A passer-by spots flames pouring out of a house and without hesitation dashes inside and rescues a child. Not surprising. Every language has a word for such an act. We call it "heroic."
The instinct to behave altruistically--to do something in which the risk outweighs the benefit to the performer--distinguishes human beings from most of the animal world perhaps as much as the ability to speak or to use tools. A good deal of what we value in civilization depends on variations of this behavior. I scratch your back today; you scratch mine tomorrow. Behavioral ecologists call this "reciprocal altruism."
This behavior in non-human animals may be the evolutionary seed of the hero's action. Recently, some biologists have suggested that genes, or clusters of genes, influence altruistic behavior. If a genetically determined behavior is beneficial, over time it will appear in more and more members of the species.
When the theory of reciprocal altruism was presented 15 years ago by Prof. Robert Trivers, now at UC Santa Cruz, it created a storm of controversy. At UCLA last month, at the Workshop on Reciprocal Altruism, 12 leading researchers met to examine the idea in the light of a decade of fieldwork.
Trivers himself led the discussion, confident that new discoveries had verified his theory. He enlarged upon its ramifications, admitting that each animal takes some risk of being cheated if its back ends up not being scratched in return. But then, Trivers said, smiling, "evolution has met the challenge with the co-evolution into the human species of a sense of fairness and justice."
Theory is fine, but in the field, other participants in the workshop pointed out, such apparently selfless acts can be called altruistic only if they occur between strangers. Otherwise, they fall into the category of "kin selection," which is not selfless at all. When an animal feeds a sibling or a cousin, she is acting in the interest of an individual who shares many of the same genes, and is in turn selfishly helping to perpetuate her own genetic heritage. So if our hero had saved his cousin from that burning house, he would not have been completely unselfish.
The same can be said for couples, such as sea gulls, that live together and have a common interest in the well-being of their offspring. When the male brings fish to his mate, it is not altruism; he is providing fuel for the female who is incubating his eggs.
Earlier generations of scientists had to be content with observing wild animals and guessing at how they were all related. Today's biologists, using sophisticated techniques, sneak into the nests of birds, bats and ground squirrels to take blood samples that reveal paternity and sorority. They have discovered that when a ground squirrel puts herself in jeopardy by sounding an alarm at the approach of a predator, she is an older female who is warning her daughters, granddaughters and sisters. Or in sea gulls, if a male loses his mate, another female will voluntarily nurture her "stepchildren," an apparently altruistic act. But sea gull females outnumber males, and this "selfless" stepmother is really making sure she has a mate for next season.
At the conference, experts in the behavior of fish, lions and chimpanzees described their studies, but one animal after another was disqualified as a reciprocal altruist on grounds that the animal actors turned out to be relatives or parents raising offspring.
It looked bad for the theory of reciprocal altruism until Gerald Wilkinson from the University of Colorado at Boulder described his work with vampire bats. These Costa Rican natives live on the blood of cattle, which they suck during nocturnal forays. Each bat takes 40 minutes to prepare the host. After drinking half her own body weight, the female bat turns over the open wound to her daughters. Back at the roost, the well-fed bats discover that about 30% of the juveniles and 10% of the adults did not find food. Vampire bats must feed at least once every two nights, or they will die. Yet there is low mortality, because the sated females regurgitate blood to their hungry chums, sharing nourishment with related and unrelated bats alike.
Female dolphins and other cetaceans may also fulfill the requirements for true altruists. Many dolphins live in changing herds, numbering from 50 to 250 individuals. Their relationships are hard to discern, but because of their long life spans--from 35 to 70 years--it is doubtful that there are large family units with tight kinship ties. Dolphins recognize each other and spend almost a third of their lives making social contact.