This region of the world is famous for yielding a series of ancient human and hominin species stretching as far back as 6 million years. In 2003, using argon–argon dating, the Upper Herto Member was dated to 160 to 154 thousand years ago. The Herto Man was, thus, a major fossil find, as, at the time, there was a significant gap in the human fossil record between 300 and 100 thousand years ago, obfuscating the evolution of ""Homo (sapiens?) rhodesiensis"" into "H. s. sapiens".