Much of our ethics stem from the genetic link to others of our species, our 'family' groups. If there is any difference between ourselves and Chimps it is our ability to include those outside of our immediate family in socially defined 'family' groups such as the evo group, the creo/ID group, the watering hole group, or any other group where the members are considered part of the 'family'. Once you get outside that family, our moral behaviour towards others resembles quite closely those of the Chimps.
The Chimp grouping is generally around 40 - 100 members where each member is part of the immediate or extended family grouping. Within that group children are taken care of by adults, arguments are mediated, and violence although frequent is generally non-life threatening. Chimps outside that group are treated quite differently. They are attacked, sometimes killed, even at times females are stolen. They may be taunted and if encountered alone tortured.
This behaviour is reflected in human grouping behaviour almost exactly. Our groups can encompass much larger numbers than those of chimps, such as Education level, City, State/Province, Country, Religion, Race, or even entire cultures such as our western culture which encompasses North America and Europe. We generally treat those of our group with respect while those belonging to outside groups can be treated quite differently. This occurs most noticeably during wars.
An interesting aspect of human ethical behaviour is our ability to create not just one group but multiple groups within groups, our interaction with the members dependent on the context, what is important to us in relation to the group identity. We expand or condense our ethical interaction, even our moral identity, with the members of each group contingent on how the actions of members in the larger group affect the members of the inner group.
For example, if you, the other Freepers, were to threaten my family I would react violently. My internal image of you would be as outsiders that I would have no compunction against putting out of my misery. I suspect each and every one of us would react the same. However, if you did not threaten my immediate family I would, as I do, accept you as part of my group, - as belonging in my inner sanctum - so to speak. If we as freepers were threatened by outsiders, such as those nasty little Democrats, I would immediately include all freepers as family and react against the outsiders by pummeling their pointy little heads. Again I suspect the rest of you would do the same. This expansion of group member inclusion, depending on the threat context, could eventually encompass all of humanity and beyond.
Even though chimps do not do this to the extent we upper apes do they do have the initial base of ethical treatment down pat. Family group not only matters to a great extent, but indeed determines the interaction between any number of individuals.
I guess what I'm trying to say in this mind addled mess is that we ain't so different from the other apes in our development of ethics.
It also means that our ethics will not be different whether we believe in a God or not. The religious absolute morals contained in so many religious texts are morals that were condensed from our natural behaviour and our cultural needs. The basic human ethic will always be part of our psyche with only slight culturally driven modifications.
By the by, the only reason culture influences our basic human ethic is population size. The larger and more anonymous the culture the more the society needs to modify and control the moral behaviour of its residents. Laws, laws, laws....
I now have a throbbing headache.
Ethics are rooted entirely in the presupposition some higher power defines what is correct for human behavior.
Examine my statement for logic (categorical or propositional). It will test true as a syllogism or true if tested in a Venn diagram using Aristotle's logic.
Objectivists don't know how to use it.