How long have we had a soft spot for dogs? A reanalysis of a prehistoric dog that was buried with two people reveals that the animal had experienced several bouts of potentially fatal illnesses, but it survived.

The Bonn-Oberkassel dog was unearthed a century ago in Germany. It was buried alongside the remains of a man in his 40s and a woman in her 20s, and all are about 14,200 years old. The animal probably lived long after dogs were domesticated, as evidence for this process stretches back at least 32,000 years. But the Bonn-Oberkassel dog is still important because it is the oldest known dog burial, says Luc Janssens at Ghent University in Belgium, which means it can help us understand why dogs were domesticated.

A common assumption is that prehistoric humans domesticated dogs to put them to work, helping with hunting, guarding settlements or used as pack animals for transport. However, Janssens and his colleagues say there is an alternative: we domesticated dogs simply because we liked having them as pets.

Their reanalysis of the dog reveals it had terrible oral health. Although only about 7 months old when it died, the dog had experienced three bouts of severe illness when it was between 19 and 23 weeks old. “The first infection would be enough to be fatal to most dogs in the wild,” says Janssens. “Then came two extra bouts, and the probability that the animal would survive without human help is very, very low.”

The researchers argue that the sick puppy would have been unable to do any useful work. In fact, keeping it alive was probably an unpleasant burden on its owners: it might have vomited 吐）regularly and had diarrhoea（腹泻）.

Its survival hints that its owners felt a bond of friendship，just like a modern dog owner. “This is the first time we find evidence to suggest that dogs were treated emotionally without expectation of any benefit,” says Janssens.

Bonds of friendship may have helped drive domestication, says Mietje Germonpre at the Royal Belgian Institute of Natural Sciences in Brussels. “Baby wolves could have been ‘adopted’ to provide company,” she says. “This raising of baby wolves as pets could have been a stepping stone，together with other motivations, on the pathway to the domestication of the dog.”

It is significant that the dog was buried, says Pat Shipman at Pennsylvania State University. 、‘When you start burying animals，it indicates a special relationship of some kind.” Nevertheless， Shipman says we can’t rule out the possibility that the Bonn-Oberkassel dog was - or could have become - a useful working dog, which might explain why its owners cared for it through its illness, in the hope that it would recover.

Owning a dog is associated with a significantly lower risk of heart disease and death, according to a comprehensive new study published by a team of Swedish researchers on Friday in the journal Scientific Reports.

The scientists followed 3.4 million people over the course of 12 years and found that adults who lived alone and owned a dog were 33 percent less likely to die during the study than adults who lived alone without dogs. In addition, the single adults with dogs were 36 percent less likely to die from heart disease.

“Dog ownership was especially prominent as a protective factor in persons living alone, which is a group reported previously to be at higher risk of heart disease and death than those living in a multi-person household,” Mwenya Mubanga, a Ph.D. student at Uppsala University in Uppsala, Sweden, and the lead junior author of the study, said in a statement announcing its findings. The link between dog ownership and lower mortality(死亡率)was less pronounced in adults who lived either with family members or partners, but still present, according to the study. “Perhaps a dog may stand in as an important family member in the single households,” Mubanga added. “Another interesting finding was that owners of dogs which were intended originally for hunting were most protected.”

The study, which is the largest to date on the health relations of owning a dog, suggested that some of the reasons dog owners may have a lower risk of mortality and heart disease were because dog owners walk more. “These kind of epidemiological (流行病学的)studies look for associations in large populations but do not provide answers on whether and how dogs could protect their owners from heart disease,” Tove Fall, a senior author of the study and a professor at Uppsala University, said in a statement

“We know that dog owners in general have a higher level of physical activity, which could be one explanation to the observed results,” Fall added. “Other explanations include an increased well-being and social contacts or effects of the dog on the bacterial microbiome(微生物菌群) in the owner.” Fall added that because all participants of dog owners in Sweden or other “European populations with similar culture regarding dog ownership.”

Humans spend about one third of their lives sleeping. But some mammals (哺乳动物), like the northern elephant seal, survive with much less sleep.

Researchers in a new study described the unusual sleep pattern of these ocean animals. They found that when these mammals go to feed on trips that can last seven months, they sleep just two hours each day. Those two hours of sleep are made up of short moments of rest lasting only 10 minutes each as they dive deep to avoid predators (捕食者). The only other mammals known to get so little sleep are African elephants.

The researchers placed a head covered with sensors on the heads of the seals that they studied. The sensors recorded sleep signals created by the seals’ brains and heart rate. The sensors also recorded the animals’ location and depth beneath the sea.

The researchers studied female seals because they go out on long open-ocean trips while males feed in coastal waters.

During dives lasting about 30 minutes, the seals went into a deep sleep called slow-wave sleep while keeping a controlled downward movement. When they then experienced rapid-eye-movement (REM) sleep, the seals fell into a turning pattern. Then, at the deepest point of their sleeping dive — up to 377 meters deep — they wake up and swim back to the surface.

Terrie Williams is a scientist at the University of California at Santa Cruz who helped write the study. She said, “It is remarkable that a wild animal will fall into deep, paralytic REM sleep when there are predators on the hunt.” She added that the seals solve this problem by going into deep sleep in the deep parts of the oceans where predators usually do not hunt them.

Williams said the brain’s ability to control awakening the sleeping seals at a depth before they drown is also a discovery about how mammalian brains work. She commented on this saying that it shows the survival control of the seals’ brains.