It is fairly easy to differenciate DNA samples from different species and exclude them. Since it has always been an issue to have contamination by foreign DNA (bacterias, fungus, virus, plancton, fauna and flora of all sorts, etc.), tools/methods/protocols are specifically made to quickly separate out (amplify the DNA we are interested in) from whatever is not to focus of the current study.

Moreover, a random anonymous sample without associated information can quickly be analysed and compared against large libraries of genome datasets/maps to ascertain and corroborate what it is from, closest species, even family trees of related inviduals and most importantly get an overview of multiple phenotype of interest.

From the day the full human genome map had been declared complete in 2003 (at 85% of the genome), research has only accelerated in improving the map while understanding the various functions of many different parts of our DNA.