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Blog Deep Read · 18 · sarahconstantin.substack.com

Sarah Constantin
Traction Was Never Evidence

Rough Diamonds · 122 posts · 2019–2026 (the site opened August 2021 and got serious in March 2022; the 2019–2021 archive was carried over from her earlier blog, Otium) · One clear break: after leaving her job to consult independently in April 2024 she went nearly silent for about thirteen months, returning in June 2025 · Still active; most recent post 19 August 2026 · This page is built on 25 posts read in full, spanning February 2019 to August 2026, six of them from the earliest period, with samples on both sides of the silence · All 25 are free and public

In January 2025, Sarah Constantin sat down to perform three autopsies: Amyris, Zymergen, and Ginkgo Bioworks — synthetic-biology unicorns, one of them valued near $5B at its peak, all three collapsed or bankrupt within about two years.

Getting to Ginkgo, she notes that in fifteen years the company reported 219 "programs," of which six were commercialized. And that its most successful products were aroma chemicals sold to a fragrance house.

Then she adds a parenthesis.

I happen to know that the peach scent gamma-decalactone has been cheaply chemically synthesizable since the turn of the 20th century.What's Behind the SynBio Bust?, 30 January 2025

She adds that lactones are what give Guerlain's Belle Epoque masterpiece Mitsouko its rich, long-lasting peach note. She knows this because she also writes a perfume blog.

A company founded on the premise that biology will manufacture everything, and its best commercial result was a smell — one a chemist could already make more cheaply in 1900. And the arithmetic that says so was sitting there in plain sight from day one.

That is the way into this mind. For eight years Sarah Constantin has been building, in public, a toolkit for answering a question that sounds almost too simple to be interesting: does this thing actually work, or does it only look like it works?

What makes the question hard is her position. She is not an insider in any of the fields she covers, and she has written that disadvantage down without flinching:

In a world where contradictory and low-quality studies are common, and where I'm a rando layman who doesn't have access to the private data or sidechannel academic gossip that would reveal non-obvious info about which studies are fatally flawed, it's not obvious that I can learn a real thing at all from sitting on my butt in front of a computer screen.How I Write, 9 February 2024

Her answer to herself: "Completionism combined with baseline skepticism." Find a literature small enough that you can finish it, then finish it. She reports, with some satisfaction, that she knows of literally every experiment anyone has run that extended lifespan in a mammal.

Her sharpest single move is a 2022 post called "Bad Ideas Can Get Surprisingly Far." Her method is to build a fictional industry and run it forward: BUZZWORD for APPLICATION.

Stipulate that the thing is technically worthless. What happens? She works through it. The industry is a few years old with, say, $500M in total revenue — "That's nothing." A large company can spend that much on value-of-information alone, in case it turns out to be great. And big companies have correlated information sources: a handful of top consultancies and enterprise software firms serve essentially all of the Fortune 500, so one endorsement lets a startup honestly claim adoption by many Fortune 500 companies — none of whom independently vetted the technology. Their executives then attend the same conferences and hear the same thought leaders.

Then the budget mechanics, which is the most damning part: the executives spending those budgets have strong personal incentives to spend down the whole pot, or they look like failures to their own bosses. So the marginal product purchased need not be useful at all.

Large companies do run serious vetting — in manufacturing it is the Factory Acceptance Test, taken very seriously, all objective specs. But she points out there are also "special isolated magisteria for pilot projects" that never touch the main production process. So "ACME MEGACORP is our customer" does not mean anyone is using the thing.

Even if BUZZWORD for APPLICATION is objectively a terrible idea on the merits […] you should expect to see at least some BUZZWORD-for-APPLICATION startups raise several rounds of VC funding, get multiple Fortune 500 clients, make the news, and even IPO.Bad Ideas Can Get Surprisingly Far, 5 November 2022

What lifts this above ordinary cynicism is that she then turns herself in for two mistakes she used to make.

The first she calls the "laziness heuristic": people are lazy, nobody would work that hard on a false premise. Wrong. There are "a lot of high-energy, career-motivated people who are willing to do tons of work if they expect to get paid or credentialed well for it, and aren't very concerned with questioning whether their entire field is based on faulty assumptions." Then the twist of the knife: maybe that tunnel vision actually makes you better at accumulating legible career accomplishments.

The second she calls an implicit "duty to be humble": I shouldn't judge someone wrong unless I can match all their accomplishments and virtues. Silly once said out loud, she admits, and yet —

most people, including my "superiors", should be expected to be wrong about lots of things. The world is vast, and being right is really hard.Bad Ideas Can Get Surprisingly Far

But she does not only dismantle. She also built a positive test, and it is the most original thing I read in her. The 2023 post "The Enchippening" asks why some technologies get exponentially cheaper (compute, genome sequencing, solar) while others stagnate for decades. Is that a Kurzweilian law of technology?

Her answer: it is not a law, it is one industry's shadow. "Every tech that is improving exponentially in the 21st century is explained by improvements in semiconductor fabrication." Solar cells, the photodetectors inside sequencers, microfluidic chips — all made with substantially the same equipment and processes as computer chips. Moore's Law, stripped down, "is about semiconductor manufacturers getting better at making smaller rectangles of flat stuff." Which yields an operational rule: be bullish on any useful technology that has newly become fabricatable on a chip. And read backwards, it is the verdict on those three synbio companies: if your thing is not downstream of that manufacturing base, don't expect exponential cost declines just because it is new and exciting.

In 2024 she landed another one, this time on AI. She worked at Palantir (2016–2017), and says what was remarkable there was not the software — that, "as far as I know," was not unique or exceptional — but that at least a third of the company by headcount descended on customer sites to install databases, teach the UI, and, crucially, negotiate for data access.

Why negotiate? Because people won't hand it over.

it's not at all unusual for it to be easier to make a multi-million dollar sale than to get the data access necessary to actually deliver the finished software tool.The Great Data Integration Schlep, 13 September 2024

Her details keep escalating: a major aerospace manufacturer storing all its airplane quality-test results as scanned handwritten PDFs ("Imagine trying to compile trends in quality performance!"); a company requiring even prospective vendors to spend over $1M of their own money building an ultra-secure room — before the sale closed; and one she witnessed herself, a data science department of maybe ten people whose entire output was a single number, a risk score, handed to another department whose head threw it in the trash. The footnote explains why: he did not believe in probabilities between zero and one. He would say things like "either it is, or it isn't."

Hence her conclusion: AI will not transform the economy the instant the models are good enough. It first has to learn from business data, and business data is on paper, in scans, inside machine tools, behind mutually contradictory IT policies. "It moves at the speed of human negotiation and learning."

The most attractive thing about this skill is that she also aims it at herself. In 2019, reading the freshly released GPT-2 samples, she found that if she wasn't concentrating she couldn't tell: unicorns named "Ovid's Unicorn" after their distinctive horn (Ovid is not a horn) that sprout four horns one sentence later; in the Tolkien sample, "the morning mist cleared, and the day turned to dusk." Her verdict is not about GPT-2:

The point is OpenAI HAS achieved the ability to pass the Turing test against humans on autopilot.Humans Who Are Not Concentrating Are Not General Intelligences, 25 February 2019

And the remedy she proposes is a rule worth carrying around. The mental motion of "I didn't really parse that paragraph, but sure, whatever, I'll take the author's word for it" is, she reports, introspectively identical to "I didn't parse it because it was bot-generated and made no sense" — the only difference being that in the first case you assume the fault is yours. So stop defaulting to humility and default to null: if you don't understand a passage, assume you're in the same epistemic state as if you'd never read it.

Finally, the instrument has a systematic bias, and she found it herself and admitted it in public. She wrote "Why I am Not An AI Doomer" in 2023; a year later, in "Rethinking AI," "I have to admit that I no longer stand by that post as it's written." She had bet nobody would build AI robots — simulation training has a poor track record, real-world training is expensive, a robot carrying GPUs can't compete on price with a hard-coded industrial one. Then Figure AI raised $675M, Skild roughly $300M, 1X over $125M, and Fei-Fei Li started a spatial-reasoning company.

"I feel a little silly about this," she wrote. And the self-diagnosis lands exactly on the instrument's blind spot:

The thing my former worldview was completely missing is selection effects, aka taking markets and incentives seriously.Rethinking AI, 24 May 2024

A gauge built to ask "does the arithmetic close today, and is anyone faking it?" is uncannily accurate on questions like the synbio bust, and systematically low on questions where enough money will eventually be thrown to change the arithmetic. Her negative judgments are far more reliable than her negative predictions — and she is the one who wrote that down.