Naked Mole-Rat Queens Rule via a $5 Molecule: Not Urine, a Skincare Ingredient
The reproductive-suppression signal in naked mole-rats has finally been found: queens alone produce isopropyl myristate. Add it to a colony that has lost its queen and peace holds; stop and the fight for the throne erupts. The same molecule also shows up in lactating women.
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The queen mystery: social suppression, not genetic
Naked mole-rats are a rare social species among mammals: a colony has only one breeding female, the queen, while the other females do not reproduce and only find food, guard the nest and care for pups. The structure resembles bees, but a bee queen is destined before birth, whereas every female naked mole-rat could in principle become queen. Melissa Holmes says this is not a genetic trait but the social environment exerting control — the question is what signal makes one female queen and suppresses all the others. Earlier work looked for pheromones only in queen urine and came up empty.
A molecule made only by queens
The team collected all kinds of odors from 16 colonies and more than 450 animals, and had in particular to pick the queen out of a pile of stacked rodents. They found a volatile molecule produced only by naked mole-rat queens: isopropyl myristate. It is structurally simple, common in plastics and skincare products, and can be bought in the lab for about $5. Gary Lewin says this made the experiments extremely easy: you can just buy it and run behavioral tests. By contrast, rodent pheromones were thought to belong in urine, but there was nothing at all in queen urine.
Add it back and peace holds; stop and war begins
Brain scans show isopropyl myristate activates the odor-processing regions in worker brains and suppresses other females from entering a sexually active state — effectively a "scent contraceptive." Add the molecule to a colony that has just lost its queen and everything stays calm, with workers behaving as if the queen were still there; once the addition stops, high-ranking females immediately begin fighting among themselves for the throne. The authors think the mechanism is clear: whoever gets pregnant first starts making the molecule and thereby suppresses all the other females. Melissa Holmes calls it the holy grail of research on naked mole-rat social structure.
The same molecule and lactating women
Isopropyl myristate is not unique to naked mole-rats. Gary Lewin notes that a study years ago measured the volatile molecules given off by the breasts of lactating women, and isopropyl myristate was among them; when researchers put the mixture on cotton swabs, newborns would start sniffing and even try to suckle. But he says that paper was an isolated case and no one followed up. Now that the molecule has such a strong social effect in naked mole-rats, researchers perhaps ought to revisit whether it does anything in other mammals.
Two cotton-candy planets and Hannibal
This week's Highlights has two number stories. One is two newly discovered exoplanets, close to Jupiter in size but more than 20 times lighter, with a density lower than cotton candy — among the lowest-density planets known; they orbit the same star, with periods of 232 days and 139 days. The other is the metabolic ledger of Hannibal crossing the Alps: the most likely route requires 15 days and 230 tons of supplies, and even with enough food, maintaining body weight would have been impossible, with the war elephants expected to lose 4%. These two segments are unrelated to the main thread but are enough to refresh your intuitions.
How novices evaluate a new game
Game research has long focused on experts, but Katie Collins's team looked at novices judging a game the first time they hear its rules. In the experiments, participants read the rules of different games and predicted who would win, whether there would be a draw, and whether they thought it would be fun. They modified tic-tac-toe and Connect Four — for example, a three-by-three board requiring two rows to win, or a five-by-five board won with three in a row — creating rule variants people had never seen. The core question is not "how to play well" but "before making the first move, how does the human brain judge whether a game is worth playing."
Three features of the "intuitive gamer" model
The team's intuitive gamer model imagines novices doing fast, shallow, probabilistic, goal-directed mental simulation. Fast means only a few simulations, more than 1 and fewer than 10; shallow means the simulated players do not think very far ahead; probabilistic means they assess which action is good but do not necessarily always pick the best one. The model explains both people's judgments about new games and data from their first actual play. Katie Collins says this shows novices are not entirely unsystematic, but do not expect them to match the optimal predictions of classical game theory.
Two implications for AI
The first AI use of this model is saving compute: in many situations, you do not need massive simulation or enormous computation to approach game-theoretic optimality. A system could work like an intuitive gamer, doing only a little thinking to quickly judge whether a path is worth exploring. The second use is AI as a thinking partner: if an AI has a more accurate model of human computation, it can simulate the user's judgment and point out ahead of time that "you may think a position will go one way, but it won't." The next step in the research is to expand from analyzing existing games to how people create new games, which is closer to open-world games.
In their own words · checked verbatim
we can just buy this stuff for. Basically $5.
Gary Lewin4:05
once someone's pregnant and they're making isopropyl marate. They're going to be the queen and nobody else can be the queen.
Gary Lewin4:05
This is like.The Holy Grail for naked Muor research for those of us interested in the social structure.
Melissa Holmes4:05
Games are a really nice framework to think about so many aspects of. What makes life so interesting?
Katie Collins11:49
Engaging in fast.Flat.Probbilistic in goal directed mental simulation.
Katie Collins16:09
So there's systematicity in how people think about a game for the first time, which is really, really cool.
Katie Collins17:21
you could imagine doing something that's kind of like the intuitive gamer where you just do a little bit of thinking to make a quick judgment for whether that path is worth exploring
Katie Collins18:42
Figures
| Purchase cost of isopropyl myristate | About $5 | 4:05 |
| Naked mole-rat colony scale | More than 450 animals across 16 colonies | 4:05 |
| Mass of the two exoplanets | About Jupiter-sized, but more than 20 times lighter | 10:34 |
| Exoplanet orbital periods | 232 days and 139 days | 10:34 |
| Number of known super-puff planets | Only a few dozen | 10:34 |
| Supplies needed for Hannibal to cross the Alps | 15 days, 230 tons of food | 10:34 |
| Expected weight loss of the war elephants | About 4% | 10:34 |
| Normal daily foraging time of African elephants | 14 hours/day | 10:34 |
Glossary
- isopropyl myristate
- A volatile ester molecule common in plastics and skincare products; this study shows it is also the reproductive-suppression signal of the naked mole-rat queen.
- naked mole-rat
- A subterranean rodent of East Africa that lives socially like bees, with only one breeding female in a colony.
- super-puff
- An exoplanet close to Jupiter in volume but extremely low in mass, with a density lower than cotton candy.
- intuitive gamer
- A computational model that explains how novices evaluate new games through fast, shallow, probabilistic, goal-directed mental simulation.
How to listen
Behavioral and chemical ecologists, engineers working on AI reasoning and cognitive modeling, and founders looking for examples of chemical signals controlling an organization.
The Hannibal segment of Highlights is unrelated to the main thread and can be skipped; the other two stories are both worth hearing.