Radiation from nuclear power accidents or bomb testing could be why in recent years, more boys are born than girls.
Initially, the effects were observed at the regional level, as in the case of the Chernobyl explosion, but recent studies have shown that atmospheric explosions affect birth rates worldwide.
The new study focused on observing people in 39 European countries and the United States between 1975 and 2007. After research showed that during 1986-1975, there were more boys born than girls, and repeating the phenomenon since 1989. Normally, by now, the number of men exceeded that of women in a constant ratio of 105 to 100.
The increase in the years 1960-1970 is attributed to the dispersion of radioactive particles into the atmosphere by testing nuclear bombs.
These tests have been commonly practiced in the late 1940s until 1963, when the Treaty on the Partial Nuclear Test Ban was signed by the United States of America, the Soviet Union and United Kingdom.
Also, scientists believe that the Chernobyl explosion affected births, but that the effects were visible only locally, because of radioactive leaks occurred, mostly at ground level. In neighboring Ukraine, such as Belarus, at that time were born, more boys than girls.
Although the biological mechanism behind this inequality has not been studied, previous research in animals have shown that increasing the number of male individuals may be caused by a deterioration of the X chromosomes in spermatozoons.
In humans, a spermatozoid contains either an X chromosome or one Y, while an ovule does not contain a Y chromosome, but only one chromosome X. If an embryo has an XY combination, it will become a boy and XX will give birth of a girl.
No one knows exactly why the X chromosomes of spermatozoons are more prone to damage by radiation than Y chromosomes, or chromosomes X in ovules, but scientists believe that these chromosomes are better isolated in ovule. Also, being larger than Y, contain more genes, and their damage leads to the formation of an abnormal embryo, which often does not survive until the time of birth.
These findings contradict conventional beliefs, which say that radiation exposure has no global effects. In addition, the researchers argue that a new “explosion ” of births of boys may be registered in the years following the events of the Fukushima nuclear plant in Japan.