I never wanted to be a prison psychologist. As a colleague remarked: “Who would want to have that sort of relationship with one’s clients?” Later on a particular colleague got me interested in the detection of criminals: psychological detective work in which perpetrators were tracked down by the behavioural shadows they left. I found forensic psychology much more interesting, but mostly because it is a difficult problem to solve, and requires well thought out protocols.
Criminology is a different matter. I have always listened politely when having crime explained to me: bad parenting, lack of self esteem, poverty, alcohol, drugs, bad marks at school, lack of early discipline, too much discipline, and sundry other hypotheses in search of an explanation.
Imagine my relief when Brian Boutwell and colleagues offer me a Unified Crime Theory with an evolutionary perspective. Is this what I have always waited for, or is it just a lump of evolutionary just-so stories?
Brian B. Boutwell, J.C. Barnes, Kevin M. Beaver, Raelynn Deaton Haynes, Joseph L. Nedelec, Chris L. Gibson. A uniﬁed crime theory: The evolutionary taxonomy. Aggression and Violent Behavior (2015) In Press. http://dx.doi.org/10.1016/j.avb.2015.09.003
The team outline a number of general issues which a theory of criminality must cover.
First, there are consistent race differences in aggressive, violent, impulsive and criminal behaviors:
Second, there are consistent sex differences across many measures of criminal behavior: men cross-culturally display greater violence than women
Third, criminal behavior is age-graded: escalates around the time of puberty and then decelerates in the early to mid-20s
Fourth, a small proportion of the population develops temperament and conduct problems very early in development, perhaps even during the ﬁrst year of life
Fifth, there are genetic inﬂuences across virtually every human outcome, including antisocial and criminal behavior, and account for about half of the variance in antisocial behavioral outcomes
Sixth, consistent variation exists across geographic areas (neighborhoods, census tracts, etc.) for measures of crime yet there has not been a consistently supported explanation for why certain areas report more disadvantage, disruption, and illegal behavior.
The authors explain the lack of a unifying theory thus: The lack of unity can be traced to the fact that for decades certain lines of research were censored from the study of crime. Evolutionary biology for example,has struggled to gain true traction in the discussion of the origins of criminal behavior. Mainstream theories of crime causation (which originate within the ﬁeld of criminology by criminologists) are generally silent on the idea that selection pressures across millions of years of evolution could have shaped the qualities of modern offending behavior.
In my phrase: criminologists have tampered with the crime scene.
The authors suggest using r-K theory to unify the understanding of crime: from the vantage point of evolution by natural selection,criminality is the product of individual variation on certain traits relevant to life history strategies. Natural variation is the key point in that it has resulted in some individuals falling further away from K than others.  Individuals falling relatively further from K will exhibit faster maturation and lower levels of parental investment. Additionally, they will display greater mating output (i.e., more effort invested in mating, instead of raising children), higher rates of disease and shorter life spans.
The authors quote compelling work on early childhood detection: Around 5–10%of the population begins displaying antisocial behaviors very early in childhood (Mofﬁtt, 1993;Mofﬁtt&Caspi,2001).These behaviors escalate with age eventually manifesting as childhood behavioral problems, transitioning next to adolescent delinquency,and ultimately to crime in adulthood. This segment of the population was termed life-course-persistent (LCP) offenders. According to Mofﬁtt (1993), the proximal predictor of LCP offending was the experience of neurological/cognitive deﬁcits coupled with family adversities including physical abuse and neglect in the ﬁrst few years of development(although other environmental insults, such as prenatal experiences, could also play a role).
Career criminals (the usual name for life-course-persistent) are more likely to possess traits representing a faster life history(i.e.,deviatingfurtherfromK)in that they disproportionately originate from disrupted homes, evince deﬁcits in impulse control, express difﬁculty with emotional and behavioral regulation, demonstrate faster physical maturation, reach sexual maturity and engage in sexual behavior at an earlier age,and father a disproportionately large number of offspring (fewer of which survive and thrive). With time and age these individuals should be less likely to engage in long standing pair bonded relationships involving high levels of parental investment.
The figure shows that life-course-persistent people are frequently in trouble with the law (exceed the threshold of lawful behaviour) the average citizen sometimes, and abstainers never.
The authors work through their initial points, and show how a life-history perspective applies to each, using the same principles. Just as an example, regarding race differences in crime, Beaver, DeLisi, et al. (2013) reported evidence that once intelligence and lifetime histories of violent behavior were held constant, race differences in criminal justice processing outcomes were no longer observed.
Here is their summary on group differences: There will be group differences in the rate of LCP offending, such that Blacks will be more likely to show signs of LCP offending than Whites, Whites will be more likely to show signs of LCP offending than Asians, and males will be more likely to show signs of LCP offending than females. Conversely, Asians and females will be more likely to exhibit behaviors consistent with Mofﬁtt's (1993) abstainer group. Once again, it is important to reiterate that these group differences will be subtle and that they only apply to the group.This means that offending rates are not expected to drastically differ between groups and that the offending behaviors of any individual may be inconsistent with the group's behavior.
There is a lot in this paper, and since it is expositional rather than data-reporting, it is worth reading the text to go through the supportive data referenced under each of the six points above.
The authors are aware that their paper might seem to be a just-so story, and suggest some initial broad testable predictions:
LCPs should be more likely to be born prematurely, to be born of lower birth weight,and to be exposed to noxious agents prenatally (indeed, Mofﬁtt  suggested many of these possibilities herself). Additionally, LCP offenders are expected to reach sexual maturity more rapidly than their same-aged peers. LCPs will be expected to have more (unprotected) sex with a larger number of partners, yet fewer of their offspring are expected to be reproductively viable and survive until adulthood. The pregnancies of LCP offenders should be more likely to end in spontaneous (and perhaps intentional) abortions, miscarriages, or to experience medical difﬁculties and complications. LCPs, ﬁnally, should be far less likely to invest heavily in their children who survive to birth.
I like the general drift of this paper. I see it as strongest when it shows that, corrected for intelligence and life stage, many of the big differences in the 6 points are reduced, all falling under a common explanatory framework. I agree that mainstream criminology has averted its attention from any explanation of which it does not approve. Of course, my disapproval of improper forensics at the crime scene should not mean unthinking approval of this over-arching theory. I would like further hypotheses to be proposed and tested. As the authors say:
It is our hope that scholars will approach the question of criminality as a scientiﬁc query in need of an answer. This type of cold empiricism is far more likely to unearth truth and avoid the trappings of ideological debates. The litmus test for our theory will be whether or not it receives empirical support and our theoretical enterprise will rise, or fall, based on the evidence that accrues either for or against our predictions.
I look forward to the testing of the hypotheses, which I believe will energize criminology in general, and cut through the gluttonous mass of ad hoc explanations for criminal behaviour.