Transcript

8.14.25 · Smithsonian Magazine

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Speaker 1: Welcome. This is Rebecca Shore for Radio Eye and to
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day I will be reading selections from smithsonianmag dot com.
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As a reminder, RADIOI is a reading service intended for
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people who are blind or have other disabilities that make
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it difficult to read printed material. Please join me now
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for the first article titled five Astounding ways humans are
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driving animal evolution, including causing lizards to grow longer legs
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and leading moth populations to become darker. When people build
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cities and introduce invasive creatures, resident critter populations sometimes adapt
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by Brian Handwork, Science correspondent, we are rapidly changing the
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world that many animal species inhabit. Humans are developing wilderness
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into cities, re engineering ecosystems by introducing invasive species, polluting
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the planet in myriad ways, and driving chain changes to
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Earth's climate. But in response, some animals are evolving at
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a surprisingly fast pace through what some have called unnatural selection.
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This process conserves traits as they become newly beneficial in
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human changed environments. Such evolution offers an edge for survival,
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but it can also come with consequences, where one trait
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improves at the expense of other important traits and such
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animal adaptations can cause unpredictable impacts on the wider ecosystem.
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We talked to four experts to learn about some of
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the strangest examples of animal evolution and how some of
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those changes may in turn affect the environment. First, urban
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lizards evolve building friendly legs and feet. Preto Rican cities
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are a much different environment from the forest's annoles usually
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call home, and the tiny lizards have made some big
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evolutionary atas adaptations to thrive in the urban landscapes. City
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lizards grow longer limbs to move quickly across open areas
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exposed to predators. They sport supersized toe pads with microscopic
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structures called lamellae that enable them to cling to smooth
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surfaces like walls, concrete, and glass. The four hundred species
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of Annollus lizards have a long evolutionary history of ecological specialization,
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especially in lemb length and toepads as they diversified, says
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Christin Winchell, a biologist at New York University. The traits
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have evolved differently to help various species specialize in different
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parts of the forest habitat, so it makes sense that
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they would co evolve over short time scales to allow
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lizards to more effectively use the urban habitat, says Winchell.
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The urban annoles can also tolerate heat almost two degrees
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fahrenheit higher than their rural relatives to live where pavement
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and metal can push their physiological limits. Although one degree
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celsius doesn't seem like a lot, when Shall writes in
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an e mail, this can make the difference of being
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able to remain active during the mid day versus needing
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to find a thermal refuge or shade, which provides more
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access to food and mates. Winchell has seen the same
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physical and genomic adaptations arise and genetically distinct populations in
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multiple locations across the island over the past twenty to
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thirty years, so this is an example of parallel adaptation,
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with changes repeatedly arising in response to the same selection
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pressure in cities, she says. She believes the lizards probably
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have many more urban adaptations, including color, claw, tail shape,
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and egg laying behavior. The urban habitat is so incredibly different,
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she notes that just about every aspect of behavior, signaling, physiology,
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and morphology could be adaptively changing in response next a
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free peanut diet alters squirrel skulls. Scientists have known diet
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drives evolution since Darwin's finches, whose various beak shapes were
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adapted to the different foods they ate. Humans alter animal
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diets in many ways, including through handouts that may lead
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to changes. In an instance where individuals offered red squirrels
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a steady diet of peanuts, the creature's skulls and jaws
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have changed. Britain's red squirrels live in fragmented populations that
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have been isolated from one another for many generations. Each
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has access to different foods to help sustain Those in
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the form be reserved near Liverpool, workers fed them peanuts
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year round during the nineteen nineties and two thousands. Unbeknownst
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to conservationists, this was changing the innnct atomy of these squirrels,
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says Phil Cox, a rodent biologist at University College London
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and co author of a study on the subject in
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Royal Society Open Science. The squirrels showed smaller, less efficient
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jaw muscles and therefore less forceful bites than other red squirrels.
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Cox believes the adaptation happened because peanuts are so easily
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picked apart, unlike the pine cones or hard hazel nuts
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that other squirrels eat. Indeed, when peanut feeding was stopped,
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the squirrels began to show a partial reversal of the
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changes to the skull. That was the point where we thought, yes,
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this really is a dietary effect. Cox says. We do
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know that rodents can undergo very rapid evolution on islands,
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and these are effectively island populations. Cox ads, However, these
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changes occurred so rapidly that it's possible they are outpacing
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even evolution. They may occur during a squirrel's lifetime via
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a process called bone modeling, in which bone mass decreases
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with reduced muscle usage. But if so, that beneficial change
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would itself become selected for and likely develop into an
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evolutionary adaptation. Next fishing fleet's prompt. Smaller cod size matters
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when it comes to fishing, but the quest for bigger
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catches is driving genetic changes among fish like cod Eric Palkovac's,
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an ecologist and evolutionary biologist from the University of California,
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Santa Cruz, says that fishermen often have a financial incentive
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to target and catch the largest fish. That's a direct
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selective pressure against large size, he says, and because fish
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get larger when they get older, it's also a selection
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against old age. Because so many of the larger older
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fish were caught, smaller individuals with traits that enabled them
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to reproduce earlier came to represent much of the population
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over time. Genetic analysis of Atlantic cod showed that overfishing
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during the twentieth century forced cod to evolve these changes
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in a matter of only decades, and this human predation
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has impacts far beyond cod. It's not just that traits
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are changing or size is changing, but also the ecological
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role of these species is changing, which has reverberating effects
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through the whole ecosystem. Pauklovax says, smaller cod eats smaller prey,
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and studies have shown they can't play the same ecological
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role that bigger top predator cod once did, which rearranges
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the larger ocean food web. Evolutionary change leads to ecological change,
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which then drives further evolutionary change. Poclovac's notes, so it
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sort of happens in a cyclical feedback. Next introduced fly
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parasites and their cricket hosts change in tandem. When humans
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introduced non native species deliberately or accidentally, the resulting evolutionary
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impacts can cascade through an ecosystem. Hawaii is home to
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an evolutionary cat and mouse game between two species that
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are both invasive and adaptable. Pacific crickets, native to Australia Island,
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hopped through the Pacific and reached Hawaii seven hundred to
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sixteen hundred years ago, likely in the canoes of Polynesian explorers.
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According to Robin Tingatella, a biologist at the University of Denver,
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their story took a dark turn when a second species
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arrived in Hawaii about thirty five years ago. Parasitic flies
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arrived from North America and used field crickets as hosts
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to carry their larvae. None of the crickets they had
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evolved with in North America were there, so they had
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to first host switch to start using the Pacific field
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cricket as a host, explains Tingatella. The flies found the
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crickets by listening for their mating songs and were so
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successful the crickets were faced with a dilemma adapt or die.
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They did so by literally changing their tune. The crickets
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evolved new quieter songs through physical changes to the wing
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instruments that create them. Crickets producing the new songs are
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less attractive to the parasitic flies, but they still managed
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to attract female crickets. This means they tend to survive
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longer and mate more successfully than those sticking to the
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old songs, thus passing on the genes involved in these
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musical mutations. Now, further research shows that the fly, in
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turn are evolving. They are developing more sensitive hearing across
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a wider range of sound frequencies. The better to evesdrop
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on the newly evolved and constantly changing mating calls with
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which the crickets are disguising themselves. This is becoming a
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classic co evolutionary story. Tinga Tella says that highlights how
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newly introduced species can lead to cascades of interesting and
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often unpredictable adaptations. Finally, moths adapt to air pollution and
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artificial light. The peppered moth is a classic example of
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evolutionary biology that was put into action by the air
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pollution of the Industrial Revolution. The moths may be white
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or black, but the white hue historically provided better camouflage
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on England's birch trees. During the nineteen fifties, scientists realized
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that industrial air pollution had made it easier for black
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moths to blend in with their sooty surroundings like birch
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trees darkened by the dirty air, because they were eaten
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by bird predators less frequently, the black moths reproduced more
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and became more common than their white relatives in polluted
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areas thanks to a specific mutation. Finally, by twenty twelve,
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thanks to air quality that improved beginning in the nineteen seventies,
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the trend had reversed as the white variant became less
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visible on clean white bark. While Europe's air has become cleaner,
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the prevalence of light pollution has grown significantly. Moths are
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famously attracted to lights, which can disrupt mating and feeding,
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or expose them to dangerous predators, but city moths may
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now be evolving to avoid this danger. When spindle ermine
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moths from rural populations and urban work ones were raised
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in the same garden, urban moths were thirty percent less
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likely to be caught in a light trap. How work
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by Evert van Derschut, a biologist at Catholic University of
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Lovent In, Belgium, found the urban moths also have slightly
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smaller wings. It may be that the moths are selecting
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for altered flight mechanics, which dampens their flight response to
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light and in turn boosts their chances of survival. If so,
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that light avoidance adaptation may come with costs like shrinking
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the moths ranges for available food or mates. Rapid evolutionary
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changes may produce such negative consequences for species and for
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wider ecosystems, Ecologist Palkovax notes, but the positive side is
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that some creatures display the flexibility to adapt to an
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increasingly anthropocentric world. We'd see a lot more extinction, he said,
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as if these species were not able to evolve. Next.
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Inside the quest to understand the link between cannabis and schizophrenia,
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recent studies have examined the relationship between the drug and
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psychoses and looked at how the brain responds to the substance.
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By Lillian Alley Staff contributor. While cannabis has become a
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mainstay in recreational dispensaries and medical clinics, scientists are still
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learning about its long term psychological impacts. The drugs increasing
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popularity both recreationally and to treat conditions like chronic pain
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and anxiety, is making some researchers and consumers concerned over
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one of its most severe side effects, psychosis. Cannabis is psychoactive,
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meaning it affects how a user's brain works. For decades,
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researchers have been identifying how cannabis brain affecting properties can
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cause symptoms of psychosis. Psychosis refers to any mental state
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where a person struggles to distinguish between what is real
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and what is not real. Psychosis is characterized by hallucinations,
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where people sense things are not there, and delusions, where
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people hold inexplicable false beliefs. Some psychoses, like schizophrenia, are chronic,
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but psychosis can be drug induced, with cannabis being considered
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one of the riskiest, if not the riskiest, drugs for
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chronic psychosis. Someone with cannabis induced psychosis is at a
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higher risk of transitioning or being subsequently diagnosed with schizophrenia,
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says Daniel Myron, a public health physician at the University
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of Ottawa than someone with methanthetamine induced psychosis or you
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know whose having psychosis related to alcohol use or opioid
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use or cocaine use. Myron is the author of a
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February report published in JAMA Network Open that looked at
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rates of psychotic disorders in the Canadian province of Ontario
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among people who were flagged for cannabis use disorder dependence
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on or abuse of cannabis, sometimes categorized as cannabis addiction.
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The study used data collected between two thousand six and
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twenty twenty two from over thirteen million people in Ontario
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and found in an association between cannabis use and psychosis onset.
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The study looked at two types of psychosis, schizophrenia spectrum
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disorder and psychosis that did not neatly fit into a
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diagnostic category. Schizophrenia's spectrum disorder includes many disorders characterized by hallucinations, delusions,
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and a struggle to function. The other diagnostic category labels
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people who may have similar symptoms but do not meet
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all the criteria for a schizophrenia diagnosis. Researchers found that
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while rates of schizophrenia stayed stable over time, the proportion
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of schizophrenia associated with cannabis use nearly tripled from three
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point seven percent to ten point three percent after the
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drug was legalized for non medical use across Canada in
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twenty eighteen. Rates of psychosis that didn't neatly fit into
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a diagnostic category almost doubled after legalization, with significant upticks
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among younger people. While the uptick occurred after cannabis legalization.
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Myron thinks this increase is in non schizophrenia diagnosis could
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also be affected by other drugs or mental health problems.
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Myron's study is also limited by how it defined cannabis addiction.
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The study identified individuals as having cannabis use disorder when
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when they visited the emergency room or were hospitalized for
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mental and behavioral disorders due to cannabis use or for
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cannabis poisoning. Peter Grinspoon, a cannabis specialist at Massachusetts General
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Hospital who was not affiliated with the study, says that
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criteria could include people who do not have cannabis addiction,
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like someone who tries cannabis for the first time and
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panics or even hallucinates. They diagnosed a person who shows
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up with an overdose. Anybody could have an overdose. Grinspoon says,
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you take a gummy the wrong size, you have an overdose.
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This overdiagnosis problem is not specific to Myron's study, he
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says across the board, Grinspoon thinks the way the medical
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community defines cannabis addiction is broken. To be diagnosed with
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cannabis use disorder, under the latest addition of the Diagnostic
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and Statistical Manual of Mental Disorder, a patient has to
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meet at least two of eleven criteria over a year,
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with two of those criteria being symptoms of drawl and tolerance.
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Since withdrawal and tolerance symptoms can occur in people taking
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cannabis according to a doctor's prescription, Grinspoon thinks these criteria
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could prompt vast overdiagnoses of cannabis addiction. We don't use
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those for medical opiates or medical benzodiazepines because everybody that
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uses them has tolerance and withdrawal, says Grinspoon, that's not addiction.
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Despite this criticism, which Grinspoon says reflects an overdiagnosis problem
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across the field, he agrees that some kind of link
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exists between cannabis and psychosis, but he says further more
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detailed research needs to be conducted, especially on causality. An
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April study in Jamma psychiatry may help identify where in
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the brain the proposed cannabis psychosis link occurs. Jessica Arens,
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a neuroscientist studying for her PhD at Canada's McGill University,
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led their research. Erins and other researchers used magnetic resonance
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brain imaging to look at and around the substantia nigra,
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a region of the brain critical for the production of dopamine,
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the feel good molecule that helps drive the brain's reward system.
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People with schizophrenia tend to produce more dopamine in the
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substantia negra, and when that dopamine breaks down, those patients
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produce a pigment called neuromelanin. Erins and her team looked
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specifically at neuromelanin. While psychosis can have environmental and genetic causes,
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Lena Polanioppon, a psychiatrist at McGill who worked on the study,
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says dopamine is where all those factors connect. To see
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whether cannabis triggered the dopamine pathway, similarly to psychosis, researchers
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took neuromelanin sensitive brain images of people diagnosed with cannabis
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use disorder and saw elevated dopamine function similar to that
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in psychosis patients. But because researchers are looking at neuromelanin,
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which can break down from chemicals other than dopamine, they
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need to find out if cannabis users have high concentrations
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because of dopamine or another chemical entirely. Matthew Hill, a
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developmental neuroscientist at the University of Calgary, says that the
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study does not appear to offer a complete causal relationship
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between cannabis use and psychotic disorders, but it does confirm
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that cannabis sparks enhanced dopamine transmission in humans, but seeing
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whether the relationship is cannabis specific is challenging since a
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similar dopamine effect has been seen with others substances, including alcohol,
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Hill says, so what actually causes the link between cannabis
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and psychosis. Researchers have proposed three popular hypotheses. That something
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that causes chronic psychosis also draws people to cannabis, that
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people with early symptoms of psychosis are self medicating with cannabis,
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and that for some people, consuming cannabis actually causes psychosis.
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All three theories could be true, with certain cases having
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different causes. I think that there is a group of
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individuals who would have never developed schizophrenia if they had
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not regularly used high potency cannabis, Myron says. I think
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the debate is more of how large is that number.
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For now, researchers have no reliable way to differentiate between
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schizophrenia cases that were directly caused by cannabis and cases
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that involve confounding variables. For example, some people experiencing the
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first symptoms of a psychotic disorder, such as paranoia, unease,
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and trouble thinking clearly may self medicate with cannabis to
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ease those symptoms. Meanwhile, people who had adverse childhood experiences
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tend to be at higher risk for schizophrenia, and they
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also tend to be a population that uses more cannabis.
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Researchers still do not know the extent to which any
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of these factors contributes to the link between schizophrenia and psychosis.
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As Grinspoon, all we know is that there is an association.
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While the nature of the link is still being researched.
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Experts agree that cannabis is particularly dangerous for young people.
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Grinspoon advocates a just say weight mindset for young people
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interested in cannabis, choosing not to use it until they
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are older. Additionally, people with family histories of schizophrenia and
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psychotic disorder, as well as bipolar disorder, should stay away
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from the drug, especially as those disorders tend to develop
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during adolescence and late teens. There is a lot of
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cannabis use that happens during adolescence, and adolescence is also
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a period when a lot of psychiatric disorders, particularly schizophrenia
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and psychotic disorders, begin to emerge, says Hill, so I
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don't doubt that there is a relationship there. As with
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all drugs, the dose makes the poison. Research suggests that
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more potent cannabis, or cannabis with more of the psychoactive
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chemical DHC, tends to be associated with worse mental side effects.
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According to Grinspoon, a relatively small dose can help with
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some anxiety symptoms and relieve nausea, while a large dose
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can cause paranoia and vomiting. As cannabis becomes more widely legalized,
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experts also advocate for firmer regulations, with Myron stating that
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looking at tobacco regulations would be a good place to start.
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Grinspoon agrees with that starting point, but believes that advertising
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for all drugs and alcohol should be banned. Cannabis advertising,
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along with alcohol and tobacco and pharmaceutical advertising, is really
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misleading and unhelpful, says Grinspoon. While regulation could be helpful,
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experts also agree that criminalization is not the answer, especially
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as it disproportionately targets and punishes people of color. Researchers
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say that users should approach cannabis with caution and moderation.
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The drug can help relieve some side effects for cancer
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patients while aggravating chronic pain in other people. And while
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new studies like Myrons and Errans may help solidify the
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link between cannabis and psychosis, researchers do not want to
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spark panic. It's not a binary, says Errands. We don't
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want to instill fear. Finally, Maria Mitchell, America's first woman
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astronomer and mentor to women in science. Maria Mitchell, the
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first widely recognized American woman scientist, gained international acclaim after
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discovering a comet in eighteen forty seven. As Vassar College's
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first astronomy professor, she advanced opportunities for women in science,
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and mentored a generation of students using one of the
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country's finest observatories by deb Warner. Maria Mitchell eighteen eighteen
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to eighteen eighty nine was already famous when she began
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teaching at Vassar College in eighteen sixty five. She was
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America's first female astronomer, indeed its first woman scientist of note.
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Matthew Vasser, the founder of the college, was so pleased
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by her recruitment that he personally took charge of buying
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the Henry Fitz telescope that would have pride of place
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at the college observatory. Mitchell was a Quaker from Nantucket
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whose family encouraged her interest in astronomy. While still a girl,
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she helped her father, an avid public school teacher, observe
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a solar eclipse and rate the chronometers used by sailors
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to determine their longitudes at sea. In her late twenties,
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she worked as a librarian in the local Athenaeum, handling
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astronomical calculations for the U. S. Coast Survey and the U. S.
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Nautical Almanac. On October first, eighteen forty seven, while observing
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the skies. With her father's telescope, she spotted a comet
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not seen before. As news of this discovery spread throughout
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the scientific community, Mitchell received a gold medal from the
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King of Denmark, thus becoming one of the first Americans
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to win any medal for science. Mitchell's moved to Poughkeepsie,
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New York, to become the professor of Astronomy at the
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newly opened Vassar College, the first school offering women resources
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comparable to those at the leading colleges for men, would
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represent a considerable step forward in the education of women
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in science. At the college observatory, Mitchell had charge of
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a large refracting telescope and other instruments. During her years
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at Vassar, she mentored many young women who would embrace
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science as a future vocation. This concludes readings from smithsonianmag
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dot com for today. Your reader has been Rebecca Shore.
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Thank you for listening, and have a great day. Nay