Complex animal societies are most successful if members minimise harms caused to one another and if collaboration occurs. In order to promote this, a moral structure inevitably develops. Hence, morality has evolved in humans and in many other species. The attitudes which people have towards other humans and individuals of other species are greatly affected by this biologically based morality. The central characteristic of religions is a structure which supports a moral code, essentially the same one in all religions. A key obligation to others is to help to promote their good welfare and to avoid causing them to have poor welfare. Human views as to which individuals should be included in the category of those to whom there are moral obligations have broadened as communication and knowledge have progressed. Many people would now include, not only all humans but sentient animals, e.g. vertebrates and cephalopods, as well. Amongst sentient animals, coping with adversity may be more difficult in those with less sophisticated brain processing.