Tracing genetic change over time using nuclear SNPs in ancient and modern cattle.

Ancient DNA has the potential of adding the dimension of time to genetic studies. With a suitable sample set it should be possible to follow genetic changes over time as they occur. To date, only a limited number of ancient DNA studies that cover a large time span have been published, and all of these studies have used mitochondrial DNA. Here, we explore SNP typing as a way to access ancient coding nuclear genes. By targeting fragments of minimal size, we typed three polymorphic sites in 111 ancient cattle remains spanning some 4000 years. We showed that there has been a decrease in heterozygosity over time, especially since the late Middle Ages. We conclude that SNPs can be used to generate a time series for nuclear markers from ancient material, and thereby to study selection on genes over time.