In the West, more left-handed males born in winter

09/01/2022

Elena Sanz | ElenaSanz_ | Madrid | Updated 01/12/2015 at 08:59 hours

The statistics leave no room for doubt: in the West many more left-handed males born in November, December and January the rest of the year. Specifically, through a study carried out in Austria and Germany on 13,000 subjects, Ulrich Tran and colleagues at the University of Vienna they showed that as of February to October 8.2% of children are born left-handed, since November until January the percentage rises to 10.5%.

For what is this? Tran rescues a theory launched in the 80s by neuroscientists Norman Geschwind and Albert Galaburdas, suggesting that increased testosterone delays ripening left hemisphere of the brain during embryonic development. And because this hemisphere is the dominant right-handers, the more testosterone is more likely to be born left-handed.

If we consider that the amount of testosterone circulating in the blood of the mother is not the same throughout the year, but varies according to the hours of light each season, more lefties born in winter than in spring or summer could be due to seasonal hormonal changes, as proposed by the authors in the journal Cortex '.

And that's not all: if you are born between December and May start to crawl around four weeks before your arrival if the world takes place between June and November, according to research by the University of Haifa in Israel. Although gather more data would be needed to identify the cause, the authors suggest that one can predict what the motor development of a baby during the first year of life to know the date of his birthday.

So, coming into the world in the coldest season of the year may also have negative effects on health, not because infants catch catch cold or flu. A study by Vanderbilt University published in Nature Neuroscience, those born in winter are at increased risk for neurological disorders such as depression and schizophrenia.

This is because the station that is born has a "dramatic" impact on the functioning of our biological clock. In experiments with mice, Douglas McMahon and his colleagues showed that those born in winter were slower activity in the brain "master clock" rodents born in summer. "The mice that grow under the winter cycle show an exaggerated response to the change of season, which is very similar to humans suffering from seasonal affective disorder called" concluded McMahon.