Define dark sheep1/7/2024 Instead, scientists turned to genetics, conducting a phylogenetic study-the study of lineages-into both subspecies of sheep. But that's not possible here because these sheep live on top of mountains, where it's rocky. "Traditionally when you're trying to figure out what species came first and how they split, you use fossils. ![]() "The separation is hard to date, because with glaciation, fossilization is a hard thing to achieve," explains Sim Zijian, PhD candidate in the Department of Biological Sciences and lead author on the study. When scientists looked into the DNA of both subspecies, however, they found it told a different story. After the glaciers melted some 10,000 years ago, this theory posits, the species diverged into the white Dall's sheep and the dark Stone's sheep that we know today. In some cases, individuals from the same species were separated in different refugia where they accumulated variances between populations over time, sometimes resulting in the formation of new species.Īn iconic symbol of the mountains of western North America, the ancestors of the two dominant varieties of thinhorn sheep were believed to have weathered the last ice age together in the Beringian refugium, which today spans Alaska and the northern Yukon. ![]() ![]() During the last ice age, most of North America was covered by inhospitable glaciers, forcing plants and animals to seek refuge in ice-free regions known as refugia.
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