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Humans Have Been Perfecting Avocados for 7,500 Years

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Humans Have Been Perfecting Avocados for 7,500 Years

Avocados are true superfoods: dense, buttery scoops of vitamins, fat and fiber, all in a hand-size package.

We worked for a long time to make them this way. According to a paper published Monday in the Proceedings of the National Academy of Sciences, people in what we today call Honduras made avocados a part of their diets at least 10,000 years ago and purposefully improved them starting more than 7,500 years ago — first by managing wild trees, and then by selectively planting new ones, to encourage thicker rinds and larger fruit.

This means fruit domestication at this site began thousands of years before the arrival of more commonly studied plants like maize.

“People were domesticating and cultivating their forests” long before they were planting crops in fields, said Amber VanDerwarker, a professor of anthropology at the University of California, Santa Barbara and an author of the paper.

Avocados first arose in central Mexico about 400,000 years ago. They were originally dispersed by megafauna: Giant ground sloths, elephantine gompotheres and burly toxodons all regularly gulped them down, choking-hazard-size pits and all. By the end of the Pleistocene epoch, around 13,000 years ago, megafauna had spread the oily fruits throughout Central and northern South America, and helped them diversify into at least three different species.

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But the mass megafaunal extinction that ended the Pleistocene left the avocados stranded: Without animals big enough to eat them whole and spread their seeds, their range began to shrink. At this point, “humans stepped in,” said Doug Kennett, a professor of environmental archaeology also at the University of California, Santa Barbara and an author of the paper. These humans — who, without the megafauna, now needed new food sources — began cultivating the fruit, “saving avocados,” Dr. Kennett said.

For the new study, researchers focused on a site in western Honduras called El Gigante, an elevated cave that people began frequenting 11,000 years ago. Over generations of living and working there, humans left heaps of discarded squash seeds, maize kernels, agave leaves and much more. Archaeologists have been sifting through it all for about 20 years.

To learn about how people at El Gigante enjoyed avocados, researchers looked at dozens of their seeds found in this “long-term trash pile,” as well as thousands of rind fragments, Dr. VanDerwarker said. They used radiocarbon dating to put these scraps in chronological order, and measured the thicknesses of the rinds and the dimensions of the seeds.

Comparing seed and rind sizes over time allowed the team to trace how humans shaped the fruit. Early on, people were “just picking wild fruits from their trees as they need to,” and the trash was littered with cherry-size seeds and thin bits of rind, Dr. VanDerwarker said.

In layers from about 7,500 years ago, the seeds had become larger and the rinds more robust. This suggests that people were managing existing trees, pruning some branches and new fruits in order to encourage the remaining ones to grow bigger.

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In layers from 4,500 years ago, seeds had reached apricot size and rind thickness had pushed beyond the plant’s natural variation — “an indicator that people had started saving seeds and planting their own trees,” Dr. VanDerwarker said. The arborculturalists favored large fruits, as well as hefty skins that helped with preservation and transport.

The study gives “new evidence for 10,000 years plus, probably, of avocado use,” said Tom Dillehay, a research professor at Vanderbilt University who was not involved with this particular study. He said he had found similar signs of longstanding avocado enjoyment in northern Peru; other evidence has been found in Mexico, Colombia and Panama. Dr. Dillehay predicts that as research continues, more sites, and more types of manipulated food plants, will be discovered.

The finding also continues an ongoing shake-up of the notion that food domestication began with animals and cereal grains. That early avocado growers were putting so much effort into their plants is “different than what was imagined even 10 or 15 years ago,” Dr. Kennett said.

While our concepts of plant husbandry come and go, some things are more timeless. One reason to want to cultivate a thick avocado rind is for ease of scooping, said Dr. VanDerwarker, inspiring other tasty imaginings: “I think people have probably been eating guacamole now for a good 10,000 years.”

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Contributor: New mothers are tempted by Ozempic but don’t have the data they need

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Contributor: New mothers are tempted by Ozempic but don’t have the data they need

My friend Sara, eight weeks after giving birth, left me a tearful voicemail. I’m a clinical psychologist specializing in postpartum depression and psychosis, but mental health wasn’t Sara’s issue. Postpartum weight gain was.

Sara told me she needed help. She’d gained 40 pounds during her pregnancy, and she was still 25 pounds overweight. “I’m going back to work and I can’t look like this,” she said. “I need to take Ozempic or something. But do you know if it’s safe?”

Great question. Unfortunately researchers don’t yet have an answer. On Dec. 1, the World Health Organization released its first guidelines on the use of GLP-1 receptor agonists such as Ozempic, generically known as semaglutide. One of the notable policy suggestions in that report is to not prescribe GLP-1s to pregnant women. Disappointingly, the report says nothing about the use of the drug by postpartum women, including those who are breastfeeding.

There was a recent Danish study that led to medical guidelines against prescribing to patients who are pregnant or breastfeeding.

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None of that is what my friend wanted to hear. I could only encourage her to speak to her own medical doctor.

Sara’s not alone. I’ve seen a trend emerging in my practice in which women use GLP-1s to shed postpartum weight. The warp speed “bounce-back” ideal of body shapes for new mothers has reemerged, despite the mental health field’s advocacy to abolish the archaic pressure of martyrdom in motherhood. GLP-1s are being sold and distributed by compound pharmacies like candy. And judging by their popularity, nothing tastes sweeter than skinny feels.

New motherhood can be a stressful time for bodies and minds, but nature has also set us up for incredible growth at that moment. Contrary to the myth of spaced-out “mommy brains,” new neuroplasticity research shows that maternal brains are rewired for immense creativity and problem solving.

How could GLP-1s affect that dynamic? We just don’t know. We do know that these drugs are associated with changes far beyond weight loss, potentially including psychiatric effects such as combating addiction.

Aside from physical effects, this points to an important unanswered research question: What effects, if any, do GLP-1s have on a woman’s brain as it is rewiring to attune to and take care of a newborn? And on a breastfeeding infant? If GLP-1s work on the pleasure center of the brain and your brain is rewiring to feel immense pleasure from a baby coo, I can’t help but wonder if that will be dampened. When a new mom wants a prescription for a GLP-1 to help shed baby weight, her medical provider should emphasize those unknowns.

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These drugs may someday be a useful tool for new mothers. GLP-1s are helping many people with conditions other than obesity. A colleague of mine was born with high blood pressure and cholesterol. She exercised every day and adopted a pescatarian diet. Nothing budged until she added a GLP-1 to her regimen, bringing her blood pressure to a healthy 120/80 and getting cholesterol under control. My brother, an otherwise healthy young man recently diagnosed with a rare idiopathic lymphedema of his left leg, is considering GLP-1s to address inflammation and could be given another chance at improving his quality of life.

I hope that GLP-1s will continue to help those who need it. And I urge everyone — especially new moms — to proceed with caution. A healthy appetite for nutritious food is natural. That food fuels us for walks with our dogs, swims along a coastline, climbs through leafy woods. It models health and balance for the young ones who are watching us for clues about how to live a healthy life.

Nicole Amoyal Pensak, a clinical psychologist and researcher, is the author of “Rattled: How to Calm New Mom Anxiety With the Power of the Postpartum Brain.”

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California issues advisory on a parasitic fly whose maggots can infest living humans

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California issues advisory on a parasitic fly whose maggots can infest living humans

A parasitic fly whose maggots can infest living livestock, birds, pets and humans could threaten California soon.

The New World Screwworm has rapidly spread northward from Panama since 2023 and farther into Central America. As of early September, the parasitic fly was present in seven states in southern Mexico, where 720 humans have been infested and six of them have died. More than 111,000 animals also have been infested, health officials said.

In early August, a person traveling from El Salvador to Maryland was discovered to have been infested, federal officials said. But the parasitic fly has not been found in the wild within a 20-mile radius of the infested person, which includes Maryland, Virginia and the District of Columbia.

After the Maryland incident, the California Department of Public Health decided to issue a health advisory this month warning that the New World Screwworm could arrive in California from an infested traveler or animal, or from the natural travel of the flies.

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Graphic images of New World Screwworm infestations show open wounds in cows, deer, pigs, chickens, horses and goats, infesting a wide swath of the body from the neck, head and mouth to the belly and legs.

The Latin species name of the fly — hominivorax — loosely translates to “maneater.”

“People have to be aware of it,” said Dr. Peter Chin-Hong, a UC San Francisco infectious diseases specialist. “As the New World Screwworm flies northward, they may start to see people at the borders — through the cattle industry — get them, too.”

Other people at higher risk include those living in rural areas where there’s an outbreak, anyone with open sores or wounds, those who are immunocompromised, the very young and very old, and people who are malnourished, the U.S. Centers for Disease Control and Prevention says.

There could be grave economic consequences should the New World Screwworm get out of hand among U.S. livestock, leading to animal deaths, decreased livestock production, and decreased availability of manure and draught animals, according to the U.S. Department of Agriculture.

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“It is not only a threat to our ranching community — but it is a threat to our food supply and our national security,” the USDA said.

Already, in May, the USDA suspended imports of live cattle, horse and bison from the Mexican border because of the parasitic fly’s spread through southern Mexico.

The New World Screwworm isn’t new to the U.S.

But it was considered eradicated in the United States in 1966, and by 1996, the economic benefit of that eradication was estimated at nearly $800 million, “with an estimated $2.8 billion benefit to the wider economy,” the USDA said.

Texas suffered an outbreak in 1976. A repeat could cost the state’s livestock producers $732 million a year and the state economy $1.8 billion, the USDA said.

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Historically, the New World Screwworm was a problem in the U.S. Southwest and expanded to the Southeast in the 1930s after a shipment of infested animals, the USDA said. Scientists in the 1950s discovered a technique that uses radiation to sterilize male parasitic flies.

Female flies that mate with the sterile male flies produce sterile eggs, “so they can’t propagate anymore,” Chin-Hong said. It was this technique that allowed the U.S., Mexico and Central America to eradicate the New World Screwworm by the 1960s.

But the parasitic fly has remained endemic in South America, Cuba, Haiti and the Dominican Republic.

In late August, the USDA said it would invest in new technology to try to accelerate the pace of sterile fly production. The agency also said it would build a sterile-fly production facility at Edinburg, Texas, which is close to the Mexico border, and would be able to produce up to 300 million sterile flies per week.

“This will be the only United States-based sterile fly facility and will work in tandem with facilities in Panama and Mexico to help eradicate the pest and protect American agriculture,” the USDA said.

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The USDA is already releasing sterile flies in southern Mexico and Central America.

The risk to humans from the fly, particularly in the U.S., is relatively low. “We have decent nutrition; people have access to medical care,” Chin-Hong said.

But infestations can happen. Open wounds are a danger, and mucus membranes can also be infested, such as inside the nose, according to the CDC.

An infestation occurs when fly maggots infest the living flesh of warm-blooded animals, the CDC says. The flies “land on the eyes or the nose or the mouth,” Chin-Hong said, or, according to the CDC, in an opening such as the genitals or a wound as small as an insect bite. A single female fly can lay 200 to 300 eggs at a time.

When they hatch, the maggots — which are called screwworms — “have these little sharp teeth or hooks in their mouths, and they chomp away at the flesh and burrow,” Chin-Hong said. After feeding for about seven days, a maggot will fall to the ground, dig into the soil and then awaken as an adult fly.

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Deaths among humans are uncommon but can happen, Chin-Hong said. Infestation should be treated as soon as possible. Symptoms can include painful skin sores or wounds that may not heal, the feeling of the larvae moving, or a foul-smelling odor, the CDC says.

Patients are treated by removal of the maggots, which need to be killed by putting them into a sealed container of concentrated ethyl or isopropyl alcohol then disposed of as biohazardous waste.

The parasitic fly has been found recently in seven Mexican states: Campeche, Chiapas, Oaxaca, Quintana Roo, Tabasco, Veracruz, and Yucatán. Officials urge travelers to keep open wounds clean and covered, avoid insect bites, and wear hats, loose-fitting long-sleeved shirts and pants, socks, and insect repellents registered by the Environmental Protection Agency as effective.

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As California installs more artificial turf, health and environmental concerns multiply

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As California installs more artificial turf, health and environmental concerns multiply

Fields of plastic, or fake turf, are spreading across the Golden State from San Diego to Del Norte counties.

Some municipalities and school districts embrace them, saying they are good for the environment and promote kids’ activity and health. But some cities, including Los Angeles, are considering banning the fields — citing concerns about children’s health and the environment.

Nowhere in the country is turf use growing faster than in California — on school athletic fields, in city parks and on residential lawns. Exact numbers are not known, but it’s estimated that 1,100 acres of the material, or the equivalent of some 870 football fields, are being installed across the state each year.

In 2025, the Laguna Beach Unified School District and the San Mateo County Office of Education both received environmental accolades from the state Department of Education for, among other efforts, installing artificial turf.

September 2016 photo of Laguna Beach High School’s new football field and track.

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(Scott Smeltzer / Daily Pilot)

“The fields do not require water, pesticides or fertilizers. They also provide year-round playing time without the need for closures for regrowth or rain damage,” said Laura Chalkley, director of communications for San Mateo Union High School District.

But a growing number of health experts, environmentalists and parents say the fields are harming children’s health and heating up the environment — and they’re pushing their cities, counties and school districts to ban them.

Terry Saucier, a Tarzana resident and chair of the SoCal Stop Artificial Turf Task Force, wants Los Angeles to do that.

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“I wish they’d stop calling it grass,” Saucier said. “It’s carpet. They’re taking green space, grass and dirt away from kids and laying down synthetic carpets.”

The L.A. City Council’s Energy and Environment Committee is studying a possible ban. It’s up for discussion in October. Other cities, including San Marino and Milbrae, already have moved to prohibit the outdoor material.

A flag football player kicks up pellets on the artificial turf at Oxnard High School.

A flag football player kicks up pellets on the artificial turf at Oxnard High School.

(Michael Owen Baker / For The Times)

Turf is designed to look and feel like grass. It consists of green blades, made of nylon or other plastic polymers, rooted in a plastic mat. In between the “grass” is a layer of fine, loose material made of recycled tires, rubber, sneaker soles, sand, olive pits or coconut.

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Researchers, including Sarah Evans, assistant professor of environmental medicine at the Icahn School of Medicine at Mount Sinai in New York, said a growing body of research shows these carpets have the potential to cause harm in three main ways: burns, chemical exposure and injuries.

“These surfaces get really hot,” she said, citing research that artificial turf can reach temperatures in excess of 160 degrees, and can cause first- and second-degree burns on skin. She said her own kids complain that their “feet feel like they’re burning … even with shoes on. So it’s really, really unsafe temperatures under a lot of conditions.”

Artificial turf at Oxnard High School.

Artificial turf at Oxnard High School.

(Michael Owen Baker / For The Times)

In addition, there are chemical exposures, including from forever chemicals, or PFAS, that have been detected in the blades; endocrine disruptors such as phthalates; and volatile chemicals such as benzo(a)pyrene and naphthalene. What the effects are when children and athletes play, roll and eat on the fields is not known. Studies of these and other chemicals found in crumbled tires have shown they can cause cancer in laboratory animals if inhaled, absorbed through the skin, or ingested, Evans said.

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There are also injuries associated with turf fields that don’t typically occur on natural fields, including to ankles and knees, she said — the result of how cleats grip the infill.

Proponents, however, say some of those harms have not been established with certainty. And heat can be mitigated by watering the fields to keep them cool, or using natural infill products such as ground up walnut shells or olive pits that don’t heat up as much.

They also point to a draft report from California’s Office of Environmental Health Hazard Assessment that examined one part of artificial turf, the loose infill, made of recycled tires. It found “no significant health risks to players, coaches, referees and spectators from on-field or off-field exposure to field-related chemicals in crumb rubber infill from synthetic turf fields based on available data.”

Melanie Taylor, president and chief executive officer of the Synthetic Turf Council said the California report, and others, “reaffirmed the safety of turf systems, and that “in areas where natural grass is not practical or sustainable, synthetic turf ensures safe, consistent, and accessible places to play, gather, and be active.”

The report came at the request of the state’s waste agency, CalRecycle, in 2015. CalRecycle asked the health hazard assessment agency to examine tire infill as a solution to the decades-old problem of millions of tires piling up in landfills. Waste officials were looking for ways to uses the old tires and needed to know if they posed health risks to people who might recreate on the ground material.

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It’s common for scientists to ask for outside review, and when the state convened an expert panel to evaluate its turf report, reviewers weren’t so sanguine about the agency’s conclusions.

Amy Kyle, one of the independent scientific advisers on the panel and a UC Berkeley environmental health scientist, said she and other advisers had concerns about several aspects of the study design and methodology — which they lodged in public discussion — but which were largely ignored.

For instance, she said, when a laboratory at UC Berkeley analyzed the chemical signatures found in the infill, it found more than 400 chemicals but could identify only roughly 180 of them.

“That fell out of the final report … or the final session of the study. Those results, they kind of left that all out,” she said.

In a transcript from one of the panel meetings in April, Kyle expressed concern about the report’s conclusions.

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“It’s not an emergency. I wouldn’t evacuate playgrounds,” she told the agency and her fellow advisers. “But if I were advising my friend on the school board about this, I would say I would try not to use this stuff. “

Other panelists agreed.

“I’m glad my kid mostly played on grass,” said John Balmes, professor of medicine at UC San Francisco.

Jocelyn Claude, a staff toxicologist for the state, reiterated that the report looked only at the tire infill, and should not be seen as an official California endorsement of synthetic turf. She noted that her office did not look at the blades, where PFAS chemicals have been detected.

“Since we only looked at the crumb rubber, there are limitations in what our results state and how they can be applied,” she said.

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Finally, Evans and Saucier have concerns for the wider environment: microplastics that slough off the turf and the heat generated by the fields of fossil-fuel derived plastic, which can make a local area hotter.

According to the Synthetic Turf Council, the average athletic field uses 400,000 pounds of infill and 40,000 pounds of artificial turf carpet. In addition, research shows that an average synthetic turf field loses between 2,000 and 3,000 pounds of microplastic fibers every year.

“So here, from cradle to grave, we are creating product that contributes to climate change and just makes the planet hotter,” Saucier said. Turf makers say they have made improvements to their products to lower the temperature but acknowledge they can get hot.

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