Brendan Maher | Sep 15, 2002 | 6 min read
Image: Ned Shaw The cell--the irreducible unit of life on Earth--has an estimated history nigh on 3.5 billion years. Scientists since Charles Darwin have attempted to trace that history to a so-called last common ancestor. Comparative physiology and fossil records can take one only so far, so many researchers are trying to reach the tree of life's roots with tools of a genetic nature. Yet, the more they dig, the more convoluted those roots appear to be. Lateral gene transfer, the square peg in