题目内容：

Humans and dogs have been working together for thousands of years, and some scientists even believe the two species have been living with one another for thousands of years． While having a dog will not improve your health if you never wanted a dog in the first place, dog lovers can benefit from living with them．

1.    Most of us know the benefits of exercise, but it can be a struggle to find the motivation to get up and get moving everyday． A dog provides strong motivations, and can make your daily walk or run less lonely and more fun．Moreover, you'll bum extra calories when helping your dog walk and doing brief training exercises with your dog． For some people, going for walks alone is scary, but a dog can make runs and walks feel more secure．l know that with Ranger．I have to walk him every day, and he's always ready each morning．Sometimes we even have an afternoon or early evening walk, which is better for my health．

2.    There's no doubt that dog ownership does come with some stresses, from making sure you've applied their weekly bath to worrying if your dog will get along with the other dogs at the dog park． But the benefits of pet ownership more than outweigh these small stresses． Research shows that a few minutes spent petting an animal． lowers blood levels of the stress hormone, which contributes to tiredness, weight gain and aging, and your pet can help kill its negative effects． A few minutes playing with your dog every day also releases powerful ¨feel-good" hormones that continue to function in the bloodstream．

3.    Many people living alone worry about thieves, and a dog can help give owners a sense of security． Thieves are less likely to break into a house with a barking dog, and your dog can help you feel less lonely whether you're just spending the night by yourself or living alone long-term．If your dog is older and struggles to move around, you can still rest easy knowing that your dog will get to a robber before you do．

4.    People who have regular positive interactions with others tend to live longer and be happier, and pets provide you with a valuable opportunity to meet and interact with other people． Even if you're shy, it's easy to strike up a conversation with another person if you're both talking about your animals． Visits to the dog park and meet--ups with other pet owners also provide pet owners with opportunities for interactions．If you're still anxious about meeting new people, consider joining a message board or online group for people with similar pets to yours． You'll quickly find yourself making new friends in addition to learning a lot about your best friend - your pet!

5.    In a fast-paced, high-stress world, depression and anxiety are at an all-time high． But pet owners have fewer mental illnesses, and animals are even used as treatment for people suffering from mental illness． If you struggle with depression, an animal can help you avoid such problems． The exercise and stress release you get from spending time with your pet may even reduce the effects of depression． Dog owners are also less stressed than people who don't own dogs, and reduced stress is strongly related with lower blood pressure, a longer life span, greater happiness and improved health．