Stars in the Daytime: Stories of Disruption, by Stan Rice, story 2. Haunted Castle

Author Stan Rice has just published another collection of short stories: Stars in the Daytime: Stories of Disruption. Stan Rice is better known as a science writer, and scientific content and themes show up in most of his stories, including those in this collection.

Here is the author’s summary from Amazon: “You cannot see stars in the daytime, but they, like hidden reality, are always there. In these nine stories, Stan Rice asks, what if God appeared in the sky, with a message for Muslims? Can a theme park haunted castle help a young woman escape from genocide? What if an old greenhouse is the site of shifting timelines? What if a hotel burglar is actually a kindly man? What if a man discovers his girlfriend thinks of him as a teddy bear, then needs him? What happens if a demon from hell changes places with a human being on Earth? In one of the stories, Ruth meets Carmen.”

The stories in this collection are: When Pigs Fly (reviewed earlier); The Haunted Castle (reviewed here); Bleeding Earth; The Book of Ruth; The Old Burrill House; The Lord Will Provide: Two Stories of Faith; The Gentleman; Ursa Minor; and You Little Demon (reviewed in later essays).

This story begins, “Arjana worked in the only place at Joyworld Moscow where you did not have to smile: The Haunted Castle.” Arjana and Zef were two Albanian teenagers from a village destroyed by the Serbs. Arjana couldn’t smile because of what she saw, especially the face of the smiling, ruthless Serbian soldier who chased her and Zef but could not find them. When they sneak onto a train going to Moscow, they find a shipment of costumes for Joyworld, and decide the best place to hide is faraway but in plain sight. Zef played a cowboy at a fake frontier town (Russians were killing Siberians at the same time white Americans were killing Natives). Arjana worked the ticket counter of Haunted Castle, a train that wound through fake graveyards and dangling ghosts. But the soldier found Zef and shot him dead; the visitors thought it was part of an act. Other visitors thought it was part of the act when the soldier found Arjana and tried to rape her. (“The fake blood looks so real!”) But a small and silent act of heroism saves Arjana.

One thing I found very interesting about this story was that Arjana’s ability to play dead was an adaptation to danger. Animal adaptations to escape from danger are as varied as the animals themselves.

An evolutionary puzzle is, why do people so intensely hate those in other racial or cultural groups? An evolutionary argument can be made for why individuals or groups, in competition with one another, would hate each other. But the intensity of hatred seems too much for biology or evolution to explain. It is almost enough to make one believe in Satan.

Blood Brain Barrier: Stories from the Borderlands of Science, story 5. Rock Bunnies

This collection of short stories by Stan Rice, who is also the author of nonfiction books of popular science and science novels, takes the reader to the frontier between science and worlds of the impossible. Readers of my science blog will appreciate the creative telling of scientifically impossible stories; readers of my religion blog will appreciate the question of whether, even if these things were possible, would they be good?

The stories in this collection are The Man Who Could Work Miracles, Light Apparel, Flow of Blood, Wisdom Builds Her House (all reviewed earlier in this blog), Rock Bunnies (reviewed here), Entropy, Olga the Science Cat, Doghouse, and Fresh Air.

In Rock Bunnies, once again, Rice takes an idea from the fiction of H. G. Wells, in this case from The Time Machine. In Wells’s novel, the human species has evolved into two: the infantile Eloi and the shabby but hard-working Morlocks, as different as any two animal species. In Rice’s story, the Urbanites are rich white technologists who have evolved into a slightly-different race that lives in artificial cities, while the dark poor Rock Bunnies live in places the whites have destroyed. This story is set in the Black Hills, which (as anyone visiting Mt. Rushmore knows) is currently covered with pine trees, but in this story, set in the future, is a desert. The Rock Bunnies leap from cliff to cliff and live off of mountain goats and little clumps of edible wild plants.

A white Urbanite graduate student out in the desert sees a Rock Bunny who, as they almost never do, fall from a cliff and injure herself, perhaps mortally. He wants to rescue her but her fellow Rock Bunny vandals have destroyed his car, and he becomes their captive. The Rock Bunny woman, however, is the niece of their chief. They develop a friendship, and the chief—whom they call the Scientist, because he keeps the spirit of science alive among his people—wants the white man to stay with them as his son-in-law.

In this view of the future, which is otherwise bleak, Rice shows that this tribe of Rock Bunnies reveres science and its practitioners. Nice fantasy.

An Urbanite helicopter comes and finds the white man. The white man assumes it is to rescue him. In this, he is quite wrong.

As in other stories in this collection, Rice makes a strong case that altruism—the evolutionary basis of love—is the most important human adaptation. This is the message of both science and religion. As in many other Rice stories, there is also the theme of racism.

River Weeds: A Novel of Love, Lust, and Poison Ivy, part three

This novel, which I introduced previously, is a kind of novel only a practicing and experienced scientist could write.

 

The author, Stan Rice, explains all the science in the book, even high-performance liquid chromatography, so that anyone can understand it. He does a particularly good job of explaining evolutionary biology, which is not surprising since he is the author of nonfiction books about evolution such as Encyclopedia of Evolution. One example is when one of the characters explains the evolutionary basis of the human aversion to incest. But what Rea’s stepfather tried to do—rape her—is not biological incest, since she is genetically unrelated to him.

The characters all have a healthy sense of humor—except Earl, of course.  For math teachers Conway and Thurman, the sense of humor is an unstoppable spring. Science offers lots of opportunities for humor, especially the Meeh coefficient and the way Darwin’s cousin Francis Galton used trigonometry to measure the buttocks of an African woman rather than to touch her. The Meeh coefficient, the wacky mathematicians insist, requires the measurement of the surface area of a naked human body. Rice takes his fellow scientists no more seriously than did the British humorist David Lodge, author of novels such as Small World: An Academic Romance. The academic world is a place where you can be weird.

Unlike some of Rice’s other novels, this one does not have a lot of religion in it. But, like probably all Rice’s novels, it addresses the meaning of life. As Rea tells her audience at the end, “A happy life consists of doing ordinary things in a grateful manner.”

River Weeds: A Novel of Love, Lust, and Poison Ivy

How could you resist a book with a title like this?

Here is the author’s summary from the Amazon website:

“Marten, a young scientist, meets Rea, a stunningly beautiful young Cherokee woman who works at her family’s convenience store. To their mutual surprise, Marten and Rea kiss within minutes of meeting. Her bitter white stepfather, Earl, forbids her to get an education. But Marten discovers Rea’s secret place down by the river where she reads and writes. This soon becomes their love nest. Marten helps Rea get involved in his research on poison ivy. She keeps a vial of urushiol, the active ingredient in poison ivy sap. Marten and Rea get married.

“Rea knows her stepfather intends, someday, to rape her. Only someday is now. Earl removes the bolt from Rea’s bedroom door. She and her mother decide to move in with Marten right away. They go to Earl’s house when they think he is away, but he is there and tries to rape Rea. During the commotion, Rea pours the urushiol extract into Earl’s whiskey, which he drinks. Urushiol takes a couple of days to induce inflammation. When Earl later pursues Marten into the swamp, he falls in and drowns because the inflammation—from inside his throat—has closed off his breathing.

“Police investigations slowly piece the story together. The Cherokee tribal defense attorney at the preliminary hearing claims Rea acted in self-defense, but the District Attorney establishes that urushiol acts slowly—a couple of days—thus Rea’s act of keeping the urushiol in her drawer was premeditated. Despite the background of vocal tribal support, Rea goes on trial for manslaughter.”

Like other Stan Rice novels, this one has a lot of science in it, but in a fun way that most readers can understand. And it also tackles some big questions—another feature typical of Rice novels. Come to think of it, I have never seen a Stan Rice novel that you can just sit back and leave your brain off the hook. As a reader of this blog, you might like this.

Is there such a thing as True Love? Or Love At First Sight? Most scientists would say no. Among them are the offbeat, weird mathematicians Conway and Thurman, and the narrator, Marten, a botanist, all of them at Drury College in Springfield, Missouri. Conway and Thurman figure out the incredible mathematical odds against the existence of True Love. And it is a calculation that readers can understand, not just something like Spock coming up with a probability estimate as if by magic.

No such thing as True Love? At least, this is what Marten thinks until he meets Rea and instantly falls for her. And she for him. They seem as different from one another as anyone can be: he is an academic, she works at an interstate C-store. But it turns out this poor woman has an insatiable thirst for science and nature; she just has never had the opportunity to pursue it, other than secretly reading books of which her bitter white stepfather Earl disapproves. You know, evolution and all that. As quickly as she falls in love with Marten, she also realizes he might be her escape from Earl and his willful ignorance.

So the conflict and plot are set up right away. Marten loses Rea almost as soon as he meets her. How far would you go to find someone you had just begun to love a few minutes previously? And then he has to rescue her from her oppressive life.

I think the readers of this blog would enjoy a novel in which scientists are real people, and non-scientists are frequently smart too.

Glass Cathedral, a Religious Novel with a Lot of Science

Stan Rice’s novel Glass Cathedral deals with big religious questions not in the form of serious debate but in good-natured banter among three of the main characters, Dan (the atheist), Emilio (the evangelical Christian), and Misty (the Christian who has deep and serious doubts about her religion). I have written in my other blog about the religious aspects of this novel.

This is the author’s summary from Amazon:

The newspaper staff writers of a small desert town assume the strange light in the sky is merely sunlight refracted by ice crystals: atheist Dan Hardy; the spiritually-searching Misty Barbour; and even the confirmed Christian editor Emilio Villanueva. Then the light turns out to be God—maybe. This is enough to make Misty leave her doubts behind and marry Emilio. Dan, who was hoping to win Misty’s affection, is skeptical, especially since God showed up on no photographic images, and everyone in town saw God differently. The government authorities declare the light was a mass hallucination.

Emilio and Misty raise money to build a glass cathedral in the desert, near the place they think God appeared. When thousands of people come for the inaugural celebration, a storm pulls the glasshouse into the sky. Misty gets trampled. At the end, Emilio and Misty, who is now disabled, conclude that God’s work is to help people, not to build a cathedral, and even Dan agrees.

 What I want to say in this science blog is that Dan arrives at his atheism thoughtfully and at great personal cost.

His interest in science began when, as a boy, he saw a horsehair worm discharged from the anus of a dead cockroach. This got him interested in reading everything he could about biology and ecology, especially parasitism, which earned him the name Buttworm Boy. In a natural world pervaded by evolutionary mercilessness, Dan sees no room for a Creator.

His atheism is challenged when he meets, becomes attracted to, and becomes physically entangled with a Mormon girl, Margaret. Margaret is not an enthusiastic Mormon, but wants Dan to join her to raise nice kids. In this way, Dan discovers that religion does not have to be correct—as Mormonism is clearly contradicted by history—in order to fill a role in a person’s life. This, however, is not enough for him.

Another main character, Misty, is a dedicated Christian, at least until her comfortable religious world is shattered by the assassination of her fiancé. The main event of the novel—God appearing in the sky out in the California desert, or not—restores her faith. But what is it that brings Misty the Christian and Dan the atheist together for meaningful discourse? It is science, of course. They see, then carefully examine, the desert wildflowers, Dan as a scientist and Misty because Jesus said to consider the lilies of the field. That is, to look closely, carefully, and thoughtfully at them. This is something that very few Christians actually do.

The novel also contains other scientific plot elements. In the glass cathedral that Misty and her husband Emilio build out in the desert, a giant band-o-rama has hundreds of tubas that happen to play the resonant frequency of the building, so that it shatters and blows away like a giant jellyfish in a desert storm.

I think the author has a lively, almost childlike, sense of wonder, at the lilies of the field and the surprises that wait within the laws of physics. I think readers of this blog would enjoy Glass Cathedral.

Meet Me In Strasbourg: a Romance Novel from which You Can Learn a Lot of Science

You would not be reading this blog if you were not interested in science. So you probably don’t read very many romance novels. I do not; but Meet Me in Strasbourg, a novel by Stan Rice is an exception. I summarized it in an earlier essay.

 

There was a prominent scientist who loved romance novels with happy endings. That scientist was Charles Darwin. Maybe he intended the novels as escapism from the heavy issues involved with his theory of evolution, and the social unrest it caused.

But Meet Me in Strasbourg is a novel that presents many scientific concepts, not as escapism but as part of the plot and character development. These are not concepts from science class, but from the direct experiences of life. Examples include:

• All perception is illusion. The brain knows nothing except what the sensory organs tell it, and all of those sensations consist of nerve impulses. It is the brain that sorts them out into sight, hearing, taste, etc. and makes sense out of them. If the brain does this incorrectly, we call them delusions.
• There is a lot about evolution in this novel, which is why I am telling you about it in this blog. This is especially true of sexual selection, Darwin’s “other theory” of 1871. Why do we find symmetrical faces beautiful? Because they indicate a person’s health and potential fitness as a mate. Is “falling in love” just craziness? Tony’s no-nonsense friend Roald explains that if falling in love—a universal experience—were just crazy, natural selection would have gotten rid of it. But falling in love promotes sexual selection. One teacher even explained to Tony why he should want Aimée to be as beautiful as possible, even though she does not need to be, since she is already engaged to Tony. You can even find out about evolution—It’s what’s for dinner. As Tony explains to his kid sister, of course you don’t like broccoli; many vegetables taste bad because they don’t want you to eat them. But it turns out the truth is a little more complicated than this.
• You can also learn about the mathematics of probability. When Aimée vanishes and goes to France, Tony decides he is going to go there and find her. Roald, the no-nonsense friend I told you about earlier, explains that the odds of him finding Aimée would be one in a million. Of course, Tony tries it anyway.
• You can learn a surprising amount about DNA, chlorophyll, hummingbirds, stellar evolution, facial symmetry, the bacteria of the human body, and nutrition in this novel. You can even learn about how the soil holds water—explained to you by a janitor.
• One of Aimée’s creative writing class stories is about green flatworms. It turns out that flatworms on the beaches of the north coast of France are one of the best examples of symbiosis: photosynthetic algae live inside of the flatworms and make food for them, in exchange for eating the worm’s waste products.

Read Meet Me in Strasbourg, by Stan Rice. You might be surprised at how much fun the intellectual life, especially science, can be.

Sexual Selection and Music: Nannerl's Story

 

Something to think about (music and sex) as spring arrives.

Back when I was taking music courses as an undergraduate at the University of California, Santa Barbara, everyone was wondering why the great musicians were male. Not all of them, of course; two female composers, Thea Musgrave and Emma Lou Diemer, were on our faculty. Clara Schumann, Robert’s wife, was an example from the nineteenth century. More recently, there was Dawn Upshaw. But this list is very short, compared to the list of famous male composers.

It is easy to attribute this solely to male oppression of females. Male domination in music is just another example of male domination of society in general.

But there is another factor at work. Males often show off to other males, and to potential female mates, in the hopes of increasing their mating opportunities, within or outside of a pair-bond, in humans as in many other animal species. While this often takes destructive forms, such as war and abuse, it can also take creative forms, especially in big-brained humans. Artistic or intellectual creativity is often a way in which males can show off. We all know of the spectacular paintings on European cave walls. But those same caves echoed the music of bone flutes and drums by which musicians (perhaps mostly male) enthralled their congregations.

This happens more often males than females because evolutionary fitness in males often results largely from the number of mates, while this is not true so much in females. For a man, reproduction can consist of a single sex act, while for a woman the whole process of pregnancy, childbirth, and raising children may be her burden alone. Thankfully, there are many of us men who are nurturing and faithful rather than rapacious. But a male can have hundreds of offspring (or thousands, for Genghis Khan) while no woman can have that many. The inevitable result of sexual competition is that some men have lots of offspring, while most of the others compete with one another for whatever women are left.

Women also compete with one another to have the best males as the fathers of their children. Also, women need to have musical ability in order to recognize it in men. Alma Schindler, herself only a passable musician, nevertheless recognized the genius of Gustav Mahler and maneuvered herself into being his wife. Nevertheless, sexual competition is stronger in men than in women.

Sexual selection must have chosen whatever genetic basis there is for musical ability, in men more than in women. But that genetic basis cannot be found only in men. Men have a Y chromosome, which is largely a lump of useless DNA. The genetic basis of musical proficiency must be found on either the X chromosome or the non-sexual chromosomes, and this means that it shows up perhaps just as frequently in girls as in boys. In the absence of ongoing sexual election, musical ability, even if it began as a male characteristic, would soon equalize itself between the sexes.

And this is why even spectacular musical ability shows up in females even if it started in males thousands of years ago.

Everyone has heard of Wolfgang Amadeus Mozart, who was clearly a musical genius. But did you know he had a sister who was perhaps just as gifted as he was? She was a superb keyboardist, and her father Leopold took her on concert tours throughout Europe at the same time as he took young Wolfgang. Audiences were perhaps even more impressed with the beautiful Maria Anna Mozart (nicknamed Nannerl) than with her little brother who could do musical tricks. But her father convinced her that her only chance for success was as a performer and teacher, and as a wife. While she continued teaching and performing until her own death, decades later than Wolfgang’s, none of her compositions survive. One movie I saw (of several that have been made) showed her, at about fifteen years old, sadly burning her compositions in the family fireplace. It turns out Wolfgang was a genius; but perhaps Nannerl was also. We will never know.

 

 

Natural and sexual selection, drivers of human evolution, are not destiny. The adaptations they provide must be continually maintained by culture, as I explained above. As culture evolves, the forces of selection can change. Thankfully they are already doing so. When I was in high school, most brass players in school bands were boys, except the very competent Linda. The girls chose flute and clarinet. When I was in California State Honor Band in 1974, I was the last chair baritone horn player. The first chair player (in the concert band) was a black girl. She was really good. I admired her for her pioneering spirit on her instrument and for the way she represented her ethnicity. This was an important part of my development, coming as I did from a racist family.

There are forces that try to suppress opportunities for women. A few years ago, there was a scandal among the Southern Baptists because male leaders often seduced females without serious punishment. The church’s response? There were a few women in positions of Southern Baptist leadership. The church removed them and forbade women to be in such positions at all.

But even religion cannot completely hide female talent. Probably every church choir director has heard of composer Natalie Sleeth. Things look pretty grim for women in conservative religion, but I suspect things will never get as bad as a Margaret Atwood novel.

The Evolution of Weirdness

Weirdness cannot be defined, but whatever it is, it evolved, which means it provided an evolutionary advantage at many times during human evolution.

One reason it cannot be defined is that what one culture, in space or time, considers weird, another culture may not. One example is psychopaths. In most cultures, most people dislike psychopaths. They are very, very smart, and almost always use their intelligence and their charisma to advance their own interests. We tend to think of the psychopathic mass murderers and other criminals, but many psychopaths (who constitute about one percent of the population) pass as ordinary people and may be surprised by their own (often genetically-based) diagnosis. A lot of politicians and preachers are psychopaths, who cultivate the goodwill of others for their own financial or sexual benefits. And they also like to shame you for suspecting that they are committing acts of evil. It takes highly-developed social intelligence to recognize a psychopath. See the book by Kevin Dutton: The Wisdom of Psychopaths: What Saints, Spies, and Serial Killers Can Teach Us about Success. New York: FSG, 2012.

The success of psychopaths depends on the social situation. Adolf Hitler was a psychopath, and he got millions of people to follow him. After Germany lost World War Two, many Germans felt mentally liberated, and wondered, What were we thinking, to follow this jerk? Germany was not a nation of psychopaths, but maybe the Nazis were a party of psychopaths.

But there are many other ways of being weird. Most of us are a little weird in a few ways. But I mean clinical weirdness. One example is Williams Syndrome [https://en.wikipedia.org/wiki/Williams_syndrome]. People with Williams Syndrome have distinctive facial characteristics, and medical problems such as heart conditions. They have diminished intelligence, overall. They are extremely talkative, and effusively express their emotions. They are almost always cheerful. I have never knowingly met one but I get the impression that it would be really hard to not like them.

One word you would not associate with Williams Syndrome is suspicious. In order to become socially powerful, within your society, you have to be suspicious of the motives of other people in your society, and certainly of people in other societies. People with Williams Syndrome will walk right up to you and trust you. This is socially awkward. But openness and the willingness to trust is an essential component of altruism, of social bonding. It’s just that these people have too much of a good thing.

Another reason weirdness cannot be defined is that each kind of weirdness has its own social and genetic basis. Williams Syndrome is associated with a specific genetic deletion that affects a specific part of the brain. There is no set of terms in any language that exactly matches the symptoms of this deletion. And, in fact, characteristics resulting from mutations can be highly modified by upbringing and social circumstances. I am thinking of a person who acts as if she has Williams Syndrome, but who looks normal, and is brilliant.

Throughout human evolution, behavior patterns have sometimes been useful and sometimes not. Since each behavior has a different set of causes, human behavior has proven to be immensely variable. This has happened not because natural selection has done a bad job on human behavior, but because both the source and the target of human behavior is constantly shifting.

 

We can be glad we have empathy and altruism in the human species. And maybe Williams Syndrome is the price we pay for it.

 

Next, I will write about the evolution of nerds. Or not. Maybe I am a bit too close to the subject to be objective.

The New Reality of the Scientific Method: Donald Trump Is Always Right

I outlined the scientific method, which is something in which anyone, not just scientists, can participate, in my previous book Scientifically Thinking. But there is a new reality about science, at least in the United States, which has developed since I wrote the book, and which I will now explain.

For many years at Southeastern Oklahoma State University, I taught the Research Methods course for science graduate students, which was pretty much the precursor of my book. I recently found, in some old papers, that I taught a similar course at The King’s College, in my first faculty job. King’s was and is a fundamentalist Christian college. Soon after I left, it also became a fundamentalist Republican college and, today, is probably a fundamentalist Trump college. When I taught the scientific method, I taught it pretty much the standard way, although technology was different back then (no internet). But that was because my department chair, although he was a leading creationist, was open to free scientific inquiry. He believed that open inquiry would lead a person to accept creationism. He did not, unlike almost all other fundamentalists, impose his views on other people.

But here is what research is usually like at fundamentalist institutions. First, instead of reaching a conclusion, you impose one. For example, you will stipulate up front that there can be no evidence that is consistent with evolution. Next, you selectively gather information that agrees with your conclusion. Last, you draw your “conclusion” from the selectively-gathered information. This is the exact opposite of the scientific method.

The result was predictable. The scientific value of creationist research is nil, for two reasons other than the above. First, creationists used this method to defend not only the Bible but their sometimes highly imaginary interpretations of it. Second, their misuse of the scientific method made their work sloppy even when it had nothing to do with evolution. Their habit of mind was that, no matter what they did, they had to be right. I documented these two things in a pair of articles I wrote a long time ago: in 1988 and in 1989.

Today we must add another dimension. Not just in creationist or fundamentalist camps, but in all publicly-funded research, the researchers must begin with the conclusion: they must begin with whatever belief the Republican party holds upon the question. For example, is global warming happening, and are humans contributing to it? The answer, fundamentalists think, must be no, even though the Bible does not mention it. The answer must be no because the fossil fuel industry says it is no. This, then, is the conclusion they reach. Are vaccines effective? Again, the required answer is no. Has gun violence reached epidemic proportions? The answer again must be no. Science, then, becomes just a propaganda arm of the Republican Party.

It has been this way for a long time, to various degrees, starting mainly with the George W. Bush administration. But now, under Donald Trump, there is yet a new version of science. You begin with the conclusion that Donald Trump is always right. Science has now become a propaganda arm of Donald Trump, and of his chosen spokespeople, such as RFK Jr. who says that vaccination is not necessary. The conclusion is that vaccination is not effective, because Donald Trump, who used to champion vaccination, says so.

For example, even under Republican presidents in the past, the website climate.gov existed. As of 2025, that URL redirects to NOAA where global warming is hidden, although at this point they still admit that today’s atmospheric carbon dioxide level (421 ppm) is comparable to the atmospheric level four million years ago, and much higher than any time during 6000 years of human civilization. But they are not allowed to draw the obvious conclusion that the Earth is getting hotter, only that it happens to be hot right now; certainly they do not blame our use of fossil fuels.

I am glad that I taught and wrote about science before Donald Trump became the sole standard of truth. I am not sure, however, that I am safe. My most recent book, Forgotten Landscapes, provides evidence that Native Americans were civilized and had a significant effect on the North American landscape. This is not the picture of Native Americans that Republicans prefer. They want to claim that Natives were savages and did not deserve to keep the land that was taken from them. Republican opposition did not prevent the publication of my book. But what will happen next?

Darwin and Fall Colors

In eastern France, one of the first plants to have red leaves is Virginia creeper (Parthenocissus quinquefolia). As the name suggests, the plant is originally from North America. Someone brought it from America and planted it in a European garden, and it spread widely from there, either by its vine branches, or by its seeds, which resemble grapes and are eaten by birds. Another plant species that has bright autumn leaf colors, including red, is another woody plant from North America: the sweetgum tree (Liquidambar styraciflua). This essay accompanies a YouTube video.

Leaves changing color in the autumn is part of a process known as senescence. It is part of a perennial plant’s way of getting ready for winter. It is a long, slow process. It must begin in late summer, before the temperatures even get chilly. The only way a leaf can “know” that autumn is coming is by measuring the length of the night, which gets longer every year starting on June 21 no matter what the temperature might be. Leaves use the pigment phytochrome to measure the length of the night.

Part of senescence is the formation of an abscission layer. This is essentially a layer of scar tissue at the base of the leaf that allows it to easily break off and blow away when senescence has finished. By the time this happens, the abscission layer has already healed up what would have been a gaping wound. As the abscission layer forms, the ability of the leaf to export molecules gradually declines. One of the reasons an old leaf is less valuable to a plant than a young leaf (as I will explain in a separate essay, with its own video) is that a young leaf does not have an abscission layer, and it is able to export sugar and other molecules rapidly to the rest of the plant. In an old leaf, there is some resistance to exporting photosynthetic products such as sugar. An old leaf produces less sugar, and in addition is less able to export that sugar to the rest of the plant.

Why do leaves turn yellow and red in the autumn? Let’s start with yellow. The yellow color is carotenoid pigments, which were present in the leaf throughout its life. In this photo, the non-water-soluble leaf pigments have been separated by a process of chromatography [ref]. You can see two green bands (chlorophyll a is emerald green, chlorophyll b is olive green) and yellow bands of carotenoids, including one faintly visible at the top. These pigments came from fresh young leaves of supermarket spinach.

Carotenoids are not directly photosynthetic, but they assist the chlorophyll in the process. When the plant recycles its chlorophyll—including the valuable magnesium atoms in the chlorophyll molecules—the yellow color that was there all along is revealed.

But why do leaves often turn red in the fall? The red color is anthocyanins. Of course, most of them do not. But in hundreds of woody plant species, autumn leaves turn red. The reason this happens is that a leaf in autumn has little photosynthesis, but it does have some, and it produces sugars, which are difficult to export. The leaf uses these sugars to manufacture anthocyanins. This especially occurs on crisply chilly but sunny autumn days.

It seems likely to me that the anthocyanins are the chance result of sugar buildup. That is, they do the plant no good, but just happen to be beautiful to us. But studies have shown that lots of woody plant species have independently evolved the ability to produce red leaves in the autumn. If something evolves over and over again, there is likely to be a good evolutionary reason for it. But what is that reason? It’s hard to say and impossible to prove.

One suggestion is that the red anthocyanins protect photosynthesis from ultraviolet radiation. When I first heard it, this explanation made no sense to me, since by the time a leaf turns red most of its useful life is past. But not quite all of it. Perhaps the red pigment protects the leaf cells from ultraviolet damage during the very important process of senescence itself.

Human plant breeders have selected many species that have bright red leaves even in the middle of the season. These plants do not grow as well as the ones with solid green leaves, but that does not matter. Their success depends not so much on growth and seed production as upon their ability to please human tastes.

We still do not know why most of the tree species that produce red leaves in the autumn are in northeastern North America and Asia. This photo shows bright autumn colors, due mostly to sugar maple (Acer saccharum) in New York.

In Europe, most native species just turn a dull yellow or maybe just degrade directly to brown. When American painters used bright red on their canvases, European painters thought they were just making it up, since there is nothing like it on the native landscapes of Europe.

If Darwin walked around his estate at Down, outside London, he would have seen red leaves in the autumn. The Down House website boasted about these colors earlier this year (the photos will probably be gone by the time you visit the site). But most of the plants with red leaves were Virginia creeper and sweetgum that were planted there.

Darwin and Dewberries

This essay accompanies a video on the Darwin channel.

All over Europe, blackberry bushes (Rubus fruticosus) form thick hedges (ronces) out in the sun that are nearly impenetrable by humans or other large animals. The vinelike branches are thick, strong, and covered with nasty thorns. At first it might seem strange that the vines would be so well protected against animals, since they produce delicious blackberries that natural selection has designed for animal dispersal. Animals eat them, the seeds pass through the gut, and come out in a new location—exactly what the plant “wants” to happen. But apparently the ronces “want” birds, not mammals, to disperse the seeds.

The blackberry bushes have numerous adaptations to life in bright sunlight. The branches are thick with sapwood that conducts water to the thick leaves, which are white on the underside, an adaptation to occasionally hot, dry conditions. Because the shrubs grow so fast, they can produce an abundance of fruits, which are first green, then red, then black when fully ripe. The flowers begin to open in spring; then, starting in July, you and other animals can feast on the berries, that is, when you can reach them. 

Meanwhile, in the shade, another species of Rubus grows: Rubus caesius, the dewberry. They are adapted to life in the shade: narrower stems that conduct less water, and they have thinner leaves, which are not white on the underside. The flowers do not open until August, and the fruits are not ripe until September. Because they grow in the shade, they grow more slowly, and are smaller. For every one dewberry, a bird may find a hundred blackberries.

They also have fewer thorns. These differences are not just due to sun vs. shade conditions; even when both of the species grow together in the shade, one can distinguish them, for example by the number of leaflets (often five in blackberries, only three in dewberries).

Clearly, blackberries are the dominant species. Dewberries hide in the shade. There appears to be competition between the two species. Blackberries rule the summer sunshine; dewberries could not possibly win in competition against them. But dewberries find a refuge from competition by blooming later. Natural selection has favored dewberries that reproduce a little bit in the late summer shade, over dewberries that might uselessly attempt to reproduce in the same place and same time as blackberries. This is evolution (a kind called temporal niche displacement) acting upon the dewberries. It spells the difference between barely surviving, and not surviving at all.

Temporal displacement keeps the species from interbreeding. I have no idea whether they could interbreed; no one knows exactly how closely related the two species are. But they don’t interbreed because they flower at different times.

And they don’t live in exactly the same places. When a bird looks for a juicy berry, a dewberry is just as good as a blackberry, but a bird is very unlikely to eat both of them. As a result, a poop-load of blackberry seeds is likely to end up in a separate location from a poop-load of dewberry seeds.

It is conceivable that natural selection also acts upon the blackberries. Right through August and September, blackberries produce big red berries that ought to turn black. But when I look for ripe blackberries in August, I find that almost all of them have withered before I, or any birds, have a chance to eat them. I find this puzzling. The weather remains good for ripe blackberries, but something makes them turn into little dried black blobs.

Thus the fact that dewberry flowers and fruits are delayed, and also the fact that the late blackberry fruits wither, both keep the two species from blending together. Evolution at work. A human parallel would be an ethnic minority that could blend in with the majority, and lose its distinctness, remains distinct and survives by living in little, separate communities.