Studying short-term spikes in the testosterone levels of Tsimane men, UC Santa Barbara anthropologists Ben Trumble and Michael Gurven have found that the act of chopping down trees –– a physically demanding task that is critical to successful farming and food production –– results in greater increases in testosterone than does a directly competitive activity such as soccer. Their research appears in the early online edition of the journal Evolution and Human Behavior.
A new study finds Tsimane men experience higher short-term testosterone spikes while chopping trees than they do playing competitive soccer.
Credit: Benjamin C. Trumble
"With the Tsimane, we see an environment that is more like that in which humans evolved, and for which our systems are calibrated," said Trumble, a postdoctoral researcher in anthropology at UCSB and the paper's lead author. The paper was written with Gurven, a UCSB professor of anthropology and co-director of the Tsimane Health and Life History Project, a collaboration between UCSB and the University of New Mexico.
According to Trumble, whose research lies at the intersection of hormones, behavior, and the environment, testosterone levels are closely related to the availability of food energy. When young men skip even a single meal, their testosterone levels can drop as much as 10 percent. Fast for a couple of days, and they decrease to castrate levels.
"The same is true for infection," he added. "An infection from a pathogen or parasite –– even injuries, burns, or surgery –– all cause an immediate decrease in testosterone."
The body uses food energy for a number of critical processes. Among them are building muscle mass and maintaining proper immune function. When food energy is limited, the body has to choose between one and the other. For populations in industrialized countries like the United States, there isn't much of a tradeoff," Trumble said. "I can go to the grocery store and gather 20,000 calories in 10 minutes without breaking a sweat. I don't have to worry about a deficit."However, for a group such as the Tsimane, who are more physically active than most Americans –– and use a lot more food energy –– but also have to grow, hunt, or fish for the vast majority of the calories they consume, the tradeoff is much greater. In addition, the Tsimane's regular exposure to pathogens and parasites requires additional calories for maintaining necessary immune function.
The acute spike in testosterone increases the muscle's ability to take in blood sugar, which, in turn, enhances soccer performance and reaction times. It turns out the same is true for tree chopping. "If you're better able to pull blood sugar into your muscle tissue, and better able to use that energy, you'll be able to chop more trees," Trumble explained.
While Tsimane men have a relatively low baseline testosterone level –– 33 percent lower than that of men living in the United States, where life is less physically demanding –– they appear to maintain their testosterone levels over the course of their lives. This is contrary to the United States and other industrialized populations, where men generally experience decreases in testosterone as they age.
"One of the important take-home messages of this study is that over the course of human evolution, we had very physical strategies for producing calories. It's important to think about how testosterone fits into that. We needed to maintain testosterone in order to maintain muscle mass, and also to spike testosterone when necessary. If you're a 50-year-old Tsimane man, for example, you probably have six or more children, and you need to be able to feed them. If you lose the ability to have the acute spikes in testosterone that increase your ability to chop trees –– chop longer and chop harder –– that would be detrimental to feeding your family."
Trumble noted that in many societies women produce a significant portion of calories, and other researchers have reported acute spikes in testosterone during physical activity for women, despite their very low baseline levels. "While we didn't measure the testosterone of women in this study, women can also produce short-term spikes, which suggests the importance of acute rises in testosterone not only for competition over mates, but also for critical daily tasks such as food production."
The paper's other co-authors include Hillard S. Kaplan and Daniel K. Cummings of the University of New Mexico, Albuquerque; and Kathleen A. O'Connor, Darryl J. Holman and Eric A. Smith of the University of Washington, Seattle.
Andrea Estrada | EurekAlert!
Win-win strategies for climate and food security
02.10.2017 | International Institute for Applied Systems Analysis (IIASA)
The personality factor: How to foster the sharing of research data
06.09.2017 | ZBW – Leibniz-Informationszentrum Wirtschaft
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
It's possible to produce hydrogen to power fuel cells by extracting the gas from seawater, but the electricity required to do it makes the process costly. UCF...
Mercury, our smallest planetary neighbor, has very little to call an atmosphere, but it does have a strange weather pattern: morning micro-meteor showers.
Recent modeling along with previously published results from NASA's MESSENGER spacecraft -- short for Mercury Surface, Space Environment, Geochemistry and...
10.10.2017 | Event News
10.10.2017 | Event News
28.09.2017 | Event News
16.10.2017 | Physics and Astronomy
16.10.2017 | Earth Sciences
16.10.2017 | Physics and Astronomy