Forensic genetics through the lens of Lewontin: population structure, ancestry and race

Abstract

In his famous 1972 paper, Richard Lewontin used ‘classical’ protein-based markers to show that greater than 85% of human genetic diversity was contained within, rather than between, populations. At that time, these same markers also formed the basis of forensic technology aiming to identify individuals. This review describes the evolution of forensic genetic methods into DNA profiling, and how the field has accounted for the apportionment of genetic diversity in considering the weight of forensic evidence. When investigative databases fail to provide a match to a crime-scene profile, specific markers can be used to seek intelligence about a suspect: these include inferences on population of origin (biogeographic ancestry) and externally visible characteristics, chiefly pigmentation of skin, hair and eyes. In this endeavour, ancestry and phenotypic variation are closely entangled. The markers used show patterns of inter- and intrapopulation diversity that are very atypical compared to the genome as a whole, and reinforce an apparent link between ancestry and racial divergence that is not systematically present otherwise. Despite the legacy of Lewontin's result, therefore, in a major area in which genetics coincides with issues of public interest, methods tend to exaggerate human differences and could thereby contribute to the reification of biological race. This article is part of the theme issue ‘Celebrating 50 years since Lewontin's apportionment of human diversity’.

Open-Access Worldwide Population STR Database Constructed Using High-Coverage Massively Parallel Sequencing Data Obtained from the 1000 Genomes Project

“…AMOVA revealed that most of the variance (97.12%) in allele frequencies occurred within populations, corroborating previous studies [ 44 , 45 ]. A study that evaluated human population structure using genotypes at 377 autosomal microsatellite loci in 1056 individuals from 52 worldwide populations revealed that the variance within populations accounts for 93 to 95% of genetic variation, while differences among major groups constitute only 3 to 5% [ 45 , 46 ]. Although the number of populations and genetic markers are quite different, the larger amount of variance within populations and lower variance among groups observed in the present study may be either due to chance or to the fact that forensic STRs do show relatively lower F ST than random STRs due to the increased heterozygosity of the former [ 46 ].…”

Celebrating 50 years since Lewontin's apportionment of human diversity

“…Jobling [27] discusses forensic genetics, an important societal application of population-genetic ideas. Although allele-frequency differences among human populations tend to be small, Lewontin forcefully pointed out that they nonetheless introduce complications when one is trying to quantify the strength of evidence provided by a genetic match between a suspect and a crime-scene sample.…”

“…[28,29]). As discussed by Novembre [2], Lewontin's paper [1] has been referenced beyond the field of human evolutionary genetics as supporting an oversimplified view of human variation, in which population structure is completely ignored even in situations in which it might be relevant, such as matching problems in forensics or transplantation, where population variation in match probabilities affects the societal use of population-genetic computations [27,29].…”

GATTACA AS A LENS ON CONTEMPORARY GENETICS Marking 25 years into the film’s “not-too-distant” future

“…Because the typical person has many distant cousins, even a database that includes only a small fraction of the population (≈2%) will include genetically detectable cousins of the majority of the population (Erlich, Shor, Pe'er, Phenotype predictions in forensic contexts, termed forensic DNA phenotyping (FDP), have been explored in the academic literature (Walsh et al, 2013;Claes et al, 2014;Kayser, 2015;Chaitanya et al, 2018;Schneider, Prainsack, & Kayser, 2019) and are currently marketed to law enforcement (Wienroth, 2018). Forensic interest in phenotype prediction focuses on so-called externally visible traits (EVTs), which might be perceived by a witness (Jobling, 2022). Sex, predicted from sex chromosome karyotype, has been used in this way for some time (Sullivan, Mannucci, & P, 1993), notwithstanding some errors resulting from imperfect matches between sex chromosome karyotype and sex, or between sex and gender identity or presentation.…”

“…Although coarse pigmentation prediction (e.g., classifying blue vs. brown eyes, but not green vs. hazel) can be reasonably accurate for eyes, hair, and skin, at least in some groups (excluding possibilities such as dyed hair, colored contact lenses, greying of hair with age, etc. ), predictive performance on most facial traits is not accurate enough for reliable face reconstruction (Schneider et al, 2019;Jobling, 2022). For some facial phenotypes, predictive accuracy is limited in principle by moderate heritability under current conditions (Šešelj, Duren, & Sherwood, 2015;Cole et al, 2017;Tsagkrasoulis, Hysi, Spector, & Montana, 2017).…”