During this pandemic we witnessed selfless behaviour by thousands of health care workers around the globe, who at great risk to themselves, struggled daily to save lives in a battle with a virus, with no end in sight, especially in crowded, poor, under-resourced regions of the world.

Such was the risk that many health care workers died and others continue to struggle with the emotional toll of witnessing so many tragedies, despite their best efforts.

But where does such day-in, day-out, strength, resilience and determination come from, to care for so long, for so many, at such great cost to themselves?

Some suggest that selfless behaviour is rooted in traditional values passed on by families, cultures, religious beliefs and backgrounds. Or is such altruistic behaviour driven by a strong professional sense of duty, obligation and commitment? Or is there something more basic at work?

Is the impulse to care for others at some risk to oneself, innate in some fashion, to being human. And going further, is caring for others, a biologically determined behavioural default widely shared with other highly social species?

Or is the “why” behind selfless behaviour far more complex and personal and related to some or all of the above or perhaps other factors? You may want to chime in on this one.

The precise evolutionary roots of moral behaviour are unknown. Perhaps it all began with maternal care – the need to care for the defenseless young – which later broadened to embrace other needs in the community, as the size, complexity and dependence on others increased in social groups.

The notion that moral behaviour has deep and widely shared evolutionary roots, comes from studies of other social primates such as chimpanzees, bonobos, rhesus monkeys and baboons, and extends to other highly social species such as whales, porpoises, elephants.

Even small-brained but highly intelligent corvid birds, such as ravens, can read the intentions of others and possess a sense of fairness (and unfairness).

Chimpanzees, for example, often help those unable to fend for themselves, by providing food, shelter and protection, and willingly provide long-term care for chronically disabled members of their troop, for months and even several years. Of course, chimpanzees can be malicious and merciless to the point of savagely killing members of neighbouring, competing troops.

But then again, humans can be calculatingly malicious, merciless and savage toward one another, something we are reminded of almost every day by news reports of domestic and racial abuse, instances of police brutality and even killings, or, as continues to happen in the Mediterranean, refusals to help boatloads of refugees at sea, with the result that many drown. The list is much longer.

The same two sides of the behavioural coin seen in chimpanzees and other animals, has been observed in our close cousins, the neanderthals in whom fossil evidence reveals both examples of violence and moral behaviour.

Evidence of long-term care is based on the observation that some neanderthals managed to survive for several years after grievous injuries and disabilities, which must have required continuing support from others in the troop for many years.

What was surprising for me was to learn that similar long-term care was provided by many of our paleolithic ancestors, including various australopith species from as early as four million years ago to as recently as a little over a million years ago.

And likewise, for several examples of homo erectus, dating as far back as one point seven million years ago to several hundred thousand years ago, and several examples of long-term care involving pre-neanderthals in Spain about 400,000 years ago.

The cumulative fossil evidence strongly suggests a mixed record – examples of great violence and other examples of long-term care – the evidence for both of which, reaches back several million years, long before there was evidence of symbolic thinking, except in the skill with which tools and weapons were fashioned – but long before any figurative art.

Social intelligence – making sense of the behaviour of others in your group – probably had similar deep evolutionary roots because it emerged in so many distantly related animals.

Perhaps it was this social intelligence that drove the evolution of moral behaviour – the need to work together for the common good – to insure the survival of the group. That makes sense to me.

Finally, a word about good and evil.

For our primate relatives and our ancient ancestors, good and bad behaviour are biological features of the species as a whole and individuals within the group, not forces beyond their biological nature as animals.

Comparatively speaking, the emergence of monotheistic moralizing gods was a late acquisition – about 5,000 years ago in Egypt and the Indian subcontinent, according to an excellent international study reported in the journal Nature in 2019. Of course, the whole notion of supra-human agency playing a role in good and evil was probably much older.

Then there’s the matter of artificial intelligence and whether AI could ever be considered sentient and moral. Let’s leave those thorny questions to another day.

Dr. William Brown is a professor of neurology at McMaster University and co-founder of the Infohealth series at the Niagara-on-the-Lake Public Library.