David Wood

Chair, London Futurists. Executive Director of LEV Foundation. Author or Lead Editor of 12 books about the future. PDA/smartphone pioneer. Symbian co-founder

[David Wood @dw2]

A thread of threads - the mini-book reviews that I have posted here during 2025. In chronological order. I happily recommend all but one of these books

[David Wood @dw2]

"If you're asking yourself, 'Which jobs will survive AI, and which jobs will disappear?' you're asking the wrong kind of question" - Correct! https://t.co/brX6KdIvmY

[David Wood @dw2]

A profound benefit of exercise: "Your legs telling your brain to grow"

[Ihtesham Ali @ihtesham2005]

A neuroscientist spent 30 years proving the 100-year dogma that the adult brain never makes new neurons was wrong, and the activity his lab identified as the strongest natural trigger of the process is more powerful than any drug ever invented.

His name is Fred Gage.

He runs the Laboratory of Genetics at the Salk Institute in California, and the paper that ended one of the longest-standing dogmas in modern neuroscience was published in 1998 in Nature Medicine. The finding is sharp enough that it should have changed every doctor's office on Earth.

The dogma he had to break was almost a century old.

Santiago Ramón y Cajal, the Spanish anatomist considered the father of modern neuroscience, declared in the early 1900s that the adult brain was structurally fixed. Once you were grown, the wiring was finished forever.

In his exact words, the founts of growth and regeneration in the brain had dried up irrevocably. Every neuron you would ever have, you already had. The only direction your brain could move from adulthood onward was downward, into decline.

This was treated as settled fact for the next 60 years.

The first person who actually tested it was a young neurobiologist named Joseph Altman.

In 1962, working at MIT, Altman injected adult rats with a radioactive form of thymidine, which is one of the four building blocks of DNA. Any cell that divides has to copy its DNA, so any new cell formed after the injection would carry the radioactive marker.

When Altman cut open the brains of those adult rats and looked at the hippocampus under a microscope, he saw radioactive new neurons glowing in the tissue. The adult brain was making new neurons. He published the finding in Science magazine and titled the paper with the question itself. Are new neurons formed in the brains of adult mammals.

The field rejected him almost universally.

Altman eventually moved from MIT to Purdue and spent the next 30 years quietly publishing more evidence with his wife Shirley Bayer. The scientific community largely ignored him. He died in 2016 having lived to see the dogma collapse, but never having received credit for being the first one to break it.

The man who finally proved Altman right was Fred Gage.

In 1998, working with the Swedish neuroscientist Peter Eriksson, Gage got access to brain tissue from five cancer patients who had died in Sweden. These patients had been given a chemical called BrdU during their treatment for tumor diagnosis.

BrdU works the same way Altman's radioactive thymidine did. It incorporates into the DNA of any dividing cell. If the patients' brains had produced new neurons during their final months of life, those neurons would carry a chemical fingerprint that could be made visible under a fluorescent microscope.

Every single one of the five hippocampi was glowing with new neurons.

The paper was published in Nature Medicine in November 1998 under the title Neurogenesis in the Adult Human Hippocampus. Five hippocampi ended a century of dogma. Cajal was wrong. Altman was right. The adult human brain manufactures fresh neurons every day for as long as it is alive.

What Gage's lab did next is the part that should change how every reader of this thinks about their own body.

One year later, Henriette van Praag, a postdoc in Gage's lab, ran an experiment to figure out what actually controls the rate of neurogenesis in adults. She put mice in five different conditions. Some learned a water maze. Some swam without learning anything. Some lived in enriched environments full of toys and tunnels. Some had standard cages. And one group simply had access to a running wheel.

Only two conditions doubled the production of new neurons. The enriched environment, and running.

When she isolated the variables further, running alone was sufficient. A mouse with nothing in its cage but a wheel produced twice as many new hippocampal neurons as a mouse without one. The water maze did not do it. Swimming did not do it. Learning by itself did not do it.

The thing that physically grew new brain cells inside an adult mammal was the rhythmic act of running.

The mechanism turned out to be a single molecule.

It is called BDNF, which stands for brain-derived neurotrophic factor. Researchers in the field nicknamed it Miracle-Gro for the brain, because it is what tells neural stem cells in the hippocampus to divide, mature, and integrate into existing circuits.

Sustained aerobic exercise raises BDNF in the hippocampus more sharply than almost any other intervention ever measured. Antidepressants raise it too. So does electroconvulsive therapy. But the natural trigger your body evolved to release the molecule is the one almost nobody uses on purpose.

Your legs telling your brain to grow.

The most important confirmation came 13 years later in human beings.

In 2011, a researcher named Kirk Erickson at the University of Pittsburgh ran a one-year randomized trial on 120 sedentary older adults whose hippocampi were already shrinking with age.

He split them into two groups. One group walked around a track for 40 minutes three times a week. The other group did stretching and toning exercises for the same amount of time. He scanned their brains at the start, at six months, and at one year.

The walkers grew their hippocampi by two percent.

In a brain that loses one to two percent of hippocampal volume every year after age 50, growing it by two percent in one year of light walking is equivalent to reversing two years of aging in twelve months.

The stretching group, doing identical session lengths without aerobic load, lost volume on schedule. Same minutes. Same effort signature from the outside. Completely different outcome inside the skull.

The paper was published in the Proceedings of the National Academy of Sciences. The editor who approved it was Fred Gage.

The comparison with drugs is the part of the story that should rearrange anyone's thinking about mental health.

Every major antidepressant on the market works partly by raising BDNF. Prozac, Zoloft, the rest of the SSRIs all converge on the same final pathway that exercise activates naturally.

The difference is that Prozac takes several weeks of daily dosing to produce measurable neurogenesis, comes with side effects, and only touches one biological mechanism.

Exercise activates 7 different pathways at once, including inflammation reduction, cortisol regulation, blood flow to the brain, endocannabinoid release, and direct stimulation of neural stem cells in the dentate gyrus.

There is no pill that does what running does to the human brain. The molecule the pills are trying to imitate is one your body manufactures on its own the moment your heart rate climbs and your feet hit the ground.

This is the part nobody talks about.

Cajal declared the brain fixed in 1900. Altman discovered new neurons in 1962 and got rejected for 30 years. Gage closed the case in 1998. Van Praag identified running as the trigger in 1999. Erickson proved it works in living humans in 2011. Half a century of research, published in the most prestigious journals on Earth, replicated in dozens of labs across multiple continents.

And the average reader of this will close this post, sit back down, and stay there for the next ten hours, while their own hippocampus quietly shrinks for the rest of the day.

The most powerful neurogenesis drug ever discovered does not need a prescription. It needs a pair of legs and a willingness to use them.

[David Wood @dw2]

Well made and provocative https://t.co/uxgWz79eSR

[David Wood @dw2]

The official trailer: Can Science Reverse Aging? | Forever Young https://t.co/iodhXSAe2k

[David Wood @dw2]

I'm looking forward to this: Wednesday evening (3rd June), Imperial College Business School: a showing of the documentary "Forever Young" followed by a Q&A with the director https://t.co/913Smv7Zbh

[David Wood @dw2]

Postscript: also check out this thread by Gerry Tsoukalas, on what their paper "actually says and what it doesn't" https://t.co/CZDkQ1EwHK

[Gerry Tsoukalas @gerrytsou]

You may have seen our paper "The AI Layoff Trap" making the rounds this week under some fairly dramatic headlines.
I'm one of the authors. Here's what it actually says and what it doesn't. 🧵

[David Wood @dw2]

Released this morning on the @LondonFuturists podcast: "The AI Automation Layoff Trap", where economists @GerryTsou and Brett Hemenway Falk make the case for introducing a "self-correcting tax" to deter companies from automating their operations too quickly

[David Wood @dw2]

Look for the episode on any of your favourite podcast apps. Or find it here: https://t.co/wZaoNUw17l

[David Wood @dw2]

Something well worth remembering 🙄

[Ihtesham Ali @ihtesham2005]

A psychologist became the most hated woman in her field for proving that the childhood memories people trust the most are often the ones their brain quietly made up.

Her name is Elizabeth Loftus.

Here's the the experiment that made her famous and its almost insultingly simple.

She gave each subject four short stories about their own childhood, collected beforehand from a parent or older sibling. Three of the stories were true. One was completely invented. The fake one always described the same scene. You were five years old, you wandered off in a shopping mall, you panicked, and an elderly stranger found you crying and walked you back to your family.

None of it had happened.

But after two short interviews, about a quarter of the people in the study didn't just accept the story. They remembered it. They started adding details nobody had given them. The color of the stranger's shirt. How scared they felt the moment they realized their parents were gone.

When Loftus finally revealed that one of the four memories was fake and asked them to guess which, many of them guessed wrong. They picked a real one.

The study was published in 1995. It was called The Formation of False Memories, and it set off a war inside psychology that is still going today.

Here is the thing she had figured out that most people get backward their entire lives.

You think memory works like a recording. Something happens, your brain saves the file, and later you press play and watch it back exactly as it was. That is not what happens. Memory is not storage. It is reconstruction.

Every time you recall something, your brain rebuilds it from scratch out of fragments and whatever information happens to be lying around at that moment. Anything close enough can get stitched into the final cut.

Loftus had proven this years earlier with a car crash. She showed people a video of two cars hitting each other, then asked how fast they were going. For one group she used the word "smashed." For another she used the word "hit." The smashed group estimated the cars were moving about seven miles an hour faster.

A week later she asked everyone whether they had seen broken glass at the scene. There was no broken glass in the video. The people who heard the word "smashed" were more than twice as likely to remember glass that was never there.

One verb. That was all it took to edit what people had seen with their own eyes.

She called it the misinformation effect, and the more she studied it, the worse the implications got.

If a single word could plant broken glass, what could a confident therapist plant over months of sessions? What could a leading question plant in a witness sitting on the stand? She started testifying in court, and across her career she consulted on roughly 300 cases, telling juries that the most convincing testimony in the room might be a memory that had assembled itself out of nothing.

People hated her for it. She got threats. She got accused of protecting abusers. And then something happened that turned her own life into the experiment.

When Loftus was 14, her mother drowned in a swimming pool. Thirty years later, at a family gathering, her uncle told her something she had never known. He said she was the one who found the body floating in the water that morning.

She had no memory of it. But the moment he said it, the memory began to arrive. She could see her mother face down with her arms out. She could feel a fireman pressing an oxygen mask over her own panicked face. The details came one by one, vivid and certain, exactly the way they had arrived for every subject she had ever studied.

Then her uncle called back. He had made a mistake. It wasn't her who found the body. It was her aunt.

The most important memory researcher alive had just watched her own brain manufacture a traumatic childhood memory from a single sentence spoken by someone she trusted. She was, in her own words, a subject in one of her own experiments.

That is the part nobody wants to sit with. Fake memories do not feel fake. They feel exactly like the real ones. There is no internal alarm, no flicker of doubt, no difference in texture between the thing that happened and the thing that was suggested to you.

You are not remembering your life. You are rebuilding it from scratch every single time, and you have no way of knowing which pieces are real.

[David Wood @dw2]

I've registered to attend this @PauseAI_UK event on Monday evening in Greenwich: "Just Don't Build AGI: Why I'm Trying to Pause AI"

https://t.co/sOKf7PwcTk

[David Wood @dw2]

For more details, and to register to attend this talk + drinks + networking event from 7:30pm onward, see https://t.co/czov22ct6h

[David Wood @dw2]

How exactly would AI cause human extinction?

Although many researchers think AI is an existential risk, specific scenarios (threat models) vary considerably.

To discuss this further, join with the Existential Risk Observatory this Saturday at the Trafalgar Tavern, Greenwich

[Daniel Faggella @danfaggella]

@jeffrsebo @dw2 Pedestal cope is a helluva drug

Humans often can’t give ground on moral value specialness, even an inch https://t.co/IMwc9RZN6y

[Jeff Sebo @jeffrsebo]

A skeptical view about AI consciousness is starting to emerge that resembles the skeptical view about animal consciousness that prevailed for much of the 20th century: Presume the entity lacks consciousness, then declare the study of consciousness in the entity beyond the reach of science due to our inability to directly observe feelings and emotions in other minds.

For animals, this was basically a recipe for locking in a presumption of non-consciousness as factory farming was on the rise. We now know that this was too simple, since science has many tools for studying phenomena we lack the ability to directly observe. But by the time the scientific study of animal consciousness picked up, factory farming was globally entrenched.

This is a cautionary tale for AI. If we presume non-consciousness now and then treat AI consciousness as beyond science, we risk repeating the mistake we made with animals. And if we wait until future AI systems are more capable, human-like, and plausibly conscious, we might once again find ourselves dependent on a globally entrenched practice of exploiting them.

As with animals, decisions about whether and how to scale up particular AI use industries should depend on many factors. But evidence regarding AI consciousness should be one of them. The sooner we start collecting serious evidence, including by adapting methods from animal welfare science, the better positioned we will be to build a future that works for everyone.

[David Wood @dw2]

RSVP here to attend this webinar (from 4pm UK time), featuring Tony Czarnecki, Managing Partner of Sustensis, who will be advancing his concept of "Civil Stewardship Democracy" https://t.co/4hiy0WLb9Q

[David Wood @dw2]

In a time of rapid progress towards superintelligence, which principles of collective governance need to be upheld, and which set aside? This Saturday, you'll have the chance to compare your answers to these questions with proposals made by other @LondonFuturists members