NASA: National Aeronautics and Space Administration


Ask an Astrobiologist
"Hi! I would like to know what would it takes to reverse earth's rotation, and what would be the consequences for life on earth if that happens? "
  1. Special Note


    Ask an Astrobiologist has received more than 2500 questions about Nibiru and 2012, with more than 200 answers posted. Please read a summary of the answers that have already been posted, view a video on these topics, use the search feature and read the FAQ’s before submitting questions on these topics.

  1. Question

    In what period of geological time did humans first appear?

    The Quaternary Period. Fossil evidence shows that several human-like lineages developed during the past million years or so. From fossils, the appearance of Homo sapiens is dated at about half a million years, and of anatomically modern Homo sapiens at about a hundred thousand years. All of these dates fall within the Quaternary Period, which corresponds to the most recent 1.5 million years. David Morrison
    NAI Senior Scientist

    June 15, 2006