However, such souls are not karmically linked to the earth. They choose to work in harmony, and often return time and time again to share life with the shame humans, however, they do not create or incur karmic debt or 'lessons'. They are, for the most part, simply present to observe sentient beings, often in preparation to embarking on a journey of sentient ensoulment themselves. In this role, they form emotional bonds to people and places, and will often return frequently. In other words, as humanity evolves, many of your domestic dogs and cats will approach human or other primate opportunities in the future.
Physical form is an adventure that many, many souls choose.
It offers many opportunities and poses many unique challenges and situations. Entities that wish to embark upon a physical adventure as a sentient being will more often than not embark upon a 'courtship' with physicality. This 'getting to know you' period will be characterized by projections of itself into the various kingdoms, if not all of them. An Soul will project itself into a rock, a mountain, in a crystal, a river, the ocean, many, many different forms in order to aquaint itself with many physical forms, and with the earth itself. However, these 'projections' are not idle, for these souls will make up the Devic kingdoms and will learn from their service to the One.