of Philosophy, Science & Law
Volume 8, May
Morris B. Hoffman*
Ten years ago E.O. Wilson, the Harvard
entomologist, wrote a remarkably ambitious book called Consilience: The Unity of Knowledge, in which he predicted that the
ever-accelerating insights of evolutionary biology would drive a fundamental
convergence of the social and natural sciences.
This essay is considerably less
ambitious. I’d like to report on the
rather remarkable inroads into the law, and into the legal academy, made by
post-Darwinian evolutionary thinking—thinking that is itself deeply resonant
with the now well-entrenched law and economics movement.
This resonance is beginning to shed light on
the mysteries of human behavior, and therefore on the mysteries of human
institutions, including law.
One point of clarification before I begin my
survey. Most readers, when they see the
phrase “law and biology,” probably think of the legal implications of medical
advances, including issues like the patentability of genes, the use of fMRI and
other brain imaging techniques to detect lying, or privacy and ethical issues
related to the sequencing of the human genome. I label this constellation of issues “the law of biology,” and although
much exciting work is being done in this area, this is not what I mean, or most
law and biology scholars mean, by the phrase “law and biology.”
Instead, what this discipline focuses on is
the biology of law, that is, what an evolutionary perspective might say about
human nature and the foundations of law. What is law? What is right and wrong? What is intentionality, when does a person
act without intentionality, and when, despite acting intentionally, should a
person’s acts be excused by the law? Are
these entirely cultural constructs, as the proponents of the Standard Social
Science Model have been trying to convince us for a hundred years? Or might there be universal evolutionary
components wired into our brains that cause us to share a sense of right and
wrong about core issues, a sense of blameworthiness and a sense of justice?
Law and biology in this foundational sense is
an interdiscipline whose time has most definitely come. Scientists, economists, lawyers and judges
now regularly meet at interdisciplinary conferences, including the annual
conferences held by the Gruter Institute for Law and Behavioral Research
and by the Society for Evolutionary Analysis in Law (“S.E.A.L.”).
Papers on law and biology are beginning to
crack the most prestigious of scientific journals, including Nature, Science
and the Royal Society’s Philosophical Transactions.
The 2007 annual conference of the American Association
for the Advancement of Science included a presentation titled “Does Neuroscience
Challenge Moral and Legal Notions of Responsibility?” In October 2007, the
MacArthur Foundation announced a $10 million three-year grant to fund the Law
and Neuroscience Project, an interdisciplinary endeavor populated by
neuroscientists, philosophers, legal theorists and judges.
The discipline is also gaining a foothold in
the nation’s law schools, where courses in law and biology have been or are
being taught in at least a dozen law schools, including
and Yale. Law review articles mentioning
the topic, which annually numbered in the handfuls as late as 1985, have
sky-rocketed to more than 300.
What in the world, reasonable readers might
well ask, does biology, or economics for that matter, have to do with the
law? The answer, most broadly, is that all
three disciplines deal with the problems of how individuals make choices, how
those choices affect society, and how, if at all, society’s institutions should
react to those choices.
Convergence of Economics and Biology
Economics is the study of human behavior,
admittedly often in a pricing context, and of the manner in which individual decisions
accumulate into markets. Ever since
Aristotle and Xenophon, humans have been puzzled by two economic mysteries:
what is the nature of property and what is price? That is, do individuals have the right to
“own” property, and what exactly are the indicia of such ownership? When they decide to sell their property does
it have an intrinsic value? If not, then
what is price?
Church thinkers in the middle ages continued
to struggle with the morality of property ownership, principally over the
question of whether the Church itself could own property. They also had fierce debates over price, and in
particular over the theological meaning of “fair” interest rates. Two of the most important medieval schools of
scholastic thought—the Dominicans and the Franciscans—arose largely over
disagreements about the morality of Church property and the nature of price.
At least in the West, post-feudal systems
largely resolved the issue of the morality of property ownership, although of
course innumerable issues continue to reside inside the question of the nature
of ownership, to the chagrin of all first-year students of property law.
As for price, it took Adam Smith and his
Scottish Enlightenment colleagues to solve its essential mystery (and, alas,
Marx to re-confound it), and to put to rest the ancient notion that goods have
any intrinsic value. Classical economics
assumed people were self-interested in a rather narrow sense—that we all make
decisions to maximize our net economic interest. Willing sellers and willing buyers agree to a
price that reflects nothing more than their own desires, which themselves are
the products of their own calculations, albeit based on imperfect information,
about maximizing their economic self-interest. The accumulation of all those somewhat arbitrary and largely unpredictable
self-interests—what Smith called “the invisible hand”—produces markets that are
fairly predictable using the tools of classical macro-economics.
But this Homo
economicus view of the human species has always ridden a little uneasily,
even with some classical economists, who sensed that the notion of
“self-interest” might be much more complicated than maximizing the value of
goods a person can accumulate. It
doesn’t take more than a few moments of reflection to know that people often
forego economic gain for other interests, including things like job
satisfaction and commitment to family. The stereotype of the starving artist resonates with us because it
reminds us of the essential truth that there is much more to life than
maximizing economic gain.
Indeed, even in situations in which these
other externalities seem to be absent, humans still regularly confound classical
economic theory by appearing to act much less selfishly than predicted. The most famous experimental example of
unexplained economic altruism in this kind of context occurs in the so-called ultimatum
game. In the most basic version of this
game, two players, strangers to each other, are randomly labeled Player A and
Player B. Player A is given $10, and
both given the following instructions: Player A may offer anywhere from $0 to $10
to Player B, but if Player B rejects the offer then neither player gets
anything. If Player B accepts, then each
retains the agreed-upon division.
If we were really purely short-run
self-interest machines, the most rational play (that is, the Nash equilibrium
is for Player A to offer $1, since he can predict that a rational Player B
would rather have $1 than no dollars and will therefore accept. But of course that’s not what we humans
actually do. Instead, we sense that
Player B might be insulted if the offer is as low as $1, and may reject it even
if it is “irrational” for him to do so. In effect, Player A makes a rational prediction about Player B’s “irrationality.”
And that’s exactly how the ultimatum games
gets played—and researchers have played it millions of times—across almost all
cultures and demographics.
industrial societies, the mean offer is around $4, and
offers lower than $3 are frequently rejected.
societies, the mean offer is the equivalent of $2.60, and the variation is
But these results are
still stunning. Whether in modern or
primitive pre-industrial societies, people do not act in the ruthlessly
“selfish” way Adam Smith predicted. Why
Economists now understand
“self-interest” to be a complicated calculation from a myriad of variables,
including strategic guesses about how competitors and other actors in the
social milieu might behave. In the end, it
seems that we act as individuals not to maximize the utility of our property but
rather to maximize our individual happiness.
And of course happiness itself can be a
complex gnarl of property ownership, selfishness, selflessness, emotion, incomplete
information and even imperfect memory about how happy we’ve been in the past. This richer notion of “self-interest” explains
the apparently altruistic behaviors classical economists could not explain.
Post-Darwinian biology took an eerily similar
path. Many biologists (and,
unfortunately, many non-scientists like Herbert Spencer and Oliver Wendell
that the ultimate products of the forces of natural selection would be animals “red
in tooth and claw” as Tennyson put it, all built like sharks, to do nothing but
kill, eat and reproduce. Relentless
self-interest machines. Übermenschen.
But of course field biologists knew that the
real world is not like that all. Natural
selection has produced an unimaginable array of species, with no apparent rule
that the newer the species the more aggressive. On the contrary, displays of
aggression in some species are much more common than actual aggression. Cooperation is common.
Individual animals regularly sacrifice their immediate
interests, and sometimes even their lives, for others, kin and non-kin alike. Early evolutionary theory could no more
explain this kind of altruism than classical economics could explain selfless
economic behavior in the ultimatum game.
Then two biologists, W.D. Hamilton and Robert
Trivers, did for the puzzle of biological altruism what neo-classical
economists did for the puzzle of economic altruism. They demonstrated that under the right
conditions, what seems to be “altruism” is in fact a strategic behavior that
can maximize individual fitness.
showed that a
set of genes that might give an animal a tendency to sacrifice its own welfare for
the welfare of its kin could, depending on its breadth, flourish across
Trivers showed that “altruism” need not even
be directed at kin to be adaptive. In
any system of sufficient complexity, behaviors that might in the short run seem
to be maladaptive might well have an adaptive advantage when viewed in the
It might have seemed like a good idea in the
short-run for our Pleistocene ancestor to steal that cache of food gathered by
the group earlier in the day. But he
might get caught, and might be punished so severely (for example, by being
ostracized from the group, or killed) that in the long run he’d be better off
not stealing it.
Investigators since Hamilton and Trivers have
been working out the details of these complex reciprocal systems, using the
tools of evolutionary theory, ethnology, primatology, information theory and
game theory, to develop a picture of human behavior, and human institutions,
resonant with the central idea that social and anti-social behaviors alike have
deep evolutionary roots.
And as biologists and their interdisciplinary
partners learn more and more about the way the human animal makes
happiness-maximizing decisions in complex social networks, insights about the
meta-rules of those networks—law—are gaining traction.
Original Sin of Social Defection
Social animals have evolved rules that
determine their group membership, and even rules about which rules, when
broken, should trigger punishment. Indeed,
that’s what it means to be a social animal. Humans are intensely social. We emerged about 100,000 years ago from
predecessor species that were themselves apparently intensely social. We’ve spent almost all of that time in small
groups of less than 100, mostly related, individuals.
Tens of thousands of years of evolution under
these conditions have attuned our brains to make us highly receptive to
cooperation with fellow group members, but always constantly probing for, and
defending against, any opening in which short-term selfishness will either go
undetected or sufficiently unpunished to be worthwhile. “Free riding” is what both economists and
biologists now call this anti-social behavior.
But don’t misunderstand. This isn’t aberrant, sociopathic
behavior. This is the profound human
struggle—the most original of original sins—built into every one of us by
evolution: when do I cooperate with the group and when do I defect? Philosophy, religion, law, and moral systems
of all kind are in some sense cultural echoes of this deeply imbedded
For the human animal there is a second
evolutionary challenge. For thousands of
generations we have had only one significant predator: ourselves.
environment has equipped us with a tendency to be profoundly suspicious of individuals
not in our group. This tendency may
explain many of the most intractable of human pestilences, including ethnic and
racial disharmony, but, as discussed below, may also help explain the puzzles of
consciousness and free will.
Evolutionary Roots of Law and Economics
Both within and between groups, humans are
and always have been incessant traders. The
evolved brains of Homo exchangius, as
we might re-label ourselves, have allowed us not only to imagine the future,
but also to be able to communicate sufficiently about it with each other to
permit time-delayed reciprocity. Exchanges need not be limited to simultaneous barter. Five bushels of wheat could be exchanged for
the promise of three skins in the
future, or, eventually, for currency. Freed from the constraints of simultaneous barter, division of labor
offered Homo exchangius the prospect
of virtually limitless exchange and the resulting creation of unimaginable wealth.
But what could poor Homo exchangius do to increase the reliability of the promises of
his generally cooperative but always probingly selfish brethren?
Answer: make sure the group has institutions
that make defecting more costly, or that are otherwise designed to foster trust. In this way, the law itself is coming to be seen
as having emerged not as an arbitrary cultural construct but as an extension of
our evolved natures as relentless free traders. Promises must be kept. Exchanges
must be voluntary. Violations of these
first two rules must be discouraged and serious violations punished. These
insights are driving many exciting legal applications, including new ways of
looking at the purposes of the criminal law,
role of apology in both civil and criminal law,
roots of property law,
arguably rootless nature of intellectual property law,
even the foundations of tort and contract.
In addition to these particular applications
of evolution to law, many law and biology scholars are exploring even deeper
foundational questions. Let me touch on
of Law’s Leverage, Time-Delayed Rationality and the Universal Sense of Relative
Owen Jones, who holds a joint appointment in
the law school and the department of biology at Vanderbilt, has written
extensively on what he has dubbed “the law of law’s leverage.” Early critics of the biological take on law often
quite rightly accused law and biology scholars of violating Hume’s naturalistic
fallacy—just because a human behavior, like rape, may have evolutionary roots
does not mean it is right.
Jones addressed the problem by making the
simple observation that even if the law is viewed in the typical post-modern
way as a cultural check on our basest impulses, it would be quite useful for us
to know which of those impulses may have biological roots (and therefore may be
more difficult to change) and which don’t.
So the “law of law’s leverage” states that
every law can be analyzed for its ability to leverage the intended change in
behavior, and that if the targeted behavior has adaptive roots the law’s
leverage will be small and it will be difficult to change the behavior; if the
targeted behavior is maladaptive the law’s leverage will be great and it will
be easy to change the behavior. This insight
could have practical, as well as descriptive, benefits, including the corollary
that reputational punishment may be more effective in some circumstances than
Jones has also written at great length about
the following problem: our biologically-driven behaviors evolved 100,000 years
ago in an environment that is quite unlike the environment today. As a result, behaviors that may have been
“rational” in the late Pleistocene—that is, adaptive—may seem completely
irrational and maladaptive today. Jones
calls this the problem of “time-shifted rationality.” As he puts it:
only should allow for, but should indeed expect, that there will be times when
a perfectly functioning brain--functioning precisely as it was designed to
function--will incline us toward behavior that, viewed only in the present
tense and measured only by outcomes in current environments, will appear to be
substantively irrational. This is simply because the brain was designed to process
information in ways tending to yield behaviors that were
substantively rational in different environments than the ones in which we now
For example, stress typically reduces people’s
sex drive and ability to digest food, a result that seems to make no adaptive
sense in the modern world. Just when we
most need our esteem and strength, as the modern world closes in on us with
things like divorces, lawsuits and business failures, our bodies seem
programmed to desert us. But when one
considers that this result was the product of an evolutionary environment in
which an existential threat required all systems to focus on fight or flight,
this partial shutdown response is perfectly rational.
As Jones puts it, “most severe and survivable
[threats 100,000 years ago] passed more quickly than multi-district litigation,
divorce proceedings or corporate takeovers.”
Like the law of law’s leverage, recognizing
time-shifted rationality may help police, legislatures and even sentencing
courts recognize that some behaviors, which on their face seem “irrational,”
might be less amenable to corrective legal action than others. Is time-shifted rationality an excuse? Of course not. But it might mean, for example, that for some
crimes we should reduce our emphasis on rehabilitation, and even on deterrence,
and focus on punishment.
For others, more socially-based forms of
opprobrium, like shaming and apology, may be appropriate.
Finally, one of the most exciting areas of
research is being done by criminologists exploring the universality of
blameworthiness. Evolutionary insights
are leading to a kind of post-Darwinian view of the central role of punishment
(and mercy) as an embedded behavior critical to our evolution and, ultimately,
our civilization. I was only half-joking
when I responded to a questioner at a law and biology conference a few years
ago who suggested that sometimes Johnny just can’t “help” himself when he robs
a gas station, by saying that as a judge I just can’t “help” myself when I then
punish Johnny. The urge to punish
free-riders is as real, and as evolutionarily important, as the urge to
free-ride. It is, in fact, at the core
of what it means to be civilized. The
challenge is to design legal institutions that can quantify the proper amount
of just desert, and thus avoid the social costs of either under- or
One of the most serious challenges to this
re-emergent retributionism is the problem of quantifying just desert. What Judge A thinks is a proper amount of
punishment for a certain crime may be completely different from what Judge B
thinks, or so goes this relativistic argument against any system grounded on
just deserts. This belief that views of
blameworthiness are highly variable has not only been an argument made at
it is the catechism behind sentencing guidelines.
But work being done by three scholars, Paul
Robinson and Rob Kurzban at the University of Pennsylvania, and John Darley at
Princeton, is challenging this relativistic view of blameworthiness, and is
suggesting instead that there is widespread, and finely-tuned, agreement about
the relative blameworthiness of different crimes. Robinson et al. wrote 24 crime narratives,
and asked participants in the study to order them from least blameworthy to
These were not grossly disparate tasks, like
deciding whether rape was more blameworthy than shoplifting. They were complex, and at least facially
required a host of nuanced judgments.
In fact, when I took part in a web-based
version of the experiment, I found myself frequently changing my mind about
whether a given scenario was more or less blameworthy than another given
scenario. I understand that the actual
subjects of the experiment also frequently changed pair-wise rankings as they
attempted to complete the ordering.
Despite the complexity and refinement of the
task, the results were breathtakingly uniform. Among the 246 participants, the pair-wise agreement was over 90%, and a
more sophisticated statistical measure of overall agreement was even more
impressive. An equally astonishing
aspect of this study is that this agreement about relative blameworthiness
crossed economic, racial, ethnic, gender, political and other demographic
lines. It seems all of us, at least
those of us who are not sociopaths, have no trouble at all making very fine
distinctions between the just deserts for different crimes, and exhibit
widespread agreement about those distinctions.
Robinson et al. acknowledge that uniformity
in relative blameworthiness does not always translate into uniformity in actual
sentences, but they suggest this is largely an artifact of what they call the
“problem of end point.” If the worst
crime in Judge A’s jurisdiction carries a death sentence, and the worst crime
in Judge B’s jurisdiction carries only 40 years, then the scales on which their
presumably identical lists of relative blameworthiness are stretched will
produce different sentences.
Of course, this is only a partial explanation
of sentence disparity. Even if Judges A
and B share the same end point, as federal judges have for the better part of a
century, there is no doubt that the identical relative scales that Robinson et
al. have posited can produce, and have produced, significant sentence variance.
But there is also no doubt that these
results, if they hold, threaten the kind of “sentencing-by-tinkering-with-a-thousand-factors”
approach of many sentencing guidelines.
Judges know what crimes are more serious than
other crimes because all humans know that, and it seems we reach those shared
conclusions not by analyzing hundreds of factoids but rather by looking at only
a very few factors, like motive and harm.
On a grander scale, this work may also go a
long way toward rescuing neo-retribution from its relativistic critics. I send Johnny to prison because he deserves
it, and because by going to prison he can earn his way back into the moral
Whether other judges agree with that theory
or not, it looks like we all have a fairly uniform and refined sense of the
difference between just and unjust deserts.
Emotion and the Probabilistic Brain
There is a giant elephant in the living room
of law and biology, and indeed in the whole New Synthesis of modern biology: brains,
not genes, cause behaviors. How,
exactly, are behavioral tendencies, let alone behaviors, encoded in the brain? Very little is known about this process. The sheer complexity of the brain is the
biggest hurdle. The average human brain
has 100 billion neurons, and each neuron connects on average to between 1,000
and 10,000 other neurons. Compare that
level of complexity with the recently-completed full wiring diagram of the
nematode, whose nervous system (one cannot call it a “brain”) has only 302
But the brain-to-behavior problem is much
more than just a problem of combinatorics. It also packs the philosophical punch of treading near the black hole of
free will and determinism. How can
behaviors, or even “behavioral tendencies,” be inherited by humans if humans
are agents operating with free will? It
is no accident that the MacArthur Law and Neuroscience Project includes several
Despite these calculational and philosophical
hazards, many of the recent efforts in law and biology have focused on
neuroscience. In fact, a whole new interdiscipline,
called neuroeconomics, is emerging to examine the physical processes that occur
in the brain when humans face this ubiquitous question of whether to cooperate
or defect. Moreover, it seems that every
day or two, neuroeconomists and traditional neuroscientists alike announce that
they have found neural correlates associated with a particular human behavior
or perception, including, among many others, perceiving motion,
seeing in 3-D,
or rejecting in the ultimatum game,
As a very general principle, the brain-imaging
work neuroscientists are doing is painting a picture of the brain that is very
much unlike the picture we have held since Rene Descartes first posited a
fundamental difference between “simple” behaviors and “complex” behaviors, or
what we might also label “reflex” and “cognition.”
The emerging modern picture is of a brain
that recruits many different areas in complex, simultaneous and
non-simultaneous cascades, and that involves seamless feedback loops between
frontal “controls” and more primitive parts. It seems that the traditional counterpoints “simple v. complex,” “reflex
v. cognition” and even “emotion v. reasoning” are losing, if they have not
already lost, all neurological distinction.
As a by-product of these neurological
insights, law and biology scholars are doing lots of work on the role of
emotion in law.
Of course, it is not difficult to imagine
why, as an evolutionary matter, our brains have come to be equipped with a
seamless and interlinking way of being able to react without thinking when
necessary (to flee that predator) and, perhaps less obviously, why emotion can
be a kind of lubricant that prevents us from being hopelessly indecisive when
we consciously ponder an important even if not life-threatening decision.
But the elephant’s still in the living room,
because none of this work suggests any mechanism by which favored genes convert
their behavioral benefits into the architecture of the brains they build. That is the $64,000 question of behavioral
neuroscience, and although no gene-to-brain-to-behavior mechanism has yet been
discovered, there is tantalizing evidence suggesting a solution, though it is
not a solution that will please apostles of traditional free will.
neuroscientists have started to suggest that, just as it is becoming apparent
that the distinction between “reflex” and “cognition” is artificial, perhaps
the distinction between “determinate” and “indeterminate” is also
artificial. Perhaps the brain—both in
its “simple” and “complex” activities—is a probability machine rather than some
contraption that inexplicably switches back and forth between
reflexive/determinate outcomes (burn your hand, pull it back) and
cognitive/indeterminate outcomes (how much to offer in the ultimatum game). Perhaps all behaviors are represented in the
brain by a set of probability distributions, which are then continuously
influenced by the interaction between ultimate causes (the initial
probabilities that evolution built into brains) and proximate causes (the
particular environmental challenges brains are called upon to solve).
In this model, a
“reflex” is just an extreme kind of probability distribution—one with a very
high probability bunched near a single action, the response. When you burn your hand, it is extremely likely
(but not determinate) that your brain will “decide” to pull the hand back. The high probability of that particular
action masks its inherently indeterminate (and “cognitive”) character. Likewise, when you decide to offer a certain
amount in the ultimatum game, you are randomly engaging a distribution of
probable behaviors, though the probabilities are more evenly distributed over a
wider range, leaving you with the conscious sense that you “decided” what to
do. But in both cases, according to the
probabilistic model, the particular “decision” is an indeterminate outcome
bounded only by the probability distribution of all outcomes.
Paul Glimcher and his colleagues have performed a series of spectacular
neurological experiments that suggest that the brain works exactly in this probabilistic
way. Using a
variety of neurobiological techniques to study the neural firings in the
brains of monkeys and humans as they make
decisions during various kinds of games, the experimenters found that when the
strength and frequency of those firings are accumulated and plotted over time,
they look virtually identical to the probabilistic outcomes in decision-making
by individual humans over time—the so-called “utility function” of modern
This is a remarkable result, suggesting an
essential unity between the way a single brain makes a single decision, and the
patterns that emerge when brains make many decisions over time.
Thus, although we
cannot predict whether the brain of any particular person will offer $4 in the
ultimatum game, we can surmise that the population-wide average of $4 reflects
the fact that the brains in that population have a probability distribution for
this behavior that peaks near $4. The
genius of the probabilistic model is that it preserves the indeterminacy (free
will?) of a particular individual’s behavior, while explaining the perfectly
determinate behavior of large groups of individuals, or of a single individual
over many trials. It also suggests the
real possibility that some behaviors are heritable, because brains have of
course been inherited.
Will, Responsibility and Excuse
But indeterminacy is hardly the same as free
will. The model of the probabilistic
brain may solve all kinds of difficult neuroscientific problems by treating free
will as a kind of exhaust fume of randomness. This kind of stochastic view of “decision” making may not even bother
most neuroscientists or modern philosophers.
But it should bother the heck out of legal
scholars and judges, since the law seems to be premised on notions of free will
and responsibility. Here again, however,
evolution may offer the glimpse of a way out.
Without tumbling too far down the rabbit hole
of free will and consciousness, let me just mention that lots of wonderful
insights are being knitted together by biologically-informed thinkers who share
the central evolutionary idea that, whatever the true nature of these difficult
self-referential notions, they most likely are the products of evolution and
therefore, at least at one time, had adaptive value.
Blessed with incredible computing power and
the ability to imagine that the future may depend on our present actions, human
brains would lose much of their effectiveness if they didn’t also come equipped
with the belief, illusion or not, that they are free to make decisions and that
those decisions will matter. That is, a
conscious ancestor, blessed and cursed with the feeling of free will, was much
more likely to survive than one without these traits.
Think of a strong, action-oriented hunter,
clear-headed and able to use his brain to figure things out, but fairly
un-reflective. Now imagine a
belly-button watching introvert obsessed with whether anything matters, whether
he really has free will, whether it’s just all a dream. Which one do you think survived to pass on
his genes to us?
There is also an important theory of mind
component to the evolutionary story of consciousness and free will. As I’ve already mentioned, when we emerged as
a separate species our principal predator was other humans.
When our ancestor saw that stranger coming
over the hill, he’d be much more likely to have survived if he had a strong
belief that the stranger was perfectly capable of forming an intention to kill and
acting on that intention.
Whatever its pedigree, there is no doubt that
humans come equipped with a powerful sense of free will. That powerful sense of free will drives a
powerful sense of responsibility when an individual breaches the social contract. We have no trouble holding people responsible
for breaking the norms that bind us because we have no trouble presuming they
were capable of deciding not to break them.
But as is often the case with evolution, a
behavior is most successful when it is flexible enough to retain its value at
the margins, when the environment changes and the margins become the norm. Or to put it another way, since the whole
function of rules for group membership and group exclusion was to stabilize the
group, to the net selective advantage of individual members, an overwrought
sense of responsibility, blameworthiness or punishability could itself have destabilized
Punishment is very costly, not just to the
person punished but also to the group and its punishment designees.
As a result, our ancestors lived in groups
that cared about, and punished, only serious violations of the social contract, and were keenly sensitive to circumstances
in which everyone might be better off if some wrongs were forgiven and went
unpunished. Contrition is an important
part of the decision to forgive, perhaps as a signaling device used by the
group to measure whether the free rider could return to the fold without
This co-evolved tendency to moderate
punishment with mercy and forgiveness may be why, at least in part, we have
fairly universal principles of criminal law that generally require mens rea
before an actor is punished,
and that recognize that even if an act is accompanied by intention, sometimes
the act must be excused because the actor suffers from some condition that affects
In the language of the criminal law, these
are the principles of culpability and excuse. No net selective advantage would have devolved to group members by
punishing a wrongdoer whose wrong was an accident, or whose mental deficiencies
prevented him from complying with the rules of the group.
Holmes wrote that even a dog knows the
difference between being kicked and being stumbled over.
Not only do humans (and maybe canines)
intuitively recognize the difference between an intentional act and an
accident, we likewise know that, with very few exceptions, accidents should not
be punished the same as intentional acts.
But this leaves us with a difficult neural tension. We have a deeply embedded sense that we
should not punish accidents the same as non-accidents, yet an equally powerful
sense that most human actions are intentional, and therefore a corresponding
skepticism about protestations by the wrongdoer that the wrong was an accident
or that the actor was sufficiently irrational to be excused. This tension is largely responsible for our
ambivalent feelings about doctrines of legal excuse, such as insanity, and the
sometimes tortured forms those doctrines take.
Law Makes a Comeback
For me, the most exciting fallout from the
consilience of law, economics and biology is that the long-discredited idea of
natural law may be making a comeback. There may well be segments of the law, maybe nearly all of it, that are
neither cultural constructs nor mere market lubricants, but instead rules that
reflect our deepest evolved natures as social animals. A core of right and wrong, if the
post-modernists would forgive me for saying. That’s a comforting thought to those of us who toil at the altars of
individual responsibility we call courtrooms.
Law and biology has reached the kind of
critical intellectual mass that law and economics reached two decades ago. An evolutionary perspective, by its very
nature, informs virtually every aspect of inquiry into the human condition, and
will therefore touch every human institution, including the law. Will this perspective change the way trial
judges sentence embezzlers, or the way appellate courts look at the
constitutionality of hate crimes, or the way legislatures define insanity? Probably not. Law and economics didn’t do much of that either.
Instead, this evolutionary perspective is the
kind of referential shift that, as two law and biology scholars recently described
it, changes everything and changes nothing.
changes nothing because evolved human nature will continue to animate those of
us who write, interpret, enforce and break laws. I once described this as the “duh effect.”
Most of these insights have a strangely
familiar and obvious character, precisely because they are insights shared by
all of us as part of our evolved natures as human beings. Is it any surprise to anyone, for example,
that stepfathers kill their infant children at rates substantially greater than
the rates at which natural fathers kill their infants.
Yet that insight is unlikely to animate legal
reforms in any obvious way. Few of us,
for example, would support a change that would presume biological fathers innocent
but stepfathers guilty of killing their infants (though one might ask whether
biological fathers should be punished more severely than step-fathers).
But the evolutionary perspective also changes
everything. It rescues the law from
political and philosophical extremists who have been claiming, from the
Sophists through the Critical Legal Studies crowd, that law is an arbitrary
exercise of raw power. Quite the
contrary, the law is an expression of a kind of deep, evolved, social
syntax. It describes a core of behaviors
that most of us know is wrong, because those behaviors represent a violation of
the 100,000-year-old accommodation between self and group that evolution has somehow
wired into (almost) all of our brains.
Likewise, an evolutionary view rescues law
from the narrow law and economics theorists, who may appreciate that deterrence
by punishment is part of the evolved accommodation, but do not appreciate (or
at least cannot explain) the moral core of that accommodation. Law is not a simple market lubricant, nor a
cumbersome contraption that needs regular efficiency tune-ups. The behaviors that humans engage in to
maximize their happiness are bounded (indeed, even defined) by underlying
principles that label some behaviors socially acceptable and some socially unacceptable.
It might make you quite happy to steal your
neighbor’s cow, and your neighbor might even be willing not to turn you into
the police for the right post-crime price. But freedom of contract and principles of supply and demand are
insufficient to explain why most psychiatrically unimpaired people derive no
happiness from stealing, or from allowing others to steal from them, even at
the right price.
The law discourages some behaviors (and
occasionally encourages others) not because those behaviors have reached some
arbitrary price equilibrium, but because those behaviors are a deeply shared
part of our moral intuitions. It is, if
the post-modernists will again forgive me, wrong to steal, whether or not the victim later agrees to recompense, because we
evolved to engage in reciprocal exchanges. Small social groups in which
everyone was stealing from one another would hardly have survived to produce Homo exchangius.
The law and biology synthesis is far from
complete. Very little is known about the
actual environment in which humans evolved, and as a result many of the
“insights” about the arguably adaptive nature of some human behaviors are
little more than guesses. There is even
less known about the meta-behaviors of that evolutionary environment, that is,
about the rules of group inclusion and exclusion that presumably evolved along
with the underlying rules themselves.
Variation is also an ever-present problem
with any evolutionarily-based analysis of behaviors. Natural selection happens only when there is
variation across populations, and that variation makes it difficult to label
one behavior “adaptive” and another “maladaptive,” even if we knew more than we
do about the ancient environment in which those behaviors evolved. Behaviors, like any other selected trait, do
not always spread uniformly, and in fact even maladaptive traits can spread by
mechanisms other than selection, like gene drift. Once human culture kicked in to become a kind
of warp speed version of natural selection, divergent traits and behaviors that
were not being selected for, but persisted at the margins of the normal
distribution, might well have become culturally adaptive. Separating out behavioral traits that were
spread by culture from those that were spread by genes is an almost impossible
task, until a set of genes associated with a behavior is actually identified.
As discussed in this essay, the
brain-to-behavior problem remains the biggest scientific barrier to a fuller
understanding of evolved human nature. The biggest philosophical barrier remains the naturalistic fallacy:
although we should never be afraid to use words like “right” and “wrong” in any
discussion of law and the evolution of moral intuitions, we should always be aware
of Hume’s command never to confuse the is with the ought.
While these and other issues should give us
great pause, and keep us skeptical and humble, they are all small potatoes
compared to the profoundly powerful referential shift this viewpoint provides. The law will never be the same after these
evolutionary insights, because our view of ourselves will never be the same.
* District Judge, Second Judicial District (
), State of
Adjunct Professor of Law, University of
School of Law; Research Fellow, Gruter Institute for Law and Behavioral
Research; and Member, Network on Decision-making, The MacArthur Foundation’s
Law and Neuroscience Project. I want to
thank Monika Gruter Cheney, Oliver Goodenough, Owen Jones, William Pizzi and
Richard Posner for their helpful comments on earlier drafts of this essay.
E.O. Wilson, Consilience:
The Unity of Knowledge (Knopf 1998).
The phrase “law and economics”
describes the discipline, pioneered by Ronald Coase, Guido Calabresi, Gary
Becker, Richard Posner and others, that uses economic concepts to analyze
law. Law and economics theorists are
especially interested in using the tools of economics to predict the way laws
will affect behaviors, with particular applications to regulatory and criminal
Students in my law and biology class
are often surprised to see that the first five sections cover philosophy,
genetics, evolution, economics and neuroscience before we even begin to touch,
at least expressly, on the legal implications of these perspectives.
See, e.g., Bettina Rockenbach &
Manfred Milinski, The Efficient Interaction of Indirect Reciprocity and Costly
Punishment, 444 Nature 718
(December 7, 2006); Ernst Fehr & Simon Gachter, Altruistic Punishment in
Humans, 415 Nature 137 (January
10, 2002); Samuel Bowles, Group Competition, Reproductive Leveling and the
Evolution of Human Altruism, 314 Science
1569 (December 8, 2006); Semir Zeki & Oliver Goodenough (eds.), Law
and the Brain, 359 Phil. Trans. Roy.
Soc. Lon. (B) 1657-1809 (November 29, 2004).
Westlaw search completed by the
author on November 28, 2007, using the search term “law and biology” and the
database “TP-ALL.” The most
comprehensive law review treatment of the issues raised by a biological
perspective on law is probably Owen D. Jones & Timothy H. Goldsmith, Law
and Behavioral Biology, 104 Colum. L.
Rev. 405 (2005). But see also E.
Donald Elliott, Law and Biology: The New Synthesis?, 41 St. Louis U. L. J. 595 (1997); Morris B. Hoffman &
Timothy H. Goldsmith, The Biological Roots of Punishment, 1 Ohio St. J. Crim. L. 627 (2004); Claire A. Hill, ed.,
Symposium: Must We Choose Between Rationality and Irrationality?, 80 Chi-Kent L. Rev. 1043 (2005); Owen
D. Jones, Law and Biology: Toward and Integrated Model of Human Behavior, 8 J. Contemp. Legal Issues 167 (1997); Bailey
Kuklin, Evolution, Politics and Law, 38
Val. U. L. Rev. 1129 (2004); Robin Bradley Kar, The Deep Structure of
Law and Morality, 84 Tex. L. Rev. 877
(2006); John O. McGinnis,
The Original Constitution and Our Origins, 19 Harv. J.L.
& Pub. Pol'y 251 (1996); Erin Ann O'Hara, Brain Plasticity and Spanish Moss in Biolegal Analysis, 53 Fla. L. Rev. 905 (2001); William H. Rodgers, Jr., Where
Environmental Law and Biology Meet: Of Panda’s Thumbs, Statutory Sleepers and
Effective Law, 65 U. Colo. L. Rev. 25
(1993); Outside of law reviews, see Lawrence A.
Frolik, ed., Law and Evolutionary
Biology (Gruter 1999); Roger D. Masters & Margaret Gruter (eds.), The Sense of Justice: Biological Foundations
of Law (Sage 1992); Semir Zeki & Oliver Goodenough (eds), Law and the Brain (Oxford 2006).
See generally Janet Coleman, A
History of Political Thought From the Middle Ages to the Renaissance 77-79 (Blackwell 2000).
The Nash equilibrium is a
mathematically rigorous description of the strategy in any sufficiently complex
n-person non-zero sum game that is, roughly speaking, immune to changes in the
other person’s strategy. See John Nash,
Equilibrium Points in N-person Games, 36 Proc.
of the Nat. Acad. of Sciences
I put these in quotes because of
course the essential lesson of these games is that our assumptions about what
is “rational” and what is “irrational” depend on premises that classical
economists have made much too narrow. As
one of my students said to me after we played the game in class, and after he
rejected the equivalent of a $2 offer (we played for candy), “It was worth more
than two lousy pieces of candy to see that bum’s face when I rejected and
deprived him of his eight pieces. That
will teach him.” See generally Francisco
Parisi & Vernon L. Smith (eds.), The
Law and Economics of Irrational Behavior (Stanford 2005).
Herbert Gintis, Game Theory Evolving: A Problem-Centered Introduction to Modeling
Strategic Behavior 252-54 (Princeton 2000).
Joseph Henrich et al., In Search of Homo Economicus: Behavioral
Experiments in Fifteen Small-Scale Societies, 91 Amer. Econ. Rev. 73, 74-75 (2001).
See, e.g., Daniel Kahneman, Toward
National Well-Being Accounts, 94 Amer.
Econ. Rev. 2429 (2004).
Kahneman, a psychologist, won the
2002 Nobel Prize in economics for, among other things, this important
paradigmatic shift from thinking about self-interest as maximizing utility to
See, e.g., Morris B. Hoffman, Book
Review: Law Without Values, The Life and
Legacy of Justice Holmes, by Albert
W. Alschuler, 54 Stan. L. Rev. 597, 605-07, 623-25 (2001) (discussing Holmes’ primitive understanding of
See, e.g., Lee Alan Dugatin, Cooperation
Among Animals (
W.D. Hamilton, The Genetical Evolution of Social Behavior, I, II,
7 J. of Theoretical Biology 1
Robert L. Trivers, The Evolution of Reciprocal
Altruism, 46 Quart. Rev. Biol. 35
See, e.g. ,Randolph M. Nesse (ed.), Evolution and the Capacity for Commitment (2001).
Of course, microorganisms were
another kind of “predator,” and in fact some biologists have begun to argue
that viruses—whose DNA is sprinkled throughout the genome of all living
things—may be the true unit of selection. That is, all of life is just a complicated kind of protein shell for the
propagation not of the individual animal’s genes, but of viral segments within
See text accompanying notes 62 to 70
See, e.g., Ernst Fehr & E.
Fischbacher, Third-Party Punishment and Social Norms, 25 Evol. Hum. Behav. 63 (2004); Stephen J. Morse, New Neuroscience, Old
Problems, in Neuroscience, and the Law:
Brain, Mind and the Scales of Justice 157-198 (B. Garland, ed., Dana
2004); Robert A. Sapolsky, The
Frontal Cortex and the Criminal Justice System, 359 Phil. Trans. Roy. Soc. (B) 1787 (2004); Hoffman &
Goldsmith, supra note 8. Notice that an evolutionary
perspective does not lead to a set of monolithic conclusions about these
difficult issues. Professor Sapolsky
argues that neuroscience may well shake the criminal law to its free-will
roots, Professor Morse argues it will have no such impact, and Professor
Goldsmith and I suggest it will reinforce, not challenge, the criminal law’s
See, e.g., Erin A. O’Hara, On Apology
and Consilience, 77 Wash. L. Rev. 1121
See, e.g., Jeffrey E. Stake, The
Property Instinct, 359 Phil. Trans. Roy.
Soc. (B) 1763 (2004).
Unlike corporeal property, whose
legal roots go back as far as recorded time, the law of intellectual property
is relatively recent. Its first
iteration—copyright—traces its origins to the 1500s, when the English monarch
granted a monopoly to the stationers’ guild. Paul Goldstein, Copyright's
Highway: From Gutenberg to the Celestial Jukebox 41-50 (1994). Does this mean we have an “instinct”
for real and personal property but not an “instinct” for intellectual property? Perhaps. But another way to look at the difference is that intellectual property
is just the application of older, traditional, property norms to a new species
of property. See Note, The More Things
Change, the More They Stay the Same: Copyright, Digital Technology and Social
Norms, 56 Stan. L. Rev. 531 (2003). No one would suggest, for example, that an
owner of a residential condominium has any less “instinct” for defending that
property from an intruder than an owner of a house. The difference in the legal contours of a
particular species of property may mask a common, and presumably
evolutionarily-based, set of values regarding its use.
See, e.g., Richard A. Epstein, A
Taste for Privacy? Evolution and the Emergence of a Naturalistic Ethic, 9 J. Legal Stud. 665 (1980).
See, e.g., Morris B. Hoffman, The
Neuroeconomic Path of the Law, 359 Phil.
Trans. Roy. Soc. (B) 1667, 1671 (2004).
In Hume’s language, the “is” is not
necessarily the “ought.”
Owen D. Jones, Time-Shifted
Rationality and the Law of Law’s Leverage, 95 Nw.
U. L. Rev. 1141, 1190-96 (2001).
See Hoffman & Goldsmith, supra
See, e.g. Bernard Bosanquet, Some Suggestions in Ethics 188, 203 (Kessenger
2007)  (“There is no
estimate which can determine degrees of moral guilt in actual individual
cases. Such a thing is wholly
Stephen Breyer, The Federal
Sentencing Guidelines and the Key Compromises upon Which They Rest, 17 Hofstra L. Rev. 1, 15-17 (1988) (“the
Commission soon realized that only a crude ranking of behavior in terms of just
desserts, based on objective and practical criteria, could be developed”).
Paul H. Robinson & John M.
Darley, Intuitions of Justice: Implications for Criminal Law and Justice
Policy, 81 S. Cal. L. Rev. 1 (2007); Paul
H. Robinson and Robert Kurzban, Concordance and Conflict in Intuitions of
Justice, 91 Minn. L. Rev. 1829
(2007). See also Paul H. Robinson,
Robert Kurzban & Owen D. Jones, The Origins of Shared Intuitions of
Justice, 60 Vand. L. Rev. 1633
For example, two of the core
scenarios were: 1) As he is walking to a party in a friend's neighborhood, John
sees a clock radio on the backseat of a car parked on the street; later that
night, on his return from the party, he checks
the car and finds it unlocked, so he takes the clock radio from the back seat; and 2) John does not have all the
tools he needs for his workshop but knows of a family two streets over who
sometimes leave unlocked the door to the detached garage next to their house; when he next sees his chance,
he enters the detached garage through
the unlocked door and takes a
medium-size electric drill, intending to keep it forever. Robinson & Kurzban, supra note 38
(Scenarios 8 and 9, Appendix A: Text of Core Scenarios).
One of the interesting questions that
future experiments may address is whether people’s first impression of relative
blameworthiness ends up being their final one, after some interim but in the
end meaningless handwringing (which is what I suspect), or whether it takes
some real cognition to reach these shared “intuitions.”
And in the post-Booker world, see United States v. Booker, 543 U.S. 220 (2005)
(striking federal sentencing guidelines but leaving them in place as
non-mandatory), a Congress considering returning to mandatory guidelines may
want to consider that to do so may largely be an exercise in futility, even if
the constitutional hurdles of Booker and
its predecessors could be overcome.
Hegel, Philosophy of Right 71 (T.M.
Knox trans., Oxford 1942) .
Robinson, Kevin McCabe (a
neuroeconomist from George Mason), Rene Marois (a neuroscientist from
Vanderbilt), Frank Krueger (a neuroscientist from NIH), Owen Jones and I are
currently designing experiments to run a version of the Robinson et al. study
in an fMRI magnet, in an effort to identify the neural correlates of these
shared intuitions of relative blameworthiness. This project is being funded, in part, by a grant from the MacArthur
Foundation’s Law and Neuroscience Project.
See Jonathan Hodgkin et al., C.
elegans: Sequence to Biology, 282 Science 2011 (December 11, 1998).
Judy Illes from the University of
British Columbia, Walter Sinott-Armstrong from Dartmouth College, Gary Watson
from the University of California Riverside, Phillip Pettit from Princeton
University, Susan Wolf from the University of North Carolina, Gideon Yaffe from
the University of Southern California, Joshua Greene from Harvard University
and Adina Roskies from Dartmouth College.
Gene R. Stoner & Thomas D.
Albright, Neural Correlates of Perceptual Motion Coherence, 358 Nature 412 (July 30, 1992).
Ken-Ichiro Tsutsui, et al., Neural
Correlates for Perception of 3D Surface Orientation from Texture Gradient, 298 Science 409 (October 11, 2002).
Jay A. Gottfried, et al., Encoding
Predictive Reward Value in Human Amygdala and Orbitofrontal Cortex, 310 Science 1104 (August 22, 2003).
See, e.g., Michael D. Rugg, et al.,
Disassociation of the Neural Correlates of Implicit and Explicit Memory, 392 Nature 595 (April 9, 1998).
Or, more accurately, listening to
music that violates harmonic expectations. Nikolaus Steinbeis et al., The Role of Harmonic Expectancy in Violations
in in Musical Emotions: Evidence from Subjective, Physiological and Neural
Responses, 18 J. Cognitive Neuroscience
1380 (August 1, 2006).
Peter Nachev, et al., Volition and
Conflict in Human Medial Frontal Cortex, 15 Curr.
Biol. 122 (2005).
Marcel Brass & Patrick Haggard,
To Do or Not to Do: The Neural Signature of Self-Control, 27 J. Neuroscience 9141 (August 22, 2007).
Alan G. Sanfey, et al., The Neural
Basis of Economic Decision-making in the Ultimatum Game, 300 Science 1755 (June 13, 2003).
Jaak Panksepp, Feeling the Pain of
Social Loss, 302 Science 237 (October
Tania Singer, et al., Empathy for
Pain Involves the Affective But Not Sensory Components of Pain, 303 Science 1157 (February 20, 2004).
Tali Sharot, et al., Neural
Mechanisms Mediating Optimism Bias, 450 Nature
102 (November 1, 2007).
Joshua D. Greene et al., An fMRI
Investigation of Emotional Engagement in Moral Judgment, 293 Science 2105 (September 14, 2001).
Ian Glynn, An Intriguing Door—The
Neural Correlates of Consciousness, 413 Nature 683 (October 18, 2001).
Descartes actually called the
non-reflex category of behaviors the “soul.” Rene Descartes, L’Homme [Treatise on Man] , (T.S. Hall, tr.,
Harvard 1972) .
See, e.g., Clair A. Hill, supra note 8; Robert H. Frank, Passion Within Reason: The Strategic Role of
Emotions (Norton 1988); Susan A. Bandes, ed., The Passions of Law (NYU 1999).
W. Glimcher, Decisions,
Uncertainty and the Brain: The Science of Neuroeconomics 322-36 (MIT 2003).
See, e.g., Sapolsky, supra note 23.
See, e.g., Francis Crick, The
Astonishing Hypothesis: The Scientific Search for the Soul (Scribner 1995); John Searle, Freedom and Neurobiology: Reflections on Free
Will, Language, and Political Power (Columbia 2006); Mary Midgley, The Ethical Primate (Taylor & Francis 2007); Anthony
Freeman, Keith Sutherland and Benjamin Libet, eds., The Volitional Brain: Toward a Neuroscience of Free Will (Imprint
See text accompanying note 21 supra.
Note that this is an oddly inverted
kind of theory of mind. The traditional
theory of mind notion is that we know what we are thinking, and we assume that
other people’s minds work like ours does. But this evolutionary explanation for consciousness and free will
suggests that its adaptive value comes from assuming other people have consciousness and intentionality.
We are also endowed, as discussed
above, with a remarkably universal sense, once an act is deemed blameworthy, of
how blameworthy it is with respect to other wrongful acts. See text accompanying notes 38 to 41 supra.
See Rockenbach & Milinski, supra
note 6; Hoffman & Goldsmith, supra note 8.
“Mens rea” is Latin for “guilty
mind.” The phrase comes from the English
legal precept “Actus non facit reum nisi
mens rea sit” [“An act is not guilty unless the mind is guilty”], which
dates from at least the time of Henry I in the early 1100s, and which was
likely based on the writings of St. Augustine. Paul Robinson, Mens Rea, University of Pennsylvania, Scholarship at Penn
Law Paper No. 35 (1999), available on line at http://lsr.nellco.org/upenn/wps/papers/35; Francis Bowes Sayre, Mens Rea, 45 Harv. L. Rev. 974, 974 (1932). Virtually every civilization that has left a record on the
matter—including the Babylonians, Jews, Egyptians, Greeks, and Romans—all
recognized the idea that both the act and intention must be judged by the
law. See, Max Radin, Intent, Criminal, in 8 Encyc. Soc. Sci. 126 (Edwin R. A.
Seligman & Alvin Johnson eds., 1932). It is true that this general rule had some
strict liability exceptions, such as the quite common ancient rule that a man
was strictly liable for the acts of his slaves, and even a strict liability
view of homicide. See 2 Pollock & Maitland, The History of English
Law 470-73 (2nd ed., 1968). But these exceptions did not displace the rule that even in ancient times—when
access to the mind was so limited, at least by modern standards—civilized
people cared both about the wrongdoer’s acts and his intentions.
Forms of the insanity defense, for
example, were well known in antiquity. See Daniel N. Robinson, Wild Beasts & Idle Humours: The Insanity
Defense from Antiquity to The present (1996). When Even the “modern” M’Naghten formulation of the defense,
adopted by the House of Lords in 1843, was a codification of formulations that
had long been the common law of
. Anthony Platt & Bernard L. Diamond, The Origins of the “Right and Wrong”
Test of Criminal Responsibility and Its
Subsequent Development in the
: An Historical Survey, 54 Cal. L. Rev. 1227 (1966)
. See generally Isaac Ray, A Treatise on the Medical Jurisprudence of Insanity (1838).
Wendell Holmes, Jr., The Common
Law 3 (Dover Ed., 1991).
See generally Stephen J. Morse &
Morris B. Hoffman, The Uneasy Entente between Legal Insanity and Mens Rea:
Beyond Clark v. Arizona, 97 J. Crim. L. & Criminology 1071 (2007).
Joshua Greene & Jonathan Cohen,
For the Law, Neuroscience Changes Nothing and Everything, 359 Phil. Trans R. Soc. Lond. (B) 1775
(2004). Greene and Cohen argue
that although neuroscience will likely not cause any significant changes in
existing legal doctrines, it could have a transformative effect on the law by
changing people’s moral intuitions about free will and responsibility.
May 2005. "Law and Biology: A Newer Synthesis?" Opening
remarks of the 2005 Conference of the Gruter Institute for Law and Behavioral
This is a slightly different, and
less gruesome, version of Posner’s famous discussion of torture. In a free society, a few people may want to
torture and a few people may be willing to torture, at the right price. There is therefore no reason to outlaw this
sort of “voluntary” torture, and indeed the high price of torture will
eventually drive the behavior beyond the means of even the wealthiest of
torturers. Richard A. Posner, The
Economics of Justice 148 (Harvard 1981). You’ve got to love the libertarian implications of such a world, but of
course it is not the real world. In the
real world psychiatrically unimpaired people derive no happiness from torturing
or being tortured.
For example, does cannibalism have
evolutionary roots? It might and might
not. It is not hard to imagine an
environment in which selective cannibalism could have been highly adaptive. David Buss has written extensively about the
fitness double-whammy enjoyed by males who kill their sexual rivals. See, e.g., David
M. Buss, The Dangerous Passion:
Why Jealousy is as Necessary as Love and Sex (Free Press 2000). Killing them then eating them could be a
triple-whammy. But evolution is a crazy
car driven, at least in the first instance, by chance. Imagining an adaptive advantage for a
particular behavior, and proving the behavior does in fact have evolutionary
roots, are two quite different things. There is growing evidence that cannibalism was common in early human
populations, including epidemiological evidence that a certain class of viral
diseases were spread by cannibalism. Simon Meade, et al., Balancing Selection at the Prion Protein Gene
Consistent with Prehistoric Kurulike Epidemics, 300 Science 5619 (April 25, 2003). But even if cannibalism happened early and
often, until a set of genes associated with cannibalism is actually found, its
evolutionary roots will remain speculative.