Tiny, bacteria-like organisms made their home in hardened lava some 3.5 billion years ago, scientists reported last week in a finding that pushes the limits of when life is known to have started on Earth. The microbes, known as archaea, dug into volcanic rock to form long tubes. A team from the United States, Norway, Canada, and South Africa found evidence of the lava-burrowing archaea in 3.5 billion-year-old rock in South Africa.