Editor- Grech et al. reported that sex ratio (male proportion) at
birth declines significantly with increase in geographical latitude in
Europe (1). Unfortunately, I am not familiar with geographical features of
Europe, but based on maps of Great World Atlas (Reader’s Digest) European
countries might be divided in two groups, the mountainous countries
(included Austria, Bulgaria, Czech Republic, Greece, Iceland, Italy,
Norway, Romania, Spain, Switzerland) and non-mountainous countries
(included Belgium, Denmark, Finland, France, Germany, Hungary, Ireland,
Luxembourg, Malta, Netherlands, Poland, Portugal, Sweden, United Kingdom).
Reanalysis of Grech’s data demonstrated that the difference between sex
ratio of mountainous areas (0.5144, total live birth = 154,890,143) and
the other ones (0.5141, total live birth = 154,689,806) is highly
significant (chi squared=36.2, df=1, P=0.00000). The present finding
might be explaining that why within the studied areas of Europe, the
lowest sex ratios are found in moderate (40-55 degrees)
latitudes (1) Therefore, the relationship between sex ratio and latitude
in Europe may be an artifact. It should be mentioned that the absolute
difference between the sex ratios of these two geographical regions is
very small which is similar to the Grech et al. data.
Mostafa Saadat
Department of Biology,
College of Sciences,
Shiraz University,
Shiraz 71454, Iran
Rapid Response:
High sex ratio in mountainous areas of Europe
Editor- Grech et al. reported that sex ratio (male proportion) at
birth declines significantly with increase in geographical latitude in
Europe (1). Unfortunately, I am not familiar with geographical features of
Europe, but based on maps of Great World Atlas (Reader’s Digest) European
countries might be divided in two groups, the mountainous countries
(included Austria, Bulgaria, Czech Republic, Greece, Iceland, Italy,
Norway, Romania, Spain, Switzerland) and non-mountainous countries
(included Belgium, Denmark, Finland, France, Germany, Hungary, Ireland,
Luxembourg, Malta, Netherlands, Poland, Portugal, Sweden, United Kingdom).
Reanalysis of Grech’s data demonstrated that the difference between sex
ratio of mountainous areas (0.5144, total live birth = 154,890,143) and
the other ones (0.5141, total live birth = 154,689,806) is highly
significant (chi squared=36.2, df=1, P=0.00000). The present finding
might be explaining that why within the studied areas of Europe, the
lowest sex ratios are found in moderate (40-55 degrees)
latitudes (1) Therefore, the relationship between sex ratio and latitude
in Europe may be an artifact. It should be mentioned that the absolute
difference between the sex ratios of these two geographical regions is
very small which is similar to the Grech et al. data.
Mostafa Saadat
Department of Biology,
College of Sciences,
Shiraz University,
Shiraz 71454, Iran
msaadat41@yahoo.com
1. Grech V, Savona-Ventura C, Vassallo-Agius P. Unexplained
differences in sex ratios at birth in Europe and North America. BMJ 2002;
324:1010-1011.
Competing interests: No competing interests