Epstein Barr virus, infectious mononucleosis and associated diseases as contributors to the costs of intimate kissing
Ewald, Paul W.
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Abstract
When evaluating whether kissing is an evolutionary adaptation, fitness costs and benefits need to be considered. Any disease transmitted by kissing needs to be considered on the cost side. Infectious mononucleosis is the prototypical disease transmitted by intimate kissing, so much so that it is commonly known as the kissing disease.
When the Epstein Barr virus was first accepted as the primary cause of infectious mononucleosis in 1968, it was generally considered a relatively benign pathogen in affluent populations. Infectious mononucleosis caused fatigue but was self limited and EBV usually caused asymptomatic infection. If that were the whole story then EBV would impose a relatively small fitness cost when spread by intimate kissing.
Over the past half-century, however, EBV has been associated with severe diseases such as cancers, multiple sclerosis and systemic lupus erythematosus, which would impose higher fitness costs that would offset the mating advantages of kissing, and make adaptive explanations based on mating advantages less tenable. This paper evaluates whether the severe consequences of EBV infection extend back deeply into human evolution or arose more recently, reflecting a mismatch between modern and ancestral conditions.
Comparative evidence indicates that infectious mononucleosis has been largely a recent consequence of EBV infection resulting from increased hygienic activites that reduce the probability of infection prior to adolescence. Infections during and after adolescence are sufficiently severe to generate symptomatic infection recognized as infectious mononucleosis, which in turn is associated with even more severe chronic diseases, such as breast cancer, multiple sclerosis, and Hodgkin's lymphoma.
The recency of these associations indicates that this collection of severe diseases would not have imposed a fitness cost on intimate kissing. The flip side of this conclusion is that intimate kissing is now more unsafe than it used to be during our evolutionary history, and humans are left without innate avoidance mechanisms that would be more consistent with the present costs of intimate kissing.
Web | DOI | Evolution and Human Behavior | Paywall
Ewald, Paul W.
[Line breaks added]
Abstract
When evaluating whether kissing is an evolutionary adaptation, fitness costs and benefits need to be considered. Any disease transmitted by kissing needs to be considered on the cost side. Infectious mononucleosis is the prototypical disease transmitted by intimate kissing, so much so that it is commonly known as the kissing disease.
When the Epstein Barr virus was first accepted as the primary cause of infectious mononucleosis in 1968, it was generally considered a relatively benign pathogen in affluent populations. Infectious mononucleosis caused fatigue but was self limited and EBV usually caused asymptomatic infection. If that were the whole story then EBV would impose a relatively small fitness cost when spread by intimate kissing.
Over the past half-century, however, EBV has been associated with severe diseases such as cancers, multiple sclerosis and systemic lupus erythematosus, which would impose higher fitness costs that would offset the mating advantages of kissing, and make adaptive explanations based on mating advantages less tenable. This paper evaluates whether the severe consequences of EBV infection extend back deeply into human evolution or arose more recently, reflecting a mismatch between modern and ancestral conditions.
Comparative evidence indicates that infectious mononucleosis has been largely a recent consequence of EBV infection resulting from increased hygienic activites that reduce the probability of infection prior to adolescence. Infections during and after adolescence are sufficiently severe to generate symptomatic infection recognized as infectious mononucleosis, which in turn is associated with even more severe chronic diseases, such as breast cancer, multiple sclerosis, and Hodgkin's lymphoma.
The recency of these associations indicates that this collection of severe diseases would not have imposed a fitness cost on intimate kissing. The flip side of this conclusion is that intimate kissing is now more unsafe than it used to be during our evolutionary history, and humans are left without innate avoidance mechanisms that would be more consistent with the present costs of intimate kissing.
Web | DOI | Evolution and Human Behavior | Paywall
