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Horses lived in the Americas for millions of years – new research helps paleontologists understand the fossils we’ve found and those that are missing from the record

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Horses lived in the Americas for millions of years – new research helps paleontologists understand the fossils we've found and those that are missing from the record

People have collected fossil horses throughout North America for centuries.
Florida Museum/Mary Warrick

Stephanie Killingsworth, University of Florida and Bruce J. MacFadden, University of Florida

Many people assume that horses first came to the Americas when Spanish explorers brought them here about 500 years ago. In fact, recent research has confirmed a European origin for horses associated with humans in the American Southwest and Great Plains.

But those weren't the first horses in North America. The Equidae, which includes domesticated varieties of horses and donkeys along with zebras and their kin, is actually native to the Americas. The fossil record reveals horse origins here more than 50 million years ago, as well as their extinction throughout the Americas during the last Ice Age about 10,000 years ago.

family tree showing horse evolution diversifying over time
Phylogeny, geographic distribution, diet and body sizes of the family Equidae over the past 55 million years.
From ‘Fossil horses–evidence for evolution.' Science. MacFadden, 2005. Reprinted with permission from AAAS.

We are paleontologists who focus our research on various types of fossils, ancient horses. Our most recent work used computer statistics to analyze gaps in the fossil record to infer more about which horse species really did and didn't in one ancient habitat in Florida.

Horses evolved as ecosystems changed

People have collected fossil horses throughout North America for centuries. Because horse fossils are abundant and widespread across the continent, scientists often point to the long span of the horse family as evidence of long-term evolutionary change.

Paleontologists like us, who study extinct mammals, almost never find complete skeletons. Instead, we focus on durable fossil teeth, which us understand ancient diets, and fossil limbs, which help clarify how these animals moved.

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Horses are eating machines. In the wild , they primarily feed on grasses that don't much nutrition, and thus they need to consume large quantities to survive. The large teeth of modern horses and their ancestors are adapted primarily for grazing on gritty grasses. They replaced smaller teeth of more primitive horses adapted to browsing on soft leafy vegetation.

We know what horses ate millions of years ago by studying distinctive microscopic scratches, pits and other wear patterns on their teeth that were created as the ancient horses chewed plant foods. And analyses of carbon preserved in fossil teeth show that coexisting horse species ate different plants; some browsed on leaves from bushes and trees, some grazed on grasses, and yet others were mixed feeders.

The change in tooth shape tracks the change in dominant vegetation types in North America, from tropical forests that then gave way to the great expansion of open prairie grasslands. As the climate and flora changed over millions of years, horses shifted from being largely forest-dwelling browsers to largely open-country grazers. Their teeth and feeding patterns adapted to the .

Another adaptation is visible on horses' feet. Modern horses have one hoofed toe on each . Many extinct fossil horses – the ancient ancestors of today's horses – had three toes per foot. The single toe on each elongated foot is good for rapid and sustained running to evade predators and for long-distance seasonal migrations. The more ancient three-toed feet provided stability on unstable or wet ground. The adaptation from three toes to one was likely in response to changing habitats.

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But even as the environment changed, one distinct species didn't completely replace another overnight. The fossil record in North America documents periods millions of years ago when multiple horse species coexisted on the ancient landscapes. Species were of different sizes and had teeth equipped for munching different plants, so they weren't competing directly for the same foods. Different habitats within these ancient ecosystems likely had some species more adapted to forests and others more adapted to grasslands.

Understanding Florida's fossil record

Paleontologists have been collecting horse fossils in Florida for over 125 years. The Florida Museum of Natural History at the of Florida, where we work, has more than 70,000 fossil horse specimens from more than a thousand locations across the state.

One of our more prolific fossil sites, Montbrook, provides a glimpse of a 5.8 million-year-old ancient stream bed. It preserved more than 30 extinct mammals, including rhinos, elephants and carnivores, as well as hundreds of bones and teeth of fossil horses.

Although six horse species are known elsewhere in Florida, we have only found four so far at Montbrook. This smaller number of horse species perplexed us, so we decided to investigate. Did the two “missing” horse species truly not live at Montbrook, or have scientists simply not discovered their fossil remains yet?

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Representative fossil horse teeth of Florida
Each of the six fossil horse species (A-F) found in Florida have distinct teeth. Scale bar = 1 centimeter.
Killingsworth & MacFadden, Paleobiology, 2024, CC BY-NC-SA

We designed a theoretical model that compares Montbrook, with only four horse species, to other fossil sites in Florida that contain all six. Using a statistical technique that scientists call “bootstrapping,” our computer essentially simulated continued fossil collecting over time. We generated 1,000 theoretical fossil collection based on the fossil species counts from the sites where all six are present, to predict the probability of collecting the species that are currently missing at Montbrook.

Results from our simulation show that the two missing horse species at Montbrook were absent for different reasons. One of the horses is likely to be truly absent; the other may still be discovered with further excavation.

About a dozen people focused on digging in soil a few feet below the surface of surrounding landscape.
Excavations are ongoing at the Montbrook fossil site in Florida.
Florida Museum/Jeff Gage

Probing ‘gaps' in the fossil record

Knowing a species is absent is just as important as knowing when one is present at a fossil site. Absences may be indicators of underlying ecological and biological drivers changing population dynamics. Coupled with other types of analyses, researchers can apply this kind of predictive modeling across many fossil species and ancient landscapes.

Ever since Charles Darwin proposed his theory of evolution, scientists have known that the fossil record is incomplete, resulting in gaps in our knowledge of the ancient past and evolutionary change. Paleontologists are challenged to explain these gaps, including which species were or were not present at particular fossil sites.

Gaps can result from certain materials, such as teeth and shells, which are often more durable than porous bone, fossilizing better than others. Likewise, different chemical conditions during fossilization, and even the amount of time spent collecting fossils at a particular site, can contribute to the lack of knowledge.

Fortunately, fossil horse teeth preserve quite well and are commonly found. As new discoveries are made, such as those from our ongoing excavations in Florida, they'll help clarify and narrow gaps in the fossil record.The Conversation

Stephanie Killingsworth, Ph.D. Student in Geological Sciences, University of Florida and Bruce J. MacFadden, Distinguished Professor and Director of Thompson Earth Systems Institute (TESI), University of Florida

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This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Brain study identifies a cost of caregiving for new fathers

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theconversation.com – Darby Saxbe, Professor of Psychology, USC Dornsife College of Letters, Arts and Sciences – 2024-05-09 07:33:13

Dads have stepped up to do more hands-on parenting over the past few decades.

Abraham Gonzalez Fernandez/Moment via Getty Images

Darby Saxbe, USC Dornsife College of Letters, Arts and Sciences

Parenting makes the heart grow fonder, and the brain grow … smaller? Several studies have revealed that the brain loses volume across the transition to parenthood. But researchers like me are still figuring out what these changes mean for .

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In a new study that looked at brain change in first-time fathers, my colleagues and I found that brain volume loss was linked with more engagement in parenting but also more sleep problems and mental symptoms. These results might point to a cost of caregiving, traditionally shouldered by women but increasingly borne by also.

Brain changes for mom come with new baby

Caring for an infant demands new motivations and skills, so it is no surprise that it might also sculpt the brain. Research in rodents first identified remodeling of both the structure and function of the brain during pregnancy and parenthood. A new body of research is unearthing similar effects in human parents, too.

In a pair of studies, researchers recruited first-time mothers for a brain scan that occurred before they became pregnant and then scanned them again a few months after birth. Gray matter – the layer of brain tissue that contains neuronal cell bodies – shrank in the mothers but not in a comparison group of women who did not become mothers.

Although a shrinking brain sounds bad, researchers theorized that this more streamlined brain could be adaptive, helping social information more efficiently and therefore facilitating sensitive caregiving. In keeping with this hypothesis, studies have linked maternal brain changes with women's degree of attachment to infants and with their responses to images of their infants. Women who lost more gray matter volume also appeared more bonded with their babies.

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New dads' brains change, too

Most studies of the parental brain have focused on women, but emerging evidence suggests that similar brain changes might occur in new fathers, too. My collaborators and I had previously identified brain volume loss in men transitioning to fatherhood, in similar parts of the brain that changed in mothers.

Before you picture the shrunken-head guy from the “Beetlejuice,” keep in mind that these changes were subtle. Fathers showed smaller, less statistically significant brain changes than mothers.

Dads vary in how invested they are in caring for the baby, so as a next step, we wanted to know how men's brain changes across the transition to fatherhood map onto their experiences of new parenthood.

To test this question, we looked more closely at 38 men we scanned in California before and after their baby's birth. During pregnancy and again at three, six and 12 months postpartum, we asked the fathers how they were feeling about their infants and how well they were sleeping. We also asked about their symptoms of depression, anxiety or other mental health problems.

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As before, we saw significant prenatal-to-postpartum brain differences across the entire cortex, the outermost layer of the brain that carries out many higher-order functions, such as language, memory, problem-solving and decision-making. On average, men in our sample lost about 1% of their gray matter volume across the transition to parenthood.

Consistent with the research on mothers, men's brain volume reductions did indeed seem to track with their parenting. If men told us during pregnancy that they wanted to take more time off from work after the birth, and felt more bonded to their unborn child, they subsequently lost more gray matter volume, especially in the frontal and parietal lobes – parts of the brain involved in executive functioning and sensorimotor processing, respectively.

3D rendering illustration of brain inside transparent head

Engaged fathers lost more brain volume in the frontal lobe, colored blue, and parietal lobe, colored yellow.

libre de droit/iStock via Getty Images Plus

Greater volume loss also emerged among fathers who told us that they spent more time with their infants at three months postpartum, took more pleasure in interacting with their infants and experienced less parenting stress. Taken together, our results dovetailed with the prior studies of mothers and suggested that more motivated, hands-on fathers lost more gray matter volume across their transition to parenthood.

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The plot thickened when we looked at mental health and sleep quality. Men who lost more brain volume also reported greater depression, anxiety, general psychological distress and worse sleep at both six and 12 months after birth. These results held up when we controlled for the same measures during pregnancy.

This finding provides a clue to a possible direction of causality: Rather than prenatal sleep problems or psychological distress predicting greater brain change, we found instead that fathers' gray matter volume loss preceded their postpartum sleep problems and mental health, above the effect of their well-being before birth.

Parenting comes with highs and lows

Importantly, this research is preliminary: We had a small sample of fathers who were willing to participate in our intensive research study. These results need to be replicated in larger and more representative groups of fathers.

Still, as one of the first longitudinal studies of male brain changes across the transition to first-time parenthood, our findings illustrate that perinatal brain changes may reflect both adaptation and vulnerability. The very same changes linked with fathers' greater investment in caregiving also seemed to heighten their risk of sleep trouble and mental health problems.

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man seated on floor with his hand to his head, supporting a crying baby

with a baby can be tough.

Prostock-Studio/iStock via Getty Images Plus

As any new parent will tell you, caring for an infant is a . Becoming a parent forces a realignment of life priorities and can bring magic and meaning to everyday life. But parenting can also be dull, repetitive, lonely and draining.

Perhaps our findings in fathers point to a cost of caregiving, a burden that has long been familiar to mothers but may be increasingly shared by men as fathers step up their participation in hands-on parenting.

The take-home message here is not that men should stop caring for . A slew of research suggests that children with involved fathers do better across the board: academically, economically and emotionally. And fathers themselves that parenthood makes their lives richer and more meaningful.

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Instead, results like these public health priorities that invest in fathers – and parents in general – through policies that reduce stress for new parents in the first months after birth, such as paid leave and workplace efforts to normalize leave-taking among men.The Conversation

Darby Saxbe, Professor of Psychology, USC Dornsife College of Letters, Arts and Sciences

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Section 702 foreign surveillance law lives on, but privacy fight continues

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theconversation.com – Peter Swire, Professor of and Ethics, Georgia Institute of Technology – 2024-05-09 07:32:58

The E. Barrett Prettyman Federal Courthouse in Washington, D.C., houses the U.S. Foreign Intelligence Surveillance Court.

AP Photo/ Evan Vucci

Peter Swire, Georgia Institute of Technology

What would you do if you had to vote in on a crucial national security program, when you also knew that the FBI had systematically ignored privacy safeguards in the program for years? That was the choice that Congress faced in April, when it ultimately decided to reauthorize Section 702 of the Foreign Intelligence Surveillance Act, known as FISA.

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Section 702 originally became law in 2008, when a great deal of previously “foreign” surveillance had shifted to the United States. In the old days, the National Security Agency carried out its communications surveillance overseas, such as keeping an eye on China or the Soviet Union. By 2008, however, the most important national security surveillance was often obtained within the U.S., such as when emails came through the United States as part of internet traffic.

Section 702 addressed this mix of foreign and domestic data gathering. Under court-approved procedures, it allows the government to gather communications, but only where the target of the surveillance is a foreign person who is outside of the U.S. Although no court approval is needed when the NSA intercepts communications overseas, Section 702 requires court-approved safeguards when the information gathering occurs in the U.S.

This lecture explains the origins and purpose of Section 702.

Privacy violations

NSA surveillance triggered headlines in 2013 when the revelations by former agency contractor Edward Snowden showed that the amount and type of government surveillance had grown far beyond what even experts realized after the terrorist attacks of Sept. 11, 2001. I was honored to be named by President Barack Obama to a special Review Group on Intelligence and Communications Technologies in 2013 to propose surveillance reforms. Our report was one of the sources for the USA Freedom Act of 2015, the biggest set of privacy reforms for surveillance since FISA was created in 1978.

Even after these reforms, however, two types of problems cast doubt on how the FBI in particular was using its FISA authorities. First, the FBI was not the procedures required by the courts for accessing information about Americans in the Section 702 databases. As a result, the FBI conducted over 3 million searches of Americans' email and other in 2021. After a public furor and changed policies, that number dropped to 119,383 in 2022.

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Second, during the 2016 campaign, the FBI began an investigation into whether people associated with the Trump campaign were coordinating activities with the government of Russia, as part of what became known as the Crossfire Hurricane investigation. Although the Department of Justice Inspector General Michael Horowitz found “no evidence that the FBI consulted” with any political in opening its investigation, he found significant violations in FISA applications. These included submitting legal documents to judges with allegations that the FBI knew were incorrect. Horowitz also found that the incident highlighted the weakness of existing rules against a politically motivated investigation.

Renewal debate

The FISA 702 authority was set to expire at the end of 2023, but Congress extended the authority until April 19, 2024. Perhaps the biggest controversy was whether access to Americans' data in the 702 databases should be available only with a warrant issued by a judge, upon showing probable cause. Privacy advocates argued that such a warrant requirement would protect Americans' constitutional rights, while the government said the requirement would be unworkable in practice.

Assistant Matthew G. Olsen explains the Justice Department's position on renewing Section 702, its opposition to a requirement for warrants to query the surveillance data about Americans' information.

The Privacy and Civil Liberties Oversight Board, an independent executive branch agency that makes nonbinding recommendations about privacy and civil liberties aspects of national security, split 3-2 in favor of requiring such a warrant.

In the House of Representatives, the motion to require a warrant resulted in a tie vote, falling short of the simple majority it needed to pass. The House eventually did reauthorize the FISA 702 program, by a vote of 273-14, but only for two years rather than the longer period sought by the administration. Soon after, as the deadline approached, the Senate approved the same law, 60-34.

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Although the warrant requirement did not pass, the law included reforms that supporters said would address the flaws in the FBI's previous actions. House Speaker Mike Johnson published a list of 56 key reforms to make FISA more protective of privacy. Some of the reforms created new safeguards to limit the FBI's ability to query the 702 databases about Americans. Others created new rules to trigger congressional and senior administration scrutiny for sensitive investigations such as those affecting political officials.

Renewal fight, Round 2

Privacy advocates, however, have been far from satisfied with the new amendments to FISA. For instance, the Electronic Privacy Information Center, the Brennan Center for Justice and FreedomWorks issued a paper stating: “Making 56 ineffective tweaks to a fundamentally broken law is not reforming it.”

These sharply conflicting viewpoints put members of Congress into a difficult spot. Many felt that the FBI deserved stricter measures to hold it accountable for its serious legal violations. I share that concern. On the other hand, I have had the during the presidential review group to learn how Section 702 is used to protect the national security of our country. In a statistic I find credible, 60% of the president's daily intelligence briefings in 2023 contained Section 702 information reported by the NSA.

The result, for now, is that Section 702 is due to expire in April 2026. Congress will once again confront a genuinely difficult : how to protect U.S. national security while also upholding Americans' privacy and the rule of law.The Conversation

Peter Swire, Professor of Law and Ethics, Georgia Institute of Technology

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watch out for foxtail seed pods that can harm your dog or cat this summer

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theconversation.com – Erik Olstad, Sciences Assistant Professor of Clinical Veterinary Medicine, of California, Davis – 2024-05-09 07:32:46

A foxtail seed pod.

Dario Argenti/Moment via Getty Images

Erik Olstad, University of California, Davis

Across much of the United States, spring is in full force. With warmer weather, people are taking their furry family members out on longer walks and spending more time outside. Alongside blooming flowers and trees, your pet might into a small, unassuming grass seed pod known as a foxtail. Despite the cute name, foxtails can pose a major threat to your pet's health.

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I am a veterinarian in California's Central Valley, and foxtails are a issue where I work, especially during the spring and summer months.

What exactly are foxtails?

A seed pod that has lots of long seeds with sticky tendrils coming off each one.

Hordeum murinum, or wall barley, is a common source of foxtails.

Curtis Clark/Wikimedia Commons, CC BY-SA

A foxtail isn't a specific plant. It is a type of grass seed pod that resembles a fox's tail. Multiple species of grass can create this type of seed pod, and foxtails are found across much of the United States. Regions of the western U.S., especially California, have the most foxtails.

The outside of the foxtail is covered in small sticky hairs designed to stick to things. You can feel them yourself if you pull a foxtail off a plant. Rub your fingers against the seed one way, and then the other, and you'll feel that one direction is smooth and the other direction is sticky.

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Foxtails aren't a big deal for people, as we don't have a lot of hair and tend to things that are itchy or painful, but it's a different story for pets.

A segment of the foxtail pod sticks to an animal's fur, where it's carried around until it eventually drops off and grows into grass. This sticky feature is great for the grass, as it helps spread the seeds around, but it also results in foxtail segments getting stuck to pets.

Once on the cat or dog, a segment of a foxtail can burrow into the skin, get stuck in the eyes, creep into ears, be inhaled into the nose, or even make its way into the lungs.

The health dangers of foxtails

The most common place where foxtails will burrow into a pet is the skin, especially in between dogs' toes. A foxtail embedded into the skin can cause irritation, redness, pain and infection. As the foxtail gets deeper into the skin, it brings harmful bacteria with it and creates a path of infection known as a draining tract.

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If a foxtail makes it into a dog's or a cat's ear, the pet will likely start shaking its head back and forth – it might look like it has an ear infection. The embedded foxtail can cause discomfort and sometimes infection.

A foxtail can stick to a pet's eye tissues, especially in cats, and migrate around the outer portions of the eye or behind the third eyelid, which is the protective tissue near the inner corner of their eye. This will cause discharge from the eye and discomfort and may scratch the eye's surface.

One of the most serious locations for a foxtail is in the lungs. Dogs may inhale foxtails while running through fields and breathing hard. The foxtail can sometimes get stuck in the nose, which will cause the pet to sneeze and look uncomfortable. Occasionally, a piece of a foxtail makes its way into the lungs, which can result in severe infection, trauma and even . Surgery and hospitalization are almost always required in these cases.

Foxtail symptoms

Pet owners can learn what symptoms to look out for in order to make sure their pet gets prompt care if they end up with a foxtail embedded somewhere.

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If you see your dog or cat chewing on their paws, this might indicate that a foxtail has ended up in between the toes. Their paws may swell or grow red. If you see even a small pimplelike swelling in between your pet's toes, they may have a foxtail stuck in their paw.

Foxtails can get into a pet's nose, ears, eyes, lungs and more.

If your pet is frequently shaking its head, this can indicate that a foxtail made its way into the ear canal. Drainage or discharge from the eye can indicate that foxtail may have made its way around the eye. Sneezing or pawing at the nose can mean the foxtail may have made its way into the nose. Foxtails in the ear canal, eyes or nose will need to be removed by a veterinarian.

Coughing or hacking might mean a foxtail has made it to the tissues around the throat or the tonsils, or even deeper into the lungs. Each one of these symptoms requires care from a veterinarian, as they can grow serious if left untreated.

Preventing foxtail risks

Foxtails are everywhere in the , but there are some preventive steps pet owners can take to minimize the risks to their pets.

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If you have foxtails in your yard, you can remove them. Sometimes you can get rid of foxtails permanently, but this isn't always easy, as grasses are particularly good at reproducing and growing quickly.

Some locations have very few foxtails, while others have lots. Bring your pet to with fewer foxtails, if possible.

Some companies make mesh nets that can a dog's head to prevent exposure to the ears, nose, eyes and mouth. Pet boots can prevent foxtails from getting stuck in their paws.

A dog wearing shoes.

Dog booties can keep your pet's feet safe when you're in a foxtail-dense area.

AP Photo/Rodrigo Abd

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Grooming your pet regularly may help catch foxtails before they burrow into the skin. Removing mats and unkempt fur can also reduce the risk. If you get your pet examined at the vet at least once a year, the veterinarian may be able to find foxtails during these checkups before they escalate into a larger problem.

Foxtails are part of living in the United States. But a few simple steps can help keep pets safe while they enjoy the outdoors.The Conversation

Erik Olstad, Health Sciences Assistant Professor of Clinical Veterinary Medicine, University of California, Davis

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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