Wednesday 29th March, 2017
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Climate change: Biofuels 'could limit jet contrails'

Climate change: Biofuels 'could limit jet contrails'

The human nose, in all its glorious forms, is one of our most distinctive characteristics, whether big, little, broad, narrow or somewhere in between. Scientists are now sniffing out some of the fac­tors that drove the evolution of the human proboscis.
Researchers said on Thursday a study using three-dimensional images of hundreds of people of East Asian, South Asian, West African and Northern European ancestry indicat­ed local climate, specifically temperature and humidity, played a key role in deter­mining the nose’s shape.
Wider noses were more common in people from warm and humid climates, they found. Narrower noses were more common in those from cold and dry climates.
The nose’s primary func­tions are breathing and smelling. It has mucous and blood capillaries inside that help warm and humidify inhaled air before it reaches more sensitive parts of the respiratory tract.
Having narrower nasal airways might help increase contact between inhaled air and tissues inside the nose carrying moisture and heat, said Penn State University geneticist Arslan Zaidi, lead author of the study pub­lished in the journal PLOS Genetics.
“This might have offered an advantage in colder cli­mates. In warmer climates, the flip side was probably true,” Zaidi said.
Our species appeared in Africa about 200,000 years ago and later migrated to other parts of the world. The researchers said people with narrower nostrils may have done better and pro­duced more offspring than those with wider nostrils in colder, drier locales, driving a gradual decline in nose width.
The finding gener­ally supports what’s called Thomson’s rule, formu­lated by British anatomist and anthropologist Arthur Thomson (1858-1935), that people from cold, dry climates tend to have lon­ger and thinner noses than people from warm, humid climates.
Zaidi said most previous evidence regarding Thom­son’s rule came from skull measurements, while this study expanded on that by analyzing external nose shape.
The researchers studied nose width, nostril width, nose height, length of the nose ridge, nose tip protru­sion, external surface area and total nostril area.
 
 

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