8.14.25

Episode Transcript

Speaker 1 (00:00):
Welcome. This is Rebecca Shore for Radio Eye and to
day I will be reading selections from smithsonianmag dot com.
As a reminder, RADIOI is a reading service intended for
people who are blind or have other disabilities that make
it difficult to read printed material. Please join me now
for the first article titled five Astounding ways humans are

(00:23):
driving animal evolution, including causing lizards to grow longer legs
and leading moth populations to become darker. When people build
cities and introduce invasive creatures, resident critter populations sometimes adapt
by Brian Handwork, Science correspondent, we are rapidly changing the

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world that many animal species inhabit. Humans are developing wilderness
into cities, re engineering ecosystems by introducing invasive species, polluting
the planet in myriad ways, and driving chain changes to
Earth's climate. But in response, some animals are evolving at
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
human changed environments. Such evolution offers an edge for survival,
but it can also come with consequences, where one trait
improves at the expense of other important traits and such
animal adaptations can cause unpredictable impacts on the wider ecosystem.

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We talked to four experts to learn about some of
the strangest examples of animal evolution and how some of
those changes may in turn affect the environment. First, urban
lizards evolve building friendly legs and feet. Preto Rican cities
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
evolutionary atas adaptations to thrive in the urban landscapes. City
lizards grow longer limbs to move quickly across open areas
exposed to predators. They sport supersized toe pads with microscopic
structures called lamellae that enable them to cling to smooth

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surfaces like walls, concrete, and glass. The four hundred species
of Annollus lizards have a long evolutionary history of ecological specialization,
especially in lemb length and toepads as they diversified, says
Christin Winchell, a biologist at New York University. The traits
have evolved differently to help various species specialize in different

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parts of the forest habitat, so it makes sense that
they would co evolve over short time scales to allow
lizards to more effectively use the urban habitat, says Winchell.
The urban annoles can also tolerate heat almost two degrees
fahrenheit higher than their rural relatives to live where pavement

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and metal can push their physiological limits. Although one degree
celsius doesn't seem like a lot, when Shall writes in
an e mail, this can make the difference of being
able to remain active during the mid day versus needing
to find a thermal refuge or shade, which provides more
access to food and mates. Winchell has seen the same

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physical and genomic adaptations arise and genetically distinct populations in
multiple locations across the island over the past twenty to
thirty years, so this is an example of parallel adaptation,
with changes repeatedly arising in response to the same selection
pressure in cities, she says. She believes the lizards probably

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have many more urban adaptations, including color, claw, tail shape,
and egg laying behavior. The urban habitat is so incredibly different,
she notes that just about every aspect of behavior, signaling, physiology,
and morphology could be adaptively changing in response next a

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free peanut diet alters squirrel skulls. Scientists have known diet
drives evolution since Darwin's finches, whose various beak shapes were
adapted to the different foods they ate. Humans alter animal
diets in many ways, including through handouts that may lead
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
have changed. Britain's red squirrels live in fragmented populations that
have been isolated from one another for many generations. Each
has access to different foods to help sustain Those in
the form be reserved near Liverpool, workers fed them peanuts

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year round during the nineteen nineties and two thousands. Unbeknownst
to conservationists, this was changing the innnct atomy of these squirrels,
says Phil Cox, a rodent biologist at University College London
and co author of a study on the subject in
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.
Cox believes the adaptation happened because peanuts are so easily
picked apart, unlike the pine cones or hard hazel nuts
that other squirrels eat. Indeed, when peanut feeding was stopped,
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,
this really is a dietary effect. Cox says. We do
know that rodents can undergo very rapid evolution on islands,
and these are effectively island populations. Cox ads, However, these
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
a process called bone modeling, in which bone mass decreases
with reduced muscle usage. But if so, that beneficial change
would itself become selected for and likely develop into an
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
catches is driving genetic changes among fish like cod Eric Palkovac's,
an ecologist and evolutionary biologist from the University of California,
Santa Cruz, says that fishermen often have a financial incentive
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
get larger when they get older, it's also a selection
against old age. Because so many of the larger older
fish were caught, smaller individuals with traits that enabled them
to reproduce earlier came to represent much of the population
over time. Genetic analysis of Atlantic cod showed that overfishing

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during the twentieth century forced cod to evolve these changes
in a matter of only decades, and this human predation
has impacts far beyond cod. It's not just that traits
are changing or size is changing, but also the ecological
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,
and studies have shown they can't play the same ecological
role that bigger top predator cod once did, which rearranges
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
sort of happens in a cyclical feedback. Next introduced fly
parasites and their cricket hosts change in tandem. When humans
introduced non native species deliberately or accidentally, the resulting evolutionary

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impacts can cascade through an ecosystem. Hawaii is home to
an evolutionary cat and mouse game between two species that
are both invasive and adaptable. Pacific crickets, native to Australia Island,
hopped through the Pacific and reached Hawaii seven hundred to
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,
their story took a dark turn when a second species
arrived in Hawaii about thirty five years ago. Parasitic flies
arrived from North America and used field crickets as hosts
to carry their larvae. None of the crickets they had

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evolved with in North America were there, so they had
to first host switch to start using the Pacific field
cricket as a host, explains Tingatella. The flies found the
crickets by listening for their mating songs and were so
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
evolved new quieter songs through physical changes to the wing
instruments that create them. Crickets producing the new songs are
less attractive to the parasitic flies, but they still managed
to attract female crickets. This means they tend to survive

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longer and mate more successfully than those sticking to the
old songs, thus passing on the genes involved in these
musical mutations. Now, further research shows that the fly, in
turn are evolving. They are developing more sensitive hearing across
a wider range of sound frequencies. The better to evesdrop

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on the newly evolved and constantly changing mating calls with
which the crickets are disguising themselves. This is becoming a
classic co evolutionary story. Tinga Tella says that highlights how
newly introduced species can lead to cascades of interesting and
often unpredictable adaptations. Finally, moths adapt to air pollution and

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artificial light. The peppered moth is a classic example of
evolutionary biology that was put into action by the air
pollution of the Industrial Revolution. The moths may be white
or black, but the white hue historically provided better camouflage
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
moths to blend in with their sooty surroundings like birch
trees darkened by the dirty air, because they were eaten
by bird predators less frequently, the black moths reproduced more
and became more common than their white relatives in polluted

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areas thanks to a specific mutation. Finally, by twenty twelve,
thanks to air quality that improved beginning in the nineteen seventies,
the trend had reversed as the white variant became less
visible on clean white bark. While Europe's air has become cleaner,
the prevalence of light pollution has grown significantly. Moths are

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famously attracted to lights, which can disrupt mating and feeding,
or expose them to dangerous predators, but city moths may
now be evolving to avoid this danger. When spindle ermine
moths from rural populations and urban work ones were raised
in the same garden, urban moths were thirty percent less

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likely to be caught in a light trap. How work
by Evert van Derschut, a biologist at Catholic University of
Lovent In, Belgium, found the urban moths also have slightly
smaller wings. It may be that the moths are selecting
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,
that light avoidance adaptation may come with costs like shrinking
the moths ranges for available food or mates. Rapid evolutionary
changes may produce such negative consequences for species and for
wider ecosystems, Ecologist Palkovax notes, but the positive side is

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that some creatures display the flexibility to adapt to an
increasingly anthropocentric world. We'd see a lot more extinction, he said,
as if these species were not able to evolve. Next.
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
psychoses and looked at how the brain responds to the substance.
By Lillian Alley Staff contributor. While cannabis has become a
mainstay in recreational dispensaries and medical clinics, scientists are still
learning about its long term psychological impacts. The drugs increasing

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popularity both recreationally and to treat conditions like chronic pain
and anxiety, is making some researchers and consumers concerned over
one of its most severe side effects, psychosis. Cannabis is psychoactive,
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
cause symptoms of psychosis. Psychosis refers to any mental state
where a person struggles to distinguish between what is real
and what is not real. Psychosis is characterized by hallucinations,
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,
but psychosis can be drug induced, with cannabis being considered
one of the riskiest, if not the riskiest, drugs for
chronic psychosis. Someone with cannabis induced psychosis is at a

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higher risk of transitioning or being subsequently diagnosed with schizophrenia,
says Daniel Myron, a public health physician at the University
of Ottawa than someone with methanthetamine induced psychosis or you
know whose having psychosis related to alcohol use or opioid
use or cocaine use. Myron is the author of a

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February report published in JAMA Network Open that looked at
rates of psychotic disorders in the Canadian province of Ontario
among people who were flagged for cannabis use disorder dependence
on or abuse of cannabis, sometimes categorized as cannabis addiction.
The study used data collected between two thousand six and

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twenty twenty two from over thirteen million people in Ontario
and found in an association between cannabis use and psychosis onset.
The study looked at two types of psychosis, schizophrenia spectrum
disorder and psychosis that did not neatly fit into a
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
people who may have similar symptoms but do not meet
all the criteria for a schizophrenia diagnosis. Researchers found that
while rates of schizophrenia stayed stable over time, the proportion
of schizophrenia associated with cannabis use nearly tripled from three

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point seven percent to ten point three percent after the
drug was legalized for non medical use across Canada in
twenty eighteen. Rates of psychosis that didn't neatly fit into
a diagnostic category almost doubled after legalization, with significant upticks
among younger people. While the uptick occurred after cannabis legalization.

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Myron thinks this increase is in non schizophrenia diagnosis could
also be affected by other drugs or mental health problems.
Myron's study is also limited by how it defined cannabis addiction.
The study identified individuals as having cannabis use disorder when
when they visited the emergency room or were hospitalized for

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mental and behavioral disorders due to cannabis use or for
cannabis poisoning. Peter Grinspoon, a cannabis specialist at Massachusetts General
Hospital who was not affiliated with the study, says that
criteria could include people who do not have cannabis addiction,
like someone who tries cannabis for the first time and

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panics or even hallucinates. They diagnosed a person who shows
up with an overdose. Anybody could have an overdose. Grinspoon says,
you take a gummy the wrong size, you have an overdose.
This overdiagnosis problem is not specific to Myron's study, he
says across the board, Grinspoon thinks the way the medical

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community defines cannabis addiction is broken. To be diagnosed with
cannabis use disorder, under the latest addition of the Diagnostic
and Statistical Manual of Mental Disorder, a patient has to
meet at least two of eleven criteria over a year,
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
cannabis according to a doctor's prescription, Grinspoon thinks these criteria
could prompt vast overdiagnoses of cannabis addiction. We don't use
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.
Despite this criticism, which Grinspoon says reflects an overdiagnosis problem
across the field, he agrees that some kind of link
exists between cannabis and psychosis, but he says further more

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detailed research needs to be conducted, especially on causality. An
April study in Jamma psychiatry may help identify where in
the brain the proposed cannabis psychosis link occurs. Jessica Arens,
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
brain imaging to look at and around the substantia nigra,
a region of the brain critical for the production of dopamine,
the feel good molecule that helps drive the brain's reward system.
People with schizophrenia tend to produce more dopamine in the

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substantia negra, and when that dopamine breaks down, those patients
produce a pigment called neuromelanin. Erins and her team looked
specifically at neuromelanin. While psychosis can have environmental and genetic causes,
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
whether cannabis triggered the dopamine pathway, similarly to psychosis, researchers
took neuromelanin sensitive brain images of people diagnosed with cannabis
use disorder and saw elevated dopamine function similar to that
in psychosis patients. But because researchers are looking at neuromelanin,

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which can break down from chemicals other than dopamine, they
need to find out if cannabis users have high concentrations
because of dopamine or another chemical entirely. Matthew Hill, a
developmental neuroscientist at the University of Calgary, says that the
study does not appear to offer a complete causal relationship

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between cannabis use and psychotic disorders, but it does confirm
that cannabis sparks enhanced dopamine transmission in humans, but seeing
whether the relationship is cannabis specific is challenging since a
similar dopamine effect has been seen with others substances, including alcohol,
Hill says, so what actually causes the link between cannabis

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and psychosis. Researchers have proposed three popular hypotheses. That something
that causes chronic psychosis also draws people to cannabis, that
people with early symptoms of psychosis are self medicating with cannabis,
and that for some people, consuming cannabis actually causes psychosis.

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All three theories could be true, with certain cases having
different causes. I think that there is a group of
individuals who would have never developed schizophrenia if they had
not regularly used high potency cannabis, Myron says. I think
the debate is more of how large is that number.

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For now, researchers have no reliable way to differentiate between
schizophrenia cases that were directly caused by cannabis and cases
that involve confounding variables. For example, some people experiencing the
first symptoms of a psychotic disorder, such as paranoia, unease,

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and trouble thinking clearly may self medicate with cannabis to
ease those symptoms. Meanwhile, people who had adverse childhood experiences
tend to be at higher risk for schizophrenia, and they
also tend to be a population that uses more cannabis.
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.
As Grinspoon, all we know is that there is an association.
While the nature of the link is still being researched.
Experts agree that cannabis is particularly dangerous for young people.
Grinspoon advocates a just say weight mindset for young people

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interested in cannabis, choosing not to use it until they
are older. Additionally, people with family histories of schizophrenia and
psychotic disorder, as well as bipolar disorder, should stay away
from the drug, especially as those disorders tend to develop
during adolescence and late teens. There is a lot of

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cannabis use that happens during adolescence, and adolescence is also
a period when a lot of psychiatric disorders, particularly schizophrenia
and psychotic disorders, begin to emerge, says Hill, so I
don't doubt that there is a relationship there. As with
all drugs, the dose makes the poison. Research suggests that

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more potent cannabis, or cannabis with more of the psychoactive
chemical DHC, tends to be associated with worse mental side effects.
According to Grinspoon, a relatively small dose can help with
some anxiety symptoms and relieve nausea, while a large dose
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
looking at tobacco regulations would be a good place to start.
Grinspoon agrees with that starting point, but believes that advertising
for all drugs and alcohol should be banned. Cannabis advertising,
along with alcohol and tobacco and pharmaceutical advertising, is really

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misleading and unhelpful, says Grinspoon. While regulation could be helpful,
experts also agree that criminalization is not the answer, especially
as it disproportionately targets and punishes people of color. Researchers
say that users should approach cannabis with caution and moderation.

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The drug can help relieve some side effects for cancer
patients while aggravating chronic pain in other people. And while
new studies like Myrons and Errans may help solidify the
link between cannabis and psychosis, researchers do not want to
spark panic. It's not a binary, says Errands. We don't
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
first widely recognized American woman scientist, gained international acclaim after
discovering a comet in eighteen forty seven. As Vassar College's
first astronomy professor, she advanced opportunities for women in science,

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and mentored a generation of students using one of the
country's finest observatories by deb Warner. Maria Mitchell eighteen eighteen
to eighteen eighty nine was already famous when she began
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.
Matthew Vasser, the founder of the college, was so pleased
by her recruitment that he personally took charge of buying
the Henry Fitz telescope that would have pride of place
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,
she helped her father, an avid public school teacher, observe
a solar eclipse and rate the chronometers used by sailors
to determine their longitudes at sea. In her late twenties,
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.
Nautical Almanac. On October first, eighteen forty seven, while observing
the skies. With her father's telescope, she spotted a comet
not seen before. As news of this discovery spread throughout

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the scientific community, Mitchell received a gold medal from the
King of Denmark, thus becoming one of the first Americans
to win any medal for science. Mitchell's moved to Poughkeepsie,
New York, to become the professor of Astronomy at the
newly opened Vassar College, the first school offering women resources

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comparable to those at the leading colleges for men, would
represent a considerable step forward in the education of women
in science. At the college observatory, Mitchell had charge of
a large refracting telescope and other instruments. During her years
at Vassar, she mentored many young women who would embrace

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science as a future vocation. This concludes readings from smithsonianmag
dot com for today. Your reader has been Rebecca Shore.
Thank you for listening, and have a great day. Nay