40 | New Scientist | 20 November 2021
T
HE evil that men do lives after
them; the good is oft interred
with their bones. So it will
be with Dzhokhar Tsarnaev.” So
said Judge George O’Toole before
sentencing Tsarnaev to death for
his part in the 2013 Boston Marathon
bombing. During the trial, it emerged
that the killer was well liked by his
teachers and friends, had been
compassionate to people with
disabilities and had apologised to
victims and their families. But, said
O’Toole, his goodness would always
be overshadowed by his hateful act.
The human capacity for both
good and evil, often within the same
person, has long been recognised and
puzzled over; O’Toole was quoting
the Roman general Mark Antony in
Shakespeare’s Julius Caesar. What is
it about us that endows us with suchdiametrically opposite propensities?
Evolutionary biology has an
answer, and it doesn’t reflect well on
human nature. Acts of both good and
evil are driven by altruism – and that
is ultimately selfishness in disguise.
For a long time, altruism was
a biological mystery. The prime
directive of evolution is to pass on
our genes to the next generation.
Engaging in costly behaviours with
no obvious survival pay-off seems to
go against that grain. The polymath
J. B. S. Haldane eventually twigged it:
individuals mostly make sacrifices
for close relatives, and hence help to
usher copies of their own genes into
the next generation. As Haldane put
it: “I would lay down my life for
two brothers or eight cousins.” Acts
of true selflessness exist, but these
are explained as reciprocal altruism,
where kindness to strangers (who
may in fact be relatives) is banked
for the future.
That’s all good, but what about
evil? Evildoers often see their acts
as being for the greater good. This
“pathological altruism” lies behindCalifornia Institute of Technology.
At issue here is the concept of entropy.
This is a measure of the amount of disorder
in a system, defined as the number of different
microscopic configurations it can have
without changing its macroscopic, or overall,
appearance. A box of hot gas has high entropy,
for example, with a vast number of equivalent
configurations with different positions and
velocities for each atom or molecule. A human,
though, has low entropy – try to reconfigure us
too much and things rapidly start to fall apart.
The crucial point is that there are more ways
for any system of particles to have high entropy
than low entropy, so things naturally tend
towards high-entropy states. Where entropy is
high, we lose any chance of knowing a system’s
precise physical configuration, because there
are so many equivalent options. If we could
gain all that information, time would still exist,
in the sense that the system could still evolve.
But time’s arrow would disappear, because
any “forwards” evolution would run equally
plausibly “backwards” from the configuration
in which we see it. “The increase of entropy is
responsible for all of our impressions that the
past is different from the future, including the
impression that time flows,” says Carroll – and
our ignorance lies at its heart.
What is true in classical physics is doubly
so in the quantum world, says Marcus Huber,
at the Institute for Quantum Optics and
Quantum Information in Vienna, Austria.
Here, uncertainties that, in the classical world,
we put down to a lack of knowledge seem to
represent uncertainties intrinsic to reality,
although that interpretation is itself up for
debate (see “Why is quantum physics so
strange?”, page 44). “Here, the state is truly
undetermined prior to a measurement, so the
lack of knowledge – and rise of entropy – is
even more fundamental,” says Huber.
For some, arguments equating time’s
passage with rising entropy are passé, anyway.
Lee Smolin at the Perimeter Institute for
Theoretical Physics in Waterloo, Canada, for
one, believes that the problem of time’s arrow
indicates a basic gap in our understanding.
Others think the gradual revelation of classical
certainties through quantum measurements
is the true source of time’s arrow.
Even if entropy is the answer, that just
shifts the question. For entropy always to
rise, the universe must have started with an
astoundingly low amount. Why so? That’s a
question we have hardly begun to tackle.
Abigail Beall
“
Why
are we
good
and
evil?
“ EVILDOERS OFTEN SEE THEIR ACTS
AS BEING FOR THE GREATER GOOD”