Visible to the naked eye, fossilized bacteria or algae were found in an ancient seabed that emerged in the current Brazilian state of Mato Grosso do Sul. Credit: Bruno Becker-Kerber/Harvard University Scientists studying ancient microfossils from Brazil have discovered that structures once believed to be traces left behind by tiny animals were actually formed by communities of microscopic bacteria and algae. The findings challenge previous ideas about when small animals first appeared on Earth