Pigs vs people: the use of pigs as analogues for humans in forensic entomology and taphonomy research

Abstract

Most studies of decomposition in forensic entomology and taphonomy have used non-human cadavers. Following the recommendation of using domestic pig cadavers as analogues for humans in forensic entomology in the 1980s, pigs became the most frequently used model cadavers in forensic sciences. They have shaped our understanding of how large vertebrate cadavers decompose in, for example, various environments, seasons and after various ante-or postmortem cadaver modifications. They have also been used to demonstrate the feasibility of several new or well-established forensic techniques. The advent of outdoor human taphonomy facilities enabled experimental comparisons of decomposition between pig and human cadavers. Recent comparisons challenged the pig-as-analogue claim in entomology and taphonomy research. In this review, we discuss in a broad methodological context the advantages and disadvantages of pig and human cadavers for forensic research and rebut the critique of pigs as analogues for humans. We conclude that experiments using human cadaver analogues (i.e. pig carcasses) are easier to replicate and more practical for controlling confounding factors than studies based solely on humans and, therefore, are likely to remain our primary epistemic source of forensic knowledge for the immediate future. We supplement these considerations with new guidelines for model cadaver choice in forensic science research. Keywords Forensic entomology. Forensic taphonomy. Pig carcasses. Human corpses. Animal models. Decomposition ecology "We are unlikely to ever know everything about every organism. Therefore, we should agree on some convenient organism(s) to study in great depth, so that we can use the experience of the past (in that organism) to build on in the future. This will lead to a body of knowledge in that 'model system' that allows us to design appropriate studies of nonmodel systems to answer important questions about their biology" [1]. "Model species are usually easy to rear, observe, or otherwise experimentally manipulate. They therefore allow knowledge to be built up rapidly and efficiently, because confounding factors are known and thus can be controlled in subsequent experiments" [2].

Estimating the Postmortem Interval of Wild Boar Carcasses

“…It is therefore necessary to estimate the time that has elapsed since the death of a wild boar (Sus scrofa) found in the field, i.e., the postmortem interval (PMI). For domestic pigs (Sus scrofa domesticus), comprehensive forensic research has been undertaken [1], but little is known about the decomposition process of wild boar, and no systematic guidelines for PMI estimation have so far been available.…”

A review of experimental design in forensic taphonomy: moving towards forensic realism

“…The aforementioned illustrates the current difficulties associated with quantifiably accounting for sources of variance and error as previously emphasized by Henssge and Madea [4] and Matuszewski et al [5] suggest that it is not possible to recommend a universal analogue for human cadavers in decomposition studies yet. Moreover, they emphasize that abandoning non-human analogues is not currently viable due to the myriad of challenges and restrictions currently limiting use of donated human cadavers for experimental taphonomic research and stress the need for further research to address these shortcomings.…”

“…The logic is that the results from such studies are more directly applicable to forensic cases than data derived from research on non-human models. This argument remains to be proven and there are several issues with it, most recently summarized by Matuszewski et al [5]. As a start, there are biographic disparities between the donor population for experimentation and the general population to which results are meant to be extrapolated, namely age, body mass and underlying medical conditions that may impact decomposition cycles.…”

“…These seemingly conclusive settlements to the debate have, however, recently been shown to be flawed. In their recent rebuttal, Matuszewski et al [5] point out that the Connor et al [14] and Dautartas et al [24] studies failed to adequately account for confounding variables, notably the influence of variant carcase size, close inter-carcase distances which may have led to crosscontamination of attendant necrophagous insect communities, and inter-annual effects (specifically in Connor et al [14]). Furthermore, they highlight that both studies incorrectly applied the TBS scale for quantifying decomposition progression and did so without any supporting measure (e.g.…”

Impact of confinement in vehicle trunks on decomposition and entomological colonization of carcasses

“…Some studies have shown differences between pig and decomposition rates in some areas [28], but so far, no differences have been seen between insect species collected from pig and human cadavers [3,29,30] and insect development is dependent on temperature rather than carcass type. A recent review has shown that using pig carcasses as human proxies is much more practical than using human cadavers as it makes controlling for confounding parameters much easier and increases the ability to replicate carcasses [31].…”