Testes size correlates with men's involvement in toddler care

“Mothers definitely have more of an impact on child development, but fathers are also important and their role is understudied,” says anthropologist James Rilling.

By Carol Clark

Men with smaller testes than others are more likely to be involved in hands-on care of their toddlers, finds a new study by anthropologists at Emory University. The Proceedings of the National Academy of Sciences (PNAS) published the results of the study on Sept. 9.

Smaller testicular volumes also correlate with more nurturing-related brain activity in fathers as they are looking at photos of their own children, the study shows.

“Our data suggest that the biology of human males reflects a trade-off between investments in mating and parenting effort,” says Emory anthropologist James Rilling, whose lab conducted the research.

The goal of the research is to determine why some fathers invest more energy in parenting than others. “It’s an important question,” Rilling says, “because previous studies have shown that children with more involved fathers have better social, psychological and educational outcomes.”

Life History Theory posits that evolution optimizes the allocation of resources toward either mating or parenting to maximize fitness. “Our study is the first to investigate whether human anatomy and brain function explain this variance in parenting effort,” says Jennifer Mascaro, who led the study as a post-doctoral fellow in the Rilling lab.

“Although there are more households with no fathers, when the fathers are around, they tend to be much more involved than in previous decades,” Mascaro notes.

While many economic, social and cultural factors likely influence a father’s level of caregiving, the researchers wanted to investigate possible biological links.

They knew that lower levels of testosterone in men have been correlated with greater paternal involvement, and that higher levels of the hormone predict divorce as well as polygamy.

The testes, in addition to producing testosterone in males, also produce sperm. “Testes volume is more highly correlated with sperm count and quality than with testosterone levels,” Mascaro says.

The study included 70 biological fathers who had a child between the ages of 1 and 2, and who were living with the child and its biological mother.

The mothers and fathers were interviewed separately about the father’s involvement in hands-on childcare, including tasks such as changing diapers, feeding and bathing a child, staying home to care for a sick child or taking the child to doctor visits.

The men’s testosterone levels were measured, and they underwent functional magnetic resonance imaging (fMRI) to measure brain activity as they viewed photos of their own child with happy, sad and neutral expressions, and similar photos of an unknown child and an unknown adult. Then, structural MRI was used to measure testicular volume.

The findings showed that both testosterone levels and testes size were inversely correlated with the amount of direct paternal caregiving reported by the parents in the study.

"Previous studies have shown that children with more involved fathers have better social, psychological and educational outcomes," Rilling says.

And the father’s testes volume also correlated with activity in the ventral tegmental area (VTA), a part of the brain system associated with reward and parental motivation. “The men with smaller testes were activating this brain region to a greater extent when looking at photos of their own child,” Mascaro says.

While testosterone levels may be more related to pre-copulatory, intrasexual competition, testicular volume may reflect post-copulatory mating investment, the researchers theorize.

Although statistically significant, the correlation between testes size and caregiving was not perfect.

“The fact that we found this variance suggests personal choice,” Rilling says. “Even though some men may be built differently, perhaps they are willing themselves to be more hands-on fathers. It might be more challenging for some men to do these kinds of caregiving activities, but that by no means excuses them.”

A key question raised by the study findings is the direction of casualty. “We’re assuming that testes size drives how involved the fathers are,” Rilling says, “but it could also be that when men become more involved as caregivers, their testes shrink. Environmental influences can change biology. We know, for instance, that testosterone levels go down when men become involved fathers.”

Another important question is whether childhood environment can affect testes size. “Some research has shown that boys who experience childhood stress shift their life strategies,” Rilling says. “Or perhaps fatherless boys react to the absence of their father by adopting a strategy emphasizing mating effort at the expense of parenting effort.”

The study focused only on direct paternal care, and not indirect forms of care, such as protecting children and earning a living to provide for them.

In the decades since the 1960s, the number of women raising children on their own in the United States has risen dramatically. “Although there are more households with no fathers, when the fathers are around, they tend to be much more involved than in previous decades,” Mascaro says.

Much of the existing scientific literature on nurturing is focused on mothers, Rilling notes. “Mothers definitely have more of an impact on child development, but fathers are also important and their role is understudied,” he says.

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Photos by iStockphoto.com

New human health major aims at culture change

“Health is something that’s not just physical,” says Brooke Healey, a junior at Emory. “It’s so much more than that.”

Healey is majoring in human health, an interdisciplinary degree launched this fall at the university that aims to give students practical skills to develop health-related careers, along with a holistic understanding of physical, mental and spiritual well-being.

“We are offering the only bachelors of human health in the country, at a time when health is being redefined,” says Michelle Lampl, director of Emory’s Center for the Study of Human Health. “For too long, our concept of ‘health’ has been limited culturally by our construct of what it is not: The disease state. We are on the cutting edge of using science not just to cure disease, but to identify, predict and support health.”

Emory is uniquely suited to pioneer the human health major, Lampl says, drawing on expert faculty and resources from throughout the humanities and sciences. The first cohort of majors includes students interested in law, political science, economics and business, as well as public health and medicine.

“Human health is a major global issue, and at the same time is a leading sector for job growth,” Lampl says.

The human health graduates, she notes, will help expand and change not just what we mean by the word “health,” but what it means to have a health-related career.



The new major builds on the Center for the Study of Human Health’s programs such as its Health 100 course, launched in 2011, that all Emory freshman are required to take. The course, rooted in predictive health research at Emory, includes classes on topics like nutrition and exercise, as well as small-group discussions to help students manage the stress of college life. Trained upperclassmen serve as mentors, in the form of peer health partners and healthy eating partners.

“The students aren’t just gaining a new perspective on their own health,” says Lisa Dupree, the center’s associate director. “They’re learning how to help their friends, families and others change their behaviors.”

College has long been associated with burning the candle at both ends, Lampl notes, a compressed time when young people are expected to achieve a great deal, while also learning to navigate daily life on their own.

“It’s such a critical period,” she says. “We want to help students step off the moving pathway, take stock of their daily decisions, and get on the right road to true well-being.”

“My peer health partner was great,” says Healey, who recently underwent training to become one herself. “A lot of the things taught to me were valuable in terms of health, stress management and adapting to the college lifestyle.” (Watch the videos, above, to hear more feedback from the students about Emory’s human health classes.)

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Science a major draw at Decatur Book Festival

Many people would say that we are on the brink of using brain imaging to diagnose mental illness.  “I’m skeptical of that,” counters Emory psychologist Scott Lilienfeld, co-author of “Brainwashed: The Seductive Appeal of Mindless Neuroscience.”

Lilienfeld will be talking about the book as part of the Science Track of the AJC Decatur Book Festival on Saturday, August 31 at 3 pm.

“Neuro-imaging is an invaluable tool,” Lilienfeld says, “but like any tool, it can be overhyped. And I think overhyping can diminish a field’s credibility.”

He recalls when he was in graduate school during the 1980s, and the field of psychology was abuzz with the promise of the nuclear medical imaging technique known as positron emission tomography, or PET.

“A lot of people – smart people, actually – were saying that PET was going to replace the DSM (the Diagnostic and Statistical Manual of Mental Illness),” Lilienfeld says. “That, of course, never came to pass.”

The Science Track, sponsored by the Atlanta Science Tavern, has grown into one of the biggest draws for the festival, August 30 to September 1.  Some of 10 Science Track titles this year include “The Genius of Dogs: How Dogs are Smarter than we Think,” co-authored by Brian Hare (an Emory alum); “My Beloved Brontosaurus: On the Road with Old Bones, New Science, and Our Favorite Dinosaurs,” by Brian Switek; and “The Bonobo and the Atheist: In Search of Humanism Among the Primates,” by Emory primatologist Frans de Waal.

Some intriguing science titles are also part of the book festival’s Atlanta Writers Showcase, including “Life Traces of the Georgia Coast,” by Emory paleontologist Anthony Martin, who will be speaking on Sunday, Sept. 1, at 3:00 pm.

Virtual Rome built from 17th-century map and computer gaming tool

In 1676, Giovanni Battista Falda published a detailed, bird's-eye map of Rome. Now, this celebrated map, along with Falda's architectural etchings and other historical materials have been transformed into a virtual, walkable experience of 17th-century Rome, using the computer gaming platform NVis360.

"I like to think of the way Falda drew Rome as almost anatomical," says Emory art historian Sarah McPhee, who headed up the project. "He wanted to show you the buildings in such crisp detail that they were essentially being taken apart on the anatomy table."

The NVis360 software, McPhee adds, "allows us eventually to take the layers apart and show the entire construction of a building. And that has huge potential for teaching and for understanding."

Watch the video, above, to learn more. You can use the gaming technology yourself to travel back to 17th-century Rome as part of the Michael C. Carlos Museum's special exhibition, "Antichita, Teatro, Magnifcenza: Renaissance and Baroque Images of Rome," from August 24 through November 17.

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Joel Bowman's view from the top of theoretical chemistry

"Imagine how sensational it would be if we could predict where and when a cloud will form," says Joel Bowman. Photo by Bryan Meltz, Emory Photo/Video.

By Carol Clark

As Joel Bowman flew across the country recently, on his way to collect the Herschbach Prize for theoretical chemistry, his attention turned to the clouds outside the jet’s window. What’s happening at the molecular level, he wondered, in a cloud at 30,000 feet?

“As we all know, clouds are essentially water in the gaseous state,” says Bowman, Samuel Candler Dobbs Professor of Theoretical Chemistry at Emory. “And, of course, it’s really cold at that altitude. So why do you find clouds at sub-zero temperatures? It’s an obvious but interesting question. The answer certainly has something to do with energy the cloud has absorbed from the sun and with potential energy surfaces: The delicate, attractive forces holding little water molecules together.”

Bowman’s work on developing potential energy surfaces is just one example of why he received the Herschbach Prize for Theory, presented in July at the Dynamics of Molecular Collisions 2013 Conference. The prize is named for Nobel Prize winning chemist Dudley Herschbach, who describes the award’s criteria as “bold and architectural work” that “addresses fundamental, challenging, frontier questions … and typically excites evangelical fervor that recruits many followers.”

The two-sided medal for the Herschbach Prize represents both theoretical (left) and experimental (right) molecular collision dynamics. The designer chose an angel for theory to symbolize “our yearning to attain an exalted, exhilarating comprehension."

Bowman was also recently elected to the International Academy of Quantum Molecular Sciences, and is lauded in the August 15 issue of the Journal of Physical Chemistry, the leading journal in its field. The cover art shows results from two of Bowman’s recent collaborations with experimentalists: One, concerning the dynamics of clusters of water molecules and another involving the complex kinetics of the chemicals in a comet. This special “Festschrift Issue” includes a tribute article to Bowman.

“These are all great honors to me,” says Bowman, who turned 65 this year and has no plans to retire. “Right now, I’m at the top of my game, the sweet spot of my career,” he says, citing four major research grants currently funding his group’s work.

Theoretical chemists do not work with chemicals: They write equations, analyze data and develop simulation models for molecular behaviors. It tends to be “a mature field,” Bowman says, where researchers hit their stride after years of experience, patience and perseverance.

Bowman is considered “one of the founding fathers of theoretical reaction dynamics,” the tribute authors write. (Click here to read the whole article, and more highlights from his career.) More recently, they add, he has made exceptional contributions to modeling potential energy surfaces, or PESs: “Without the PESs emerging from Joel’s group, many theorists would be unable to apply powerful methods of modern quantum dynamics to some of the most challenging problems of great current interest.”

Those problems include the molecular dynamics of water, a puzzle that particularly intrigues Bowman these days. During that cross-country plane flight, while most other passengers were probably trying not to think about things like turbulence and a stormy sky, Bowman took out his iPhone to make a video of lightning shooting through dark clouds (see below).



“What’s going on inside a cloud is extremely complicated, involving chemistry, physics, fluid dynamics and heat transfer, among other things,” Bowman says. “Clouds are full of energy, but parts of them can be cold while other parts are warming up. That’s a recipe for turbulence. Suddenly you can get a violent storm and boom! And all the action is taking place in what seems like just a simple little cloud. It’s mostly water.”

Currently, weather forecasting depends greatly on receiving continuous data from satellites and observing approaching fronts and other activity. “We can measure wind direction, high-and-low pressure, and use that information to create models, but that’s not nearly the level of data my research focuses on,” Bowman says.

Potential energy surfaces describe how water molecules bind together, and how much energy it takes to break them up into individual molecules.

“Imagine how sensational it would be if we could predict where and when a cloud will form,” Bowman says. “We’re getting closer to that ability, but we’re not there yet.”

Solving these kinds of puzzles could not only improve the accuracy of 10-day weather forecasts, it could help us predict long-term climate change, he says. “We don’t currently have the knowledge or the theoretical tools to fully understand what our climate will be like 20 to 30 years from now.”

Bowman is also exploring molecular mysteries underlying questions such as why we need water to live. “We know that we are made up of 70 to 80 percent water, and that without water, you cannot have life,” Bowman says. “And yet, from a chemical standpoint, we don’t really understand how water molecules interact with biological systems.”

"When I look at clouds, all kinds of questions come to my mind," Bowman says. Photo by Bryan Meltz, Emory Photo/Video.

Bowman joined Emory in 1986, during a time of rapid growth for the chemistry department. He has served as department chair, and helped establish Emory’s Emerson Center for Scientific Computation, becoming its acting director from 1991 to 1993. The center’s supercomputers are crucial to the Bowman Group’s work.

“Computer power has changed the field enormously,” Bowman says. “We can address problems and think about complicated chemical reactions in ways that people couldn’t dream of 20 years ago. Today, the computer winds up being almost like a laboratory where you can go in and do experiments.”

One challenge is to formulate the right question and get it onto the computer in a reasonable way, Bowman says. “Once you find the right question, and pose it correctly, getting the answer is often fairly straight-forward. Of course, then you have to interpret and understand the result that the computer spits out.”

While many of Bowman’s high-impact publications are collaborations with experimentalists, the theoretical work often begins with three or four members of his group sitting at a round table in his office, discussing a problem. “For me, the biggest joy is bouncing ideas around with my students and post-docs, questioning what’s known,” Bowman says. “And, of course, the discovery of things is a thrill. I get so excited they have to calm me down sometimes.”

Theoretical chemistry “is such a complex subject, involving math, physics, chemistry and computer science,” Bowman says. “Rather than intense focus on one thing, it involves carrying around a lot of data in your brain and thinking about many different things at the same time. That’s why when I look at clouds, all kinds of questions come to my mind and I start scratching my head.”

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