r/DidYouKnowNow

Nuttall's white-crowned sparrow is the non-migratory subspecies that occupies the San Francisco Bay Area, and it has been recorded more thoroughly than almost any songbird population on earth. Luis Baptista started systematically mapping its dialects out of the California Academy of Sciences in the 1970s. Elizabeth Derryberry's lab has carried the recording program since the mid-2000s. The archive now runs to tens of thousands of individual songs.

The song is about two seconds: an opening sequence of clear whistles, then a trill. The whistle portion is broadly conserved across the subspecies. The trill is where the variation lives — pitch trajectory, syllable count, syllable structure, frequency modulation. That's the part that differs between the Presidio and Lake Merced and the Marin Headlands and Golden Gate Park and the Berkeley hills, and by the late 1970s a trained ear could assign an individual bird to a neighborhood from a single decent recording.

Some of those dialect boundaries are only a few hundred metres apart, across territory lines, with no geographic obstacle of any kind between them.

The 2024 paper

Luo, Lipshutz, Phillips, Brumfield and Derryberry ran three analyses on the same birds and published in PLOS One in May 2024.

Acoustic: 175 songs from 82 male sparrows recorded 2010-2022, trill structure quantified and clustered into 18 dialect categories.

Genetic: the same individuals genotyped with SNP markers to test whether dialect zones correspond to genetically distinguishable populations.

Playback: females from each zone exposed to their local dialect versus an adjacent zone's dialect, to test whether dialect functions as a mate-recognition cue rather than a passive geographic marker.

All three converged. Females responded preferentially to local dialect even where the adjacent zone was a few hundred metres away. And sparrows in a given dialect zone showed measurable genetic differentiation from sparrows in neighbouring zones — inside a contiguous range with no physical barrier and continuous opportunity for gene flow.

The proposed mechanism is that the culturally transmitted mate-choice preference is doing the isolating work that geography does in the standard allopatric model. The dialect is learned, not inherited. It determines which males a neighbourhood's females preferentially breed with. And the genetic consequences are accumulating on a timescale short enough that a single human research lineage has watched it happen.

Why the dialects don't blur

Marler established the learning mechanism in the 1960s and 70s: white-crowned sparrows acquire song from adult tutors during a critical period roughly 10 to 50 days post-hatching, followed by a sensorimotor phase to around 200 days where the juvenile shapes its own output toward the memorised template using auditory feedback. Birds deprived of tutors during the sensory phase produce abnormal isolate song. Birds deafened after crystallisation keep singing what they already learned, which means the template is stored neurally and doesn't need ongoing feedback.

Add natal philopatry — juveniles tend to settle in or adjacent to the territory they hatched in — and the tutor pool available during the critical period is statistically dominated by adult males singing the local trill. Juveniles typically learn from several tutors and end up producing something like a composite that sits inside the local structural envelope.

The result is a cultural lineage that has outlived every individual carrying it many times over. White-crowned sparrows live two to five years. The Presidio dialect Baptista recorded in the late 1970s is still the Presidio dialect, roughly fifteen to twenty generations later.

COVID separated inheritance from performance

Derryberry's lab had a 2012 finding that Bay Area sparrows had shifted song minimum frequency upward by around 200 Hz across three decades of rising traffic noise — an adaptation that preserved transmission range in a noisier soundscape but carried a cost, since lower-frequency songs are harder to produce and appear to be the ones females rate more highly. The urban birds had made themselves audible at the expense of being attractive.

Then in March 2020 the shutdown dropped Golden Gate Bridge traffic to levels last seen around 1954, and Jennifer Phillips went out on a bike with a recorder rig to the same sites the lab had baselined in 2015 and 2016.

Urban song amplitude fell about 30 percent. Minimum frequency dropped about 35 Hz. Transmission distance more than doubled. Performance measures relevant to female assessment improved. The rural controls at Point Reyes, where there had been little traffic noise to begin with, showed no equivalent shift.

What did not change was the dialect. The Presidio dialect stayed the Presidio dialect. Amplitude, frequency and range are delivery parameters, plastic on a scale of weeks. The trill structure is the cultural inheritance, stable across generations. The 2020 paper measured the first. The 2024 paper measured the second. Traffic has since recovered and so have the delivery parameters, with no lasting mark on the dialect structure.

Full write-up on Baptista's mapping, the Derryberry long-term record, the 2020 shutdown study, and the 2024 genetic finding:

https://unteachablecourses.com/white-crowned-sparrows-san-francisco-dialects/

The question I'd genuinely like an answer to is about the causal claim, because philopatry is a confound that could produce both patterns on its own. If juveniles settle near where they hatched, you get dialect stability and spatial genetic structure without the dialect necessarily doing any isolating work — limited dispersal alone generates isolation-by-distance. The playback result is the evidence that's supposed to break the tie, but preference in a playback trial isn't the same thing as realised assortative mating in the field, and 175 songs from 82 birds across 18 categories is roughly four or five individuals per dialect. Is there work that actually separates these — dispersal-distance data allowing an isolation-by-distance null, or parentage assignment showing females who do disperse across a boundary preferentially pairing with males singing their natal dialect rather than their new local one? That second design seems like the decisive test and I can't tell whether anyone has run it.

Between 2001 and 2006 Nakheel dredged sand off the Persian Gulf seabed and sprayed it into the shape of a palm tree. 5.72 square kilometres of new land. 94 million cubic metres of marine sand. Around $12 billion. It added 78 kilometres of coastline to Dubai, which was the whole economic case — beachfront commands premiums inland property doesn't, so manufacturing coastline is manufacturing margin.

What it doesn't have is a foundation. There's no concrete base, no seawall at the trunk. It's sand for the fronds and trunk, plus a crescent rock breakwater to shield the fronds from open-ocean wave action — 7 million tonnes of rock, quarried in the Hajar Mountains and barged 100 kilometres.

Which makes it structurally different from everything else people file it alongside. The Falkirk Wheel is steel and concrete with a 120-year design life. The Wuppertal Schwebebahn is structural steel and has been running since 1901. The Palm Jumeirah is built out of the one material water is specifically good at relocating, and its service life is a function of how much money Dubai spends putting sand back versus how fast the Gulf takes it away.

The maintenance is existential, not preventive

NASA satellite data has the island subsiding at roughly 5 mm/year. The fronds lose sand continuously to wave action and tidal currents — one major replenishment operation moved over 3.5 million cubic metres.

Dredged marine sand is a worse structural material than it looks, because it lacks what natural coastal sand has: shell fragment content, organic matter, and the compaction history that gives a natural beach cohesion. You're placing a poorly-graded, uncompacted, cohesionless fill and then asking it to hold a shape against continuous hydraulic loading.

The comparison worth drawing is the Delta Works, which protects land that exists naturally and would flood without intervention. Failure there means inundation of terrain that still exists underneath. Palm Jumeirah protects land that doesn't exist naturally and would dissolve without intervention. Failure means the terrain stops being terrain. Same category of engineering, fundamentally different failure mode.

Self-defeating by construction

The dredging buried roughly 1.2 square kilometres of coral reef under sediment.

Coral reef is a natural breakwater. It dissipates wave energy before it reaches shore — which is exactly the function the 7-million-tonne rock crescent was built to perform. The construction destroyed the free, self-maintaining, self-repairing wave attenuation structure and replaced it with a quarried one that requires monitoring and repair, on the same site, to protect the thing that was built on top of the first one.

The sediment plume also smothered oyster beds and seagrass under about five centimetres of silt across a wide radius, and turbidity cut light penetration enough to kill photosynthetic organisms in the affected zone. Artificial reef structures have since been installed along the breakwater with some documented recovery, but the remediation is cosmetic against the scale of the original loss.

Two consequences nobody designed for

The first is downstream erosion. Dubai's beaches lose 10,000 to 15,000 cubic metres of sand a year naturally. The island disrupts alongshore sediment transport — the mechanism that moves sand from one beach to the next along the coast. Sand that would have travelled east now accumulates on the western side of the island, and the beaches east of it starve. Some sections have retreated at up to 10 metres per year, and Dubai has spent millions on seawalls, groynes, and rock revetments to arrest erosion the island itself caused.

The second is water quality. The crescent breakwater that protects the fronds from storm waves also prevents tidal flushing, so the lagoons don't circulate properly. That produces stagnant zones, algal blooms, and the smell tourists have been reporting since it opened. Engineers deepened channels and installed circulation infrastructure — you're now running engineered water movement to substitute for the tidal exchange the breakwater blocks. Partially effective.

Both are the same class of problem: a structure that solves its primary design objective by interrupting a natural transport process, and then requires secondary infrastructure to replace the process it interrupted.

They're building the bigger one

Palm Jebel Ali — 50 percent larger, shelved after 2008 — relaunched in 2023. Redesigned masterplan with 80 hotels, homes for 35,000 families, six marinas. Jan De Nul took an AED 810 million marine works contract covering dredging, reclamation, beach profiling, and sand placement. First eight fronds targeted site-ready by early 2025, completion revised to 2027.

Meanwhile The World — 300 islands arranged as a world map, four kilometres offshore — sat largely undeveloped for a decade after the crash, visibly dissolving on satellite imagery. Individual island owners carry their own shoreline protection costs, running into millions of dirhams annually per island, which is a reasonable explanation for why most of them remain empty. A Monaco-themed resort opened in 2022 and a Sweden Island development is in progress.

Full write-up on the construction, the sediment transport problem, the reef loss, and Palm Jebel Ali: https://unteachablecourses.com/palm-jumeirah-dubai-artificial-islands-2026/

The engineering question I'd actually like an answer to: is there a design approach for large-scale sand reclamation that gets you to something self-sustaining, or is perpetual replenishment inherent to the method? Geotextile containment, cement or polymer stabilisation of the fill, deliberately engineered reef structures as primary rather than supplementary wave attenuation — do any of these change the maintenance curve meaningfully at 5+ km² scale, or is the honest answer that if you build land out of cohesionless dredged fill in open water, you have signed up for an annual sand budget in perpetuity and the only variable is its size?

Colonel Thomas S. Meacham was a New York dairyman with a flair for spectacle. In 1835 he set out to make the largest wheel of cheese the republic had ever seen — roughly 150 cows' worth of milk, four feet across, two feet thick, 1,400 pounds. He paraded it through New York on a flag-draped wagon pulled by two dozen horses, decorated with patriotic mottoes, accompanied by a band representing all twenty-four states, and then shipped it to Washington as a gift to the president.

Meacham had voted for Henry Clay. He didn't like Jackson. The cheese was an advertisement for New York dairy, and it remains one of the more successful pieces of agricultural marketing in American history — for reasons entirely outside its maker's control.

The wheel sat in the White House entrance hall for the better part of two years, aging. By contemporary accounts it could be smelled from blocks away.

What Jackson did with it

The conventional move was available and obvious: serve it at a refined reception for senators and foreign ministers, thank the donor, move on.

Instead, as his second term wound down, Jackson announced an open house on Washington's Birthday in 1837 and invited the entire city to come eat it.

Thousands showed up. They brought their own crackers. They came in through the windows when the doors jammed. Ragamuffins elbowed diplomats in full court dress. They hacked at the wheel with knives and finished all 1,400 pounds in about two hours, grinding a substantial quantity of it into the carpets, the curtains, and the floorboards of the East Room.

A contemporary wit recorded that the carpet was slippery with cheese and that nothing else was discussed in Washington that day. The incoming Van Buren administration had to strip the drapes, air the rugs for days, and whitewash the walls to get rid of the smell.

Why it worked

The cheese levee enacted the entire Jacksonian creed in dairy form: the government and its houses belong to ordinary people rather than to a refined class, and the spectacle of the crowd taking possession isn't a problem to be managed — it's the point.

Jackson understood something decades before anyone had a word for it, which is that an aristocrat recoiling in disgust at the sight of common people eating in the president's foyer isn't a public relations problem. It's a campaign advertisement. The people who were horrified were horrified in exactly the way that confirmed the thesis, and their horror did more work than any speech could have.

Harry Truman, renovating the place generations later, grumbled about old Andy Jackson's rough backwoodsmen tramping across the carpets in muddy boots and grinding cheese into them — which is precisely the reaction the event was designed to produce in precisely the kind of person who would say it, still landing a century after the man who staged it was dead.

The smell lasted weeks. The symbolism has lasted centuries.

It had a dress rehearsal

Eight years earlier, at his 1829 inauguration, an enormous crowd followed Jackson from the Capitol to the White House and the public reception became something closer to a riot. Thousands jammed the mansion, stood on silk chairs in muddy boots to get a look at Old Hickory, broke thousands of dollars of china and glassware, and pressed in so densely that the new president had to be evacuated out a back door to a hotel. Staff eventually lured the crowd onto the lawn by hauling the tubs of spiked orange punch outside.

A horrified Supreme Court justice called it the reign of King Mob. To Jackson it was the entire idea.

The part the cheese story usually leaves out

The same conviction — that the people's will should sweep aside the genteel restraints of the elite — is not separable from what Jackson did with it when it turned on people who couldn't vote.

He signed the Indian Removal Act on 28 May 1830. When the Cherokee fought removal in court and won at the Supreme Court in Worcester v. Georgia in 1832, the federal government declined to enforce the ruling. The expulsion was carried out under his successor in 1838 but set irreversibly in motion by Jackson: roughly sixteen thousand Cherokee driven from their homes at gunpoint, around four thousand dead of exposure, disease, and starvation on the march. Across all the removed nations the dead numbered well over ten thousand.

He was also one of the largest slaveholders ever to hold the office, with roughly 150 people enslaved at the Hermitage. In 1804 he placed an advertisement for a man who had escaped, offering a fifty-dollar reward and then ten dollars extra for every hundred lashes anyone would lay on him, up to three hundred.

His "people" was a category with violent borders, and the democracy he expanded so dramatically was a democracy for white men built on the land of the expelled and the labour of the enslaved. Both facts are the same man in the same skin, and the cheese party doesn't sit in a separate compartment from the removal order.

Full write-up on Meacham, the cheese levee, the 1829 inaugural riot, the Bank war, and the removal:

https://unteachablecourses.com/andrew-jackson-big-cheese/

The thing I find genuinely interesting as a matter of political technique: the cheese wasn't Jackson's idea, wasn't made by a supporter, and wasn't intended as a political object at all. He inherited a marketing prop from a man who'd voted against him and converted it into the founding set piece of American populism, essentially by choosing a guest list. Are there other cases where a president took an object or event they had no hand in creating and turned it into that durable a piece of political symbolism — or is the cheese unusual precisely because the raw material was so accidental?

At CES 2025 in Las Vegas, in the same hall as Atlas, Optimus, and Figure 02, there was a Realbotix unit on display. Everything else in that room was pitching warehouse logistics, manufacturing assembly, and eventually folding your laundry. Realbotix was pitching conversation.

The company got there by one of the stranger corporate paths in robotics.

The genealogy

It starts with Matt McMullen, who trained in Hollywood special-effects fabrication and founded Abyss Creations in San Marcos, California in 1996 to make hyper-realistic silicone mannequins. Customer demand pushed the product line somewhere he hadn't planned, and by the mid-2010s Abyss had shipped four to five thousand units at $6,000 to $15,000 apiece and had become the most identifiable name in its category. The 2007 Ryan Gosling film Lars and the Real Girl was, in attention terms, the moment the product entered general awareness.

In 2016 McMullen decided the next step was animatronics and conversational AI, spun up a sister company called Realbotix, and staffed it with engineers poached from Hanson Robotics — the Hong Kong outfit behind Sophia, the platform Saudi Arabia granted citizenship to in 2017. The Harmony app launched on Android in April 2017 at $30 a year. The first robotic head shipped late that year at around $10,000.

Then in July 2024 a Toronto investor named Andrew Kiguel — previously chief executive of a publicly traded cryptocurrency holding company called Tokens.com — bought Abyss Creations outright and reverse-merged it into a public shell. The twenty-eight-year-old founder-led silicone manufacturer became Realbotix Corp, ticker XBOTF, with an "embodied AI" thesis and quarterly filings.

The product

The current platform is an animatronic head module mated to a customised silicone body, $8,000 to $20,000 depending on configuration, running the Harmony AI app with persistent memory of your stated preferences.

The feature that separates it from everything else in robotics is magnetic face-swap. The face detaches. You can click on a different one — Harmony, Solana, several others released since — on the same head and the same body. No other robotics company ships a product where the head is a platform and the face is a peripheral.

There's a male variant called Henry: six feet, eighty-four pounds, eleven thousand dollars and up, British accent in the default voice configuration. Commercial footprint substantially smaller than the female-form line, which is the kind of sentence that appears in an annual report now.

The pivot nobody expected

The parent holding entity, Simulacra Corporation, runs three subsidiaries. Abyss Creations does the silicone. Realbotix does the AI and animatronics. And Anthropomorphic Figure Dynamics does medical simulation and military training under contracts with Johns Hopkins Hospital and Department of Defense clients.

Same hardware substrate. Same hyper-realistic silicone bodies, same animatronic faces, same manufacturing line in San Marcos. Different invoice header. A surgical resident practising on an AFD training model is practising on the descendant of a Hollywood special-effects mannequin that took a thirty-year detour, and the engineering that makes a face convincing in one market makes it convincing in the other.

It is a legitimately good business pivot and it should not be as funny as it is.

Everyone else said not it

Here's the genuinely unusual industrial fact. Every commercial robotics vertical has multiple serious players fighting for share — warehouse, inspection, agriculture, eldercare, defense, disaster response. Except this one.

Boston Dynamics, Agility, Apptronik, Figure, 1X, and Tesla have all publicly committed to staying out. Several have gone further and built hardware constraints into their platforms — articulation limits, materials choices — that make repurposing structurally awkward rather than merely against policy.

None of them are constrained technically. Any of them could enter with modest engineering changes and would immediately be the largest player in the category. They've collectively decided the brand risk exceeds the revenue and left the entire market to a handful of specialists.

An entire industry looking at a profitable adjacent market and unanimously deciding to leave it alone doesn't have an obvious parallel anywhere else in tech.

The robots are the small part

Combined global installed base of dedicated companion robots — Realbotix plus EXDOLL in Dalian plus DS Doll plus AI-Tech's Emma line in the UK plus Synthea Amatus in Barcelona — is, by every available estimate, in the low five figures of units shipped. Total. Ever. Tens of millions of dollars in an industry where humanoid robotics carries north of $50 billion in venture valuation.

Meanwhile the software side has Replika at roughly 30 million accumulated accounts, Character.AI past 20 million, and a long tail of dedicated apps generating north of $200 million a year in subscriptions. Replika's most-discussed moment came in February 2023 when Luka Inc. pulled a paid feature that 500,000+ subscribers had specifically signed up for, generating the kind of user revolt that gets its own subreddit nickname and, seven weeks later, a partial reversal for legacy accounts.

Three orders of magnitude more users on the software side. The hardware is the part that gets written about and the part that barely exists.

Japan built a coffee maker

The Japanese version of this category skipped the robot entirely. Gatebox, launched by Tokyo's Vinclu in 2016, is a tabletop device roughly the size of a drip coffee maker with a transparent display column projecting a holographic-effect anime character — usually the default Hikari Azuma, voiced by professional voice actress Saori Goto. It responds to spoken Japanese, texts you during the day, and turns the lights on when you get home.

The company has issued more than 4,000 "marriage certificates" through its internal registry. Japanese civil law recognises exactly none of them, which Gatebox is fully aware of and has never claimed otherwise. It's a ceremonial feature in a consumer product, and four thousand people used it.

No actuators. No servos. No silicone. A display column and a conversational model, outselling the entire physical robot category several times over.

Underneath, it's the same parts bin

The supply chain is unremarkable, which is its own kind of interesting. Same semiconductors as every other robot. Same lithium-ion chemistry. Same rare-earth permanent magnets in the small servos — the neodymium and dysprosium bottleneck that constrains every actuator on earth applies here identically. The only distinctive input is platinum-cure medical-grade silicone, sourced from a handful of specialty chemical suppliers in California, Japan, and Germany that mostly serve the entertainment special-effects industry McMullen came out of in the first place.

Full write-up on the Realbotix corporate history, the Harmony platform, Gatebox, and the non-entry pledge:

https://unteachablecourses.com/romance-companionship-sex-robotics-2026/

The question I keep coming back to is the pledge, because it has the same shape as the weaponisation letter those same companies signed in 2022 — voluntary, non-binding, and already under pressure from Ghost Robotics happily filling the gap Boston Dynamics left. Voluntary abstention holds while a market is small and the reputational math is obvious. Both of those are variables. I can't find a case anywhere in tech where an entire industry's collective decision to skip a profitable adjacent market survived a decade of a specialist proving it out — has anyone got one?