Science

As I reported before, Bari Weiss, former NYT columnist and then founder of The Free Press, has become Editor-in-Chief of CBS News as the Free Press has joined Paramount, which owns CBS.  I was wary of this for one reason: how this might slant CBS News, though I never watch it anyway. The Free Press is heterodox and, most disturbingly, seems to be soft on religion. Will that infect CBS?

On Saturday night Weiss made her first appearance as a CBS news person, hosting a 45-minute “town hall meeting” with Erika Kirk, the widow of recently assassinated Charlie Kirk, head of  the conservative organization Turning Point USA (TPUSA).  I’ve put the video below.

It was not a propitious interview; in fact, it was pretty boring and repetitive. But that might have been because Erika Kirk seems to be a one-note person, devoted not only to dutifully following the principles of her husband, whom she idolized, but especially devoted to proselytizing about Jesus and God. For religion is one of the main pivots of both Kirk and TPUSA. (Kirk recently issued a book urging us all to rest on the Biblical Sabbath, called Stop, in the Name of God: Why Honoring the Sabbath Will Transform Your Life.)

The format of this town hall will probably be the one Weiss uses in her future town halls, and she promises many of them. She interviews a subject, and then select members of the audience (an audience relevant to the speaker’s beliefs) ask questions. You can see the video below.

First, let me note that Kirk is entitled to her beliefs, though I don’t think Weiss did her any favors by allowing her to proselytize ad infinitum in the interview.  Second, I do have immense sympathy for Ms. Kirk, who is left with two small children after her husband’s brutal assassination.  And the joy and glee that came out when Kirk was killed was unseemly, and surely deeply hurtful to Erika. This is not a critique of Erika Kirk, but of the show itself. And I’ll add that though I think Kirk’s murder was abhorrent and reprehensible, I still disagreed with almost all of his political stands, stands instantiated in TPUSA.

What struck me most were two things: Kirk’s evasion of any questions that were “hard”, like one asking her if she condemned Trump’s violent political rhetoric or whether words could constitute violence. Her response was almost invariably to say that the Lord (aka Jesus) will take care of everything.  For example, when she was asked whether she’d condemn Trump’s political rhetoric that was sometimes violent, she simply said that the problem was “so much deeper than just one person.” When asked to respond to Charlie’s opposition to the Civil Rights Act, she simply said that she was in favor of merit. (The Civil Rights Act was not “affirmative action” it was enacted to give blacks their Constitutional rights.)

The other issue was Kirk’s incessant proselytyzing. When asked why, she thought, God/Jesus allowed Kirk to be murdered, she said that it unleashed a big revival (I doubt it), that “the Lord is moving in ways we have no idea, and that God is going to use Charlie’s death to show the world something. Big.  God, she thinks, will use the event to allow her “to bring glory to her and his kingdom.”

The father of a murdered Jewish person asks Erika about growing antisemitism on the Right, and will she condemn individuals spreading that hate? She responds simply that we all need the Lord and Saviour (she’s referring to Jesus, but the guy asking questions was a Jew). She adds, “You cannot separate the Old Testament from the New Testament,” but I doubt she believes that. Kirk himself, though a supporter of Israel, made several remarks that seem overtly antisemitic, and TPUSA is aligned heavily with the Christian right. You do not tout Jesus to Jews.

It is God and Jesus all the way down, and Weiss did not question the foundations of Kirk’s faith, which perhaps would have been an unfair question give Erika’s emotionality.

Kirk reiterates constantly the fact that Charlie only wanted to have conversations, but that’s a bit of dissimulation, for Charlie Kirk was firm in his right-wing ideology and I doubt the conversations would ever have changed his mind. I applaud the desire to have mutual, civil, and nonviolent exchanges of views, but those conversations should be conducted in a way that each person should be able to tell us what evidence would change their minds. Charlie would never change his mind, despite the fact that he sat behind tables with signs making provocative statements and adding . . . “Change my mind.”

To her credit, Weiss and others do try to ask some hard question, like how does she intend to take up Charlie’s mission while maintaining a family. (Answer: the Lord will help her do it, and, anyway TPUSA is not a job, but her family.) When asked how she was able to trust God in the “midst of unfair and immense suffering,” Erika cites the story of Job, who was made by God to suffer for no good reason, but in the end came out okay simply because Job prayed for his friends, which made the angry God change His mind. I have never understood the point of that story, but theologians have tied themselves in knots trying to interpret it in a way that puts God in a good light.

Kirk’s views are all summed up in her answer to Weiss’s question about how she met Charlie. Erika responds that the Lord helped her to find Charlie in a job interview, and Erika asked God if Charlie was the right guy. He was, for, as Erika says, “If I remain in the jetstream of God’s will, then he will provide for you.”  And that’s pretty much her answer to every question in the town hall.

This was not a good first foray of Weiss into t.v. journalism, but surely things will improve as Weiss interviews people who don’t cling to superstition. But the goddiness of this show struck me as overbearing and unevidenced, and I hope religion is not a frequent “Town Hall Topic”.

One more note before I get to the video. Variety weighed in on the Town Hall, and not in a positive way; click to read:

The content:

During a Saturday-night town hall led by Bari Weiss, the recently named editor in chief of CBS News, most of Madison Avenue sought an off-ramp.

The program featured an in-depth interview with Erika Kirk, the CEO of the conservative advocacy organization Turning Point USA and the widow of Charlie Kirk, the group’s former leader. He was assassinated during one of the organization’s events at Utah Valley University, throwing a harsh spotlight on the political and cultural divides present in the U.S.

The event marked a new offering from CBS News. The organization does not typically host town halls or debates on trending issues or with newsmakers. And the choice of Weiss as moderator also raised eyebrows, because in most modern TV-news organizations, senior editorial executives remain off camera, rather than appearing in front of it.

More may be on the way. During the program, Weiss told viewers that “CBS is going to have many more conversations like this in the weeks and months ahead, so stay tuned. More town halls. More debates. More talking about the things that matter.” That would suggest CBS is planning to devote more hours to the programs.

The news special aired at 8 p.m. on Saturday, one of the least-watched hours in broadcast TV. And that may have contributed to a relative dearth of top advertisers appearing to support the show. During the hour, commercial breaks were largely filled with spots from direct-response advertisers, including the dietary supplement SuperBeets; the home-repair service HomeServe.com; and CarFax, a supplier of auto ownership data. Viewers of the telecast on WCBS, CBS’ flagship station in New York, even saw a commercial for Chia Pet, the terra-cotta figure that sprouts plant life after a few weeks.

Now, after that long introduction, here’s the video. Feel free and encouraged to weigh in below.

A new theory proposes that the universe’s fundamental forces and particle properties may arise from the geometry of hidden extra dimensions. These dimensions could twist and evolve over time, forming stable structures that generate mass and symmetry breaking on their own. The approach may even explain cosmic expansion and predict a new particle. It hints at a universe built entirely from geometry.

A new theory proposes that the universe’s fundamental forces and particle properties may arise from the geometry of hidden extra dimensions. These dimensions could twist and evolve over time, forming stable structures that generate mass and symmetry breaking on their own. The approach may even explain cosmic expansion and predict a new particle. It hints at a universe built entirely from geometry.

Susan Harrison is back from Belize with bird photos for us. (And if you have any photos of your own, please send them in!).  Susan’s captions are indented, and you can enlarge her photos by clicking on them.

Belize:  the Crooked Tree Wildlife Sanctuary

Your correspondent has just returned from a birding trip to Belize, a wonderful country that has preserved over 30% of its land area for wildlife, and where a relatively small-scale and bird-friendly style of agriculture is widely practiced.  Today’s photos are from the last place we visited, the Crooked Tree Wildlife Sanctuary, a massive complex of lagoons, swamps and forests in middle northern Belize.  Our exceptionally talented guide grew up here when the small village of Crooked Tree was accessible only by boat in the wet season.  When not guiding birdwatchers, he farms coconuts and avocados here.

We were most fortunate to see the elusive Sungrebe (Heliornis fulica).  Despite its name, this waterbird haunts densely shaded riverbanks and is not a grebe; it has no close relatives.  On the heels of a heavy downpour, we observed this one rapidly plucking damselflies off of overhanging foliage.

Sungrebe:

Another exciting sighting was a colony of Boat-Billed Herons (Cochlearius cochlearius).  These nocturnal hunters do not seize their prey like other herons but instead use their enormous bills in a baleen-like fashion.  During daytime they hide in dense thickets.  This one showed us a yawn.

Boat-billed Heron:

Among the many large, fish-devouring water birds were Bare-throated Tiger Herons (Tigrisoma mexicanum) and Anhingas (Anhinga anhinga).

Bare-throated Tiger Heron:

Anhinga:

We watched as Limpkins (Aramis guarauna), a weird wading bird in its own family, speared and gobbled Apple Snails (Pomacea), this bird’s single food source.  At the same time, these snails were equally of interest to Snail Kites (Rostrhamus sociabilis), who sometimes plucked them away from the Limpkins instead of from the mud.

Limpkin, with a Northern Jacana (Jacana spinosa) in front:

Northern Jacana closeup, showing its massive feet:

Snail Kites:

Skulking by the shore we saw several Russet-naped Wood Rails (Aramides albiventris), an almost comical bird that makes all other rails seem drab indeed.

Russet-naped Wood Rail:

Raptors were also abundant, and two of the more exciting finds were Black-collared Hawks (Busarellus nigricollis) and a Gray-headed Kite (Leptodon cayanensis).

Black-collared Hawk adult and immature:

Gray-headed Kite:

We also saw many wonderful land birds at Crooked Tree, of which I’ll show just a few of the most special.  Yellow-headed Amazons (Amazona oratrix) are among the many parrots that visit Crooked Tree to feed on the local cashew crop; this species is endangered because its intelligence makes it popular in the pet trade.

Yellow-headed Amazons:

Rufous-tailed Jacamars (Galbula ruficauda) resemble giant hummingbirds but are actually insectivores more closely related to woodpeckers and toucans.    The cliffs that Jacamars require for nesting are scarce in low-lying Belize, but Mayan ruins serve the purpose nicely.  We saw this Jacamar at the impressive Lamanai ruins complex.

Rufous-tailed Jacamar:

Detail of the Jaguar Temple at the Lamanai ruins, in which the rectangular holes create a stylized jaguar face:

Olive-throated Parakeets (Eupsittula nana) occurred everywhere we went in Belize, but only in the Caribbean Pine (Pinus caribaea) woodlands of Crooked Tree did they pose low enough for decent photos.

Olive-throated Parakeets:

What’s up, people? You don’t have cats or holiday decorations? If you do, see below.

This is a reminder to send in your photo of cats with a Christmas theme (or Hanukah theme, as we now have three Jewish cats.  The instructions are here and we have acquired only about 12 photos. (Note: the cat below is AI generated;  we don’t want those!)

Remember, one photo per submission, please! I’ll make the Deadline 9 a.m. December 24; the day before Koynezaa.

Scientists have discovered a crucial clue to understanding one of nature's most spectacular light shows, the aurora. Research from the University of Southampton reveals that just before these magnetospheric substorms erupt, a distinct pattern of low frequency radio waves appears above the aurora, radio emissions that surge in strength precisely as mysterious "auroral beads" transform into full storms. This radio signature, detected by spacecraft and ground observatories across multiple events, provides the first direct evidence of the physical processes triggering these dramatic celestial displays, and may explain similar phenomena occurring in the magnetospheres of Jupiter and Saturn.

Scientists at Southwest Research Institute have opened a new laboratory dedicated to answering one of astronomy's most fundamental questions, where do planets come from? The Nebular Origins of the Universe Research (NOUR) Laboratory will recreate the extreme conditions found in interstellar clouds, vast regions of ice, gas, and dust that existed before our Solar System formed to trace how these primordial materials ultimately evolved into the worlds we see today. By simulating the chemistry of pre-planetary environments in specialised vacuum chambers, researchers aim to understand how the building blocks of life, including the components of DNA and RNA, formed in the darkness of space billions of years ago.

A “House of Cards” is a wonderful English phrase that it seems is now primarily associated with a Netflix political drama. However, its original meaning is of a system that is fundamentally unstable. It’s also the term Sarah Thiele, originally a PhD student at the University of British Columbia, and now at Princeton, and her co-authors used to describe our current satellite mega-constellation system in a new paper available in pre-print on arXiv.

After the first protons and neutrons formed, after the first light elements formed, the universe…wasn’t really all that great.

Many industries are eyeing up hydrogen as a source of clean energy, but with supplies of green hydrogen limited, we should prioritise the areas where it could have the most positive impact on carbon emissions, say researchers

Hot Jupiters were once cosmic oddities, but unraveling how they moved so close to their stars has remained a stubborn mystery. Scientists have long debated whether these giants were violently flung inward or peacefully drifted through their birth disks. A new approach from researchers in Tokyo cracks open this puzzle by using the timescale of orbital circularization as a diagnostic.

Scientists have achieved an unprecedented view of the Sun by coordinating observations between two of the most powerful solar instruments ever built. For the first time, observations from the Inouye Solar Telescope in Hawaii and the European Space Agency's Solar Orbiter spacecraft have captured the same solar region simultaneously from different vantage points. This created a stereoscopic view that reveals intricate details of tiny "campfire" features scattered across the Sun's surface. These fleeting brightening, though individually small, occur in such vast numbers that they may collectively shape how the Sun's outer atmosphere is heated and how plasma erupts into space.

Researchers in Sweden have unveiled a way to create high-performance electronic electrodes using nothing more than visible light and specially designed water-soluble monomers. This gentle, chemical-free approach lets conductive plastics form directly on surfaces ranging from glass to textiles to living skin, enabling surprisingly versatile electronic and medical applications.

The FDA sent a letter to the supplement industry assuring that it would make it easier for them to hide disclaimers (which we like to call "quack Miranda warnings") about unproven health claims for supplements. What does this tell us about MAHA?

The post The FDA under MAHA control: Weakening the quack Miranda warning on supplements first appeared on Science-Based Medicine.

Astronomers have performed the deepest radio observations ever of Omega Centauri, searching for signs of an intermediate mass black hole thought to lurk at its center. Despite 170 hours of observations with the Australia Telescope Compact Array achieving unprecedented sensitivity, they detected absolutely nothing where the black hole should be. If an intermediate mass black hole exists in this massive star cluster, as suggested by fast moving stars discovered earlier this year, it must be accreting material at an extraordinarily low rate, barely feeding at all compared to other known black holes.

Researchers have discovered that a close encounter with a rogue planet or brown dwarf during the Sun's early years could have triggered the reshuffling of our Solar System's giant planets. Running 3000 simulations of stellar flybys, the team found that substellar objects passing within 20 astronomical units of the young Sun could destabilise the planets' orbits just enough to match their current configuration without destroying the delicate Kuiper belt. This flyby scenario represents a new possible explanation for one of the Solar System's defining events, with roughly a 1-5 percent probability depending on how common free floating planets actually are in young star clusters.

Astronomers at the University of Tokyo have used gravitational lensing to measure how fast the universe is expanding, adding weight to one of cosmology's most intriguing mysteries. Their technique exploits the way massive galaxies bend light from distant quasars, creating multiple distorted images that arrive at different times. The measurement supports recent observations showing the universe expands faster than predictions based on the early universe suggest, strengthening evidence that the "Hubble tension" represents genuine new physics rather than experimental error.

Researchers using NASA’s James Webb Space Telescope have detected the strongest evidence yet for an atmosphere on a rocky planet outside our solar system. Observations of the ultra-hot super-Earth TOI-561 b suggest that the exoplanet is surrounded by a thick blanket of gases above a global magma ocean.

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.

Athayde Tonhasca Júnior has returned with his patented text-and-photo piece on (you guess it) pollination. Athayde’s captions and IDs are indented, and you can enlarge his photos by clicking on them.

Delicate trade agreements

In one of the regular letters to his close friend, explorer and botanist Joseph Hooker, Charles Darwin vented his frustration at a puzzle he hadn’t been able to crack: …I will return the 3 Melastomateds; I do not want them & indeed have cuttings; I am very low about them, & have wasted enormous labour over them & cannot yet get a glimpse of the meaning of the parts. (Darwin, 1862). The ‘Melastomateds’ cuttings belonged to the family Melastomataceae, a huge group (some 5,000 known species) of mostly tropical shrubs, trees, herbs and lianas. The ‘parts’ whose meaning eluded Darwin were the stamens and anthers.

A complete, hermaphroditic flower. The pistil comprises the ovary, the style (a pillar-like stalk through which pollen germinates to reach the ovary) and the stigma (a sticky tip at the top of the style that receives pollen). The stamen has a filament that supports the anther, where pollen is produced © Anjubaba, Wikimedia Commons:

For a range of Melastomataceae species and at least 15 other flowering plant families, there are two (sometimes three) types of morphologically distinct stamens and anthers in each flower, a condition known as heteranthery. Typically, one set comprises short, colourful stamens located at the centre of the flower. The other set has longer, less colourful stamens that are deflected to the flower’s side and curved inwards. Darwin wrote a whole book about flower morphologies and their bearings in natural selection (Darwin, 1877), but the relevance – if any – of heteranthery puzzled him. He suspected the condition was related to reproduction, but he couldn’t figure out how.

An Asian melastoma (Melastoma candidum) flower with shorter stamens/yellow anthers, and longer stamens/reddish anthers © Hachiman et al., 2024:

Darwin got his answer from his correspondent and enthusiastic evolutionist Fritz Müller (1822- 1897) working in faraway southern Brazil. Müller, a Prussian immigrant, was a brilliant naturalist who wrote about biology, morphology, systematics and evolution of plants, marine invertebrates, butterflies, ants, termites and other insects. Müller discovered the nutritious bodies (today called Müllerian bodies), which are plant glands that secrete ant food, and demonstrated that pairs of poisonous, unpalatable species benefit from evolving a similar appearance to reduce their chances of being attacked, a form of protection we know as Müllerian mimicry.

Fritz Müller kitted out to go exploring a Brazilian tropical forest © O Município;

From his observations of Melastomataceae, Fritz Müller and his botanist brother Hermann – who stayed in Prussia – proposed that the two types of stamen played different roles. One type was specialised in transferring pollen to flower visitors; the other was responsible for feeding them. But why would a plant come to such an elaborate ruse?

Most Melastomataceae and many heterantherous species are pollinated by bees, but their flowers don’t produce any nectar: pollen is their sole food reward. This creates a dilemma. Plants must hand out pollen, otherwise bees wouldn’t pay a visit. But the giveaway must be sparing, otherwise reproduction could be curtailed or prevented altogether. Heterantherous plants sorted this problem by dividing up pollen allocation. The showy, central stamens attract bees, who store the collected pollen in their pollen baskets (scopa): this pollen is no longer available for fertilisation. The longer stamens that curve away from the centre are in a convenient position to sneak on a foraging bee and deposit pollen on parts of her body from where they are not easily scooped up by grooming. With luck, these pollen grains will be transported to another plant’s stigma.

Xylocopa flavifrons (A) and Amegilla urens (B) collecting pollen from Melastoma malabathricum‘s feeding stamens (yellow) and being exposed to pollinating stamens (red). Arrows indicate the pollen-receiving stigmas © Hachiman et al., 2024:

The Müller brothers’ ‘division of labour hypothesis’, as it is known today, was a revelation to Darwin: I have had a letter from Fritz Müller suggesting a novel and very curious explanation of certain plants producing two sets of anthers of different colour. This has set me on fire to renew the laborious experiments which I made on this subject, now 20 years ago (Darwin, 1887).

Division of labour is beautifully exemplified by the pollination of Rhynchanthera grandiflora, a shrub native to the Neotropical region. This plant has flowers with four short stamens and one long stamen, all of them with upwards-facing anthers. A bee lands on a flower, grabs the short stamens and starts flexing her thoracic muscles at high frequency, generating vibrations that are transmitted to the anthers. These moves, known as ‘buzz pollination’, release pollen that lands on the bee. This tricky form of pollen extraction is restricted to some specialised bees such as bumble bees (Bombus spp.) and carpenter bees (Xylocopa spp.). Pollen released from anthers in the short stamens is scooped up by the bee. Pollen from the anther on the long stamen shoots up and sticks to the bee’s dorsal side (Konzmann et al., 2020).

L: A R. grandiflora flower. R: A bumble bee buzz-pollinating depresses the long stamen with its abdomen. The dotted line and cone show the mean direction and scattering angle, respectively, of the released pollen © Konzmann et al., 2020:

The division of labour hypothesis has been confirmed for a few other heterantherous, bee-pollinated species. But, as is invariably the case in biology, things are a bit more complicated.

The hypothesis requires that both types of stamens produce pollen at the same time. But that’s not the case for speckled clarkia (Clarkia cylindrica) and elegant clarkia (C. unguiculata), both natives to western North America. These plants have two types of stamens that mature gradually and at different times. Moreover, pollen from both types of stamens is collected for food and transferred between flowers in equal proportions, so there’s no indication of labour division. For Kay et al. (2020), heteranthery in Clarkia spp. and possibly other heterantherous plants is a mechanism to dispense pollen gradually, during several visits by bees. This strategy would enhance pollination because a bee with only a few pollen grains attached to her body is likely to move to another flower without wasting time grooming herself to remove pollen from her body. Why then bother with two types of stamens? Different morphologies and development times represent additional insurance against excessive pollen harvesting.

A speckled clarkia is a miserly pollen-giver © U.S. National Park Service, Wikimedia Commons:

We don’t have enough studies to assess the relative significance of the division-of-labour hypothesis or the pollen-dosing strategy. Either way, dividing up the pollen stock or releasing it slowly are tactics to give away as little as possible a metabolically expensive product without discouraging flower visitors, who aim to gather as much of it and as fast as possible. The morphological adaptations exhibited by heterantherous plants are examples of the true nature of plant-pollinator interactions: an equilibrium between two parties with conflicting interests fine-tuned by natural selection.

References

Darwin, C.R. 1862. Letter no. 3762, Darwin Correspondence Project, https://www.darwinproject.ac.uk/.
Darwin, C.R. 1877. The Different Forms of Flowers on Plants of the Same Species. John Murray.
Darwin, F. (ed). 1887. The Life and Letters of Charles Darwin, Including an Autobiographical Chapter. John Murray.
Hachiman, S. et al. 2024. Division of labour between dimorphic stamens in Melastoma candidum (Melastomataceae): Role of stamen strength in the biomechanics of pollination. Journal of Pollination Ecology 37: 284–302.
Kay, K.M. et al. 2020. Darwin’s vexing contrivance: a new hypothesis for why some flowers have two kinds of anther. Proceedings of the Royal Society B 287: 20202593.
Konzmann, S. et al. 2020. Morphological specialization of heterantherous Rhynchanthera grandiflora (Melastomataceae) accommodates pollinator diversity. Plant Biology 22: 583-590.