If you want a son, girls, you should marry an old man, according to a report in the journal Nature.
Dr John Manning and colleagues at the University of Liverpool, England, looked at 301 families from diverse backgrounds and found a high correlation between the gap in parents' ages and the sex of each couple's first child. If the man was older than the woman, their first offspring was more likely to be male. In pairs with men up to five years older than their wives, there were 117 sons and 84 daughters; with a gap of five to 15 years, there were 37 sons and 20 daughters. With older wives, daughters prevailed.
The authors did the research because it had been noted that male births increased in relation to female births after a war. They suggested that perhaps, in wartime, women preferred to marry older men. Although the authors did not have a biological explanation for the phenomenon, they speculated women might unwittingly influence the success of sperm that carried sex-determining chromosomes.
Express traffic A super-fast global computer network 1,000 times faster than the current one is on the way.
Ideas for its use range from holographic conferences or helping medical students test their surgical skills on holographically produced joints to using electron microscopes halfway round the world.
The National Aeronautics and Space Administration, along with other US federal agencies - such as the original Internet creator, the National Science Foundation, and the Defence Advanced Research Projects Agency - is a partner in the creation of the next-generation Internet, for which the Clinton administration has recommended US$300 million (HK$2.32 billion) in funding over three years.
Meanwhile a consortium of 112 US universities has already constructed a second research Internet, called I2, to which about 20 of them were linked last month through high-speed networks.
Each campus has to pledge US$500,000 to build the network base and support further research.
Europe has also has got in on the act, with its Ten-34 system now linking 26 universities across the continent and handling large amounts of data.
Poor chicks Penguin parents in Argentina are having to travel so far in search of food that their chicks are starving to death, a study in Argentina indicates.
Transmitters fixed to two Magellanic penguin parents showed they swam up 240 kilometres from the rookery in search of food, in trips that could take three weeks. And, if the food seeker is killed during the hunt, the bird's mate can only wait at the nest while the chicks die, since to leave them would mean quick death due to predators.
The Punta Tombo rookery suffered a 20 per cent decline in breeding pairs between 1987 and 1995, the researchers found.
They blame over-fishing and oil pollution for having forced the penguins further from home to find fish.
Extra quarks US physicists believe they have discovered a previously unknown particle, which they call an exotic meson. Matter consists of atoms whose nuclei are made of protons and neutrons, each containing three quarks, with particles called gluons holding them together.
Another particle, which survives briefly after creation in accelerator laboratories, is the meson, containing a quark and an anti-quark.
The suspected new meson is not one of these well-known kinds. One theory the team is investigating is that the new particle may contain four quarks - two normal ones and two anti-quarks - bound together by gluons.
This would make the exotic meson the only known particle containing more than three quarks.
Science is edited by Elisabeth Tacey. Tel: 2565-2264.