Morality various from people to people. Even without religious influence, there are certain ways people like to be treated and will actively petition/force/get others to agree with this.
Human males have less empathy towards the children of others than females do. In past ages, it was moral to slaughter the children of an enemy to prevent that enemy from ever growing strong enough to retaliate.
Love, affection, considerate treatment, assistance, emotional support, loyalty, fidelity, avoidance of possessions being taken by others, cooperation are all pretty well basic instincts. So is the protection of off spring.
In ancient times, even mentioned in the Bible, apparently siblings found it acceptable to cheat each other out of power, even to exterminating one and another. Some of that still goes on today. In some cultures, the family bond is more powerful and does not tolerate this, which creates a unified front against any hostile forces and gives the family a greater chance of survival.
In some cultures, it is moral to have sex play among siblings, but not to produce children. Even that was not considered immoral all of the time, but was eventually enforced as being so because of the potential for producing defective off spring, plus a race is strengthened with a variable, ever mutating genetic pool, not a narrow one. So, not having sex with your brother or sister is less based on morality than on racial strengthening.
Killing humans opens various conflicts. In the past it was acceptable to kill those who angered or endangered you. Called self survival. You have a problem? You exterminate the problem. Good for you, but bad for them. Killing competitors without consequences is generally unacceptable because then anyone can kill anyone for any reason, which eventually weakens a comprehensive society. Plus, if you kill Joe, then Joe’s friend can knock you off and your friend can knock Joe’s friend off, then Joe’s friend’s son will kill you friend’s son and, well, you get the picture.
Plus, you can knock off potential innovators of society. What would have happened had Edison, who was not the most agreeable person in the world, was knocked off before developing ways to make and transmit electricity? What if Rospierre (pardon spelling) had been killed before initiating the French revolution? Unhampered killing is dangerous for society and can make things real complicated, so preventing this with various forms of retaliation is created. Morality or common sense?
Most religions set down guidelines designed to improve the societies they affect. Some religions sanction killing in the name of the religion. Morality or a human instigated way to promote the desired religion and to circumvent common laws made by the general masses?
Morality seems to vary according to the influences on general society at any given time.
At one time, taking over a company that did not want to sell would be considered immoral. Technically, the opposing company is stealing the other company or forcing their will upon them. Today, it is considered acceptable practice to steal a company away from those who built it.
Even stealing things. Is it immoral to do this or is it not acceptable because people want to keep what they have?
Some people consider alcoholic drink immoral but in other areas not only is it considered moral, but virtually a sign of being part of society. Now, could strong drink have evolved into being considered immoral because of it’s addictive and destructive effects on some people? If that is the case, then becoming considered so would be actually an accepted survival belief. Cut down the drinkers by making it a bad thing and you cut down on the incidents of tremendous harm it can cause, which then is much better for society as a whole.
Morality could be a commonly desired form of actions and considerations created and enforced by a society to improve the lot of its members and provide universal stability and to promote various forms of intellectual and species progress and development.
Religions might just enforce these sets of rules. Almost all basic religions have similar commandments, which indicates a universal desire to be treated within certain ways and various punishments designated for failing to follow these rules, which act to keep people in line.