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!
New study: How does Europe become a leading player for software and IT services?
03.04.2017 | Fraunhofer-Institut für System- und Innovationsforschung (ISI)
Reusable carbon nanotubes could be the water filter of the future, says RIT study
30.03.2017 | Rochester Institute of Technology
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.
In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...
Dental plaque and the viscous brown slime in drainpipes are two familiar examples of bacterial biofilms. Removing such bacterial depositions from surfaces is...
23.05.2017 | Event News
22.05.2017 | Event News
17.05.2017 | Event News
23.05.2017 | Physics and Astronomy
23.05.2017 | Life Sciences
23.05.2017 | Medical Engineering