But biologists are beginning to form a generally sunnier view of
humankind. Their conclusions are derived in part from testing very young
children, and partly from comparing human children with those of
chimpanzees, hoping that the differences will point to what is
distinctively human.

The somewhat surprising answer at which some biologists have arrived
is that babies are innately sociable and helpful to others. Of course
every animal must to some extent be selfish to survive. But the
biologists also see in humans a natural willingness to help.

When infants 18 months old see an unrelated adult whose hands are
full and who needs assistance opening a door or picking up a dropped
clothespin, they will immediately help, Michael Tomasello writes in “Why We Cooperate,” a book
published in October. Dr. Tomasello, a developmental psychologist, is
co-director of the Max Planck Institute for Evolutionary Anthropology in
Leipzig, Germany.

The helping behavior seems to be innate because it appears so early and before many parents start teaching children the rules of polite behavior.

“It’s probably safe to assume that they haven’t been explicitly and
directly taught to do this,” said Elizabeth Spelke, a developmental
psychologist at Harvard. “On the other hand, they’ve had lots of
opportunities to experience acts of helping by others. I think the jury
is out on the innateness question.”

But Dr. Tomasello finds the helping is not enhanced by rewards,
suggesting that it is not influenced by training. It seems to occur
across cultures that have different timetables for teaching social
rules. And helping behavior can even be seen in infant chimpanzees under
the right experimental conditions.

For all these reasons, Dr. Tomasello concludes that helping is a natural inclination, not something imposed by parents or culture.

Infants will help with information, as well as in practical ways.
From the age of 12 months they will point at objects that an adult
pretends to have lost. Chimpanzees, by contrast, never point at things
for each other, and when they point for people, it seems to be as a
command to go fetch something rather than to share information.

For parents who may think their children somehow skipped the
cooperative phase, Dr. Tomasello offers the reassuring advice that
children are often more cooperative outside the home, which is why
parents may be surprised to hear from a teacher or coach how nice their
child is. “In families, the competitive element is in ascendancy,” he
said.

As children grow older, they become more selective in their
helpfulness. Starting around age 3, they will share more generously with
a child who was previously nice to them. Another behavior that emerges
at the same age is a sense of social norms. “Most social norms are about
being nice to other people,” Dr. Tomasello said in an interview, “so
children learn social norms because they want to be part of the group.”

Children not only feel they should obey these rules themselves, but
also that they should make others in the group do the same. Even
3-year-olds are willing to enforce social norms. If they are shown how
to play a game, and a puppet then joins in with its own idea of the
rules, the children will object, some of them vociferously.

Where do they get this idea of group rules, the sense of “we who do
it this way”? Dr. Tomasello believes children develop what he calls
“shared intentionality,” a notion of what others expect to happen and
hence a sense of a group “we.” It is from this shared intentionality
that children derive their sense of norms and of expecting others to
obey them.

Shared intentionality, in Dr. Tomasello’s view, is close to the
essence of what distinguishes people from chimpanzees. A group of human
children will use all kinds of words and gestures to form goals and
coordinate activities, but young chimps seem to have little interest in
what may be their companions’ minds.

If children are naturally helpful and sociable, what system of
child-rearing best takes advantage of this surprising propensity? Dr.
Tomasello says that the approach known as inductive parenting works best
because it reinforces the child’s natural propensity to cooperate with
others. Inductive parenting is simply communicating with children about
the effect of their actions on others and emphasizing the logic of
social cooperation.

“Children are altruistic by nature,” he writes, and though they are
also naturally selfish, all parents need do is try to tip the balance
toward social behavior.

The shared intentionality lies at the basis of human society, Dr.
Tomasello argues. From it flow ideas of norms, of punishing those who
violate the norms and of shame and guilt for punishing oneself. Shared
intentionality evolved very early in the human lineage, he believes, and
its probable purpose was for cooperation in gathering food.
Anthropologists report that when men cooperate in hunting, they can take
down large game, which single hunters generally cannot do. Chimpanzees
gather to hunt colobus monkeys, but Dr. Tomasello argues this is far
less of a cooperative endeavor because the participants act on an ad hoc
basis and do not really share their catch.

An interesting bodily reflection of humans’ shared intentionality is
the sclera, or whites, of the eyes. All 200 or so species of primates
have dark eyes and a barely visible sclera. All, that is, except humans,
whose sclera is three times as large, a feature that makes it much
easier to follow the direction of someone else’s gaze. Chimps will
follow a person’s gaze, but by looking at his head, even if his eyes are
closed. Babies follow a person’s eyes, even if the experimenter keeps
his head still.

Advertising what one is looking at could be a risk. Dr. Tomasello
argues that the behavior evolved “in cooperative social groups in which
monitoring one another’s focus was to everyone’s benefit in completing
joint tasks.”

This could have happened at some point early in human evolution, when
in order to survive, people were forced to cooperate in hunting game or
gathering fruit. The path to obligatory cooperation — one that other
primates did not take — led to social rules and their enforcement, to
human altruism and to language.

“Humans putting their heads together in shared cooperative activities
are thus the originators of human culture,” Dr. Tomasello writes.

A similar conclusion has been reached independently by Hillard S.
Kaplan, an anthropologist at the University of New
Mexico. Modern humans have lived for most of their existence as
hunter gatherers, so much of human nature has presumably been shaped for
survival in such conditions. From study of existing hunter gatherer
peoples, Dr. Kaplan has found evidence of cooperation woven into many
levels of human activity.

The division of labor between men and women — men gather 68 percent
of the calories in foraging societies — requires cooperation between the sexes. Young
people in these societies consume more than they produce until age 20,  which in turn requires cooperation between the generations. This long period of dependency was needed to develop the special skills required for the hunter gatherer way of life.

The structure of early human societies, including their “high levels
of cooperation between kin and nonkin,” was thus an adaptation to the
“specialized foraging niche” of food resources that were too difficult
for other primates to capture, Dr. Kaplan and colleagues wrote recently
in The Philosophical Transactions of the Royal Society. We evolved to be
nice to each other, in other words, because there was no alternative.

Much the same conclusion is reached by Frans de Waal in another book
published in October, “The Age of Empathy.” Dr. de Waal, a
primatologist, has long studied the cooperative side of primate behavior
and believes that aggression, which he has also studied, is often
overrated as a human motivation.

“We’re preprogrammed to reach out,” Dr. de Waal writes. “Empathy is
an automated response over which we have limited control.” The only
people emotionally immune to another’s situation, he notes, are
psychopaths.

Indeed, it is in our biological nature, not our political
institutions, that we should put our trust, in his view. Our empathy is
innate and cannot be changed or long suppressed. “In fact,” Dr. de Waal
writes, “I’d argue that biology constitutes our greatest hope. One can
only shudder at the thought that the humaneness of our societies would
depend on the whims of politics, culture or religion.”

The basic sociability of human nature does not mean, of course, that
people are nice to each other all the time. Social structure requires
that things be done to maintain it, some of which involve negative
attitudes toward others. The instinct for enforcing norms is powerful,
as is the instinct for fairness. Experiments have shown that people will
reject unfair distributions of money even it means they receive
nothing.

“Humans clearly evolved the ability to detect inequities, control
immediate desires, foresee the virtues of norm following and gain the
personal, emotional rewards that come from seeing another punished,”
write three Harvard biologists, Marc Hauser, Katherine McAuliffe and
Peter R. Blake, in reviewing their experiments with tamarin monkeys and
young children.

If people do bad things to others in their group, they can behave
even worse to those outside it. Indeed the human capacity for
cooperation “seems to have evolved mainly for interactions within the
local group,” Dr. Tomasello writes.

Sociality, the binding together of members of a group, is the first
requirement of defense, since without it people will not put the group’s
interests ahead of their own or be willing to sacrifice their lives in
battle. Lawrence H. Keeley, an anthropologist who has traced aggression
among early peoples, writes in his book “War Before Civilization” that,
“Warfare is ultimately not a denial of the human capacity for
cooperation, but merely the most destructive expression of it.”

The roots of human cooperation may lie in human aggression. We are selfish by nature, yet also follow rules requiring us to be nice to others.

“That’s why we have moral dilemmas,” Dr. Tomasello said, “because we are both selfish and altruistic at the same time.”