Duties according to individual nature - not birth

The following is from the Bhagavad Gita:

“Brahmanas, ksatriyas, vaisyas and sudras are distinguished by the qualities born of their own natures in accordance with the material modes, O chastiser of the enemy.

“Peacefulness, self-control, austerity, purity, tolerance, honesty, knowledge, wisdom and religiousness–these are the natural qualities by which the brahmanas work.

“Heroism, power, determination, resourcefulness, courage in battle, generosity and leadership are the natural qualities of work for the ksatriyas.

“Farming, cow protection and business are the natural work for the vaisyas, and for thesudras there is labor and service to others.

“By following his qualities of work, every man can become perfect. Now please hear from Me how this can be done.

“By worship of the Lord, who is the source of all beings and who is all-pervading, a man can attain perfection through performing his own work.

“It is better to engage in one’s own occupation, even though one may perform it imperfectly, than to accept another’s occupation and perform it perfectly. Duties prescribed according to one’s nature are never affected by sinful reactions.