They usually change and change over time. Ideas about whether certain behaviors are moral, such as having premarital sex, engaging in same-sex relationships and using cannabis, have changed over time. However, it would be misleading to view morality only as a result of evolution. Although some human traits, such as skin color, are determined solely by our genes, morality is very different, since it is also determined both by our nature and by the society in which we live.
Many moral rules and values vary between different cultures and also change over time. For example, bullfighting is considered a cruel form of entertainment or even torture for animals in North America and in most European countries, but they are still very popular in Spain and Colombia, where they are considered a form of expression, despite the obvious suffering of the animals. An example of a change in morality over time is our attitude toward slavery. Most people in today's world think it's immoral to have slaves, but that wasn't the case a century ago.
The research on moral change conducted by three Australian psychologists is an interesting attempt. It's good to see some strong statements about attitudes related to morality through empirical research compared to abstract philosophical writings on morality. While this attempt to map the changing moral values of a society is interesting, there are some fundamental problems in the assumptions that make such a study possible. Tracking moral values through the use of moral terms in published books (those in Google's database) is interesting, but it can say little about social positions on morality.
Another way to understand the role that the brain plays in morality is to use magnetic resonance imaging or electrophysiology (EEG) scanners to obtain images of the brain as it works. Hopefully, science will also help us to understand why some people, such as psychopaths, cannot act morally and to discover ways to help them. If they opposed it and defended a personal moral code, they were opposed and even accused of being evil. Therefore, these early trends (in childhood) are considered the basis of adult morality, but they are not exactly the same as it.
In these experiments, neuroscientists presented children and adults with moral tasks or activities and observed which regions of the brain were activated while the participants performed these activities. Finally, chemicals in the brain can also be explored to see if they might play a role in moral behaviors (see box). In addition, the uniformity in the use of certain moral terms may say little about having equivalent moral beliefs.