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A Taste For Fat May Have Made Us Human, Says Study

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Long before human ancestors began hunting large mammals for meat, a fatty diet provided them with the nutrition to develop bigger brains, posits a new paper in Current Anthropology.

The paper argues that our early ancestors acquired a taste for fat by eating marrow scavenged from the skeletal remains of large animals that had been killed and eaten by other predators. The argument challenges the widely held view among anthropologists that eating meat was the critical factor in setting the stage for the evolution of humans.

Our ancestors likely began acquiring a taste for fat 4 million years ago, which explains why we crave it today,” says Jessica Thompson, the paper’s lead author and an anthropologist at Yale University.

“The reservoirs of fat in the long bones of carcasses were a huge calorie package on a calorie-poor landscape. That could have been what gave an ancestral population the advantage it needed to set off the chain of human evolution.”

Thompson, who recently joined Yale’s faculty, completed the paper while on the faculty at Emory University.

While focusing on fat over meat may seem like a subtle distinction, the difference is significant, Thompson says. The nutrients of meat and fat are different, as are the technologies required to access them. Meat eating is traditionally paired with the manufacture of sharp, flaked-stone tools, while obtaining fat-rich marrow only required smashing bones with a rock, Thompson notes.

The authors review evidence that a craving for marrow could have fueled not just a growing brain size, but the quest to go beyond smashing bones with rocks to make more sophisticated tools and to hunt large animals.

That’s how all technology originated — taking one thing and using it to alter something else,” Thompson says.

“That’s the origin of the iPhone right there.”

Co-authors of the paper include anthropologists Susana Carvalho of Oxford University, Curtis Marean of Arizona State University, and Zeresenay Alemseged of the University of Chicago.

The human brain consumes 20% of the body’s energy at rest, or twice that of the brains of other primates, which are almost exclusively vegetarian. It’s a mystery to scientists how our human ancestors met the calorie demands to develop and sustain our larger brains.

A meat-centered paradigm for human evolution hypothesizes that an ape population began more actively hunting and eating small game, which became an evolutionary stepping stone to the human behavior of hunting large animals.

The paper argues that this theory does not make nutritional sense.

“The meat of wild animals is lean,” Thompson says.

“It actually takes more work to metabolize lean protein than you get back.”

In fact, eating lean meat without a good source of fat can lead to protein poisoning and acute malnutrition. Early Arctic explorers, who attempted to survive on rabbit meat exclusively, described the condition as “rabbit starvation.”

This protein problem, coupled with the energy required for an upright ape with small canines to capture and eat small animals, would seem to rule out eating meat as a pathway to fueling brain growth, Thompson says.

The new paper presents a new hypothesis, going back about 4 million years, to the Pliocene. As the human ancestor began walking primarily on two legs, heavily forested regions of Africa were breaking into mosaics, creating open grasslands.

Our human ancestors were likely awkward creatures,” Thompson says.

“They weren’t good in trees, like chimpanzees are, but they weren’t necessarily all that good on the ground either. So, what did the first upright walking apes in our lineage do to make them so successful? At this stage, there was already a small increase in the size of the brains. How were they feeding that?”

Thompson and her co-authors propose that our early ancestors wielded rocks as they foraged on open grassland. After a predator had finished eating a large mammal, these upright apes explored the leftovers by smashing them and discovered the marrow hidden in the limb bones.

The bones sealed up the marrow like a Tupperware container, preventing bacterial growth,” Thompson says.

And the only things that could crack open these containers, she adds, were the bone-cracking jaws of hyenas or a clever ape wielding a rock.

The hypothesis offers an explanation for how the human ancestor may have garnered the extra calories needed to foster a larger brain, long before there is evidence for controlled fire, which could have mitigated the problem of bacteria in rotting, scavenged meat. The fat hypothesis also predates by more than 1 million years most evidence for even basic toolmaking of simple stone flakes.

Scientists ought to begin looking for evidence of bone-smashing behavior in early human ancestors, Thompson said.

Paleoanthropologists are looking for mostly complete bones, and then concentrating on identifying the animal that died,” Thompson says.

“But instead of just wondering about the bone’s creature of origin, we should be asking, ‘What broke this bone?’ We need to start collecting tiny pieces of shattered bone to help piece together this kind of behavioral information.”

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Children Carry Evidence Of Toxins From Home Flooring And Furniture

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Children living in homes with all vinyl flooring or flame-retardant chemicals in the sofa have significantly higher concentrations of potentially harmful semi-volatile organic compounds (SVOCs) in their blood or urine than children from homes where these materials are not present, according to a new Duke University-led study.

The researchers presented their findings Sunday, Feb. 17 at the annual meeting of the American Association for the Advancement of Science in Washington, D.C.

They found that children living in homes where the sofa in the main living area contained flame-retardant polybrominated diphenyl ethers (PBDEs) in its foam had a six-fold higher concentration of PBDEs in their blood serum.

Exposure to PBDEs has been linked in laboratory tests to neurodevelopmental delays, obesity, endocrine and thyroid disruption, cancer and other diseases.

Children from homes that had vinyl flooring in all areas were found to have concentrations of benzyl butyl phthalate metabolite in their urine that were 15 times higher than those in children living with no vinyl flooring.

Benzyl butyl phthalate has been linked to respiratory disorders, skin irritations, multiple myeolma and reproductive disorders.

“SVOCs are widely used in electronics, furniture and building materials and can be detected in nearly all indoor environments,” said Heather Stapleton, an environmental chemist at Duke’s Nicholas School of the Environment, who led the research.

“Human exposure to them is widespread, particularly for young children who spend most of their time indoors and have greater exposure to chemicals found in household dust.”

“Nonetheless, there has been little research on the relative contribution of specific products and materials to children’s overall exposure to SVOCs,” she noted.

To address that gap, in 2014 Stapleton and colleagues from Duke, the Centers for Disease Control & Prevention, and Boston University began a three-year study of in-home exposures to SVOCs among 203 children from 190 families.

“Our primary goal was to investigate links between specific products and children’s exposures, and to determine how the exposure happened — was it through breathing, skin contact or inadvertent dust inhalation,” Stapleton said.

To that end, the team analyzed samples of indoor air, indoor dust and foam collected from furniture in each of the children’s homes, along with a handwipe sample, urine and blood from each child.

“We quantified 44 biomarkers of exposure to phthalates, organophosphate esters, brominated flame retardants, parabens, phenols, antibacterial agents and perfluoroalkyl and polyfluoroalkyl substances (PFAS),” Stapleton said.

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Your Home Is A Hidden Source Of Air Pollution

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Cooking, cleaning and other routine household activities generate significant levels of volatile and particulate chemicals inside the average home, leading to indoor air quality levels on par with a polluted major city, University of Colorado Boulder researchers have found.

What’s more, airborne chemicals that originate inside a house don’t stay there: Volatile organic compounds (VOCs) from products such as shampoo, perfume and cleaning solutions eventually escape outside and contribute to ozone and fine particle formation, making up an even greater source of global atmospheric air pollution than cars and trucks do.

The previously underexplored relationship between households and air quality drew focus today at the 2019 AAAS Annual Meeting in Washington, D.C., where researchers from CU Boulder’s Cooperative Institute for Research in Environmental Sciences (CIRES) and the university’s Department of Mechanical Engineering presented their recent findings during a panel discussion.

“Homes have never been considered an important source of outdoor air pollution and the moment is right to start exploring that,” said Marina Vance, an assistant professor of mechanical engineering at CU Boulder.

“We wanted to know: How do basic activities like cooking and cleaning change the chemistry of a house?”

In 2018, Vance co-led the collaborative HOMEChem field campaign, which used advanced sensors and cameras to monitor the indoor air quality of a 1,200-square-foot manufactured home on the University of Texas Austin campus. Over the course of a month, Vance and her colleagues conducted a variety of daily household activities, including cooking a full Thanksgiving dinner in the middle of the Texas summer.

While the HOMEChem experiment’s results are still pending, Vance said that it’s apparent that homes need to be well ventilated while cooking and cleaning, because even basic tasks like boiling water over a stovetop flame can contribute to high levels of gaseous air pollutants and suspended particulates, with negative health impacts.

To her team’s surprise, the measured indoor concentrations were high enough that that their sensitive instruments needed to be recalibrated almost immediately.

“Even the simple act of making toast raised particle levels far higher than expected,” Vance said.

“We had to go adjust many of the instruments.”

Indoor and outdoor experts are collaborating to paint a more complete picture of air quality, said Joost de Gouw, a CIRES Visiting Professor. Last year, de Gouw and his colleagues published results in the journal Science showing that regulations on automobiles had pushed transportation-derived emissions down in recent decades while the relative importance of household chemical pollutants had only gone up.

“Many traditional sources like fossil fuel-burning vehicles have become much cleaner than they used to be,” said de Gouw.

“Ozone and fine particulates are monitored by the EPA, but data for airborne toxins like formaldehyde and benzene and compounds like alcohols and ketones that originate from the home are very sparse.”

While de Gouw says that it is too early on in the research to make recommendations on policy or consumer behavior, he said that it’s encouraging that the scientific community is now thinking about the “esosphere,” derived from the Greek word ‘eso,’ which translates to ‘inner.’

“There was originally skepticism about whether or not these products actually contributed to air pollution in a meaningful way, but no longer,” de Gouw said.

“Moving forward, we need to re-focus research efforts on these sources and give them the same attention we have given to fossil fuels. The picture that we have in our heads about the atmosphere should now include a house.”

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Diet Drinks May Be Associated With Strokes Among Post-Menopausal Women

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Among post-menopausal women, drinking multiple diet drinks daily was associated with an increase in the risk of having a stroke caused by a blocked artery, especially small arteries, according to research published in Stroke, a journal of the American Heart Association.

This is one of the first studies to look at the association between drinking artificially sweetened beverages and the risk of specific types of stroke in a large, racially diverse group of post-menopausal women. While this study identifies an association between diet drinks and stroke, it does not prove cause and effect because it was an observational study based on self-reported information about diet drink consumption.

Compared with women who consumed diet drinks less than once a week or not at all, women who consumed two or more artificially sweetened beverages per day were:

  • 23 percent more likely to have a stroke;
  • 31 percent more likely to have a clot-caused (ischemic) stroke;
  • 29 percent more likely to develop heart disease (fatal or non-fatal heart attack); and
  • 16 percent more likely to die from any cause.

Researchers found risks were higher for certain women. Heavy intake of diet drinks, defined as two or more times daily, more than doubled stroke risk in:

  • women without previous heart disease or diabetes, who were 2.44 times as likely to have a common type of stroke caused by blockage of one of the very small arteries within the brain;
  • obese women without previous heart disease or diabetes, who were 2.03 times as likely to have a clot-caused stroke; and
  • African-American women without previous heart disease or diabetes, who were 3.93 times as likely to have a clot-caused stroke.

“Many well-meaning people, especially those who are overweight or obese, drink low-calorie sweetened drinks to cut calories in their diet. Our research and other observational studies have shown that artificially sweetened beverages may not be harmless and high consumption is associated with a higher risk of stroke and heart disease,” said Yasmin Mossavar-Rahmani, Ph.D., lead author of the study and associate professor of clinical epidemiology and population health at the Albert Einstein College of Medicine in the Bronx, New York.

Researchers analyzed data on 81,714 postmenopausal women (age 50-79 years at the start) participating in the Women’s Health Initiative study that tracked health outcomes for an average of 11.9 years after they enrolled between 1993 and 1998. At their three-year evaluation, the women reported how often in the previous three months they had consumed diet drinks such as low calorie, artificially sweetened colas, sodas and fruit drinks. The data collected did not include information about the specific artificial sweetener the drinks contained.

The results were obtained after adjusting for various stroke risk factors such as age, high blood pressure, and smoking. These results in postmenopausal women may not be generalizable to men or younger women. The study is also limited by having only the women’s self-report of diet drink intake.

“We don’t know specifically what types of artificially sweetened beverages they were consuming, so we don’t know which artificial sweeteners may be harmful and which may be harmless,” Mossavar-Rahmani said.

The American Heart Association recently published a science advisory that found there was inadequate scientific research to conclude that low-calorie sweetened beverages do – or do not – alter risk factors for heart disease and stroke in young children, teens or adults. The Association recognizes diet drinks may help replace high calorie, sugary beverages, but recommends water (plain, carbonated and unsweetened flavored) as the best choice for a no calorie drink.

“Unfortunately, current research simply does not provide enough evidence to distinguish between the effects of different low-calorie sweeteners on heart and brain health. This study adds to the evidence that limiting use of diet beverages is the most prudent thing to do for your health,” said Rachel K. Johnson, Ph.D., R.D., professor of nutrition emeritus, University of Vermont and the chair of the writing group for the American Heart Association’s science advisory, Low-Calorie Sweetened Beverages and Cardiometabolic Health.

“The American Heart Association suggests water as the best choice for a no-calorie beverage. However, for some adults, diet drinks with low calorie sweeteners may be helpful as they transition to adopting water as their primary drink. Since long-term clinical trial data are not available on the effects of low-calorie sweetened drinks and cardiovascular health, given their lack of nutritional value, it may be prudent to limit their prolonged use” said Johnson.

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