The 1930s and early 1940s were a good time to fish for sardines (沙丁鱼) off California. Centered on Monterey Bay, catches increased dramatically and supported the state’s economy. But the situation began to change in 1946, and sardine catches eventually fell from an average of 234,000 tons to just 24,000 tons. The industry went belly-up.

Scientists have guessed for decades about what caused this phenomenon, but they lacked data to test their theories. Now researchers have finally found one apparent cause: cycles of ocean upwelling, a defining feature of the West Coast sea environment in which deep, nutrient-rich water rises to the nutrient-poor surface and restores the food supply there. The key that unlocked this phenomenon turned out to be old seaweed specimens (标本) gathered around the U. S.

“Plants are just sitting there, recording data about the state of the ocean,” says Kyle Van Houtan, chief scientist at the Monterey Bay Aquarium and senior author of the new study. Van Houtan and others had suspected the impact of upwelling, but scientists only started measuring the process in Monterey Bay in 1946. Historic seaweed specimens, Van Houtan realized, might fill in the blanks for earlier years—similar to the way ice cores can help reconstruct CO₂ levels from times before researchers started collecting real-time measurements.

For the new study, the scientists relied on the fact that deeper water near Monterey typically hosts more of a particular nitrogen isotope (氮同位素). Looking at modern upwelling data and recently collected seaweed, they found that higher levels of this nitrogen in the plants’ cells corresponded with periods of more upwelling. Next they measured the isotope levels in 70 historic specimens of the red seaweed Gelidium, gathered from Monterey as far back as 1878. The results suggested a gradual increase in upwelling and then a dramatic decrease, which lined up with the sardine population’s growth and decline.

“This paper is an excellent example of the creative detective work of historical ecology,” says Loren McClenachan, a marine ecologist at Colby College, who was not involved in the research. “There are thousands and thousands of similar specimens in collections around the world, and applying similar methods could teach us a great deal about long-term ocean change.”

Both humans and animals have enemies. It is easy for us to know the difference between our friends and our enemies. But can other animals do the same? Elephants can! They can use their sense of vision and smell to tell the difference between people who mean a threat and those who do not. In Kenya, researchers find that elephants react differently to clothing worn by men of the Maasai and Kamba ethnic groups. Young Maasai men hunt animals and thus mean a threat to elephants; Kamba men are mainly farmers and are not a danger to elephants.

In an experiment conducted by animal scientists, elephants were first presented with clean clothing or clothing that had been worn for five days by either a Maasai or a Kamba man. When the elephants noticed the smell of clothing worn by a Maasai man, they moved away from the smell faster and took longer to relax than when they noticed the smells of either clean clothing or clothing worn by a Kamba man.

Clothing color also plays a role. In the same study, when the elephants saw red clothing not worn before, they reacted angrily, as red is typically worn by Maasai men. Rather than running away as they did with the smell, the elephants acted angrily toward the red clothing.

The researchers believe that the elephants’ emotional reactions are due to their different senses of smell and sight. Smelling a possible danger means that a threat is nearby and the best thing to do is run away and hide. Seeing a potential threat without its smell means that risk is low. Therefore, instead of showing fear and running away, the elephants express their anger and become aggressive.

Researchers say they have translated the meaning of gestures that wild chimpanzees (黑猩猩) use to communicate. They say wild chimps communicate 19 specific messages to one another with a “vocabulary” of 66 gestures. The scientists discovered this by following and filming groups of chimps in Uganda, and examining more than 5,000 incidents of these meaningful exchanges.

Dr Catherine Hobaiter, who led the research, said that this was the only form of intentional communication to be recorded in the animal kingdom. Only humans and chimps, she said, had a system of communication where they deliberately sent a message to another group member.

“That’s what’s so amazing about chimp gestures,” she said. “They’re the only thing that looks like human language in that respect.”

Although previous research has shown that apes and monkeys can understand complex information from another animal’s call, the animals do not appear to use their voices intentionally to communicate messages. This was a significant difference between calls and gestures, Dr Hobaiter said.

Chimps will check to see if they have the attention of the animal with which they wish to communicate. In one case, a mother presents her foot to her crying baby, signaling: “Climb on me.” The youngster immediately jumps on to its mothers back and they travel off together. “The big message from this study is that there is another species (物种) out there. that is meaningful in its communication, so that’s not unique to humans,” said Dr Hobaiter.

Dr Susanne Shultz, an evolutionary biologist from the University of Manchester, said the study was praiseworthy in seeking to enrich our knowledge of the evolution of human language. But, she added, the results were “a little disappointing”.

“The vagueness of the gesture meanings suggests either that the chimps have little to communicate, or we are still missing a lot of the information contained in their gestures and actions,” she said. “Moreover, the meanings seem to not go beyond what other animal convey with non-verbal communication. So, it seems the gulf remains. ”