Perhaps is Ayalas theory a help in this discussion.
Francisco Ayala, a professor of ecology and evolutionary biology at the University of California, Irvine, has proposed a Darwin-inspired explanation of how human morality might have evolved in 2010.
Read more at:https://phys.org/news/2010-05-professor-complex-evolution-human-morality.html#jCp
“Many biologists, including sociobiologists, argue that morality is a biologically determined trait,” Ayala told PhysOrg.com. “Most philosophers and theologians see morality as a product of cultural evolution and/or religious faith. I distinguish between the ‘capacity for ethics,’ which is biologically determined as a result of biological evolution; and the ‘moral codes’ or ethical norms, which are largely outcomes of cultural evolution, including religious beliefs.Ayala further explains that the capacity for moral behavior is not adaptive in itself, but it is a consequence of a higher intellectual ability that is adaptive, being directly promoted through natural selection due to its ability to improve survival rates (such as by allowing us to construct tools, develop hunting strategies, etc.). Ayala identifies three necessary conditions for moral behavior that could have evolved with intelligence: the ability to anticipate the consequences of our actions, to evaluate such consequences, and to choose accordingly how to act. While overall intellectual capacities evolved gradually, he speculates that the three necessary conditions for moral behavior only came about after crossing an evolutionary threshold, as they require abilities such as the formation of abstract concepts. And only after humans possessed all three abilities could we possess a moral capacity.
https://www.youtube.com/watch?v=KLgKC1snRLc
Here a German articel about the same subject
http://www.spiegel.de/wissenschaft/mensch/ursprung-des-guten-die-moral-als-nebenprodukt-der-evolution-a-692653.html
For me the best article about orgin of ethics is this
http://www.swr.de/swr2/programm/sendungen/wissen/ra1-ursprung-der-ethik/-/id=660374/did=15253686/nid=660374/174ogtb/index.html
with this comment about babies:
"From the beginning they have a moral sense and a moral knowledge about good and evil. But in many of them it has not yet become an inner personal need to evaluate the world morally urgently and act accordingly."
I attached a google translation from this article by M. Hubert.