Tropics are a boon for baby girls

April 1, 2009

Couples hoping for a baby girl might be best advised to go and live in Africa, if a study published on Wednesday is correct.

It points to big differences in the proportions of male to female births between tropical latitudes and temperate and sub-arctic latitudes.

This gap remains even when local cultural and social preferences -- such as the preferences for males in India and China, resulting in the abortion of female foetuses -- are taken into account.

University of Georgia endocrinologist Kristen Navara looked at official data collected from 202 countries over a decade, from 1997-2006, and published in the Central Intelligence Agency (CIA) World Factbook.

Averaged around the world, there were 51.3 percent male births to 48.7 female births, she found.

But this average masked big differences according to latitude: in tropical latitudes, male dominance fell to 51.1 percent of births. In tropical sub-Saharan Africa, it was just 50.8 percent.

"Significantly more females were produced at tropical latitudes," she told AFP. "This relationship emerged despite enormous lifestyle and socio-economic variation among countries and continents."

Navara, whose paper appears in the British journal Biology Letters, said more research is needed to explain the puzzle.

She speculated that human gametes -- sperm and eggs -- may be affected by ambient light and temperature, and this could exert a bias in favour of one gender or another.

Previous studies in small mammals (Siberian hamsters, house mice and meadow voles) have discovered that these animals produce more males during the winter months or when daylight hours are fewer.

In China, the pro-male bias was 52.8 percent while in India it was 51.2 percent, slightly below the global mean, Navara said.

(c) 2009 AFP

Explore further: Female candidates get fewer votes: Study

Related Stories

Female candidates get fewer votes: Study

November 21, 2007

Female candidates get fewer votes, according to ANU research released today that analysed the performance of nearly 17,000 candidates who ran for the House of Representatives between 1903 and 2004.

Study notes decline in male births in the US and Japan

April 9, 2007

A study published in this week’s online edition of Environmental Health Perspectives reports that during the past thirty years, the number of male births has decreased each year in the U.S. and Japan.

Recommended for you

Closer look reveals tubule structure of endoplasmic reticulum

October 28, 2016

(—A team of researchers from the U.S. and the U.K. has used high-resolution imaging techniques to get a closer look at the endoplasmic reticulum (ET), a cellular organelle, and in so doing, has found that its structure ...

Computer model is 'crystal ball' for E. coli bacteria

October 28, 2016

It's difficult to make predictions, especially about the future, and even more so when they involve the reactions of living cells—huge numbers of genes, proteins and enzymes, embedded in complex pathways and feedback loops. ...

Ten months in the air without landing

October 27, 2016

Common swifts are known for their impressive aerial abilities, capturing food and nest material while in flight. Now, by attaching data loggers to the birds, researchers reporting in the Cell Press journal Current Biology ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

1 / 5 (3) Apr 01, 2009
This aint Science folks!!!!

Apparently this woman has never learned about statistics and MARGIN OF ERROR

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.