Animals were(I would say HAVE BEEN) part of human beings lifefor long time ago .The (Don't use articles when you want to generalize) Investigators are convinced that owning domestic animals have many benefits. Some people are (have?) the opinion that too much money is now being spent on (not quite sure but I think you must put "A" here) variety of pets such as dogs, cats, birds, and so on. It is argued that keeping pets is not reasonable, while there are hundreds of famishing people around the world. Although, it is not easy to say the exact answer, as this is one of the controversial issues in our modern world. In my point of view, it includes both negative and positive effects.
One of the most obvious characteristics of a person keeping domestic animals is that he/she becomes more attentive than those of others. For instance, in my early years I grew up with dogs, cats, hamsters and tortoises as my companions. Personally, I think that when I became an adult, I became more attentive to others. Furthermore, many researchers have found that pets can be companion for people who would otherwise be living alone, and not just elderly. There are at least two benefits here: Dogs need lots of exercise, which is beneficial for health of the owner (The owner's health). Also, while out walking (Walking out) there is opportunity to meet people, thus decreasing isolation and loneliness. As a fact, like everything, there are disadvantages.
The most dangerous thing (about) keeping pets is spreading infections and diseases. According to science, the saliva of pets (pets' saliva) compounds (Saliva is the noun) different types of bacterium (plural form: BACTERIA) and coccus (plural form: COCCI) . Usually, pets daily clean themselves with the help of their beak or tongue. And it is very frightening for those people who keep them. Because, pets show their love by licking their masters. Besides, people consider that it is not rational to spend more and more money on pets to treat dogs like children. (not sure but I think you should separate theses clauses with a comma instead of a point) While people are dying of hunger all over the world. For instance, in many rich countries domestic animals are given better food to eat than poor people. Those who hold this point of view would seem that human beings are not so important than (AS) animals. In addition to this, it is not hygienic to keep pets. Because, there are so many garbages (GARBAGE is its own plural) due to pets. Birds throw their hackles, cats and dogs their wools.
However, I believe that pets have a lot of benefits, teaching things such as attentiveness, responsibility and kindness. But people should think twice before spending huge amount of money for pet's pleasure. There are thousand of people who are dying of hunger. Human beings should not leave poor people in their difficult moments. As we are humans, we should behave towards others accordingly (TO) our own values and needs.
I am not native! I hope this will help you! write if you have any question! Nice job by the way.
Student or Learner