Complex sentence: Prothrombin G20210A was identified in the 1990s, is almost exclusively present in Caucasians, and is estimated to have originated in that population slightly over 20,000 years ago.
Split into simpler sentences: Prothrombin G20210A was identified in the 1990s, is almost exclusively present in Caucasians. It is estimated to have originated in that population slightly over 20,000 years ago.