1. Introduction

Mitochondrial DNA (mtDNA) is particularly well-suited for medical, population, archaeological, and forensic genetic investigations due to its high copy number per cell, greater stability against degradation compared to nuclear DNA, and maternal mode of inheritance. Its accelerated evolutionary rate has produced sequence variation, generated by the sequential accumulation of mutations along radiating maternal lineages during human migration and dispersal. Since the early 1990s, population studies of mtDNA sequences (mitotypes) have been extensively documented in scientific literature and online resources, significantly enhancing our understanding of global mtDNA variation.

In 1999, the forensic genetics community recognized the need to standardize and consolidate individual, decentralized mtDNA datasets. This initiative began under the auspices of EDNAP (European DNA Profiling Group), giving rise to EMPOP, which has since become a cornerstone of mtDNA research and harmonization.

EMPOP - The EDNAP MtDNA Population Database

Through critical discussions on data quality, supported by mtDNA blind studies (e.g., Parson et al., 2004), it became evident that both genetic studies in general and mtDNA studies in particular often fell short of the expected and necessary quality standards. Many datasets contained phantom mutations (Bandelt et al., 2002), primarily arising from transcription errors (Parson et al., 2004), sample mix-ups (Bandelt et al., 2004), and data misinterpretations (Parson, 2007). These findings underscored the critical need for rigorous quality control and standardization in mtDNA research.

The first seven years of the EMPOP project were dedicated to:

  1. Identifying sources and causes of errors in mtDNA datasets, such as transcription mistakes and sample mix-ups (Bandelt et al., 2006).
  2. Developing software tools to visualize and address these errors (Zimmermann et al., 2014).
  3. Establishing robust laboratory protocols for generating high-quality mtDNA data (Brandstätter et al., 2004; Berger et al., 2009).

In 2006, the first version of EMPOP went online. By 2010, leading forensic genetics journals mandated authors to quality-check their mtDNA data through EMPOP before submitting manuscripts for peer review (see CONTRIBUTE tab). This requirement has significantly improved the quality of published forensic genetics data. With the advent of Next Generation Massively Parallel Sequencing (MPS) technologies, forensically oriented laboratory protocols were developed (e.g., PEC, caphyb), and commercial products became available through multiple vendors (e.g., TFS, VEROGEN, PROMEGA, NIMAGEN), further advancing the field.