Dear Reader: So, a good friend recently asked me for my thoughts about a piece recently published in “Scientific American“: Males Aren’t Larger Than Females in Most Mammalian Species: A new study corrects a biased assumption promoted by Charles Darwin 150 years ago and repeated ever since.
As my analysis of this article goes deep into the science-weeds, I am publishing it at Temple of Mut today.
The piece was written by Rachel Nuwer, whose educational background is in environmental science and journalism. We’ll be returning to her background in a bit, but I would like to examine the article itself before I do.
Friends from Legal Insurrection may recall I refer to Scientific American as the Bud Light of scientific journals. That particular article stemmed from the magazine’s editor using an example of a bird that has 2 distinct genders based on 4 chromosomes to argue the avian’s existence supported “non-binary” gender identities. She was heavily critiqued for the example by an exceptional evolutionary biologist.
So, I took a deep breath and waded into this article…trying to keep an open mind that some legitimate science would be covered in “Males Aren’t Larger Than Females in Most Mammalian Species“.
Let’s start with the opening paragraphs:
“In The Descent of Man, Charles Darwin posits that in most species of mammals, males are larger than females. Although Darwin did not cite evidence to back up this claim, his view on sexual size dimorphism was readily accepted as fact, and it still dominates today.
“But Darwin, in this case, seems to have been wrong. An analysis of 429 mammalian species published in Nature Communications reveals that just 45 percent feature males that are larger than females. Nearly an equal number of species, 39 percent, have sexes that are about the same size. And in 16 percent of species, females are larger than males.“
True, English naturalist Charles Darwin studied and published at during the Victorian era. His seminal work, The Origin of Species, was written in an era when the modern approach to science and research into biology were being developed. And perhaps it is worthwhile to take a look at the data he collected and analyze it with fresh eyes.
By why? Is it for the love of science?
No…apparently it is an attempt to fight the patriarchy.
The next paragraph heads into the anti-Western/anti-Male territory that is sadly dominating current “scientific” thinking today:
“There’s been this really strong inertia toward the larger male narrative, but it was just based on Darwin’s hand-wavy statement, and the evidence doesn’t really support it,” says the study’s lead author Kaia Tombak, a postdoctoral evolutionary biologist at Purdue University. That this narrative has endured for so long “may reflect Western societal biases that tend to look at issues through a male lens.”
Perhaps the reason for not looking hard at the previous data collected wasn’t “strong inertia”, but that the relative size of males to females in a species is better able to be captured with the tools and equipment modern biologists have access to…thanks to progress made in Western technology.
Perhaps it is funding for project related to biology is directed at more urgent concerns (e.g., medicine) or more intriguing efforts (the origin of humankind).
However, I doubt that biological researchers in decades past decided that they were going to promote the patriarchy by fudging numbers related to male and female shrews.
“Western societal biases that tend to look at issues through a male lens” is the kind of victim-oriented- focus that drives too much of our scientific discourse today. Apparently, we are no longer allowed to look for knowledge for knowledge sake…but we have to support a social justice agenda while we obliterate an iconic work of Western science.
I will take a hard pass on that questionable thinking.
Tombak, the researcher whose work was reviewed in the piece, decided to pursue the issue male vs female size measurements during the covid lockdowns. Based on her review, she deemed Darwin’s work “arbitrary”.
But Tombak did manage to find a hero scientist. Female, of course.
Tombak and her colleagues did find one paper that clearly bucked the trend in terms of the conclusions its author came to: a study from 1976 by biologist Katherine Ralls. She looked at size patterns across mammalian taxa and found that most species did not exhibit extreme sexual size dimorphism and that larger females were surprisingly common as well. Her findings, however, were frequently either overlooked or misconstrued, Tombak says. “By then, the narrative about larger males had been around for 100 years, so it kept going,” she adds.
As Tombak gives herself a pat on the back for her victim think, which is promoted by Nuwer and Scientific American, it seems like a good moment to review some information related to sexual dimorphism and species.
To begin with, the Nature Communications work looked at 429 mammal species. There are over 6400 mammal species currently known. So, the findings impact about 6.7% of known animals. Any statement about sexual dimorphism and the evolutionary reasons behind it from that data set is quite a stretch.
Furthermore, there are a number of orders among the mammals, and differences between the biological needs and evolutionary drivers are important to consider…not just the gender. So, measurements between the sexes of bats, rodents, and Eulipotyphla (moles, shrews and hedgehogs) — which are the animals that Ralls analyzed — likely reveal a different set of data points than those of canines, primates, and felines (as seen in the image above).
As I just mentioned primates, let’s take a look at some fun research related to human dimorphism. A 2022 study concluded that:
Human sexual dimorphism is driven by sexual selection on males…and natural selection on females.
“Human sexual dimorphism has been widely misunderstood. A large literature has underestimated the effect of differences in body composition and the role of male contest competition for mates. It is often assumed that sexually dimorphic traits reflect a history of sexual selection, but natural selection frequently builds different phenotypes in males and females.
“The relatively small sex difference in stature (∼7%) and its decrease during human evolution have been widely presumed to indicate decreased male contest competition for mates. However, females likely increased in stature relative to males in order to successfully deliver large-brained neonates through a bipedally-adapted pelvis.
“Despite the relatively small differences in stature and body mass (∼16%), there are marked sex differences in body composition. Across multiple samples from groups with different nutrition, males typically have 36% more lean body mass, 65% more muscle mass, and 72% more arm muscle than women, yielding parallel sex differences in strength. These sex differences in muscle and strength are comparable to those seen in primates where sexual selection, arising from aggressive male mating competition, has produced high levels of dimorphism.
“Body fat percentage shows a reverse pattern, with females having ∼1.6 times more than males and depositing that fat in different body regions than males. We argue that these sex differences in adipose arise mainly from natural selection on women to accumulate neurodevelopmental resources.“
Back in 2020, another group of scientists took a look at human arm power and force.
Not surprisingly, their work confirmed at men, indeed, have significantly more upper body strength.
“The results of this study add to a set of recently identified characters indicating that sexual selection on male aggressive performance has played a role in the evolution of the human musculoskeletal system and the evolution of sexual dimorphism in hominins.“
I have been the beneficiary of this “aggressive performance”. Some personal examples: A man protected me from a dog poised to attack; another gentleman scared off a rattlesnake in my toddler’s way; and, 2 Marines escorted me back to my car when a group of counter-protesters were poised to harass me. Additionally, I am very grateful for the upper body strength my son has, when I ask him to open a jar for me.
Viva La difference. God bless “toxic masculinity”.
Now, let’s look at an entirely different primate…and how that the study on the species and its conclusions were manipulated. Based on his observations, one researcher asserted that bonobos (i.e., pygmy chimpanzees) had lots of sexual partners and were peace-loving, egalitarian, matriarchal.
Essentially, bonobos had a life that any human would envy. Huffington Post, Salon, LiveScience, CBS News all ran with the story.
It turns out, the bonobo research was flawed.
“Observing bonobos in their remote forest habitat is very difficult. For this reason, writes Saxon, early research frequently focused on captive bonobos and artificial feeding sites. These groups were often quite small, had many sub-adult bonobos, and, of course, the captive bonobos were not living in natural settings.
“Juvenile and adolescent bonobos turned out to be far more sexually inclined than adults are. Rich concentrated food stores (artificial feeding sites) induce near-panic in bonobo groups and this provokes sexual behavior. It is not representative of typical bonobo life in the African wild.“
Science should be about seeking the truth, not about promoting a social justice agenda.
The conclusion of the Scientific American piece is the pitch-perfect end to an agenda piece.
“The questioning and reevaluation of prevailing assumptions about sex differences is part of an ongoing process that I call the female turn,” she says. “Perceptions about females have [changed] and are still changing away from passive, coy and mating with one male—and now, in mammals, being generally smaller than males.”
Now that I have completed by analysis of the article, I would like to take a look at the author…Rachel Nuwer. I have discovered that for articles like the one I just reviewed, it is worthwhile looking at the background and mindset of writers.
Nuwer graduated with a Master’s Degree in science journalism from New York University, and has a background in environmental science and conservation ecology. Her twitter feed, I assert, reflects the standard progressive orthodoxy that doesn’t question agenda-driven narratives.
Nuwer is deeply unhappy people are tuning out the media (I explore the reasons for the imminent extinction at Legal Insurrection).
Finally, how Kenyan herders are impacting….climate change.
In conclusion: Tombak is not engaging in meaningful science and Nuwer is not engaging in honest reporting. They are both engaging in advocacy.
Little wonder trust in both science and journalism is collapsing.
Thank you, dear reader, for allowing me to share this analysis and a little bit of real science with you today. I hope my friend appreciates it.
Temple of Mut 