It may have been the Sophists of ancient Greece who first put humanity on the “map” giving humanity a philosophical context. It was a step away from the pre-Socratic philosophers who were mostly interested in the phusis, the physical elements of nature. Yet after Protagoras, mankind was suddenly made the “measure of all things” and was a subject worth studying.
Socrates, in fact, realized that every human being had a universal capacity, regardless of sex or social status; everyone could reason and through logic and the constant questioning of values, they were able to attain states of truth and wisdom. One of the points Socrates may not have completely agreed with is the Sophist claim that truth is relative and mostly depends on one's culture and upbringing.
The practical Romans were less interested in the study of humanistic values, but preferred to look for bravery and heroism in each individual, in addition to politics and rhetoric. They were more interested in how to manipulate people and gain control over them and how to conquer various other territories of the endless seeming Roman Empire.
The power-hungry and greedy Roman emperors and nobility gradually fell to the new surge of a simple Christian faith. These followers of the new “sect” had built on stoicism, and, as a result, gained power over many of the Roman territories. This “new” philosophy may have been popular precisely because of its humanistic values. All were equals and equally deserving of the heavenly afterlife, as long as they were morally sound. In fact, the weak and suffering were given a special place in Christian thought.
The religious movement crystallized into a powerful structure with the Catholic Church according humans a special place in their cosmology, but there were still various hierarchies with God at the top, followed by the priests, while the large masses of illiterate people ought to follow each and every command of the scripture-savvy elite.
At the same time, mankind was tainted with sin, something that went back to pre-human times of Adam and Eve according to the Scriptures. And the equality that had existed at the surge of Christianity was tipped over in favor of the patriarchy. Crusades took place for the dominion and supremacy of one's beliefs, and the Holy Inquisition ensured that blasphemers and liberal men and women got what they deserved. In all this, humans were merely pawns, and what mattered most was to overcome carnal pleasure and to turn into a saint.
The Middle Ages ended with the advent of the Renaissance, and again we were faced with a return to an era of humanism, which was self-consciously and deliberately influenced by ancient Greek and some Roman philosophy. But they took it a step further. Mankind was not only the measure of all things; they had become a marvelous god-like creature that had an immense amount of potential. The Renaissance humanists were overly optimistic in their outlook and did not cease praising the greatness of mankind and their accomplishments.
This led to radical changes in society and religious structure with the Reformation, and unfortunately demonstrated that the Renaissance humanists had overstated the greatness of mankind since humanity continued to engage in bitter national and religious wars. The Enlightenment had a more cautious approach; they praised mankind's ability to reason and believed that with reason and the growing branch of science, one could actually find peace in the world.
During this time, the humanitarian aspects had their strongest impact, and slavery was finally condemned as an unjust practice. Mankind was born free and had natural rights, something that even today, at least theoretically, is strongly supported by the international committee.
The Romantics rebelled towards a world where reason was predominant, yet feelings and intuition were not given much value. They wanted passion over logic and preferred drama over peaceful outcomes. A person who bridled with passion and fervor was seen as a true human being as opposed to the cold automatic reflexes of rational thought.
Finally, we move to the existentialist phase which defined humanism in terms of human responsibility. This may be the Renaissance and Enlightenment minus the optimism. Each has to find his or her own truth because existence precedes essence. Humanity becomes their own definition through their acts. They are free, but with it come angst, indecision, fear and insecurity. It is a modern conception of humanity that has shed some of their previous religious values; now people are left with only their own judgment.
As we can see, humanity has come a long way. Humans have become the focus of various studies, whether in philosophy, political science, psychology, or biology. We may have come to understand several processes better, but we are still miles away from understanding what it is that makes us human, what human nature really is. But fortunately all these humanist tendencies have gradually led to a more tolerant and accepting worldview, and we can only hope to build on and contribute to this age-old track.