The date estimated for the divergence of a domestic lineage from a wild one does not necessarily indicate the start of the domestication process but it does provide an upper boundary. The divergence of the lineage that led to the domestic horse from the lineage that led to the modern Przewalski's horse is estimated to have occurred around 45,000 YBP but the archaeological record indicates 5,500 YBP. The variance can be due to modern wild populations not being the direct ancestor of the domestic ones, or to a divergence caused by changes in the climate, topography, or other environmental influences. Recent studies indicate that a genetic divergence occurred between the dog's and modern wolves 20,000–40,000 YBP; however, this is the upper time-limit for domestication because it represents the time of divergence and not the time of domestication.