BBC Knowledge Asia Edition

Why can’t everybody

roll their tongues?

Scientists aren’t sure. There is a
long-standing myth that tongue rolling is
controlled by a single gene, but this was
based on a single piece of flawed research
and was debunked as early as 1952.
Tongue rolling seems to be an ability that
comes with practice, not something you
are born with. The most likely explanation
is that because tongue rolling isn’t useful
for speaking, whistling, talking, kissing or
anything else apart from showing off at
parties, some of us just never got around to
mastering the skill. LV

Seawater tastes salty because of

the action of rain on exposed rocks. The

compounds most likely to find their way

into the sea are, naturally enough, the

most water-soluble ones, and these are

rich in chlorine and sodium ions – the raw

ingredients for common salt. As this process

has been operating for billions of years,

there’s no doubt oceans have gotten saltier

over time. In fact, the real mystery is why

they aren’t now saturated with the stuff,

making them as lifeless as the Dead Sea.

Somehow, the concentration has remained

at just a few per cent for at least half a

billion years. Exactly how isn’t clear, but

one theory, suggested by British ecologist

James Lovelock, involves the vast, mat-like

colonies of bacteria found in coastal lagoons

around the world. The Sun’s heat triggers

evaporation of the water, leaving its salt

content trapped on the coast and unable to

dissolve back into the sea. RM

Men tend to seek more short-

term relationships and look for physical

attractiveness. Women also seek good

looking short-term mates, but for long-

term partners they’re more interested

in resources, seeking a man who will

provide for them and any children. There

are trade-offs between looks and health,

and the desire to find someone similar in

education, religion, intelligence, and wanting

a family. Few people are aware of these

underlying reasons, yet the same effects

have been measured in 37 cultures across

six continents. As for sexual orientation,

many genetic, hormonal and other effects

contribute to people finding others of their

own sex more attractive. SB

Why are people only

attracted to certain

other people?

The Dead Sea is about 10

times saltier than normal

seawater

Are the oceans getting saltier?

PHOTO: GETTY, ALAMY X2, ISTOCK X3, SCIENCE PHOTO LIBRARY

Attraction is a trade-off between

looks, health and similar beliefs...

how romantic

It’s a manifestation of an optical

phenomenon called bokeh, which

is Japanese for the effect of camera

equipment on out-of-focus images. In

the case of raindrops, it’s a result of the

blades of the camera diaphragm creating

a polygonal-shaped aperture. The exact

shape varies on the vintage and type of

the camera. RM

Why do raindrops

appear hexagonal on

camera lenses?