Those of us who grew up watching Lassie understand that collies were bred specifically to rescue small boys from the inky bowels of abandoned mineshafts, or upturned dinghies about to plummet over vertiginous waterfalls. Likewise, Flipper taught us that—contrary to Richard Dawkins’ mercenary, dystopian planet of the genes—Nature is in fact a benevolent force, where good is as palpable and cardinal as earth, wind, fire or water.

When Dawkins published The Selfish Gene in 1976, he upset more than the pious; he affronted our notion of nobility. By recasting us—and all living things—as robotic slaves, compelled by our genes to find their next vessel, he reduced our existence to that of genetic messengers. We greatly prefer to believe that life is more virtuous, more mean­ingful, than that.

In 2004, lifesaver Rob Howes, swim­ming off Whangarei’s Ocean Beach with his daughter Niccy and two of her friends, was surprised when a pod of bottlenose dolphins began circling them, slapping the surface with their tails and herding them closer together. When he drifted from the group, he told the New Zealand Press Association, two of the bigger dolphins herded him back, and that’s when he spotted a shark.

Howes said the three-metre great white had been heading towards him, and the dolphins had deliberately put themselves in harm’s way. “They had corralled us up to protect us,” he said at the time.

The human record brims with accounts of people who owe their lives to a benevo­lent bestiary: after children fell into their enclosures, zoo gorillas have shielded them from less-compassionate inmates. Pigs have plucked infants from swimming pools. A British girl insists a Thai elephant saved her from the maelstrom of the Boxing Day tsunami in 2004.

Across wider nature, though, altruism is measured in the ledger of evolutionary biology, not in newspaper-column centimetres but in reproductive success. Here, altruism is functional, not moral, and means that one creature’s beneficence may boost the breeding potential of another, at a cost to itself. This would sound like a matter of conscious choice, were it not for the fact that ‘altruism’ is performed every day by millions of organisms with no capacity for rational thought. Sterile worker bees, ants and termites clearly have nothing to lose or gain reproductively, but devote their lives to propagating instead the DNA of their queen—a charity even Darwin couldn’t fathom.

Altruism at the individual level can never endure­ because it disadvantages that individual, natural selection would soon stamp it out­ but a group of, say, vervet monkeys or meerkats, comprised mostly of altruists prepared to put their own interests aside for the greater good, might well do better than a group of egocentrics. If those two groups compete for food or territory, then the altruists’ genes should flourish, allowing the behaviour to evolve. As individuals, the altruists would be doomed, but as a collective, they will out-compete their selfish rivals.

Vampire bats, for instance, are known to share some of their night’s bloody takings with others in their group that didn’t fare so well. Begging behaviour in the bats is well entrenched and documented, and an individual has recourse to it any time his or her luck fails. But why?

It turns out that blood is pretty poor fuel for a mammal with a high metabolism that has to flap to get anywhere. To survive, a vampire bat must consume at least 50 per cent of its own body weight in blood each evening. But up to 30 per cent of bats in observed colonies make fruitless forays on a given night. Two bad nights on the trot, and the creature will die.

Begging and gifting arose as a way of creating some slack in a lethally tight budget. However, the bats’ lending criteria are strict:studies have shown that they overwhelmingly share only with known roost-mates, which are usually relatives. Furthermore, such buddy systems are mostly confined to individuals with a proven track record of reciprocity, and the risk is well managed—a bat close to starvation will gain a 12-hour stay of execution from a donation, whereas the donor, having recently fed, loses much less than 12 hours’ worth of fuel, and still has 36 hours to find another meal.

Whenever an altruistic creature shares food, or alerts about a predator, you can be pretty sure the beneficiary carries at least some of its genes—a behaviour known as ‘kin selection’. This is how an altruistic gene can, in principle, spread by natural selection­ altruism promotes the spread of altruism.

Dawkins’ disciples offer such calculating kin selection as evidence for his ‘gene’s­eye-view of evolution’, in which mercenary genes compete for global domination, using us hapless individual organisms as mere couriers. But other theories contend that an individual’s reproductive fitness also confers a benefit on the fitness of every other creature in the population, a concept called ‘inclusive fitness’.

All the same, on some nebulous shore between altruism and kin selection, sacrifices are sometimes nihilistic: in a bizarre transac­tion called matriphagy, some female spiders actually invite their offspring to devour them. Studies of Amaurobius ferox showed that, having eaten their mother, spiderlings were two and a half times heavier, moulted sooner and faster, and gained a larger body mass before heading out into the world. These enfants terribles were also more successful hunters, and enjoyed a higher survival rate. Studies that separated mothers from their broods before matriphagy found that while they produced second clutches, the rescued A. ferox mothers achieved lower overall reproductive success than those that gave up their lives.

Our own idea of altruism is, thankfully, different from a spider’s: when we toss a coin into a beggar’s cap, or wave someone into a queue of traffic, we know it’s unlikely to boost our reproductive success. Instead, say some dispassionate psychologists, we’re simply ducking our responsibilities to ourselves—a behaviour they call “ego defence”—in which we suppress our own anxieties by helping others. Taking up emotional residence in someone else’s life, say researchers, helps us avoid acknowl­edging or dealing with the issues in our own. Carers of the disabled or elderly, for instance,have suffered anxiety and distress when their role ended.

Then there’s the view of Nietzsche, who proposed that because an altruistic act makes us feel better about ourselves, lifts the esteem with which we might be regarded—or simply insures against the guilt of having done nothing—it is only ever done, by definition, out of self-interest. Maybe; but what about anonymous donors? They get no recognition for their kind deeds, and clearly prefer it that way. In 2006, researchers wired up the brains of 19 volunteers who were given money, then offered the choice of anony­mously donating it to a charity, or keeping it. The MRIs revealed that study subjects who gave the money away again experienced ‘warm fuzzies’ in the same reward centre of the brain—the nucleus accumbens—that was stimulated when they received the money in the first place.

Another MRI study the following year found that some people act selflessly, not for neural reward, but because they figure it could be an investment.

Study subjects were found to subconsciously assess a social relationship before doing someone a favour, which suggests that we run a quick cost-benefit exercise to establish whether that someone would do the same for us if our fates were reversed.

And that finding helps illuminate the origins of altruism in humans, which are starting to look suspiciously like kin selec­tion all over again. A study at the Santa Fe Institute in New Mexico analysed the genetic relationships within groups of contempo­rary hunter-gatherers, including Australian Aborigines, Siberian Inuit and some African tribes. The data provided the blueprint for an estimate of genetic variation among ancestral hunter-gatherers from the Pleistocene and early Holocene, between 150,000 and 10,000 years ago. As individuals, the study found, those early humans were probably more closely related than previously thought. But comparisons between discrete groups of those people found much bigger genetic differences than expected: precisely the sort of social structure that would have favoured altruistic behaviour. And like the present-day volunteers, neolithic foragers would have carefully calculated the cost of, say, defending the group against rivals, against the benefit of receiving shared food should they be injured.

Maybe it is just primal reckoning, but let’s not cheapen altruism: last year, New Zealanders gave nearly $800 million and donated more than a million hours of their time to charities. Altruism may not separate us from the animals, but it’s noble just the same.