 The general focus on common variants in genomics was criticized by other authors who claimed that the focus of geneticists should rather be on rare variants (McClellan &amp; King 2010). These rare variants, they claim, are where the missing heritability will be found. The problem with the rare variants is that they cannot be picked up in GWAS that use SNP databases, as SNPs are by definition common variants. Also, finding rare variants is a technical challenge as researchers have to analyse the genomic data of a very large number of individuals to do so reliably. This hunt for rare variants is a major reason behind the current push for the sequencing of millions (rather than a couple of hundreds or thousands) of genomes. As discussed earlier, such large-scale approaches have become feasible in recent years due to the reduced cost and increased speed of next-generation DNA sequencing.