Evolution What the Fossils Say and Why it Matters

FIGURE 7.1. A diorama of how life might have looked on this planet for almost the first 80 percent (3
billion years) of its history. The most complex form of life was the cyanobacterial mats forming domed
stromatolites. If an alien had visited earth through most of its first 3.5 billion years, it would have seen
nothing more complex than a mat of scum on the surf zone and probably left unimpressed with life on
this planet. (Drawing by Carl Buell)