Sometime in the early 1960s, a significant thing happened in Sydney, Australia. The city discovered its harbor. Then, one after another, Sydney discovered lots of things that were just sort of there — broad parks, superb beaches, and a culturally diverse population. But it is the harbor that makes the city.

Andrew Reynolds, a cheerful fellow in his early 30s, pilots Sydney ferryboats for a living. I spent the whole morning shuttling back and forth across the harbor. After our third run Andrew shut down the engine, and we went our separate ways — he for a lunch break, I to explore the city.

“I’ll miss these old boats,” he said as we parted.

“How do you mean?” I asked.

“Oh, they’re replacing them with catamarans. Catamarans are faster, but they’re not so elegant, and they’re not fun to pilot. But that’s progress, I guess.”

Everywhere in Sydney these days, change and progress are the watchwords (口号), and traditions are increasingly rare. Shirley Fitzgerald, the city’s official historian, told me that in its rush to modernity in the 1970s, Sydney swept aside much of its past, including many of its finest buildings. “Sydney is confused about itself,” she said. “We can’t seem to make up our minds whether we want a modern city or a traditional one. It’s a conflict that we aren’t getting any better at resolving (解决).”

On the other hand, being young and old at the same time has its attractions. I considered this when I met a thoughtful young businessman named Anthony. “Many people say that we lack culture in this country,” he told me. “What people forget is that the Italians, when they came to Australia, brought 2000 years of their culture, the Greeks some 3000 years, and the Chinese more still. We’ve got a foundation built on ancient cultures but with a drive and dynamism of a young country. It’s a pretty hard combination to beat.”

He is right, but I can’t help wishing they would keep those old ferries.

Which statement will the author probably agree with?

Humans have long gained pleasure from the smells of the natural world. For the most part, though, human beings are not their target market. For plants, fragrances are a way to interact with insects and other animals. Their attraction for people happens simply by chance.

In chemical terms, most natural fragrances are made up of volatiles — so called because of their tendency to change states suddenly. Volatiles evaporate easily, drifting into noses. In plants’ reproductive processes, smelly volatiles attract pollinators (授粉昆虫). But their natural applications are much more varied. If an insect chews through the leaves of some Bursera plants, out shoots a sticky, smelly liquid to trap it. Coyote tobacco plants are even more crafty: upon sensing the smell of hungry caterpillars, they produce volatiles that attract predators to kill the pests.

What is truly amazing is just how wily plants can be in using their scents for reproduction. White flowers often emit their scent at night to attract nocturnal pollinators such as moths. They produce a dilute nectar (稀释的花蜜) that encourages moths to keep moving, rather than linger at a single bloom—all the better to increase pollination. Other flowers change their fragrance after being successfully pollinated, as a signal for insects to go elsewhere.

But though “Scent” is a story of plants’ cleverness, it is also a tale of the human kind. People have long used fragrances for their own purposes, particularly for use in religious ceremonies: perfume recipes on the walls of an Egyptian temple in Edfu demonstrate just how long ingredients have been mixed in pursuit of the best blend. So highly prized were some scents that, to scare off competitors, Arab traders spread a legend about giant eagles that guarded cinnamon.

Eventually scientists no longer needed natural sources for fragrances. In 1866 a fragrance molecule was produced for the first time. Sixteen years later, Houbigant Parfum released Fougère Royale, the first “modern fantasy perfume” that creates an imaginary scent rather than copying a natural one. Nowadays fragrance–making is dominated by man–made compounds, which can be reliably and affordably produced in large quantities.

That has led to the mass production of smelly products, from toilet paper to toothpaste. Scent is accordingly big business. It is said that a world–famous fragrance and flavour manufacturer that claims people interact with its products up to 30 times a day, had sales of €3.8bn last year.

A new study found that some methods for measuring a species’ generation time might underestimate (低估) the likelihood that some species would die out.

A species’ generation time is how long it takes for a generation to be replaced by its mature offspring (后代). This is different for every species and dramatically impacts how quickly a species can respond to changes in its environment. The generation time of a mouse is only a few months, whereas the African elephant has the generation time of 22 years. The longer the generation time, the slower a species can adapt to environmental changes and therefore it may be more likely to go extinct.

In some risk assessment models, population reduction is measured on the scale of three times a species’ generation time. If a species is believed to mature and produce offspring in five years, then how much its population has declined will be measured over a 15-year interval. But if a species’ generation time is underestimated, so is the threat status of the species.

We tested the influence of errors in different measures of generation time, including those used by the IUCN Red List assessments and found that these errors could potentially lead to an overly optimistic assessment of extinction risk for some species.

To overcome this, we compared different types of errors in seven commonly used measures of generation time. We proposed a new estimate which predicted a species’ generation time from its body mass and reproductive lifespan.

Still, the lack of data is a tough problem for making accurate calculations. We’re planning to explore how to fill some of these knowledge gaps by comparing survival and reproduction data from wild and captive (被关起来的) populations, using data from nearly 1,200 zoos and aquariums over 40 years, on more than 21,000 species.