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Researchers have discovered that children's brains can contain cells with their mother's DNA and that these cells can persist for decades. The findings, which were posted to the preprint database bioRxiv June 10 but have not been peer-reviewed yet, are part of a growing body of work showing that a mother and fetus exchange cells during pregnancy ‪—‬ a phenomenon known as "microchimerism." Previously, scientists had found that a mother's brain harbors cells with her children's DNA. The findings are important for several reasons, said Amy Boddy, co-director of the Microchimerism, Human Health and Evolution Project at the University of California, Santa Barbara, who was not involved in the study. Past work mostly found evidence of maternal microchimerism in infancy, and in blood samples, she told Live Science in an email. "What's exciting here is that it's tissue, not blood; it's real human data, not an animal model; and the methods are cutting-edge." More broadly, the work reinforces the idea that microchimerism is "a normal process of mammalian biology," Boddy said.Hunting down maternal cells in the brainBefore this study, there was sparse evidence for maternal microchimeric cells in brains, mostly because it is hard for researchers to get samples of human brain tissue and DNA from both parents and their children.To overcome this challenge, a team led by Sami Kanaan, a staff scientist at the Fred Hutchinson Cancer Center in Seattle, analyzed brain tissue that had been surgically removed from dozens of children with severe epilepsy as part of their treatment. The patients ranged in age from 28 days to 19 years at the time of their surgery, and their mothers provided DNA samples through cheek swabs.Kanaan's team used a tool called quantitative PCR to identify and count maternal cells hiding among millions of cells in the children's brains. Out of 37 mother-child pairs, 26 children ‪—‬ 70% ‪—‬ had their mother's cells in their brains. These maternal cells were distributed across multiple regions of the brain, including the frontal, temporal and parietal lobes, which sit on the brain's outer surface, and the hippocampus, which is buried deep inside. Each sample had, on average, about 2.2 maternal cells per 100,000, though one sample from the hippocampus had 459 maternal cells per 100,000 and 11 children had no evidence of maternal DNA in their brains.That prevalence is probably underestimated, Boddy said, "due to the limits of detecting rare cells at low frequency with this method."Being a firstborn child seemed to increase the odds of having maternal cells in the brain. Of the children who carried their mother's cells, 14 were firstborns and 12 were later-born. In contrast, among the children who didn't have these cells, only one was a firstborn and 10 were later-born.Using a technique called single nucleus RNA sequencing, which reveals what a cell is doing by showing which genes within the cells are switched on, the researchers found that the maternal cells had transformed into several types of brain cells. Likely, these cells were originally leukocytes and stem cells and had been transferred to the fetus via the placenta or during pregnancy or breastfeeding. The transformed cells included neurons; oligodendrocytes, which produce the protective sheath around neurons; astrocytes, which support many brain functions and help fuel neurons; microglia, the brain's immune cells; and endothelial cells, which line blood vessels."Being able to use single-nucleus RNA sequencing to identify what type of cells the maternal microchimeric cells actually are is amazing," Boddy said. "We've been so limited in understanding the function of these cells, and papers like this, with these methods, are getting us closer."During pregnancy, the mother and fetus exchange cells — a phenomenon called "microchimerism." (Image credit: Rhenizara S via Getty Images)Checking healthy brainsTo see whether these findings also applied to people without epilepsy, the researchers examined brain autopsy data from 29 individuals with no known neurodevelopmental conditions, ranging in age from 22 weeks of gestation to 40 years. They also analyzed brain tissue from three men in their late 80s and early 90s without any known brain conditions originally collected as part of an Alzheimer's disease study. In total, the researchers found foreign cells in 25 of 32 people — about 78% — including in the brain of a man in his 90s. The researchers suspect these foreign cells are maternal, but they couldn't confirm it because they didn't have DNA from the mothers. It is possible that the foreign cells came from a twin; an older sibling; a past pregnancy, miscarriage or abortion (in females); or, rarely, from a maternal grandmother, the team wrote in their paper.As in the epilepsy patients, these cells had matured into several types of working brain cells. In younger brains, they most often became a specific kind of neuron, a layer 2/3 neuron, while in older brains, maternal cells were more likely to be microglia. Given that these microchimeric cells take on very different roles, it would be interesting to know whether that diversity reflects their origins ‪—‬ for example, whether they came from a mother, an older biological sibling or a maternal grandmother, said Dr. Sing Sing Way, a microchimerism researcher at Cincinnati Children's Hospital Medical Center who was not involved in the study.The number of maternal cells declined with age, but they never completely disappeared.Related stories'It doesn't lie. So who are you?': What happens when DNA tests show a woman is not the mother of the child she gave birth to?Diagnostic dilemma: Woman had her twin brother's XY chromosomes — but only in her bloodWhy does a mother's body keep some of her baby's cells after birth?Boddy said the findings mostly raise new questions. "Do we maybe need microchimeric cells to 'help out'?" she asked. "Is diversity of cells in the brain important, or is it just a byproduct of being a placental mammal?”Because microchimeric cells appear to be common, Boddy suspects they "are doing an important job in the brain, so understanding their function could be very important for understanding healthy brain development."By using new analytical tools to pinpoint microchimeric cells, the study "pushes the boundaries" of previous research, but future studies would benefit from larger and more uniform datasets, Way said. That would mean obtaining more brain biopsies, analyzing more cells from each sample, collecting specimens at different ages, and sampling similar brain regions across individuals to better compare the results.This article is for informational purposes only and is not meant to offer medical advice.

Quick factsWhat it is: The collision-prone galaxy cluster MACS J0553.4-3342Where it is: In the constellation ColumbaWhen it was shared: July 2026Around 100 years ago, Albert Einstein made an audacious prediction about space. The frequently right (but occasionally wrong) physicist theorized that, just as the curved lens of a magnifying glass bends light to increase an object's apparent size, massive celestial objects can curve the very fabric of the universe with their gravity — causing distant sources of light to bend, warp, and appear magnified as their rays pass through the region on their way to Earth.Today, this phenomenon — called gravitational lensing — has been confirmed through dozens of telescope observations, and is a crucial tool that observatories like the James Webb Space Telescope (JWST) use to probe the light of the oldest, faintest galaxies in the universe. And in this newly released JWST image of a tumultuous young galaxy cluster, Einstein’s gravitational funhouse effect is on full display. In the foreground, two bright white points of light ringed with white halos signify the gravitational center of MACS J0553.4-3342, a gargantuan collection of bound galaxies located in the constellation Columba (the dove). These two white beacons are massive elliptical galaxies, each wreathed in their own sub-cluster of smaller galaxies, according to a statement from the European Space Agency (ESA). And the two clusters are not getting along.Studying the galaxies’ light as it appeared roughly 4.4 billion years ago, astronomers can tell the clusters are in the messy process of merging together. The two principal elliptical galaxies have already slammed through each other once, and now sit at a distance of around 1 million light-years apart (that’s about 10 Milky Ways lined up in a row). Eventually, that gap will close as the massive galaxies swoop back toward each other, finally combining into one.A full-size view of JWST's observations (Image credit: ESA/Webb, NASA & CSA, S. Fujimoto)But the real jewels in this galactic trove are hidden in the contorted, orange arcs of light that bookend the cluster on either side. Here, the magnifying effect of gravitational lensing is acting in full force — allowing JWST to detect the light of several faint galaxies from less than a billion years after the Big Bang. Three bright dots in the arc on the left are actually three repeated images of a single galaxy, according to ESA. The trippy effect appears several times throughout the image, with each elongated orange streak cracking open a warped window onto an ancient corner of the universe that would otherwise be impossible to see.Through observations like these, scientists using JWST have discovered that the oldest stars and galaxies in the universe have grown larger and faster than our leading theories of cosmology predict should be possible. Using one cosmic oddity to uncover another, this gravitational lens could keep astronomers busy for decades to come.See more space photos of the week: 'Human minds should not go through this' The Artemis II crew recalls the unreal moment when Earth disappeared Hidden structure in 1st Vera Rubin image First-light images from the Vera C. Rubin Observatory reveal a 163,000-light-year stream of stars emanating from a nearby galaxy. JWST peeps the 'Eye of God' A spectacular James Webb telescope image reveals intricate structures inside the Helix Nebula.

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Nowadays, the word "weapon" may evoke modern-day technologies such as firearms, blades and missiles. Yet archaeological evidence shows that weapons have existed for hundreds of thousands of years. Of course, early humans wielded weapons that looked quite different from those used today. So what is the oldest weapon?Generally, weapons are defined as objects used to impart violence on other living beings, said Ben Fitzhugh, a professor of anthropology at the University of Washington in Seattle. That includes objects used in interpersonal conflict among hominins (a group that includes modern Homo sapiens and our relatives that evolved following the split from chimps and bonobos) and for hunting, Fitzhugh told Live Science.Sign up for our newsletter(Image credit: Marilyn Perkins / Future)Sign up for our weekly Life's Little Mysteries newsletter to get the latest mysteries before they appear online.But archaeologists don't automatically consider just any object that could cause harm to be a weapon; context and intent matter, Rolf Warming, founding director of the Society for Combat Archaeology and a doctoral candidate in archaeology at Stockholm University, told Live Science in an email. For instance, experts excavating a site with potential weapons might look for evidence of hunting, such as butchered animal bones; or artifacts like pointed bone tools that can be used to craft weapons. They may also consider what objects were made out of and residue or wear marks on the weapons themselves, which can help determine how they were used.According to Warming, archaeologists generally consider three finds as contenders for the oldest evidence of weaponry in the archaeological record: the Clacton spear, the Schöningen spears and throwing sticks, and the Kathu Pan 1 spear points. Clacton spearScientists have estimated that the Clacton spear is over 400,000 years old. Experts think the uncovered 15-inch-long (37 centimeters) spear point was broken off from a longer shaft, perhaps by accident while the user was hunting, or deliberately as a ritual. It's made from yew wood and was worked with a tool to a sharp point on one end. The broken end was never found. Excavated in 1911 from Clacton-on-Sea in Essex, England, the Clacton spear is now on display in London's Natural History Museum, where it is labeled as the oldest preserved wooden spear fragment in the world. Archaeologists believe it was fashioned by either Homo heidelbergensis or Neanderthals — two hominins that predate H. sapiens. In fact, the spear appears to be older than our species, as the oldest known H. sapiens fossils date to around 300,000 years ago. The Clacton spear's shape, size and wood suggest that it was a thrusting weapon and that its makers engaged in cooperative hunting strategies.Schöningen spears and throwing sticksDifferent views of a throwing stick from Schöningen, a contender for one of the world's oldest weapons. (Image credit: Photograph by Volker Minkus)Since 1992, archaeologists have excavated between 20 and 25 wooden weapons at a site in Schöningen, Germany, including complete and fragmented spears, and throwing sticks made predominantly from spruce and pine wood. They're considered the oldest completely preserved wooden weapons in the world, according to the Schöningen Research Museum; today, archaeologists' varying estimates place the weapons' age between 200,000 and 300,000 years old. Their creation has historically been attributed to H. heidelbergensis, an early human species that lived about 700,000 to 200,000 years ago throughout Europe, parts of Africa, and possibly in what is now China. More recent dating suggests the spears could potentially be the work of Neanderthals, according to a 2025 study. Scientists think these spears, which average just over 6.6 feet (2 meters) long, were used as thrusting weapons, throwing weapons or some combination of both to hunt larger game mammals, like horses, according to a 2024 study. The shorter throwing sticks are believed to be projectile weapons and average around 26 inches (65 centimeters) long. "In fact, the [Schöningen weapons] were found in association with butchered horses," Fitzhugh noted. The spears were sharpened, hardened and blackened using fire. "These things were shaped in a dynamically sophisticated way," he said. According to Warming, the Schöningen weapons suggest hominins had clear material knowledge and used different hunting tactics depending how far they were from their target. Kathu Pan 1 spear pointsHafted spear tips — stone points attached to some form of handle or shaft — became more common in the archaeological record between 200,000 and 300,000 years ago across Africa and Eurasia, and were previously thought to be created by Neanderthals or H. sapiens. However, 500,000-year-old stone points excavated from the Kathu Pan archaeological site in South Africa have signs of wear on the edges, and the shape of their base is consistent with hafted spears, suggesting they were used as weapons. Their age predates both Neanderthals and H. sapiens, and the location they were found in suggests they could have been created by H. heidelbergensis, who lived in regions of southern Africa at that time. Archeologists think they could have been used as spear ambush weapons. But some researchers have contested this evidence, arguing that it's "indirect" or even controversial, as no wooden shafts were uncovered with the spear points to solidify them as weapons as opposed to stone tools. Something older?Related mysteriesHas there ever been a period in human history without war?Were the Vikings really that violent?Did Roman gladiators really fight to the death?These are some of the earliest examples of weapons in the archaeological record, but there may be older weapons that have not survived throughout time. While hominins likely used organic materials like wood, sinew, fiber and adhesives to create objects and weapons, these materials break down or are destroyed over time, Warming noted. Studying these ancient weapons gives us perspective about the present. After all, weapons are more than tools of harm: Warming said they are material clues that give us glimpses into how our early relatives combined materials, used their imaginations, shared knowledge and cooperated in groups.Yet among these three important finds, Warming said that when inquiring about the oldest known weapon in the world, that "Clacton is the safest answer." Can you identify these historical objects of war? Test your smarts with our weapons of the world quiz!