1) An obvious reason why people are kissing is that it gives them pleasure. This is what could very well compensate the infection risk, without the necessity of an evolutionary advantage...
It is a well known fact that a Cytomegalovirus infection can lead to severe fetal anomalies or even fetal loss, if it happens during pregnancy, so that it is certainly better to have it before pregnancy.
A similar behavior is geophagy:
"Geophagy is the practice of eating earthy or soil-like substances such as clay, and chalk, in order to obtain essential nutrients such as sulfur and phosphorus from the soil. This practice is widespread among animals in the wild, as well as in human societies. Human geophagy is closely related to pica, a classified eating disorder in the DSM-IV characterized by abnormal cravings for nonfood items.
The many possible health benefits of geophagy remain under study and are much debated. Since it is very common among animals, there is clearly some evolutionary advantage in this behaviour.
Geophagy is most often seen in rural or preindustrial societies among children and pregnant women."
Source and further information:
http://en.wikipedia.org/wiki/Geophagy
2) Here the article's abstract:
"Kissing as an evolutionary adaptation to protect against Human Cytomegalovirus-like teratogenesis
C.A. Hendriea, G. Brewerb
Received 14 September 2009; accepted 17 September 2009. published online 15 October 2009.
Corrected Proof"
"Mouth to mouth sexual kissing is seen in more than 90% of human cultures. Various theories have been put forward to account for this but none offer a full explanation within an evolutionary framework. As mouth to mouth sexual kissing exposes each participant to the diseases of the other, it must confer significant benefit. Human Cytomegalovirus (HCMV) is a ubiquitous infection that carries a severe teratogenic risk if primary infection is acquired during certain critical periods. As HCMV is present in salivary gland epithelial cells and sheds from periodontitis induced lesions, female inoculation with a specific male’s HCMV is most efficiently achieved through mouth to mouth contact and saliva exchange, particularly where the flow of saliva is from the male to the typically shorter female. The current hypothesis proposes that mouth to mouth sexual kissing enables females to control when they become infected with a particular male’s HCMV and so protect their offspring from the threat of teratogenesis from primary infection during vulnerable times in their development. Females only gain this benefit if they also avoid becoming infected by other males. Hence HCMV induced teratogenesis is a strong viral pressure towards the development of monogamy as well as kissing as a behavioural strategy to protect against it."
Source and further information:
http://www.medical-hypotheses.com/article/S0306-9877(09 )00638-0/abstract
3) It must be said that Medical Hypotheses is not a "normal" scientific journal:
"Medical Hypotheses is a medical journal published by Elsevier that is intended to provide a forum for unconventional ideas without the traditional filter of scientific peer review. According to the journal's website, it publishes "radical ideas, so long as they are coherent and clearly expressed". Submitted papers are not sent to other scientists for peer review, but are chosen instead by the journal's editor-in-chief based on whether or not he considers the submitted work to be interesting and important. The journal's stated policy is that the authors, rather than peer reviewers or the editor, hold responsibility for the integrity, precision and accuracy of their work."
Source and further information:
http://en.wikipedia.org/wiki/Medical_Hypotheses
4) "Pregnancy and congenital infection:
HCMV is one of the TORCH infections that lead to congenital abnormalities. These are: toxoplasmosis, rubella, herpes simplex, and cytomegalovirus. Congenital HCMV infection occurs when the mother suffers a primary infection (or reactivation) during pregnancy. Due to the lower seroprevalence of HCMV in industrialized countries and higher socioeconomic groups, congenital infections are actually more common than in poorer communities, where more women of child-bearing age are already seropositive. In industrialized countries up to 8% of HCMV seronegative mothers contract primary HCMV infection during pregnancy, of which roughly 50% will transmit to the fetus. Between 22-38% of infected fetuses are then born with symptoms, which may include pneumonia, gastrointestinal, retinal and neurological disease. HCMV infection occurs in roughly 1% of all neonates with those who are not congenitally infected contracting the infection possibly through breast milk. Other sources of neonatal infection are bodily fluids which are known to contain high titres in shedding individuals: saliva (<107copies/ml) and urine (<105copies/ml ) seem common routes of transmission.
The incidence of primary CMV infection in pregnant women in the United States varies from 1% to 3%. Healthy pregnant women are not at special risk for disease from CMV infection. When infected with CMV, most women have no symptoms and very few have a disease resembling mononucleosis. It is their developing fetuses that may be at risk for congenital CMV disease. CMV remains the most important cause of congenital viral infection in the United States. HCMV is the most common cause of congenital infection in humans and intrauterine primary infections are second only to Down's syndrome as a known cause of mental retardation.
For infants who are infected by their mothers before birth, two potential adverse scenarios exist:
- Generalized infection may occur in the infant, and can cause complications such as low birth weight, microcephaly, seizures, petechial rash similar to the "blueberry muffin" rash of congenital rubella syndrome, and moderate hepatosplenomegaly (with jaundice). Though severe cases can be fatal, with supportive treatment most infants with CMV disease will survive. However, from 80% to 90% will have complications within the first few years of life that may include hearing loss, vision impairment, and varying degrees of mental retardation.
- Another 5% to 10% of infants who are infected but without symptoms at birth will subsequently have varying degrees of hearing and mental or coordination problems.
However, these risks appear to be almost exclusively associated with women who previously have not been infected with CMV and who are having their first infection with the virus during pregnancy. Even in this case, two-thirds of the infants will not become infected, and only 10% to 15% of the remaining third will have symptoms at the time of birth. There appears to be little risk of CMV-related complications for women who have been infected at least 6 months prior to conception. For this group, which makes up 50% to 80% of the women of child-bearing age, the rate of newborn CMV infection is 1%, and these infants appear to have no significant illness or abnormalities.
The virus can also be transmitted to the infant at delivery from contact with genital secretions or later in infancy through breast milk. However, these infections usually result in little or no clinical illness in the infant.
To summarize, during a pregnancy when a woman who has never had CMV infection becomes infected with CMV, there is a potential risk that after birth the infant may have CMV-related complications, the most common of which are associated with hearing loss, visual impairment, or diminished mental and motor capabilities. On the other hand, infants and children who acquire CMV after birth have few, if any, symptoms or complications."
Source and further information:
http://en.wikipedia.org/wiki/Cytomegalovirus
Further information:
http://en.wikipedia.org/wiki/TORCH_complex
Pumpkin Etoile Nov, 08 2009 at 04:16 AM
MuslimYamaka Nov, 07 2009 at 08:06 PM
WelbyQuentin Nov, 07 2009 at 05:00 PM
iwnit Nov, 09 2009 at 02:37 AM
