27, 2026 • 8:15 am

Doug Hayes of Richmond, Virginia, has sent some dance photos (H. sapiens in action). Doug’s captions are indented, and you can enlarge his photos by clicking on them.

The most recent photoshoot with Starr Foster Dance. The company is currently rehearsing new choreography for their upcoming show, “Shouting Distance” which will premiere April 9th – 12th at the Firehouse Theater. Once again, my friend Starrene Foster asked the dancers to perform several leaps, some derived from the choreography that will be performed during the show.

The core company members (L to R) Sarah Carrington, Roya Baker-Vahdani, Madison Ernstes, Molly Huey, Shannon Comerford:

A basic group jump. While it looks simple, it took a couple of tries to get everyone off the ground at the same time:

Roya, Molly and Shannon strike a dramatic pose:

Shannon, Roya and Molly:

Sarah and Madison defy gravity:

Madison makes it look effortless:

Another incredible leap by Madison:

Roya sitting on air:

An aerial split by Shannon:

Molly gives a new meaning to “high kick”:

Floating through air with the greatest of ease:

Molly does an easy leap:

Starr had an idea to photograph Shannon looking into a hallway. The door was featureless, painted dark gray and the floor where Shannon is standing was the same light gray as the hallway floor and walls. Starr asked if I could make the door look like an apartment door and make the floor hardwood. Rather than spend several hours looking for proper flooring and doors, then doing the tedious compositing in Photoshop, I turned to AI. Google’s Gemini AI has a photo editing feature called “Nano Banana” – I’m not making this up. Nano Banana is incorporated into the latest version of Adobe Photoshop, but one has to pay to use it when editing high resolution images. By logging into Gemini AI directly, Nano Banana is free to use unless you need to use some of the more advanced editing features. It only took two prompts to get the result I wanted and only about three minutes to get the final image. There is a second image featuring Shannon at the door, but the AI made two different-looking doors, and the hardwood floor was different in each. It took about three prompts to get Nano Banana to understand that the doors and floors should match, but it finally “understood” and gave me what I wanted. I have been using AI for the past few months to restore old faded and damaged photos. The results have been amazing and saved hours of tedious retouch work in Photoshop. While AI has gotten better, it still requires human input to correct some errors. In the photo of Shannon, the AI put a doorknob and deadbolt on the right side of the door. Sometimes I wonder if the computers are just screwing with us to see if we notice.

Photo information: Sony A1 II mirrorless camera body, Sony GM 24-70 zoom lens, Westcott 400 electronic flash units, Westcott wireless flash controller. Photos edited with Adobe Photoshop and Google’s Gemini AI. The electronic flash units have a “freeze” mode which fires the flash in sync with the camera which is in burst mode – about 15 frames per second or the equivalent of a 1/10,000 of a second shutter speed. ISO 1250.

Earliest evidence for humans making fire: 400,000 years ago

December 14, 2025 • 10:50 am

Although, as the authors of this new Nature article note, there is some evidence of human fire use in Africa going back 1.6 million years, they don’t consider the evidence definitive because “the evidence for early fire use is limited and often ambiguous, typically consisting of associations between heated materials and stone tools.”   They also note that there is more direct evidence but it’s quite recent:

. . . . direct evidence of fire-making by pre-Homo sapiens hominins has, until recently, been limited to a few dozen handaxes from several French Neanderthal sites, dating to around 50 ka, that exhibit use-wear traces consistent with experimental tools that were struck with pyrite to create sparks.

In this paper the authors investigate a site in Sussex, dated about 400,000 years ago, that has several lines of evidence suggesting regular use of fire, and controlled use, since there were materials like pyrite that could be used to strike sparks.  Note that the paper considers this the earliest evidence for making fire, not simply using fire.  The authors consider their work to provide pretty definitive evidence of fire-making and fire use in H. sapiens. (Note that we are the only species to use fire.)

Click the headline below to read the article, or you can find the pdf here.

The evidence came from an unused clay pit in the Breckland area of Suffolk, with deposits of clay and silt as well as human artifacts like hand axes. The evidence for persistent fire use at this site (the authors suggest at least two groups of humans, and comes from five observations and experiments. I’ve put them below under the letters.

a.) Red clayey silt (RCS) in the layers, silt that seems to have required prolonged heating to form. Here’s what it looks like.  The unexcavated section is in the top photo, and the bottom is the partly excavated area which is an enlargement of the box in (a). I’ve put a red arrow in (a) at the RCS layer thought to reflect heating of the sediments by the presence of “hearths”: areas where cooking or other uses of fire regularly took place. The layer is more obvious in the bottom photo:

The authors say that the red layer reflecs heating or sediments containing iron:

The reddening is attributable to the formation of haematite—a mineral produced through heating of iron-rich sediments. Its distribution is homogeneous and not associated with particular microfacies or voids, indicating that it was preserved in situ.

b.) Experimental heating of the non-red sediments. The authors showed that the magnetic properties of material in the RCS differ markedly from unheated “control” samples of material taken from the lower layer (“YBCS” in second photo above). But by heating the YCBS layer extensively, it assumed some of the magnetic properties of the RCS, suggesting that the RCS involved heating of clays by fire. As they say (bolding is mine):

Three samples were taken from the RCS and two from the adjacent YBCS, which served as unheated control samples. The magnetic properties of the RCS (Supplementary Information, section 5) differ markedly from those of the unheated control samples, exhibiting elevated levels of secondary fine-grained ferrimagnetic and superparamagnetic minerals of pyrogenic origin, unlike the control samples. To assess whether these characteristics could result from heating, a series of experiments of single and multiple heating events of varying durations, was conducted. The aim was to determine whether the reddening could have arisen from one or multiple heating events, as repeated, localized burning is more typical of human than natural fire events (S.H. et al. manuscript in preparation).

The closest experimental analogue in terms of the minerology and grain size distribution, was observed after 12 or more heating events, each lasting 4 h at temperatures of 400 °C or 600 °C. Although the archaeological samples exhibit substantially lower magnetic susceptibility values, this may result from post-depositional mixing with unheated illuviated clay. Overall, the experiments indicate that the magnetic properties of the RCS result from an indeterminate number of short-duration heating events, consistent with repeated human use (Fig. 3).

Note that prolonged heating—nearly 50 hours of heating at 400-600 degrees C, was required to approximate the magnetic properties of the presumed fire-use layer.  This suggests also that the heating did not reflect wildfires, but repeated, localized, and intentional burning.

c.) Infrared spectroscopy of heated control samples changed in infrared absorbtion spectra of the “control” samples, making it closer to that of the presumed hearth layer of RCS.

d.)  The area contained four handaxes that showed marks of heat-shattering.  Here is a picture of a handaxe with “closeup of fractured surface caused by fire.”:

Presumably this is based on experiments using recently made handaxes, with some treated by fire and then compared to unheated controls.

e.) Fragments of pyrite were found in the heated area, and pyrite  is used with flint to produce fire (before that, people presumably had to get fire from lightning burns and somehow preserve it). Moreover, pyrite was not found in this locality; the nearest accessible mineral was about 15 km away, suggesting that people picked it up and brought it to the site to strike against flint (flint was also found in the area). As the authors note:

The occurrence of pyrite at Barnham warrants further consideration. Pyrite is a naturally occurring iron sulfide mineral that can be struck against flint to produce sparks to ignite tinder. Its use for this purpose is well documented in ethnographic accounts worldwide. Pyrite has been recovered from European archaeological sites dating from the late Middle Palaeolithic to the historic periods, occasionally bearing wear traces consistent with use for fire-making and, in some cases, found in association with flint striking tools.

Here are some fragments of pyrite; caption is from paper:

(from paper): b, Fragment of pyrite found on the surface of palaeosol in Area IV(6). c, Fragment of pyrite from palaeosol in Area VI, found in association with concentrations of heated flint.

e.) The heated sites were located in areas amenable to prolonged fire use. This is weak evidence, but I present it nevertheless. From the authors:

Notably, all three sites occupy marginal locations, away from the main river valleys and associated with small ponds or springs. In the absence of caves, these locations probably provided safer, more sheltered environments for domestic activities. Taken together, these findings present a strong case for controlled fire use across the Breckland region during MIS 11.

The upshot:  We often forget that any meat eaten by people before the advent of cooking would have to be raw, and raw meat is tough and, at least to us, somewhat unpalatable. (I do like a very rare steak, as well as steak tartare, though.) But our ancestors didn’t grind up meat, though they may have pounded it to make a kind of raw Pleistocene schnitzel. By making meat more palatable, cooking would promote eating more of it, and that itself could change the selective pressures on humans, giving them the extra nutrients they’d need if they were to evolve big brains (brains use a lot of energy!).  This is one (disputed) theory for a rapid increase of human brain size that lasted between 800,000 and 200,000 years ago, though brain size was also getting bigger, albeit at a slower pace, before then. Cooking has also been suggested to have changed human social behavior (and perhaps social evolution), with pair bonding and mutual aid increasing as a way to gather, store, and protect food that needed to be cooked. And more complex social behavior could itself have promoted the evolution of larger brains to figure out how to regulate and get along in your small social group.

These theories, while suggestive, really should be downgraded to “hypotheses,” since there isn’t much evidence to support them—only correlation and speculation. However, they are interesting to contemplate, even if we never can get strong evidence for them.  At the end of the paper, the authors do seem to sign onto some of these, but not strongly.

The kernel of this paper is the several lines of evidence that do, to my mind, support the idea that humans were making and using fire at least 400,000 year ago.  Here’s what the authors say about the advantages, evolutionary and otherwise, of controlling fire:

The advantage of fire-making lies in its predictability, which facilitated better planning of seasonal routines, the establishment of domestic sites in preferred locations and increased structuring of the landscape through enculturation. Year-round access to fire would have provided an enhanced communal focus, potentially as a catalyst for social evolution. It would have enabled routine cooking, could have expanded the consumption of roots, tubers and meat, reduced energy required for digestion and increased protein intake. These dietary improvements may have contributed to increase in brain size, enhanced cognition and the development of more complex social relationships, as articulated in the Social Brain Hypothesis. Moreover, controlled fire use was instrumental in advancing other technologies, such as the production of glues for hafting. The widespread appearance of Levallois points from Africa to Eurasia by MIS 7 (243–191 ka), often interpreted as spear-tips, provides strong evidence of effective hafting. This interpretation is supported by use-wear evidence and the identification of heat-synthesized birch bark tar as a stone tool adhesive.

Same-sex sexual behavior documented in many mammals: does it mean that similar behavior in humans is “natural”?

April 29, 2025 • 9:45 am

The Naturalistic Fallacy, which most of you surely know, it the erroneous equation of what does exist with what should exist.  Discussed extensively by Hume, it is the false equation of “is” with “ought”. In biology, it takes the form of observing some behavior in animals that is similar to a behavior in humans, and then justifying or saying the human behavior “natural”  or “good” because we see it in other species.

But this is a bad argument, for it cuts both ways. After all, animals show a lot of behavior that would be considered reprehensible or even immoral in humans.  In fact, Joan Roughgarden wrote a book, Evolution’s Rainbow, which describes sex and gender diversity in nature as an explicit way of justifying similar behaviors in humans as good—because they are natural. I reviewed the book for TLS and wrote this bit (review no longer online but I can send a copy).

Coyne, J. A.  2004.  Charm schools. (Review of Evolution’s Rainbow, by Joan Roughgarden). Times Literary Supplement, London. July 30, 2004 (No. 5287), p. 5.

But regardless of the truth of Darwin’s theory, should we consult nature to determine which of our behaviours are to be considered normal or moral? Homosexuality may indeed occur in species other than our own, but so do infanticide, robbery and extra-pair copulation.  If the gay cause is somehow boosted by parallels from nature, then so are the causes of child-killers, thieves and adulterers. And given the cultural milieu in which human sexuality and gender are expressed, how closely can we compare ourselves to other species? In what sense does a fish who changes sex resemble a transgendered person? The fish presumably experiences neither distressing feelings about inhabiting the wrong body, nor ostracism by other fish. In some baboons, the only males who show homosexual behaviour are those denied access to females by more dominant males. How can this possibly be equated to human homosexuality?

The step from “natural” to “ethical” is even riskier. As the philosopher G. E. Moore argued, identifying what is good or right by using any natural property is committing the “naturalistic fallacy”: there is no valid way to deduce “ought” from “is”. If no animals showed homosexual behaviour, would discrimination against gay humans be more justified? Certainly not. Roughgarden’s philosophical strategy is as problematic as her biological one.

Now a 2022 paper in Nature Communications had the potential to demonstrate the same fallacy, but fortunately the authors went to great lengths to avoid that  The same, however, is not true of a new take on this paper in a new article in ZME Science, which gave a précis of the paper and stepped on the Fallacy’s tail.

First the Nature paper itself, which you can access by clicking on the article below, or by reading the pdf here.

It’s a good paper on the evolution and phylogeny of “same-sex sexual behavior” in mammals, which they define as “transient courtship or mating interactions between members of the same sex“.  

Note that it’s “transient,” which explicitly excludes homosexuality, most notably in humans, which is a persistent sexual attraction to members of one’s own biological sex.  This form of transient sexual interaction is surprisingly common—a conservative estimate is 4% of all animal species, and, as the authors say, [includes] “all main groups from invertebrates such as insects, spiders, echinoderms, and nematodes, to vertebrates such as fish, amphibians, reptiles, birds, and mammals.”

Now there are two ways to explain a behavior that seems on its face maladaptive. Why would you engage in sexual behavior that doesn’t involve passing on your genes? One hypothesis is that it’s just a nonadaptive byproduct of other behaviors: a general drive to mate when the appropriate mates aren’t available, or simply mistaken identity.  But the authors investigate two hypotheses that it is adaptive, and give some tentative evidence for that.

First, the results:

  • The authors did a comprehensive survey of same-sex behavior (defined above) in 2546 species of mammals, and superimposed species with and without such behavior on their phylogenetic tree. The object was to see how many times the behavior evolved independently, and whether it was present in the common ancestor of a group (and thus could be passed along to its descendants). Here’s one of those phylogenies with the caption. (You needn’t worry about the details or summary, as I’ll give it below).
(from paper) Phylogenetic distribution of the presence of same-sex sexual behaviour in males and females in the subset III (see methods). The state of the mammalian ancestral nodes was assessed using maximum likelihood estimation (black: same-sex sexual behaviour displayed by females; yellow: same-sex sexual behaviour displayed by males; purple: same-sex sexual behaviour displayed by both sexes). The silhouettes of representative mammals (downloaded from http://www.phylopic.org) illustrate the main mammalian clades. They have a Public Domain license without copyright (http://creativecommons.org/licenses/by/3.0).

A summary:

  •  The behavior was reported in 261 mammalian species
  • Same-sex sexual behavior appears to be equally common in males and females, and the behavior in both sexes tends to be correlated across groups. That is, male and female same-sex behavior is more likely to both appear in the same species than if it either were distributed randomly among groups.
  • It was not possible tell, using phylogenetic analysis, whether same-sex behavior was likely to be a trait in the ancestor of all mammals, but was NOT likely to be a trait in the ancestor of all placental mammals.
  • The behavior seems to have evolved independently in many lineages, so same-sex sexual behavior seems to be a case of “convergent evolution.”
  • The behavior is correlated with whether or not a species is social. If it is social, there’s a significantly higher probability of same-sex sexual behavior. (Remember that this is a correlation and doesn’t imply that sociality prompts the evolution of such behavior. The behavior could simply result from iondividuals in social species being closer to other individuals than those in non-social species.)
  • The common ancestor of all primates does seem to have possessed same-sex sexual behavior.

The association of same-sex sexual behavior with sociality leads the authors to conclude that the behavior evolved by natural selection as a way to enforce inter-individual harmony required by sociality. They mention two such advantages:

1.) Same-sex sexual behavior is a way of creating and maintaining social bonds between individuals in a group; it’s a bonding mechanism.
2.) The behavior could also help prevent or resolve conflicts between members of a group, allowing a hierarchy to develop without injury of death to group members.

The authors mention that these effects have been demonstrated in some species like bottlenose dolphins and American bison, but I’m not familiar with this work, and such conclusions seem to me to be extraordinarily difficult to arrive at. However, I’ll take the authors’ word for it.

The authors are, to be sure, careful in their conclusions. First, they note that nonadaptive hypotheses, like “mistaken identity” could also contribute to the behavior.

Second, and the big one, they note that the behavior they studied is not the same as homosexual behavior like we find in humans.  They do add, however, that it humans do show same-sex sexual behavior in humans (I presume they’re referring to “bisexual” people who have sex with both males and females). From the paper:

However, same-sex sexual behaviour is operationally defined here as any temporary sexual contact between members of the same sex2. This behaviour should be distinguished from homosexuality as a more permanent same sex preference, as found in humans. For this reason, our findings cannot be used to infer the evolution of sexual orientation, identity, and preference or the prevalence of homosexuality as categories of sexual beings Nevertheless, even taking into account this cautionary note, by using phylogenetic inference, our study may provide a potential explanation on the evolutionary history of the occurrence of same-sex sexual behaviour in humans.

They may be right, but I think they should have added that even if same-sex sexual behavior was rare or nonexistent in mammals, its existence in humans is not made “ethical” or “natural” in our species. That would be an example of the naturalistic fallacy, and I emphasize that they do not commit it.  I’d would also emphasize, as I did above, that any sexual behavior between consenting human adults is not for us to judge, regardless of whether or not other species show it, and that such behaviors are fine so long as they’re legal. We don’t need to justify same-sex sexual behavior in humans by seeing it elsewhere in nature. But perhaps this stuff doesn’t belong in a scientific paper. But I want to emphasize it here, as I did in my review of Roughgarden’s book.

As I said, the authors don’t commit the naturalistic fallacy, but the new ZME Science paper below comes close to it. Click headline to read:

Up until the end, this article is okay, but then it can’t resist diving into our own species (bolding is mine).

However, the researchers distinguish between SSSB and sexual orientation. While SSSB involves occasional same-sex interactions, sexual orientation encompasses consistent patterns of attraction and identity, particularly prominent in humans.

While SSSB in animals supports the naturalness of such behaviors, human experiences of sexuality include layers of identity, culture, and personal meaning that go beyond biological explanations. Homosexuality in humans often involves stable sexual orientations and relationships, distinct from the transient or context-dependent SSSB observed in some animal species.

Ultimately, the widespread occurrence of SSSB in mammals, especially primates, strongly suggests that such behaviors are natural and adaptive. Normalizing same-sex behavior as a part of this spectrum aligns with both biological evidence and a broader understanding of human social and emotional complexity.

The last paragraph explicitly says that the results show that homosexuality (one of “such behaviors”) is “natural and adaptive”, as are all “same-sex behaviors” in humans.  The Nature paper says nothing of the sort.  The authors of the Nature paper explicitly exclude homosexuality as not a behavior they studied, but ZME Science lumps it in with other same-sex sexual behaviors, dwspite homosexuality being very different from SSSB.

Again, you do NOT need to justify same-sex sexual behavior, whether it be transient or permanent, by finding examples in the natural world. If we didn’t find any other species with homosexual behavior, would that make it wrong or bad in humans? Of course not! “Is” does not equal “ought,” and I’ll add the corollary that “not is” does not equal “not ought”. The Nature paper is valuable it looking at the evolution of a behavior and testing hypotheses about its adaptiveness, but of course adaptiveness or evolution has nothing to do with the ethics of behaviors between consenting human adults.

Readers’ wildlife photos

January 31, 2025 • 8:15 am

Today’s wildlife comprises primates: Homo sapiens engaging in what they call “sport,” and the photos from Doug Hayes of Richmond, Virginia. Doug, you may recall, has sent photos of dancers, and here he photographs sledders.  His captions are indented, and you can enlarge his photos by clicking on them.

A batch of human wildlife photos! The recent snow here in Richmond, Virginia brought out the neighbors of all ages to Forest Hill Park for a day of sledding and snowboarding. It was a sunny Saturday morning with temperatures in the low 40s F. A good time was had by all!

Why just sled when you can levitate?:

Wipeout!:

A snowboarder getting in on the fun:

Some of the sledders built a snow ramp at the end of the run for that extra boost:

Powder:

Traffic jam at the bottom of the hill:

Nothing says cool like sliding downhill at breakneck speed, nonchalantly smoking a pipe and holding a cup of coffee!:

Double wipeout!:

Not scared!:

Flying off the ramp:

Should have kept the glasses on!:

The more, the merrier!:

New paper doubts estimates of how often women hunted in hunter-gatherer societies

March 4, 2024 • 11:45 am

Twitter is good for some stuff, and the best are 1.) cat and duck pictures and 2.) finding out about new science papers, often before they’re published.  Remember the conflict last year about the frequency of women hunting in hunter-gatherer societies (see my posts here). The original paper in PLoS One by Anderson et al. claimed that not only did women engage in hunting in these societies more often than we thought (79% of a sample of such societies showed women participated in hunting), but they also hunted big game more often than we thought. The paper was meant to dispel “The myth of man the hunter” (part of its title) and was clearly meant to promulgate some kind of sex equity in hunting, though a separation of gender roles doesn’t demean women.

The paper was criticized a lot for using biased data (see the set of links above), and the bias, it seemed, either intentionally or fortuitously dispelled what was seen as a misogynistic view: men hunted and women stayed home to grow food, mend things, and take care of the children. It was certainly treated in the popular literature as a blow to both misogyny and the view that sexes had “roles” consistent across societies.

Then I saw this tweet by Alexander, who does cognitive and behavioral neuroscience, and it pointed to a not-yet-published paper on BiorΧiv whose claims, when you read it blow Anderson et al. out of the water.  Now remember, it isn’t yet peer-reviewed, but its accusations—there are 15 authors—are devastating. If it’s true, Anderson et al. are guilty of incredibly sloppy scholarship.  And also perhaps ideologically-biased scholarship, since every error or miscoding they used biased the results in favor or women hunting more frequently or taking larger game.

First, the tweet.

Click below to see the pdf of the paper:

Venkataraman et al. find that the paper commits every error that it was possible to make in the paper: leaving out important papers, including irrelevant papers, using duplicate papers, mis-coding their societies, getting the wrong values for “big” versus “small” game, and many others.

Rather than go through the mistakes, I’m just going to show you the last three paragraphs of Venkataraman et al., which summarize the errors they found in Anderson et al.  Read it. If they’re even close to being right, PLoS ONE should retract the Anderson et al. paper.

We have outlined several conceptual and methodological concerns with Anderson et al.’s (2023) analysis. Specifically, Anderson et al.’s (2023) analysis is not reproducible because their sampling criteria are not clear and 35% of the societies in their sample do not come from DPLACE, the database they claim was the source of all the societies in their sample. Moreover, these 35% were not included in their analysis, and authoritative sources on hunting in the societies in the Anderson et al. (2023) sample were not consulted. Additionally, there are at least 18 societies in D-PLACE with information on hunting that were inexplicably omitted from their analysis, none of which provide evidence for women hunters.

Finally, there were numerous coding errors. Of the 50/63 (79%) societies that Anderson et al. (2023) coded as ones in which women hunt, for example, our re-coding found that women rarely or never hunted in 16/50 (32%); we also found 2 false negatives. Overall, we found evidence in the biased Anderson et al. (2023) data set that in 35/63 (56%) societies, women hunt “Sometimes” or “Frequently”. Moreover, compared to the 17/63 (27%) societies in which women were claimed to hunt big game regularly, our re-coding found that this was true for only 9/63 (14%). A precise estimate of women’s hunting in foraging societies must await a future thorough and unbiased analysis of the ethnographic record (see, e.g., [10]), but it is certainly far less than the Anderson et al. (2023) estimate and is very unlikely to overturn the current view that it is relatively uncommon.

The fundamental issue is that women’s hunting is not a binary phenomenon, and treating it as such, especially with a very low threshold for classifying a society as one in which women hunt, obfuscates gendered divisions of labor within groups. Anthropologists have long recognized that the nature of cooperation in foragers is complex and multi-faceted, and women’s and men’s subsistence activities play important and often complementary roles. Moreover, women’s hunting has been studied for decades, and anthropologists have a good understanding of when and why it occurs. Yet, to focus on hunting at the expense of other critical activities – from gathering and food processing, to water and firewood collection, to the manufacture of clothing, shelters, and tools, to pregnancy, childbirth, nursing, childcare, and healthcare, to education, marriages, rituals, politics, and conflict resolution – is to downplay the complexity, and thereby the importance of women’s roles in the foraging lifeway. To build a more complete picture of the lives of foragers in the present and the past, it serves no one to misrepresent reality. In correcting the misapprehension that women do not hunt, we should not replace one myth with another

The truth is the truth, and, as Venkataraman et al. note repeatedly, the truth does not work to the detriment of women in these societies, who, with a frequent division of labor, work at least as hard as do the men.

h/t: cesar

The biology of quitting: when you should hold ’em and when you should fold ’em

April 20, 2023 • 12:30 pm

Someone called this Big Think piece to my attention because some quotes from me are in it. And they are, but that’s not the important part, which is the evolutionary biology of giving up, and I guess I’m the Expert Evolutionist in this take.  The piece is by Julia Keller, a prolific author and journalist who won a Pulitzer Prize for feature writing in 2004, and this is an excerpt from her new book  Quitting: A Life Strategy: The Myth of Perseverance and How the New Science of Giving Up Can Set You Free. which came out April 18.

Although I had some association with Julia when she wrote for the Chicago Tribune (I think she helped me get a free-speech op-ed published), I don’t remember even speaking to her on this topic, but it must have been quite a while back. At any rate, I certainly want to be set free from my maladaptive compulsions, which include persisting when I should give up, so I’ll be reading her book.

Click on the screenshot to read:

The science involved is largely evolutionary: it pays you to give up when you leave more offspring by quitting than by persisting. Or to couch it more accurately, genes that enable you to assess a situation (consciously or not) and give up at the right point—right before the relative reproductive gain from persisting turns into a relative loss compared to other gene forms affecting quitting—will come to dominate over the “nevertheless she persisted” genes.  Keller engages the reader by drawing at the outset a comparison between Simone Biles stopping her gymnastic performance in the 2021 Tokyo games, and, on the other hand, a honeybee deciding whether or not to sting a potential predator of the nest.

If the bee does sting, she invariably dies (her innards are ripped out with the sting), and can no longer protect the nest. But if that suicidal act drives away a potential predator, copies of the “sting now” gene are saved in all the other nest’s workers, who are her half sisters. (And of course they’re saved in her mother—the queen, the only female who can pass on her genes.) If a worker doesn’t sting, every copy of that gene might be lost if the nest is destroyed, for if the nest goes, so goes the queen, and every gene is lost.  On the other hand, a potential predator might not actually prey on a nest, so why give up your life if it has no result? You have to know when stinging is liable to pay off and when it isn’t.

Inexorably, natural selection will preserve genes that succeed in this reproductive calculus by promoting stinging at the right time and place—or, on the other hand refraining from stinging if it’s liable to have no effect on colony (ergo queen) survival.  And in fact, as you see below, honeybees, while they surely don’t consciously do this calculus, they behave as if they do, and they do it correctly.  Often natural selection favors animals making “decisions” that cannot be conscious, but have been molded by selection to look as if they were conscious. 

As for Simone Biles, well, you can read about her. Her decision was clearly a conscious one, but also bred in us by selection—selection to avoid damaging our bodies, which of course can severely limit our chance to pass on our genes. This is why we usually flee danger when there is nothing to gain by meeting it. (She did have something to gain—gold medals—which is why she’s like the bees.)

Why do young men street race their cars on the street, a dangerous practice? What do they have to gain? Well, risk-taking is particularly prevalent in postpubescent males compared to females, and I bet you can guess why.

I’ll first be a bit self aggrandizing and show how I’m quoted on evolution, and then get to the very cool bee story. It’s a short piece, and you might think of other “quitting vs. non quitting” behaviors of animals that could have evolved. (Hint: one involves cat domestication.)

“Perseverance, in a biological sense, doesn’t make sense unless it’s working.”

That’s Jerry Coyne, emeritus professor at the University of Chicago, one of the top evolutionary biologists of his generation. [JAC: a BIT overstated, but I appreciate it.] I’ve called Coyne to ask him about animals and quitting. I want to know why human beings tend to adhere to the Gospel of Grit—while other creatures on this magnificently diverse earth of ours follow a different strategy. Their lives are marked by purposeful halts, fortuitous side steps, canny retreats, nick‑of‑time recalculations, wily workarounds, and deliberate do‑overs, not to mention loops, pivots, and complete reversals.

Other animals, that is, quit on a regular basis. And they don’t obsess about it, either.

In the wild, Coyne points out, perseverance has no special status. Animals do what they do because it furthers their agenda: to last long enough to reproduce, ensuring the continuation of their genetic material.

We’re animals, too, of course. And despite all the complex wonders that human beings have created—from Audis to algebra, from hot-fudge sundaes to haiku, from suspension bridges to Bridgerton—at bottom our instincts are always goading us toward the same basic, no‑nonsense goal: to stick around so that we can pass along little copies of ourselves. [JAC: note how this is an individual-centric view rather than the correct gene-centric one, but it’s good enough.] It’s axiomatic: the best way to survive is to give up on whatever’s not contributing to survival. To waste as few resources as possible on the ineffective. “Human behavior has been molded to help us obtain a favorable outcome,” Coyne tells me. We go for what works. We’re biased toward results. Yet somewhere between the impulse to follow what strikes us as the most promising path—which means quitting an unpromising path—and the simple act of giving up, something often gets in the way. And that’s the mystery that intrigues me: When quitting is the right thing to do, why don’t we always do it?

Well, who ever said that every aspect of human behavior was molded by natural selection? Please don’t think that I was implying that it was, as we have a cultural veneer on top of the behaviors conditioned by our genes. In this piece Keller doesn’t get to the subject of why we don’t quit when we should. I’m sure that’s in the book.

Now the very cool bee story:

Justin O. Schmidt is a renowned entomologist and author of The Sting of the Wild, a nifty book about a nasty thing: stinging insects. Living creatures, he tells me, echoing Coyne, have two goals, and those goals are rock-bottom rudimentary: “To eat and not be eaten.” If something’s not working, an animal stops doing it—and with a notable absence of fuss or excuse-making. . . .

. . . For a honeybee, the drive to survive carries within it the commitment to make sure there will be more honeybees. And so she defends her colony with reckless abandon. When a honeybee stings a potential predator, she dies, because the sting eviscerates her. (Only the females sting.) Given those odds—a 100 percent mortality rate after stinging—what honeybee in her right mind would make the decision to sting if it didn’t bring some benefit?

That’s why, Schmidt explains to me from his lab in Tucson, sometimes she stands down. When a creature that may pose a threat approaches the colony, the honeybee might very well not sting. She chooses, in effect, to quit—to not take the next step and rush forward to defend the nest, at the cost of her life.

His experiments, the results of which he published in 2020 in Insectes Sociaux, an international scientific journal focusing on social insects such as bees, ants, and wasps, reveal that honeybees make a calculation on the fly, as it were. They decide if a predator is close enough to the colony to be a legitimate threat and, further, if the colony has enough reproductive potential at that point to warrant her ultimate sacrifice. If the moment meets those criteria—genuine peril (check), fertile colony (check)—the honeybees are fierce fighters, happy to perish for the greater good.

But if not… well, no. They don’t engage. “Bees must make life‑or‑death decisions based on risk-benefit evaluations,” Schmidt tells me. Like a gymnast facing a dizzyingly difficult maneuver that could prove to be lethal, they weigh the danger of their next move against what’s at stake, measuring the imminent peril against the chances of success and the potential reward. They calculate odds.

And if the ratio doesn’t make sense, they quit.

That’s a bit oversimplified, for the calculus is not only unconscious (I doubt bees can weigh threats this way), but the decision capability has been molded by competition over evolutionary time between different forms of genes with different propensities to sting or give up. Further, individual worker bees are sterile, and so what’s at stake is the number of gene copies in the nest as a whole—and especially in the queen. The asymmetrical relatedness between the queen, her workers, and their useless drone brothers (produced by unfertilized eggs) makes the calculus especially complicated.

On the other hand, explaining the gene calculus to lay readers is hard, and it might be better to read the seminal work on how this all operates: Dawkins’s The Selfish Gene. 

Here’s Schmidt’s short paper (click to read; if it’s paywalled, ask for a copy). He died just this February.