The evolutionary development of humanity does not occur in a straight line. Generally a power of capacity is introduced, it then needs time to get integrated into the human framework and then get disseminated widely to become a general capacity of mankind. During the integration and dissemination phase, there are periods of resistance to the new line of action, and even outright strong opposition based on an attempt to preserve the status quo unchanged. The capacity for reflective thought, for instance, is seen as a threat to the segment of humanity that acts primarily on vital impulse of desire.
As long as there is an established capacity at work, it acts within a framework that circumscribes and limits its action. This limitation is not generally seen or recognized as long as we remain immersed in the characteristic action of that power or capacity. It is only when we begin to reach the outside limits of a particular capacity that we begin to recognize both its inherent limitations and the need to achieve a new standpoint outside the framework, in order to bring to bear upon the problems created by the limitations we now can see, a new power, a new insight, a new capacity.
The Avatar does not take birth to simply work through the issues of integration and dissemination; rather, the Avatar takes birth at just those moments when a new capability, a new order of conscious force, a new spiritual impetus, is absolutely essential to break through the limitations, overcome the obstacles and resolve the inherent conflicts of the prior stage.
Humanity has had major lines of development occur within an existing framework that do not qualify as actions calling forth an Avatar. Sri Aurobindo provides the examples of the Reformation or the French Revolution where such actions, even exceptional new insights, could occur without the Avatar. “…they were not great spiritual events, but intellectual and practical changes, one in religious, the other in social and political ideas, forms and motives, and the modification of the general consciousness brought about was a mental and dynamic, but not a spiritual modification.”
“But when the crisis has a spiritual seed or intention, then a complete or a partial manifestation of the God-consciousness in a human mind and soul comes as its originator or leader. That is the Avatar.”
Sri Aurobindo, Essays on the Gita, First Series, Chapter 17, The Divine Birth and Divine Works, pp. 159-160