Human beings were present on Earth toward the end of the Cenozoic Era?

Well possibly. The Cenozoic or Age of the Mammals is the current geological era of the earth that began 65.5 million years ago. When it ends is not so much when we decide but more when nature decides. An extinction or genetic mutations leading to a new genus different than mammals and becoming the dominant life form will mark the end of this era. So whether we can say humans arrived toward the end of the Cenozoic era is for history to decide.