A reference regarding the pinnacle of creation would be any research project comparing the human species to an animal species like my cousin Chilly Chimp. At the moment, my favorite research paper is “Basic Math in Monkeys and College Students”
plosbiology.org/article/info:doi%2F10.1371%2Fjournal.pbio.0050328
The underlying thought of this research and other similar ones is that humans are different only by degrees from other animals. While the monkeys compared favorably with the college students, common sense would offer that there are humans who are higher on the degree scale when it comes to math used in physics. Music enjoyed in acoustically engineered buildings is higher in degrees than that of alley cats at night. Even though my atheist discussion partner changed alley cats to evening song birds, humans still had the edge in degrees. Thus, some could see humans as the pinnacle of creation based on the degree scale.
It is my observation that many non-theist morality principles are discovered through relativism and subjective thinking. Some seem to merge, e.g., as I understand Utilitarianism, social harmony would be an useful and productive goal. Basically, the various philosophers are considering the needs of the people near at hand. There is nothing wrong with that except when the near at hand clashes with the goal of those afar. Regardless, most people consider their special group of people as worthy of respect.
Now, if one wishes to help the O.P. then a common ground needs to be determined. The common denominator is the human person. When people of any faith or no faith look in the mirror, they still see a human person and not an alley cat or an evening song bird. This is why I consider that the basis for morality is that the human person is worthy of profound respect.
Blessings,
granny
The quest for truth is worthy of the adventures of the journey.