The evolutionary rates presented here for class II aPMV-1 are compatible with the rates estimated for other RNA viruses (e.g. [56, 57, 58] ), suggesting that class II aPMV-1 is also a rapidly evolving RNA virus. The relatively lower evolutionary rate for genotype II is consistent with the rate that was previously reported for avirulent NDV [33] . The larger effective population size, which counters the impact of genetic drift, is a possible explanation for lower evolutionary rates of genotype II. Based on these rate estimates, the TMRCA of this virus is estimated to be between 1868-1891, which is earlier than the first recorded outbreak of ND in Indonesia and England in the 1920's [2] . However, our data are in line with observations by Macpherson [59] , who suggested that an outbreak of disease in domestic birds that occurred in Northwest Scotland from 1897-1898 was due to NDV.