So what were the clues that made people start to
think? Paleontologists had long recognized that fossils from the east
coast of South America and the west coast of Africa had many fossilís
in common. Biologists had also noted that living animals like garden
snails, earthworms, mussels, and mud minnows also "linked"
across the ocean. By the late 1800's, naturalists who explored new
territories accumulated more evidence of these biological and
Some scientists developed these elaborate
"land bridge" theories. Organisms would be able to walk freely
along these connections. However, many scientists realized this land
bridge theory had some serious problems. Geologists started to visualize
a moving continent or what they called "continental drift" to
account for similarities.