On the Tendency of Varieties to Depart Indefinitely from the Original Type

I agree with this reading.  In the animal world there are certain species that will develop in different environments, yet are exactly alike, and this determines how they adapt to their environment in order to survive.  A cat, for instance, has the natural instinct and ability to hunt for food by crouching low to the ground and moving slowly to obtain a close proximity to their target just before pouncing on it.  This is then followed by the use of their claws and sharp teeth to capture, kill, and eat their prey. All cats, whether in the wild or domesticated, have this ability that is mainly instinctual, but also learned from their parents.  What differs the two is the environmental needs for these behaviors and the way in which they adapt to them.  The natural environment of a wild cat such as a leopard, tiger, or puma requires them to make use of these behaviors on a daily basis in order to survive.  Where the domestic cat which is fed and cared for by us humans,  has no need for this as its environment does not require it.  The difference in environment and needs for survival is what makes these cats stray from their original parent specie and in some form recreate itself into a subspecies. 

I think this also applies to the human race.  Our environment and how we adapt to it determines what is required of us in order to survive.  Upon our birth, our parents mold us by caring for us, teaching us the knowledge they possess, and raise us to be much like they are.  They introduce us to things like customs, human interaction, behavior, religion, morals, and values.  Once we mature and become independent, we then begin to adapt ourselves to the environment we choose to live in thus branching out from what we were first taught and introduced to.  Some of the ways of our parents still are carried on to who we become as adults, but its inevitable that we do form our own individual character and choose our environment.  It is then that our choice of environment determines our needs for survival.  People who have chosen to live the street life and doing the wrong thing, often resort to violence, theft, and a life of struggling to live.  Where people who choose to live their life in a positive way, holding a stable job, maintaining a roof over their heads, and so on do not need to resort to violence or theft as their environment doesn't call for it.  They have made it possible to have their resources available and easily accessible to them. In sum, varieties do have the tendency to depart indefinitely from the original type.