We are very proud of our Weekly podcast, which we have been putting out every week for over five years. In that time the podcast has won a number of awards and been listened to in over 160 countries. We love being able to bring science to new audiences, and we love the flexibility, informality and intimacy that conversation brings to science reporting.

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But it is time to shake things up. We have relaunched and renamed our weekly show. Introducing: The world, the universe and us. Hosted by me and my colleague Penny Sarchet, we will be joined each week by expert journalists and scientists to discuss the latest science news, and what it really means. From the evolution of intelligent life to the mysteries of consciousness, from the threat of the climate crisis to the search for dark matter, The world, the universe and us is your essential weekly dose of science and wonder in uncertain times.

The show draws on 91av’s unparalleled depth of reporting to put the stories that matter into context. Feed your curiosity with a podcast that will restore your sense of optimism and nourish your brain. Get it, as they say, wherever you get your podcasts. And we are also on – do come and say hello.

Cannabis is having a moment. Half of Americans live in a state with legal marijuana and 9 in 10 people nationwide support legalisation in some form. This is a stark difference from mere decades ago, when prohibition was the norm in the entire US. Meanwhile, if you live in Malta, Uruguay, Canada – and maybe soon, Germany – your entire country is one with legal recreational pot. And access to medical marijuana extends to even more countries, including the UK and Australia.

But as medical and recreational use become more popular and increasingly accessible, how exactly did we get to this moment of change? What has research been able to tell us – so far – about how the plant produces its euphoric effects, or what medical purposes it may be able to serve or how it might be harmful? And how could our relationship with this unassuming leaf change in coming decades?

In the first episode of a special 3-part podcast series, Christie Taylor and the rest of the 91av reporting team start at the beginning: 27.8 million years ago, when hops and hemp diverged in family Cannabaceae. A million years ago, when Cannabis indica and Cannabis sativa diverged into two differently psychoactive strains. And 12,000 years ago, when humans first domesticated cannabis for mundane household use, not yet dreaming of the euphoric experiences to come.

But of course, it all comes back to the high, and we go there too – the evidence, though still sparse, of drug-related use dating back at least to 500 BC. And, a thousand years later, perhaps the first recorded reference to a ritual not unlike hotboxing.

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The science of cannabis

As the use of marijuana and its compounds rises around the world, 91av explores the latest research on the medical potential of cannabis, how it is grown and its environmental impact, the way cannabis affects our bodies and minds and what the marijuana of the future will look like.

Explore our coverage

Transcript

Christie Taylor: It’s a sunny November morning in Manhattan and I’m buying weed for my job.

Sasha Nugent: So right now, we have pre-rolls, tinctures, flower, edibles, and drinks, and that’s an array of things that we have. Vapes as well. We have flower and we offer it in eighth and one ounces, and we even have a three ounce bag, and three ounce is the max in New York that you’re able to purchase in a day.

Christie Taylor: That’s Sasha Nugent. She’s the so-called ‘Budmaster’ at Housing Works Cannabis Co. It’s the retail extension of a local AIDS non-profit and also the first recreational dispensary to be licensed in New York City, and if you’ve never been inside a licensed dispensary before, you may be shocked at how normal a retail experience it feels like. Two big display cases wrap around the retail area filled with colourful packages of merchandise, like gummies infused with THC, the main ingredient that gets people high, or CBD, a secondary ingredient that seems to have a more calming, chill effect. Pastel rainbow signs next to the row of cash registers have slogans like ‘make love, not drug war’, and ‘spark up your inner activist’, and ‘we’re smoking out stigma’. The product labels range from slightly goofy and psychedelic to what I can only describe as a colourful fruit salad, and for the Apple Store types, there’s sleek and minimalist black and white packaging.

Sasha Nugent: On a slow day, anywhere from, like, Sunday to Wednesday, we see about 550 to 700 people depending on the day. On our busier days, Thursday through Saturday, we can see upwards of 1,000 unique customers.

Christie Taylor: The normality of this experience has only become possible recently. New York State only legalised recreational cannabis in 2021. Other states went sooner and there has been a dramatic wave of various degrees of legalisation across the US, and even across the world. We are in a new normal when it comes to cannabis, but what do we really know about the science of it? Where did the plant come from? What does it do to our health, for good or for bad? I’m Christie Taylor. I’m a podcast producer for 91av, and this is the first episode in our three-part series about the science of cannabis, how we got here, what we know, and what the future may hold. This is part of a huge month-long reporting effort from more than half a dozen journalists and you can read their work over at newscientist.com/cannabis. We’ve investigated cannabis and creativity, mapped the still languishing landscape of medical research, and questioned the environmental cost of industrial scale hemp harvests, but today I’m starting at the beginning, how we got to this moment where I can walk into a store, buy a federally controlled substance, and just tell you about it, and why our relationship with cannabis is possibly one of the oldest relationships our species has had with a domesticated plant.

If you want to feel really old, it’s been 87 years since the movie Reefer Madness debuted. It’s a hyperbolic fictional warning about young people driven to psychosis with multiple murders and deaths all because they had some weed. ‘These high school boys and girls are having a hop at the local soda fountain, innocent of a new and deadly menace lurking behind closed doors.’ (Advert played 03.25-03.32). But now, walk through many neighbourhoods in New York City and you’ll see something you didn’t used to, storefront after storefront with names like ‘Magic Garden’, ‘Smacked Village’, ‘Weed World’, or just ‘Gotham’. The fonts run from cartoonish to classy, and storefront signs, as in other cities with legal recreational and medical weed, will advertise under no uncertain circumstances that they have THC, CBD, or just the unmistakeable green seven-pointed leaf shape that screams ‘marijuana’. In states with legal cannabis, medical or otherwise, you can speak frankly with salespeople about dosages and strains. Do you want help sleeping, or daytime relaxation, pain or appetite management, or a sense of calm while getting your work done? Or do you just want to get stoned off your ass, watch some dumb TV, and laugh uncontrollably while making up new words for hedgehog? No judgement. No, really. Please, no judgement.

Sasha Nugent: I am just like you. I have trouble sleeping and I also have anxiety, so after, like, a day at work, I love the Offline from Off Hours. Like, they don’t pay me. That’s one of my favourite ones.

Christie Taylor: Outside the dispensaries, at corner stores and bodegas, you can still buy THC-infused seltzers and mocktails, cannabis cocktails, and skin lotions featuring CBD. In states like Wisconsin that haven’t legalised cannabis, purveyors get around it with a less potent form of THC called Delta-8. It’s derived from non-psychoactive cannabis and so remains, for now, legal in the US through a loophole in a 2018 agriculture law. Some of the greater glow of legality is in the name of medical applications, which are very real but still under investigation in the case of some treatments. In states where weed is legal only in medical contexts, your doctor can still usually get you a dispensary card for ALS, Parkinson’s disease, chronic pain, cancer and chemo side effects, and mental health conditions like PTSD, and the number of people enrolled in medical marijuana programmes in the US? It more than quadrupled between 2016 and 2020 to a whopping 3 million. People use it for nausea, pain, and glaucoma symptoms. It’s showing legitimate promise as a treatment for multiple sclerosis and rare forms of epilepsy, but when we look at this moment in our relationship with cannabis, it’s also clear that the years of prohibition have cost us research. Because the US federal government still bans weed, scientists have struggled for funding, or simply a sufficient legal supply to study.

How we get high: Unlocking the secrets of the endocannabinoid system

The endocannabinoid system that helps cannabis get us high is also vital to many other aspects of our health. Now we’re finally starting to understand why – and what that means for devising new treatments

The late Dr. Raphael Mechoulam, the Israeli scientist who first isolated THC from cannabis in the 1950s, he even had to get his first samples from the police, and as its therapeutic potential gains greater excitement, the federal ban on weed is still undermining scientific research that might bring clarity on both the benefits and the risks of its consumption. This research is needed more than ever. At Housing Works, I’m presented with three seemingly equal products, gummy edibles, that might help me sleep better. They all advertise their properties in terms of milligrams of THC and other calming compounds, so I pick one called Snoozeberry solely by the promise that it would taste like blueberry, a flavour I liked, and I’m charmed maybe just a little bit by the twinkling stars on the soothing deep blue packaging.

Sasha Nugent: Perfect. So this is your receipt, and would you like a bag?

Christie Taylor: Yes, I’ll take a bag.

Sasha Nugent: No problem. I’ll grab one for you.

Christie Taylor: Okay.

Sasha Nugent: So we also offer delivery, so I put a delivery flyer in case you’re in one of our delivery zones, and I also put a little sticker with our QR code in case you want to order it in advance.

Christie Taylor: Alright. Thank you so much.

Sasha Nugent: Thank you so much. It was great meeting you.

Christie Taylor: Yes, great meeting you too. You’re not high. A revolution has been baking toward the popularity and acceptance of weed. Legalisation of cannabis for recreational use has swung hugely into favour in the last 10 years. Uruguay legalised recreational use of marijuana in 2013, Canada in 2018, Malta 2021. Lawmakers in Germany may soon vote on a bill to do the same, and medical marijuana is even more widely legalised, including in the UK and Australia. In the US, there’s no national approval of cannabis in any context. Instead, it’s a state by state patchwork, but one that is increasingly pro-pot, with 38 states and Washington, DC all moving to legalise marijuana. Nearly half of those are states that support both medical and recreational use, including, just weeks ago, the state of Ohio, and if you ask we, the people, there’s overwhelming support for national legalisation. Nearly 7 in 10 Americans say ‘yes’.

Alexis Wnuk: That’s actually triple what it was 30 years ago.

Christie Taylor: 91av’s Alexis Wnuk dug into the data explaining this shift and she found the swing in attitudes is even more dramatic than that.

Alexis Wnuk: So if you ask people specifically about recreational and medical uses, it’s more like 9 in 10 people in favour of legalising it in some capacity. Younger people and those on the political left continue to support legalisation in greater numbers than older people and people on the political right, but we’ve seen a surge in support across all age groups and the entire political spectrum.

6 charts that explain the cannabis revolution

As popular discussion of cannabis has moved away from the drug trade and toward potential medical applications, views about safety and support for legalisation have changed hugely in the US

Christie Taylor: Republican support, while still quite a bit lower than other groups, tripled between 1990 and 2016. This also seems to align with a shift in how people perceive the dangers of cannabis. For the 50 years that the US has tracked these perceptions, people have always seen cannabis as less dangerous than drugs like cocaine or heroin, but in the early 2000s, that gap got even bigger.

Alexis Wnuk: Around 20% of people surveyed in 1997 said that smoking marijuana once or twice a week posed minimal or no risk of harm, but by 2021, which is the most recent data we have, half of people surveyed thought this, and we know this wasn’t just because perceptions of all drugs were changing, because people still ranked other drugs at about the same level of danger as they did 30 years ago.

Christie Taylor: So why have people swung so comparatively hard for cannabis in recent decades? The biggest reason is medical marijuana. If you look back at the surveys, 98% of people who supported legalisation said that medical use was a very important or somewhat important reason why.

Alexis Wnuk: In the 1980s and ’90s, we started seeing studies that suggested cannabis could reduce nausea and improve appetite in people with HIV (TC 00:10:00) and in those undergoing chemotherapy for cancer, and this started creeping into the national conversation on marijuana. I came across a study from 2019 by researchers at John Jay College here in New York City where they tracked media coverage of marijuana over the years. They took the New York Times, one of the most read newspapers in the nation, as a case study, and what they found was that in the late ’90s, articles about medical use of cannabis started making up more and more of the coverage. At the same time, there’s less and less coverage dealing with marijuana trafficking or abuse.

Christie Taylor: Headlines about multimillion-dollar pot busts declined. You were more likely to see stories like the 1993 headline about a 79 year old woman who was growing weed to help her son, who had multiple sclerosis, eat better, or a pot-smoking club in San Francisco reserved for the sick and dying. 1996 is also when you saw California become the first state to allow cannabis for medicinal purposes with a doctor’s supervision.

Alexis Wnuk: Obviously, we can’t know for sure whether the media coverage actually changed people’s attitudes or whether it was just following the shift in attitudes but what we do know is that, in this time period, we saw a big uptick in coverage of medical marijuana and the people who could benefit from it, so instead of fearmongering and crime, you were much more likely to see a focus on compassionate use for people who were critically ill.

Christie Taylor: There are a lot of other reasons ranking highly as well. Nearly as important for some people was freeing up law enforcement to do other work, followed by the argument that it’s someone’s personal choice to consume it. Deeper in the survey data, there’s support for the argument that tax revenue from legal weed could support local governments, or that it just might be safer to have legal oversight for weed, and if you go back to the perceptions of risk, there were people that said that using weed is already safe and so there’s no reason to outlaw it. Half of Americans now live in a state with legal recreational cannabis and there’s no sign that the wave is slowing down. The thing is, the weed zeitgeist, this wave of stigma oscillating into mania, isn’t the first time that our species has used this plant, whether for highs or healing. It’s one of the first crops human beings ever cultivated, starting 12,000 years ago. Think the oldest profession but make it agriculture, and until 100 years ago, it was one of our species most important sources of fibre, shelved only thanks to the rise of synthetic fibres such as nylon, but what was cannabis doing before humans met hemp?

A million years of marijuana: How cannabis became our favourite weed

Cannabis was one of the first crops that humans cultivated about 12,000 years ago. But medicinal and psychoactive uses are much more recent

First, we should also talk about humulus, marijuana’s cousin in family Cannabaceae. You know it as hops, which flavours our beer, but fossils of the two plants have been confused for each other numerous times over the years, which is why genetics may be the better arbiter of when hops and herb diverted in the evolutionary tree. The evolution of plants like cannabis is hard to study. You need fossils, and soft matter doesn’t make the same impressions in stone that bones or teeth might, but the traces do exist and modern genomic science is also increasingly helping us use living plants to scry backward in time. It’s a kind of timekeeping that relies on mutations. A molecular clock. Scientists can count how many mutations the two plants have gathered over time and use that to determine that hops and cannabis diverted into separate species around 27.8 million years ago. Hops went on to become a funky-smelling climbing plant integral to beer but not particularly psychoactive on its own, but cannabis? It’s a funky-smelling, wind-pollinated, herbaceous ground plant that’s rich in oils and protein. It gets you high and it slows you down, and as fossil pollen indicates, it may have originally evolved on the Tibetan plateau at dizzying elevations with an arid climate and harsh, inhospitable levels of UV radiation from the Sun. Chelsea Whyte tracked down this high-elevation history.

Chelsea Whyte: This also may be why the plant possesses its calming properties. THC and CBD, as well as other cannabinoids, seem to protect plants from UV rays, and cannabis may have developed these compounds as an adaptation to its early habitat.

Christie Taylor: And then there’s the question of cannabis sativa and cannabis indica. Seasoned pot consumers know these two psychoactive species of cannabis can feel very different in the body and brain but the fact that you can be discerning down to the level of Latin names might not have anything to do with human husbandry. The same molecular clock method of genetic analysis shows that indica and sativa diverged more than 1 million years ago, back when our distant ancestor, homo habilis, was hunting on the plains of Africa.

Chelsea Whyte: We’d had tools for about 1.5 million years at that point. That’s what homo habilis was known for, but we haven’t found any evidence for those long ago ancestors consuming cannabis in any way, nor is there evidence that cannabis had particularly high levels of THC at the time, so while it’s fun to wonder if there were Stone Age stoners, there’s no actual sign of it.

Christie Taylor: What we do find is evidence of human cultivation 12,000 years ago in East Asia, by people who seemed to use the plant for ordinary household needs. Oil, rope, bow strings. We know this because while the original wild strain we started with may be extinct, it’s closest living relative seems to be in Northwest China and the genomic record matches the archaeological. There’s pottery that’s been marked by hemp cords dating from the same millennium, for example, and once we began to cultivate cannabis, it spread, and spread, and spread.

Chelsea Whyte: It’s almost cliché at this point to say there’s a reason it’s called weed because it flourishes in a wide variety of conditions and doesn’t need too much tending. Whenever groups of people exchanged goods with others, cannabis went too. Farmers, trade, conquest, you name it.

Christie Taylor: It started about 5,000 years ago when the Yamnaya people migrated from the Eurasian Steppe and brought cannabis to parts of Europe and the Middle East. A thousand years later, pot entered Korea through trade with China, and South Asia via Indo-Aryan peoples migrating from central Asia.

Chelsea Whyte: Around 2000 BC, the western Eurasian Steppe was home to a nomadic people called the Scythians, and they carried it on horseback from the Middle East to what is now Russia and Ukraine.

Christie Taylor: Germanic tribes took it west to Britain as the Anglo-Saxons conquered. It was in Northern Africa by 1400 AD and spread from there to the southern tip, and then, as European colonialism so well facilitated, cannabis crossed the Atlantic and spread across North and South America. We’ll talk more in a future episode about the current state of medical uses of cannabis and what we know about them. At the moment, the earliest evidence of therapeutic use dates back to a Chinese shaman who was buried with a stash of cannabis sativa in 700 BC, but medical records suggest people have been trying to heal with cannabis for thousands of years, starting 5,000 years ago in the reign of Chinese emperor Shennong. He claimed cannabis could cure a wide range of ailments such as malaria, menstrual problems, and gout, and maybe paradoxically, he prescribed it for absent-mindedness as well. Western doctors weren’t using cannabis until much more recently, the late 19th and early 20th century, when one of Queen Victoria’s doctors used the plant to treat a wide variety of pain-related illnesses, including some of her premenstrual symptoms.

How humans brought cannabis to every corner of the globe

Cannabis originated in East Asia but can now be found growing on every continent except Antarctica – thanks to human trade and cultivation

The drug was even listed in the US Pharmacopeia, the country’s official compendium of medical drug information, but then it was outlawed in 1942, decades into a rising crackdown and prohibition of the plant. We wouldn’t come full circle again until 1996, when California residents passed Proposition 215 and made medical marijuana legal again. So when, you ask, did we start getting stoned? Was it the Stone Age or was it much later? Was there a single moment when early humans inhaled some skunky sativa smoke and realised they felt pretty dope about it?

Chelsea Whyte: The evidence here is pretty spotty but we know that wild cannabis plants have only trace amounts of the psychoactive compounds that get us giddy, including THC and CBD, so researchers have looked for evidence of plants with higher concentrations which we would have had to cultivate specifically.

Christie Taylor: We have a long, long history with this plant but only 4,000 years ago do we start to see the evidence of humans nurturing specific strains for specific purposes, whether for fibre or drugs.

Chelsea Whyte: You can actually see in the way different strains diverge what uses they were bred for. Those bred for fibre have more gene mutations that inhibit the stems from branching out, so they have taller stems and more fibre in the main stem, but the plants that were bred for drug use have mutations supporting more branching, which also means more flowers. Those plants are shorter but they also tend to have more THC.

Christie Taylor: Beyond Emperor Shennong’s medicinal mention 4,500 years ago, the first trace of toking only emerged in 2019 in the mountains of Western China. Researchers exploring ancient tombs found wooden fire pits called braziers with traces of THC at much, much higher concentrations than in wild cannabis. These date back to 500 BC, 2,500 years ago, and they suggest that people at that time were inhaling the potent smoke of a strain of cannabis that they had cultivated specifically for the high, but instead of the joints, pipes or bongs you may be familiar with, these braziers would likely have been filled with red hot pebbles that the cannabis was then put on top of. The smoke from the smouldering plant could then be inhaled. And remember those Scythians marauding through Russia and Ukraine on horseback? The Greek geographer and historian Herodotus, writing in the 5th century AD, describes a ritual that may be the first recorded instance of hotboxing.

Herodotus: ‘They set up three poles leaning together to a point, and cover these over with woollen mats. Then, in the place so enclosed, to the best of their power, they make a pit in the centre beneath the poles and the mats, (TC 00:20:00) and throw red hot stones into it. The Scythians then take the seed of this hemp and, creeping under the mats, they throw it on the red hot stones, and being so thrown, it smoulders and sends forth so much steam that no Greek vapour bath could surpass it. The Scythians howl in their joy at the vapour bath.’

Christie Taylor: So weed has been with us for 12,000 years and we’ve found it at least some level of therapeutic for 4,500 of those years. People have used, and continue to use, it for physical ailments, emotional balm, and a certain mental letting loose, but as the wave of cannabis legalisation in the US and worldwide gathers momentum, what do we actually know about how it affects us, body and brain? Stay tuned for the next episode where we’ll look at what happens to your brain on drugs, and what the past prohibitions on pot have done to limit our knowledge of how it behaves, even as the need for that knowledge is greater than ever.

Why we know so little about cannabis – and why scientists are worried

While research on marijuana has surged in the last 20 years, our understanding of the drug is decades behind that of other substances, like tobacco and alcohol

ÌýAs I mentioned earlier, this podcast is part of a massive reporting effort, spanning many months of work from the 91av team. You can go to newscientist.com/cannabis to read much, much more about the history of our relationship with weed and what research is starting to reveal. Thanks to Chelsea Whyte, Alexis Wnuk, and Grace Wade for helping me research and write this episode, and to Timothy Revell and Chelsea Whyte for edits. Thanks also to Timothy Revell for his expert voice acting. New York studio production is by Hugo Fonseca, and our audio and sound design is by Ollie Guillou. I’m Christie Taylor. Bye for now.

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