Human friends make people live longer. Pets do not make a person live longer. Not eating pets does make you live longer. More research is needed on pets and longevity. [1]
Facts and myths about pets - [2]

Are Pets a Positive Substitute for Human Relationships?

There is some evidence that people who score high on pet attachment indices have fewer social networks (Stallones, Marx, Garrity, & Johnson, 1990) and more prevalent negative life events, such as bereavement (Nynke, 1990, as cited in Brown & Katcher, 1997). Another study found that cats appear to be an additional source of emotional support, especially for those participants who are strongly attached to their animals (Stammbach & Turner, 1999). According to Melson (2003) many pet-owning children derive emotional support from their pet because of the lack of human social support. - [3]
Pets facilitate social support (conversations with strangers when walking down the street)

Pets and Health