Geneticists Found the Great Depression Left a Mark on American DNA — And You Still Carry It?

[00:00:00]There is a photograph most of you have already seen. A woman in a dustb blown leanto. Three children turned away from the camera. Her hand against her cheek, her eyes fixed on something past the edge of the frame. Dorothia Lang took it in 1936 in a California pea pickers camp. We call her the migrant mother.

[00:00:25]And for 90 years, we have looked [music] at that face and read hunger, worry, exhaustion.

[00:00:33]What almost no one has asked is a different question.

[00:00:37]Not what that hunger did to her. What it may have written into her children and her children's children in a language we could not read until recently.

[00:00:49]That language has a name, DNA methylation.

[00:00:54]It sits at the center of a field called transgenerational epigenetic inheritance and it is the reason we are going to talk about the Dutch hunger winter of 1944 a cohort of villagers in Overcolics Sweden, the oops multi-generation study, a growth gene called IGF2 and the roughly 2 million Americans the Dust Bowl drove off their land. Some of you carry the descendants of that hunger in your family tree. A few of you may carry something more literal than that.

[00:01:32]So, let's do this [music] the way it deserves to be done. Carefully, slowly, and with the evidence on the table where you can see it.

[00:01:44]Start with what is not in dispute because everything downstream depends on getting this part exactly right. Your DNA is not a fixed photograph. It is closer to a piano. The keys, the sequence of letters, the A, C, G, and T, those almost never change across your lifetime. But which keys get played and which stay silent? That can change.

[00:02:15]One of the ways the body silences a key is by attaching a small chemical tag, a methyl group, onto a specific spot on a gene. That is DNA methylation.

[00:02:29]When a gene picks up heavy methylation in the right place, it tends to go quiet. When that methylation lifts, the gene can speak again.

[00:02:40]Nothing about the underlying sequence moves.

[00:02:44]The instructions are the same.

[00:02:47]What changes is the volume.

[00:02:50]Now, here is the part that turned this from ordinary biology into something that reaches across [music] generations under severe stress. And famine is one of the most severe stresses a human body can face. that pattern of tags can shift and in certain cases the shift does not wash out. It stays. It can be measured decades later. And under specific conditions, [music] a version of it can appear in the next generation and the one after that in people who never went hungry a day in their lives.

[00:03:29]That is not a theory somebody sketched on a napkin.

[00:03:34]It came out of one of the darkest winters in modern European history.

[00:03:40]In the final months of the Second World War, the Nazi occupation imposed a food blockade on the Western Netherlands.

[00:03:49]From roughly November of 1944 into the spring of 1945, official rations in cities like Amsterdam collapsed to somewhere near 400 to 500 calories a day. People ate tulip bulbs. They ate sugar beets meant for cattle. They burned furniture to stay warm. Around 18 to 22,000 people died before the Allied liberation broke the blockade in May.

[00:04:22]The Dutch have a name for it that never softened.

[00:04:26]The hunger winter. The hunger winter.

[00:04:31]And here is what made it in the coldest scientific sense a natural experiment unlike almost any other. It had a hard start date and a hard end date. It struck a wellocumented population with careful medical records in a wealthy country and then it stopped.

[00:04:52]Researchers knew almost exactly who was in the womb during those months and when. Decades later, a team led by Bastion Hyman's and the epidemiologist LH Lumi went looking for those individuals.

[00:05:08]They found people who had been conceived at the height of the famine, tracked them down in late middle age, and read their DNA.

[00:05:17]The results were published in the proceedings of the National Academy of Sciences in 2008. The title is worth saying in full because it says exactly what they found. Persistent epigenetic differences associated with prenatal exposure to famine in humans.

[00:05:36]Persistent Six decades on.

[00:05:41]The gene at the center of it was IGF2.

[00:05:45]Insulin-like growth factor 2. It is one of the master switches for growth in the womb. One of the most important genes for how a fetus develops. And in the people conceived during the hunger winter, that gene carried measurably altered methylation.

[00:06:04]less methylation, [music] specifically in a key control region, compared with their own brothers and sisters [music] who had been conceived before or after the famine. Think about that comparison for a second. Not strangers, siblings, [music] same parents, same household, same genes, separated only by whether they were conceived while their mother was starving. And more than 60 years later, that difference was still legible in their blood. It did not stay a laboratory curiosity either. The hunger winter cohort has been followed for decades. And the people exposed to famine in the womb, especially in early pregnancy, went on to show higher rates of obesity, of altered cholesterol, of type 2 diabetes and heart disease across their lives. A famine their mothers suffered before they were even born appeared to have set the thermostat of their metabolism and left it there.

[00:07:11]There is a name for the bigger idea this sits inside and it predates the methylation work by more than a decade.

[00:07:19]In 1992, the British epidemiologist David Barker working with the physician CN Hails proposed what they called the thrifty phenotype hypothesis published in the journal Diabetia.

[00:07:35]The argument was that when a fetus develops under scarcity, [music] it makes a bet. It quietly rewires itself for a hungry world, a body built to hoard every calorie because that is the world it expects to be born [music] into. If that child is then born into plenty, the thrifty wiring becomes a liability and the risk of obesity, diabetes, and heart disease climbs.

[00:08:06]>> [music] >> Barker built that case from dusty British birth records long before anyone could read a single methyl tag.

[00:08:13]What the Dutch hunger winter added 16 years later was the physical mechanism sitting underneath his [music] statistics.

[00:08:22]The altered methylation on IGF2 was in a sense the thrifty bet written directly into the chemistry. [music] And Holland was not the only siege scientists were able to study.

[00:08:34]Lennengrad, the city we now call St. Petersburg, endured a German blockade for nearly 900 days between 1941 and [music] 1944, and hundreds of thousands of its people starved in the streets. Researchers followed those survivors, too. What they found was actually more tangled [music] than the Dutch results, and the reason is instructive.

[00:09:01]Unlike the sharp start and stop of the hunger winter, Lennenrad's hunger dragged on for years before birth and long after.

[00:09:12]The cleanest [music] fingerprint of famine shows up when the famine itself has a clean edge. Hold on to that idea because it is going to matter enormously when we cross the Atlantic.

[00:09:27]So that is the first pillar and it is a strong one. A single timelimited famine, a chemical mark on a named growth gene measurable more than half a century later tied to lifelong health outcomes.

[00:09:44]That is not hype. That is peerreed, replicated, and about as close to settled as this young [music] field gets. But the hunger winter only reaches one generation.

[00:09:58]The people carrying that mark were the ones in the womb.

[00:10:03]To ask whether hunger can reach further down the family line, whether it can touch a grandchild, you have to go north, far north to a remote parish just below the Arctic [music] Circle.

[00:10:19]Overcallic sits in the Norbotton region of northern Sweden, a country of pine, snow, and long isolation.

[00:10:29]In the 18th and 19th centuries, [music] it was so cut off that when the harvest failed, there was no relief wagon coming over the hill. [music] Some years, the crops were destroyed and people came close to starvation.

[00:10:44]Other years the harvest was abundant and there was more than enough. And crucially the local records, births, [music] deaths and detailed harvest data were kept meticulously for generation after generation.

[00:11:02]A Swedish researcher named Lars Olaf Byron realized that this gave him [music] something almost no scientist ever gets. a way to line up how much food a specific ancestor had in a specific year of childhood against the health and lifespan of that ancestors descendants.

[00:11:22]What Byron and later the British geneticist Marcus Pembrey found in the overcalics data was strange, specific and hard to explain any other way. It came down to a narrow window they called the slow growth period. That is the stretch just before puberty roughly ages 9 to 12 [music] in boys when the body is not yet in its growth spurt.

[00:11:51]The finding was this. Whether a boy and overcal feasted or starved during those few particular years appeared to predict the health and lifespan not of his own children but of his grandsons.

[00:12:06]A paternal grandfather who went through famine in his slow growth period was linked to grandsons with in some measures longer survival.

[00:12:16]A grandfather who gorged during a season of plenty in that same window was linked to grandsons who died earlier with more diabetes [music] and heart disease.

[00:12:27]Pembry and Byron published this line of work in the European Journal of Human Genetics in 2006 under a title that names the mechanism directly sex specific male line transgenerational responses in humans. sit with those two words, sex specific male line, because here is the detail that most popular videos on this subject quietly smooth over and this audience deserves it straight.

[00:13:00]The signal did not spray out in all directions. It traveled down a specific channel.

[00:13:07]grandfather to grandson along the paternal line apparently carried through the sperm cell line itself.

[00:13:16]The grandfather's early experience of feast or famine seemed to leave a setting that surfaced two generations later in the boys who carried his Y chromosome.

[00:13:27]That is a far stranger and more precise claim than trauma echoes through the family. And it is exactly the kind of specificity that should make you lean in rather than roll your eyes.

[00:13:42]Overcallics was a small sample and small samples invite doubt. So the real test was whether a much larger more rigorous study could see the same shadow. That test came in 2018.

[00:13:58]The Yupsala multi-generation study pulled together records on tens of thousands of individuals across three generations in Sweden.

[00:14:08]The paper landed in Nature Communications in 2018 and its title is blunt. Paternal grandfather's access to food predicts all cause and cancer mortality in grandsons.

[00:14:24]Once again, the effect ran down the male line. grandfather to grandson. And once again, it keyed on that pre-puberty slow growth window. But the Upsala result carried a twist that is easy to get backward. So, let me say it carefully because it is the most counterintuitive fact in this whole story. The danger signal was not only starvation, it was abundance.

[00:14:51]A paternal grandfather who had good access to food, a surplus during his slow growth period was linked to higher all-c cause mortality and higher cancer mortality in his grandsons.

[00:15:06]Feast in the grandfather tracked with a shorter life in the grandson.

[00:15:12]Think about what that does to the simple version of this story. It is not just that hunger scars the line. It is that the body seems to record the swing itself, the extreme in either direction, and pass a note about it forward. And if there is one American generation that lived the entire swing, from a decade of dazzling excess straight into the worst hunger the country had seen in living memory, you already know who it was.

[00:15:45]Now we reach the hinge of this entire video and I am going to be completely straight with you because you would catch me if I weren't. There is no Dust Bowl epigenetic study. Let me say that again plainly so no one walks away misquing this. No team has published a DNA methylation study on the descendants of the Ois.

[00:16:11]No peer-reviewed paper has measured IGF-2 in the grandchildren of dust pneumonia survivors.

[00:16:19]If another channel tells you scientists have proven the Dust Bowl rewrote American DNA, they are selling you something the literature does not contain. We are not going to do that here. What we can [music] do is something more honest and frankly more interesting. We can lay the real documented American famine [music] next to the real documented science and ask what one implies about the other carefully labeled as a hypothesis the studies make plausible, not a result anyone has confirmed.

[00:16:57]So let's walk the American side of it because a lot of you had family who lived it.

[00:17:03]The 1920s roared. Wheat prices were high. The rains came and farmers across the southern plains tore up the deeprooted native grasses that had held that soil down for 10,000 years, [music] replacing them with wheat fence line to fence line.

[00:17:23]Then at the start of the 1930s, two things hit at once. The Great Depression [music] gutted crop prices and a brutal yearslong drought settled over the plains and would not leave. The exposed top soil dried to powder and the wind which had always blown across that flat country picked it up. They called the storms black blizzards. Walls of dirt thousands of feet high rolling across Oklahoma, Texas, Kansas, Colorado, and New Mexico, turning noon into midnight.

[00:18:06]The worst of them came on April 14th, 1935.

[00:18:12]A Sunday, witnesses described a clear, warm morning that collapsed in the space of minutes into a churning black wall that swallowed the sun. They named it Black Sunday. An associated press reporter caught in it coined the phrase that named the whole region, the dust bowl. By some estimates, the planes lost hundreds of millions of tons of top soil in a single year. the living skin of the land simply lifting up and flying east.

[00:18:46]And it flew a long way. Later that same spring, a soil scientist named [music] Hugh Hammond Bennett sat in front of a congressional committee in Washington trying to convince skeptical lawmakers that the erosion out west was a national emergency.

[00:19:05]He had timed his testimony on purpose to a weather forecast.

[00:19:10]As he spoke, a cloud of plains dust [music] carried on the high winds, rolled all the way across the country, [music] and dimmed the sky over the capital, and the light coming through the committee room windows turned a dirty brown. Bennett gestured toward the glass. This gentleman, he [music] told them, is what I have been talking about.

[00:19:32]Congress passed the Soil Conservation Act [music] within weeks and Bennett became known as the father of American soil conservation. [music] The politics matter less than the image.

[00:19:45]The soil of Oklahoma was drifting over the dome of the United States capital.

[00:19:51]That is the scale of the machine those children were born [music] inside.

[00:19:57]And the hunger that followed was not metaphorical.

[00:20:01]Families ate what little they could grow in dying [music] gardens. Children breathed air so thick with grit that a sickness spread through [music] the plains that doctors called dust pneumonia. The fine silt packing into young lungs, killing the very old and the very young [music] first. Milk cows died, chickens suffocated, and the malnutrition of those years [music] fell hardest exactly as it did in Holland. on pregnant mothers and small children.

[00:20:34]So they left. Roughly 2 and a2 million people pulled up and abandoned the planes during the 1930s in one of the largest internal migrations in American history.

[00:20:46]Many of them, the Oklahomaman especially, loaded everything they owned onto a battered Model T and drove west on Route 66 toward California, chasing rumors of work in the orchards and cotton fields.

[00:21:02]John Steinbeck put the Jode family on that road in the Grapes of Wrath, and the book won the Pulitzer Prize because it was true.

[00:21:12]The migrants were met at the California line with [music] contempt and a slur, okies, and with wages that barely kept a family alive.

[00:21:24]They starved in ditches beside fields full of fruit.

[00:21:30]That is the American famine.

[00:21:32]Documented, photographed, [music] and still inside living memory for some of the oldest people watching this. If you are getting value from this, take a second [music] to subscribe to Anglo Origins.

[00:21:48]We do this the careful way. Real [music] studies, real sources, no fairy tales.

[00:21:55]And there is more of it coming. Now, let's connect the two halves.

[00:22:01]Here is the honest hypothesis, and I am labeling it as a hypothesis on purpose. The famine epigenetics findings were built on the Dutch hunger winter, on overcolics, on oops.

[00:22:18]Every one of those was a population that suffered severe timed nutritional stress. And in everyone, that stress left a measurable methylation signal that reached at least into children and in the Swedish work into grandsons.

[00:22:36]The Dust Bowl and the Great Depression delivered the same category of insult to the American plains.

[00:22:44]Severe childhood malnutrition, starvation in pregnancy, a whole cohort of children whose slow growth period, that same pre-puberty window, the Swedish studies flagged, fell squarely inside the worst of the hunger. Do the arithmetic on a single life.

[00:23:06]A boy born on an Oklahoma farm in 1927 would [music] have reached that slow growth window ages 9 to 12 between 1936 and 1939.

[00:23:20]Black Sunday the dust pneumonia years the long drive west dead center. If the overcalics pattern means what it appears to mean, that is a boy whose future grandsons might carry the setting laid down in those exact years.

[00:23:40]And there was not a handful of those boys. There were hundreds of thousands of them scattered from the Texas panhandle [music] to the labor camps of California's central valley. Their grandsons and greatgrandsons are statistically some of the very people most likely to be watching a channel like this one. The biology that responded in a Dutch fetus or an overcallex farm boy is not different biology because the child was in Oklahoma. It is the same human machinery meeting the same kind of stress.

[00:24:19]So the reasonable science grounded expectation is this. If anyone ever tests the descendants of the dust bowl generation the way Hyman's and Lumi tested the hunger winter cohort, it would not be surprising to find altered methylation signatures tied to that ancestral hunger particularly through genes involved in growth and metabolism and particularly if the Swedish pattern holds running down the paternal line to grandsons. That is a defensible prediction. It is not a finding. Nobody has looked. And the title of this video that you still carry it lives right there in that gap between what the science makes plausible and what anyone has actually measured in an American family.

[00:25:12]Which brings us to the part that separates an honest video from a hype video. And it is the most important few minutes in this entire story.

[00:25:23]The mechanism is real.

[00:25:26]The limits are real too.

[00:25:29]Here is the first hard limit. Almost everything solid we have is about children and grandchildren.

[00:25:37]The hunger winter mark was measured in the people who were in the womb.

[00:25:42]The overcolics and uppala signals reached grandsons.

[00:25:47]But true multigenerational inheritance in humans, a mark passing cleanly to great grandchildren and beyond, in people generations removed from the original hunger, is genuinely contested among scientists, in laboratory animals, in mice, and in tiny worms. Researchers have tracked epigenetic effects across several generations under controlled conditions.

[00:26:15]In humans, it is much harder to prove because we live long lives. [music] We choose our own diets. We inherit our parents' habits and their neighborhoods and their poverty along with their genes. And untangling a chemical mark from all of that is brutally difficult.

[00:26:35]Serious biologists disagree in print about how far these marks really travel in people. Anyone who tells you it is settled is skipping the argument. Here is the second hard limit and it cuts against the title. So I am going to say it out loud.

[00:26:55]Epigenetic marks can fade.

[00:26:59]Methylation is not a tattoo.

[00:27:03]The body actively reprograms much of its methylation twice in two great erasing waves. Once shortly after fertilization and once as the germ cells, the future eggs and sperm are being formed.

[00:27:20]Each wave strips most of the tags off the genome and resets it close to a blank state.

[00:27:28]For a famine mark to reach a grandchild, it has to survive that eraser, slip through both waves without being wiped clean. And that is exactly the step the skeptics keep pointing at. Some marks clearly do survive [music] or the overcalics grandsons make no sense at all. But how many survive, how reliably, and across how many generations, that is the genuine open argument in the field right now. And it is why some effects that show up in grandchildren may weaken or vanish entirely further down the line.

[00:28:08]So the honest reading of you still carry it is not a certainty. It is a possibility, a plausible one supported by real mechanisms, but not something a test can confirm in you today.

[00:28:23]And that [music] is the last piece because I do not want to leave you with only a maybe.

[00:28:31]Let me tell you what is genuinely knowable right now about your own line.

[00:28:38]You can know your family's oral history of hunger. The grandmother who saved tinfoil and string until the day she died. The grandfather who would not let a scrap of food leave the table. Those habits were real [music] and they were downstream of real starvation. And they are data. So write them down.

[00:29:01]>> [music] >> the specific stories, who went hungry, where, and how old they were when it happened.

[00:29:09]If your grandfather was a boy on the planes in the 1930s, note the year he was born, because that tells you whether the hunger caught him in the womb, in infancy, or in that pre-puberty slow growth window the Swedish records kept flagging. Ordinary genealogy stops at names and dates. This is the rare case where the age at which an ancestor suffered may turn out to matter as much as the ancestors name. You cannot order the methylation test today. But you can gather right now the exact information that test would one day need in order to make sense of your line.

[00:29:53]You can know the documented health patterns [music] in the descendants of severe deprivation because the metabolic risks that showed up in the hunger winter cohort, [music] the diabetes, the heart disease, the weight the body clings to are the same patterns [music] clinicians see clustering in families with deep histories of poverty [music] and hunger. And you can know what a future test might reveal. the consumer kits you already own, the ancestry DNA [music] and the 23 and me, they read your sequence, the letters. They do not read your methylation, the tags on top of the letters. But methylation testing exists in research labs right now.

[00:30:40]>> [snorts] >> It is plausible that within your lifetime, [music] a descendant of the dust bowl could send in a sample and get back not just where their ancestors came [music] from, but an echo of what those ancestors survived.

[00:30:54]Until that day, hold both truths at once, the way this audience [music] always does best.

[00:31:02]The science of inherited hunger is real [music] and it is remarkable and it has been measured in the children and grandchildren of the starving in Holland [music] and in Sweden. And the specific claim about your dust bowl DNA is for now a hypothesis. [music] The evidence makes reasonable, not a fact anyone has printed out. The migrant mother's real name [music] was Florence Owens Thompson. She had 10 children. She lived until 1983.

[00:31:35]Somewhere out there, her descendants are walking around today, [music] carrying her sequence for certain and possibly, just possibly, a faint chemical signature of the winter she went hungry.

[00:31:49]Science cannot yet read that signature in her family.

[00:31:53]But for the first time in human history, we know what it would even look like.

[00:31:59]And that for a generation of people trying to find themselves in their own DNA might be the most honest reveal of all.

[00:32:10]If this is the kind of careful sourced history you want more of, [music] subscribe to Anglo Origins and tell me in the comments what your own family carried out of the depression.

[00:32:24]Read them and I will see you in the next one.