Testosterone and Social Status

When animals rise in social status, their testosterone levels increase as well. This change produces the increased confidence that accrues to social status as well as increased aggression. Some high-status animals often look healthier but may have a shorter lifespan.

The Silverback Gorilla

Each gorilla group has a single dominant male, known as the silverback. The distinctive silver color of the animal's back is essentially a visible readout of its testosterone level.

Gorillas also illustrate that the Darwinian consequences of social status are considerable for this species. Only the dominant male gets to breed.

Males are selected for large size because the largest individuals can intimidate breeding rivals. Males are much bigger than females as a result. Some species, such as gibbons are monogamous so there are minimal size differences between males and females whereas humans have slight size differences indicating a history of selection for male-male competition.

Exposure to testosterone early in development is associated with social dominance in women and men (1). Experiments found that testosterone injection can increase dominance-seeking in men (who have low levels of stress hormones) but not in women.

Testosterone and Sexuality and Aggression

High-ranking male primates experience increased testosterone production but the connection between sex hormones and status in female primates is less clear-cut. Testosterone does play an important role in the sexual behavior of most primates, females as well as males, humans included. The sex hormone increases mating effort in male primates and this partly explains why high-ranking males have greater reproductive success. Dominant males are generally in better physical condition making them more attractive to females, an advantage that is magnified by sexually selected traits like the gorilla's silver back.

Although alpha males produce more offspring, there is a price to be paid in terms of higher mortality and reduced life expectancy. There are at least three reasons that dominant males experience health problems. They are exposed to aggressive challenges from aspiring young males who want to unseat them and take their place. Fights often cause minor wounds that are liable to become infected undermining overall health and strength. Testosterone also suppresses the immune system so that dominant males tend to have a shorter life expectancy. Dominant males play a central role in protecting the group from attacks by predators which exposes them to attacks that can cause injury or even death.

Life can therefore be difficult at the top of a primate status hierarchy due to physiological wear and tear and enhanced competition. Dominant females can experience similar pressures. Dominant female Barbary macaques have higher testosterone levels than the other females in the group. In general, high testosterone is associated with a greater willingness to mate in both female and male primates, although female receptivity is limited to brief periods of estrus (or sexual heat).

High-status female macaques are more likely to produce male offspring than female offspring. The Darwinian logic here is that males are larger and require a bigger biological investment than females. This is possible for a high-ranking female because the others defer to her in respect to access to food and shelter. Low-status females have trouble raising males that are big and strong enough to climb the status hierarchy and thus focus on females who are more reproductively successful. Offspring of dominant females have an easier time because their mother's high status rubs off on them, so to speak.

What Testosterone Reveals About Human Social Status

Many social primates have large differences in social status. Bonobos (or pygmy chimpanzees) have no status distinctions to speak of and defuse social tension using sexual activity that is homosexual as well as heterosexual. Ancestral human societies probably lacked much status differentiation either.

Even so, once an elite class emerges in complex societies based on differential access to resources, many of the prototypical aspects of testosterone-based primate societies emerge.

Elite status in humans has many distinguishable biological markers. Higher-income people enjoy improved physical condition. They are taller, indicating better nutrition. They live considerably longer perhaps because wealthy people are in better control of their lives and experience lower stress levels associated with the difficulties of daily living. They may also receive preferential treatment throughout their lives given that high-status individuals mostly have elite ancestries as is true of the Barbary macaques.

Successful people are said to walk faster and hold their heads higher, giving them a more confident gaze. While it would be wrong to attribute social status to a person's hormone profile alone, there is a clear pattern of testosterone-related biological traits that signal dominance in other primate species. In many primates, staring directly at another is an assertion of social dominance. The same is evidently true of the human species.