In 2018, a literature review found that most genetic studies conducted over the last two decades were based on modern dog breeds and extant wolf populations, with their findings dependent on a number of assumptions. These studies assumed that the extant wolf was the ancestor of the dog, did not consider genetic admixture between wolves and dogs, nor the impact of incomplete lineage sorting. These pre-genomic studies have suggested an origin of dogs in Southeast Asia, East Asia, Central Asia, the Middle East, or Europe. More recently, the field of Paleogenomics applies the latest molecular technologies to fossil remains that still contain useful ancient DNA.