There's a lot of arguments about when humans first started keeping animals as companions. Some think most hunting peoples kept an animal or two and it may even pre-date humans as we know them. Others think it started with the domestication of dogs anywhere from roughly 13,000 to 30,000 years ago. After dogs would come domesticated animals used largely for food, milk, and labor, followed by cats kept as companions like dogs before them. As centuries have gone on many people have become bored with the same old pets and have explored the idea of domesticating more exotic animals as companions. These animals generally cost a good sum of money not to mention the cost of upkeep. Here are some of the more expensive animals to be kept as pets if "man's best friend" isn't exciting enough for you.

10. White-Tufted Marmoset - $2,000

It's become increasingly popular to keep monkeys and apes as pets and this little guy is one of the more popular primates to keep as a pet due to its tiny size. Don't let the size fool you into thinking these are easy critters to take care of. While food won't send you to the poor house other aspects of upkeep might. A vet familiar with the species is necessary to have on hand in case it falls ill. They also live 20 years on average so unless you teach them how to use the toilet (which might be hard considering their tiny size) you're looking at twenty years worth of diapers. Another downside of their size is they'll more than likely need to be caged at night so they aren't lost or even sat on when you wake up in the morning.

9. Rhesus Macaque - $4,000

The Rhesus Macaque, like the Marmoset, incurs high maintenance costs due to a long lifespan. These creatures have an average life span of 25 years. They also eat a varied diet much like a human that includes whole fruits and vegetables, nuts, and even some fully cooked fish and yogurt. Over time their diet has become rather varied due to humans keeping and breeding them mainly for experimentation.  If you're going to own one of these guys be prepared have the equivalent a son or daughter who has decided to not grow up, get  a job, and leave the house.

Rhesus Macaques will also need a specialized vet so their health care cost is higher than most domesticated animals. Be warned: Health care costs won't stop at the Macaque. They're known to carry a range of diseases so you might find yourself in and out of the hospital as well. They're also known to get agitated and attack their owners from time to time.

While a number of primates make the list, it should be noted it is not recommended. Another added cost is fines around $5,000 in areas that don't permit these types of animals as pets.