When Strega Nona goes over the mountain to visit her friend Strega Amelia, Big Anthony sings to the pot and feeds the whole town. Then he sings the verse that stops it. Without the three kisses, the verse does no good. Pasta pours out of the windows and doors and down the road, until it nearly buries the town. Strega Nona comes home, blows three kisses, and the pot goes still (Figure 1). Then she hands Big Anthony a fork. “So start eating.”

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Figure 1. Strega Nona read aloud by Mary Steenburgen, with Tomie dePaola’s pictures (Storyline Online, SAG-AFTRA Foundation, 2016). YouTube embed.

In Tomie dePaola’s 1975 picture book, the pot stops only because Strega Nona comes home.

A cell cannot wait for anyone to come home. It copies its recipes out all day, and copies that never stopped would bury it the way the pasta buried the town. Every copy it makes is built to be taken apart, and the cell’s enzymes take it apart after it has been read.

A cell’s copy works like a recipe card. A cook copies one recipe onto a card, takes the card to the counter and cooks from it. A splash of sauce later, the card goes in the bin, and the cookbook on the shelf was never touched.

A previous essay called the genes a cookbook. The recipes a cell has copied out to the counter make up a layer of their own.

The cards are where a common worry lives, at dinner tables and pharmacy counters. Your mother calls the night before her COVID shot, and her voice on the speaker is tight: “Can the mRNA change my DNA?” You know the shot hands her cells a recipe. You cannot tell her what stops that copy, and she moves the appointment back a month.

mRNA, short for messenger RNA, is the real name for a card (Figure 2). The answer to her question is in how a card is made and thrown away. So is the reason HIV stays in a body for life: it brings what a vaccine’s card lacks, a way to write its card into the book.

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Figure 2. From DNA to RNA in molecular models: the copying machine opens the double helix and spins out one strand of RNA. DNA Learning Center, Cold Spring Harbor Laboratory. YouTube embed.

What the Copy Carries

On a football field in an imagined film, every letter of DNA is a sprite holding a bead. Two strands of sprites twist into a double line, and an imp with a twitching nose walks it, fixing wrong pairs. A second imp waits at the sideline and never fixes anything. This one goes by Quill, a courier built for reading. Quill carries an empty thread, waiting for something worth copying onto it.

Somewhere inside the double line is the wing-shimmer verse: a stretch of letters that holds the recipe for the shimmer on a wing. Just before the verse begins, a few dozen beads form a pattern unlike anything nearby. This pattern is a flag. It marks where reading starts and carries no recipe of its own.

Narrator: A verse like this one has a real name: a gene, a stretch of DNA that gets read. Most DNA codes for no protein at all. The genes in this story are read and built into proteins, working parts of the body, like the enzyme that lets a body digest the milk in a morning coffee. The flag is real too. A short marker just before each gene, called a promoter, tells the reading machinery where to start. Whether a courier ever reaches that flag is decided elsewhere, by caps that put a verse to sleep.

Quill flies straight for the flag. It slips in between the two strands and pries the partners apart, one pair at a time, like unzipping a jacket. Unlike a jacket’s, this zip closes again right behind Quill, so only a few pairs are ever open at once.

Quill reads down one open strand, letter by letter, and threads a new strand as it goes. An A on the open strand pulls in a paler, imp-only bead standing in for T. A T pulls in an A, a C pulls in a G, and a G pulls in a C. If the sprites hold A-T-C-G, Quill writes U-A-G-C, with U for its pale bead. At the end of the verse, Quill snaps free, and the two strands fall back together, sealed. The verse is the recipe. Quill’s thread is the card, and the book never left the shelf (Figure 3).

Figure 3. From gene to card. Quill reads the open strand past the flag and writes one new strand, with U where the partner strand has T. The verse’s letters are invented; the pairing rules are real. The peach flag letters, TATA, come from a real promoter piece, the TATA box. Drawn for this piece.

Narrator: RNA uses a related letter, uracil (U), wherever DNA would use T. The book stays in the nucleus, a walled room in the middle of the cell. The card is carried out of it to be read. A cell’s own cards are short-lived: in mouse cells, half of a typical card is gone in about nine hours.

But Quill’s card is not ready to cook from yet.

What the Copy Leaves Out

Quill writes down every letter of the verse, and its first card comes out too long. An old family cookbook has chatty paragraphs between the steps: a story about the aunt who wrote it, a note on where to buy the cheese. A cook copying the recipe leaves the chatter off. Quill’s first copy keeps the chatter. Before the card leaves the room, a crew of cutters snips out the chatty stretches and joins the steps end to end.

Narrator: The steps are exons, the chatty stretches are introns, and the cutting is splicing. A cell can also keep or drop a step, so one gene can make more than one protein.

One smudge on the page can make the cutters drop a step that matters. Spinal muscular atrophy (SMA) is a disease that kills the nerve cells that move the muscles. In its worst form, babies lose the strength to breathe. Those nerve cells need a protein called SMN, and its recipe is in the book twice, SMN1 and a spare, SMN2. A child with SMA has no working copy of SMN1. The spare differs from SMN1 in a handful of letters, and one of them, in exon 7, is the one that matters. That letter does not change the protein, but it makes the cutters skip exon 7 on most cards.

In 2006, a lab found a short stretch just past exon 7 that tells the cutters to skip it. Nusinersen is a made-to-order strand of letters that sticks over that stretch, so exon 7 stays on the card. In the trial that led to its approval, 37 of 73 treated infants reached new movement milestones, such as holding up their heads or sitting. None of the 37 given a sham procedure instead did. On December 23, 2016, nusinersen became the first drug approved for SMA. Infants who had been sick for a shorter time were more likely to benefit.

A New York City pilot added SMA to the newborn blood-spot screen and found one baby in 3,826. She was first treated at 15 days old, and at a year she was meeting all her milestones. Each state decides which conditions its newborn screen covers, so the question for a family is whether SMA is on that list, in time for nusinersen.

What Breaks the Copy Down

Nusinersen patches a card the cell wrote. An mRNA vaccine goes further: it is a whole card, written in a lab and handed to the cell in a shot. Its recipe is for one harmless piece of a virus: for COVID-19, the spike protein. The card comes wrapped in a tiny bubble of fat that slips into cells near the shot. The cell cooks from it and makes the piece, which the immune system learns to recognize.

A card like that took decades to make work. Cells treat loose RNA from outside as a sign of a virus. So a card made in a lab set off the body’s alarms, and little protein got made. In 2005, Katalin Karikó and Drew Weissman found the fix. They swapped Quill’s pale U bead for a slightly altered one, of a kind the cell’s own RNA already carries, and the alarms stayed quiet. Their altered cards also made more protein. The work won them the 2023 Nobel Prize in Physiology or Medicine (Figure 4).

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Figure 4. Katalin Karikó and Drew Weissman tell the story behind the mRNA vaccines (Penn Medicine, 2023). YouTube embed.

The vaccine’s card is never carried into the room where the book is kept. It brings no pen that writes RNA letters back into DNA letters, and no glue to paste a page in. After the protein piece is made, the cell breaks the card down. No room, no pen, no glue: that is the answer for a parent on the phone the night before a shot. The same answer holds for anyone who gets an mRNA shot every fall.

Narrator: The CDC says these vaccines “do not enter the nucleus” and “do not affect or interact with our DNA.” The pen and the glue are real enzymes, reverse transcriptase and integrase.

Narrator: A card from a vaccine does not vanish in an hour. In 2022, a team at Stanford looked inside lymph nodes, the immune system’s meeting places, of people who had had the shot. In some, they found vaccine mRNA up to eight weeks later. A card that lasts that long has more time to teach, and in the end it is broken down like the rest.

The immune system keeps the lesson after the card is gone. What it remembers is the protein piece, the dish, and not the card it was cooked from. A virus that wants to stay has to do what the vaccine’s card cannot.

What Pastes the Copy In

HIV carries its recipes on cards, and it brings the pen and the glue with it. HIV infects a kind of immune cell called a CD4 cell. Inside, its reverse transcriptase reads the card and writes it out again as a page in DNA letters. Its integrase carries that page into the nucleus, cuts the cell’s book open and glues the page in (Figure 5). From then on, the cell’s own couriers copy the virus’s recipes along with the cell’s.

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Figure 5. HIV’s life cycle, animated: reverse transcriptase writes the card out in DNA letters, and integrase glues the new page into the cell’s DNA. HHMI BioInteractive. YouTube embed.

The glued page is why HIV stays. Some infected cells go to rest with the page inside them, copying nothing. Medicine can stop the virus from copying, but no medicine yet reaches a page in a closed book. In 1997, a team at Johns Hopkins studied 22 patients on treatment. The drugs had kept the virus down in them for up to 30 months. From their resting cells, the team recovered virus that could still copy itself. Those resting cells are why HIV treatment lasts a lifetime.

The pen was once thought impossible. Textbooks drew the flow of a cell’s information as one-way arrows: DNA to RNA to protein. In 1970, Howard Temin and Satoshi Mizutani found an enzyme that writes RNA back into DNA, and David Baltimore found it separately. They found it in viruses that cause cancer in chickens and mice. A news story in Nature called the finding “Central dogma reversed.” Later in 1970, Francis Crick, who had named the central dogma in 1958, answered in the same journal. RNA to DNA was one of his “special transfers,” rare but allowed. “I have never suggested that it cannot occur,” he wrote. What his rule forbids is information getting back out of protein. HIV bends the one-way picture in the textbooks, not Crick’s rule.

Narrator: PrEP, short for pre-exposure prophylaxis, takes the tools away before the virus arrives. The daily pill first approved for it, in July 2012, jams reverse transcriptase, so the card is never written in DNA letters. A shot every two months, approved in December 2021, blocks integrase: the glue. A shot twice a year, approved in June 2025, jams the protein shell the virus travels in. Taken as prescribed, PrEP lowers the risk of getting HIV from sex by about 99 percent, and from injecting drugs by at least 74 percent. Of 100 people who would have caught HIV from sex, about one still would. Every form starts with a negative HIV test.

Narrator: The CDC advises everyone from 13 to 64 to be tested at least once, and one question at a checkup can check: has this person ever been tested?

Whichever book or virus a card came from, its next stop is the builders, who cook from it. A vaccine’s card then goes in the bin. Unless PrEP stops the virus first, HIV’s card ends as a page glued into the book.

A Closing Invitation. The pot ran over because Big Anthony could start a copy and not stop it. A cell’s cards are made to be thrown away, and the one card that stays has to bring its own glue.

1. Settle the dinner worry. Think of the last time mRNA vaccines came up, at a pharmacy counter or across a dinner table, and kept someone up worrying that night. Picture Quill’s card: read, broken down, never written into the double line. Which worry is left for the next time, once the gene worry is gone?
2. Check for a glued page. Tonight, scroll the lab results in the patient portal on your phone for an HIV test. If you find none, or have no portal, what would make your next checkup the visit you ask?
3. Ask which steps were checked. When a baby is coming in your family or a friend’s, ask the hospital which conditions the newborn blood-spot test, the heel prick, covers, and whether SMA, the muscle disease, is one. Found at birth, it can be treated within weeks. Which grandparent-to-be in your circle would want to know before the baby comes?

Strega Nona never needed a bigger pot. Ask in time, and you are the one who stops the pot. Every card a cell writes carries its own three kisses.

Worth remembering Save as image

Your cells copy each recipe, cook from the copy and throw it away. That lets a body change what it makes within hours, and your DNA stays untouched. A virus that pastes its copy in can stay for life.

Where This Came From

The cutting step was found in 1977 by two teams, led by Phillip Sharp at MIT and Richard Roberts at Cold Spring Harbor Laboratory. Both saw that a virus’s mRNA was stitched together from pieces lying far apart in its DNA. They shared the 1993 Nobel Prize in Physiology or Medicine. Temin and Baltimore shared the 1975 prize with Renato Dulbecco for the work on tumor viruses that found the pen.

Intellectual Honesty Note. The sprites, Quill, the cutters, the football field and the recipe cards are invented staging. Real transcription is done by an enzyme, RNA polymerase, and splicing by a large machine called the spliceosome. Quill’s first copy is called pre-mRNA. The nine hours is a median from one study in mouse cells; human cards vary widely. Human cells make a little reverse transcriptase of their own, from repeated stretches of DNA called LINE-1 that make up about 17 percent of the genome; the vaccine brings none. The PrEP drugs are tenofovir with emtricitabine (pills), cabotegravir (every two months) and lenacapavir (twice a year). The shots are approved for HIV risk from sex, so the 74 percent figure for injecting drugs is for pills. The one in 100 is this piece’s own arithmetic from the 99 percent.

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Near the edge of the frame, a few cells hang straight down, long and bumpy, like peanut shells made of wax (Figure 1). In each one, a larva floats on a pool of thick white jelly, far more than it can eat.

Figure 1. Two queen cells on the comb, one turn of a loop. A larva fed royal jelly in each will come out a queen, and the queen will lay the eggs of the workers who feed the next one. Photograph by Piscisgate (2014), Wikimedia Commons, CC BY-SA 4.0.

Any female larva in the hive can grow into a queen or a worker. Her genes do not decide which. The larvae in the hanging cells become queens. A queen lives for years and can lay more than a thousand eggs a day. A worker lives a few weeks in summer and usually lays none.

Food decides which. The white jelly is royal jelly (Figure 2), a rich food made in glands in the workers’ heads. The workers feed it to a few larvae for as long as they are larvae. The rest get a plainer mix with pollen and honey in it, and become workers. Food cannot rewrite a gene. So what does it change?

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Figure 2. How royal jelly makes a queen, from SciShow (2015), YouTube embed. The video credits one jelly protein, royalactin. A later team could not reproduce that result.

Think of a larva’s genes as a cookbook. Each gene is a recipe for one molecule the body uses, and every larva in the hive carries the same book. Cells can stick small chemical marks onto some of the recipes, like notes in the margin that say “skip this one.” Biologists call them methylation marks. They help decide which recipes the cell cooks and which it skips.

In 2008, a team at the Australian National University, in Canberra, tested whether those notes were what the jelly changed. The team switched off one gene in newly hatched larvae: the recipe for the enzyme that writes the notes. Then they fed the larvae a worker’s diet. Most of them came out as queens, with full ovaries. The team called the result “a royal jelly-like effect.” Each larva kept the cookbook it was born with. What changed was which recipes got cooked.

Which bee each larva became depended on what its cookbook was connected to: the notes, the food, and the workers who chose which larvae to feed. Any cookbook raises five questions: what it counts, what it keeps, what it answers, what it misses, and what it cannot decide.

Say you mail a spit sample to a DNA testing company, and the report comes back: you probably cannot digest milk as an adult. You start drinking your coffee black, bitter at the first sip. You stop buying cheese, pay extra for lactose-free milk and read every label in the shop. Your partner switches to oat milk so the fridge needs only one carton. By your next checkup, you have gone months without an easy source of calcium.

Here is how such a report could be wrong. For most people in the world, the body puts the recipe for digesting milk away after childhood. Some people carry a one-letter difference in the cookbook that keeps the recipe in use. In Europe, most people who have one share the same spelling. Many families who kept cattle in East Africa carry a different spelling that keeps the same recipe in use. Say the test looks only for the European spelling. A person who carries the East African one gets a report that finds nothing it knows and says the recipe is closed. That person gave up milk for nothing. The test read the right page, looked for the wrong spelling, and never asked where the family came from. Systems thinking has a question for any test result that costs someone milk, cheese and calcium: what else is that result connected to?

What the Cookbook Counts

Counting human genes started as a bet. In May 2000, at Cold Spring Harbor, the geneticist Ewan Birney opened a pool on how many genes human DNA would turn out to hold. Biology was about to get its first full cookbook for a person: every gene, every recipe (Figure 3).

Figure 3. The human genome printed as books at the Wellcome Collection, in London: a volume or more for each chromosome, from 1 to 22, then X and Y, in type almost too small to read. Photograph by Russ London (2010), Wikimedia Commons, CC BY-SA 3.0.

The guesses ran from about 20,000 to more than 200,000. In 2003, the count came in at 24,847. The closest guess, 25,947, belonged to Lee Rowen, who worked at the Institute for Systems Biology. She won $600 and a signed copy of The Double Helix.

Later counts settled lower, near 20,000. The worm C. elegans, about a millimeter long, has a little over 20,000 genes of its own. A person and a worm carry cookbooks of about the same size, so the number of recipes could not be what makes a person a person. In Donella Meadows’ definition of a system, the parts matter less than the rules that connect them. Here the parts are the genes, and the rules decide which recipes get cooked, when, and how much. Two kitchens with the same book can serve very different dinners.

A full gene count is one example of omics: measuring one layer of a living thing all at once. Each layer takes the suffix -ome. Two of them explain the bees.

In this piece’s kitchen, the genome is the cookbook, and the epigenome is the notes in its margins. The genome is the layer the walkthrough of DNA, transcription, and translation takes apart. The epigenome is the layer the natural experiment on methylation follows.

The book also closes some recipes on its own schedule, and a single letter can keep one open for life.

What the Cookbook Keeps

Milk is the recipe most bodies put away. Babies make their own enzyme for lactose, the sugar in milk. The enzyme is called lactase, and in most mammals the body stops making it after weaning. A short stretch of DNA near the gene closes the recipe after childhood. In about a third of adults alive today, the recipe stays open. The European spelling is a single changed letter in that stretch, and it keeps lactase coming for life.

The East African spellings are other one-letter differences nearby, and each arose on its own. In 2007, the geneticist Sarah Tishkoff and her colleagues traced the most common of them, carried by many herding peoples in Kenya and Tanzania. It had spread fast, over roughly the last seven thousand years.

Why keep that page open? Herds. Herds put fresh milk within reach. Adults who carried the spelling could digest the milk, got more food from it, and more of their children lived to carry the spelling too. The more people could drink milk, the more a herd was worth, and herding spread further. In Meadows’ terms for feedback, that is a reinforcing loop: a change that feeds itself. Even this loop has a ceiling. A herd can grow only as large as the grass and water around it allow. The cookbook kept the page. The herds outside made it worth keeping.

A DNA sample can show which spelling someone carries. It cannot show the herds that made the spelling worth carrying, or the grass and water that capped the herds. So a kit report that rules out milk earns one email to the company within the week: which spellings did the test look for? A parent who skips the email may cut milk from the children’s plates too, on a test that never looked for the spelling the family carries. A parent who already cut the milk can still ask.

What the Cookbook Answers

The herds and their milk changed the book over thousands of years. The body asks the book questions every day, and it answers within hours.

In 2012, Romain Barrès and his colleagues put eight sedentary men on an exercise bike twice, at least a week apart. One ride was easy, at 40 percent of each man’s maximum effort, and one was hard, at 80 percent. Both rides stopped once the rider had burned 400 calories. With a needle, the researchers took small plugs of thigh muscle before each ride, right after it, and three hours later.

One recipe they read was PGC-1α, which tells a cell to build more of its energy supply. Right after the hard ride, the notes on PGC-1α had dropped to about half their resting level. Three hours later, the muscle was cooking that recipe several times as much as at rest. After the easy ride, the notes barely moved, yet the recipe still got cooked more. The notes are one rule among several.

That energy supply is mitochondria (Figure 4), the parts of a cell that burn fuel. Over months of training, more mitochondria mean more capacity for the next ride.

The ride changes the notes. The notes change which recipes get copied out to the counter, a layer called the transcriptome. The copies change which dishes get made, the proteome. The dishes change what the body can do on the next ride. The cookbook answers the ride, and the answer shapes the next question.

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Figure 4. What more mitochondria do for a cyclist, from Pedaling to the Top (2025), YouTube embed. Thumbnail: two mitochondria in lung tissue, electron micrograph by Louisa Howard, public domain.

To see the answer, the team had to sample the muscle three times in one day. Many omics studies draw one tube of blood from each person, once. Peter Senge defines systems thinking as seeing “patterns of change rather than static ‘snapshots.’” One tube is a snapshot. It can show the notes in the margins, but not which ride wrote them.

What the Cookbook Misses

Reading 5.4 million genomes still left out the meals. In 2022, a study led by the geneticist Loïc Yengo pooled those genomes. It found 12,111 small spellings tied to height, each with a tiny effect. Together, in people of European ancestry, they account for about 40 percent of how much heights differ. In other ancestries, the share falls to about 10 to 20 percent. Part of the 60 percent the spellings miss is genetic and not yet mapped.

The rest sits on the plate. In the 1800s, Dutch soldiers averaged about 165 centimeters, shorter than men in most of Europe. Dutch men are now the tallest in the world. They stand about 20 centimeters taller, most of a head above those soldiers. A cookbook cannot change that fast. Food, health, and living conditions can.

Say a youth basketball coach ranks twelve-year-olds by a height score built from those 12,111 spellings and cuts the bottom three. A parent shown the ranking can ask which people the score was built on. The score says less for players outside the ancestry it was built on, and nothing about what their childhood meals will add.

What the Cookbook Cannot Decide

A cell can hold a recipe and still never cook it.

Malaria kills close to 600,000 people a year, most of them young children in Africa. One of the main malaria drugs is artemisinin (Figure 5), which comes from a plant called sweet wormwood. The supply of wormwood swings. A short harvest sends the price up, so more farmers plant wormwood. Once their crops flood the market, the price falls, and the next shortage begins.

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Figure 5. A short history of malaria drugs, from NPR’s Skunk Bear (2012), YouTube embed.

In 2003, a team led by the chemical engineer Jay Keasling, at Berkeley, looked for a steadier source. They copied recipes from baker’s yeast and one from wormwood into E. coli, and the bacteria made an early form of the drug. The team then moved the work into yeast itself. In April 2013, the drug company Sanofi started making artemisinin with yeast in Garessio, in northern Italy. That year, the factory made about 8 percent of the world’s supply.

By 2015, farmers had a great year. So much wormwood grew that artemisinin from the plants sold for less than $250 a kilogram. Sanofi needed $350 to $400 to break even. That is at least $100 a kilogram above the plants. Sanofi’s rivals would not buy from it, and the world wanted no more of the drug than before.

“If that price is already very low and there’s a bumper crop,” Keasling said, “there’s no reason to fire up a fermenter.” The fermenter, the steel tank where the yeast grows, stood idle. The yeast still had the recipe. The price of wormwood decided.

That is the edge of every cookbook. No page inside the yeast held the price of wormwood. The jelly, the herds, the ride, the meals and the market all came from outside the book, and each one decided what got cooked.

A test report that says to give up a daily food has read one book. A friend holding such a report can ask three things first. What did the test look for? Which people was it built on? What else is the result connected to? The larva’s cookbook could not say which bee it would become. The jelly in its cell could.

A Closing Reflection. The cookbook counted, kept, answered and missed, and it did not decide. The jelly, the herds, the ride, the plate and the price of wormwood each changed which recipes reached the table, and none rewrote a recipe.

1. Spot the idle fermenter. Right now, look around for something you paid for that still works and stands unused: a bread maker in the cupboard, an app on the phone in your hand. It still has its recipe. What around it changed?
2. Read the margin notes. Think back to one habit that changed this year. Something around you changed first: a new gym on your street, an office move that added forty minutes to the commute, a friend who started walking at six. Which of your own recipes got cooked more, which got skipped, and who at home noticed first?
3. Ask which spelling. When the next report tells you to give up a food, from a DNA kit or your next checkup, ask what the test looked for before the shopping changes. One question may keep the cheese on the table. Who would give the food up with you, the one who cooks or the one who shops?

Open a packet of baker’s yeast and smell it. Split the dough: one bowl by a warm window, one in a cool corner. Look again in an hour. Same packet, same recipe. One bowl rose like a queen.

Worth remembering Save as image

You can read every page of the cookbook and still not know what is for dinner. Your genes hold the recipes; what gets cooked is decided outside the book.

Where This Came From

This piece follows systems thinking into a single cell. Konopka’s post on systems thinking (2026) started it.

Intellectual Honesty Note. The cookbook is this piece’s image, not a biologist’s term: genes as recipes, methylation marks as notes in the margin, gene variants as spellings, RNA copies as recipes copied out, proteins as dishes. A methylation mark does not always mean “skip”; on the genes in the exercise study, fewer marks went with more activity. The hive scene is built from standard beekeeping descriptions, not one hive.

The stakes paragraph’s report is hypothetical, and which spellings a kit tests depends on the kit. This piece reads lactase persistence as a reinforcing loop with a grazing ceiling. It adds the exercise loop’s last step, “more capacity for the next ride.” Its point about a snapshot not naming the ride is its own reading, not a finding. The stretch of DNA near the lactase gene is an enhancer, which raises a gene’s activity; “closes the recipe” simplifies how it is turned down. The exercise study measured single rides, not months of training. The 60 percent and the $100 gap are subtractions made here from the cited numbers, and the ride’s “about half” and “several times” are read off the exercise paper’s Figure 2. The protein step and the link from PGC-1α to mitochondria are standard physiology. The bee experiment switched the methylation enzyme off by hand; how much methylation steers caste in an ordinary hive is still debated (Oldroyd and Yagound, 2021).

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