These early ancestors of modern Eurasians disperse into parts of the world that had more seasonal sunshine and much lowerlevels of sun radiation.
这些现代欧亚混血儿的早期祖先分散到世界各地,那里有更多的季节性日照和更低水平的太阳辐射。
2
The areas that are now desert were, like all arid regions, very susceptible to cycles of higher and lowerlevels of rainfall, resulting in major, sudden changes in distributions of plants and animals.