The caste system existed long before Europeans ruled India. Caste system has roots in the Vedic society.
"The varnas originated in Vedic society (c. 1500–500 BCE). The first three groups, Brahmins, Kshatriyas and Vaishya have parallels with other Indo-European societies, while the addition of the Shudras is probably a Brahmanical invention from northern India."
... "there is no evidence in the Rigveda for an elaborate, much-subdivided and overarching caste system" [1]
Caste and any discrimination is abhorrent, and like others have commented is a more recent phenomenon. In old times and today, anyone can become a priest/Brahmin by learning. [2]
The "Caste system" has European roots connected to the monopoly of one book, one god and the all powerful church.
In Europe the king was the representative of god and got his powers through the church. Then came the merchants, landowners who funded the state. Artisans took the next rung. The unskilled workers took the most menial jobs came last.
We call this today as the class system but this was the original caste system imported from Europe and applied on the native population of India.
While one can not deny that there were/are different communities and a kind of class hierarchies in India just like in the rest of the world. The rigid caste system is actually the work of the Church. In India each community had its own gods and its own chieftains and priests.
As with any traditional profession in India, tree climbing is caste based and caste is based on birth. A persons profession is decided based on which family they are born into. In every village or town, there will be a family who does this job generation after generation. The castes who perform low level jobs such as tree climbing, weaving, farm labor etc. are collectively known as the Shudras. Shudras are the lowest level in the caste pyramid and were historically oppressed and were denied basic rights such as education.
Being illiterate and unorganized, they don't have any negotiating power, which is the reason for lower pay. They also had no choice because they were told that they were "born" to do this work.
The reason for shortage of harvesters is that, the latest generation does not want to take up the family job because of poor pay and low status. The younger generation wants to get educated and move to big cities to find better jobs, thanks to the progressive reforms and loosening of the caste system in the recent decades, at-least in urban areas. The current generation of tree climbers will probably be the last or second last generation who does this job.
"The varnas originated in Vedic society (c. 1500–500 BCE). The first three groups, Brahmins, Kshatriyas and Vaishya have parallels with other Indo-European societies, while the addition of the Shudras is probably a Brahmanical invention from northern India."
Source: https://en.wikipedia.org/wiki/Caste_system_in_India#Vedic_va...