Tracks in the Australian desert may be
of the oldest multi-celled organisms. The grooves may have
been made by creatures similar to worms which were crawling around
one billion years ago. Another theory is that groups of single-celled creatures
moving together could have also been responsible.
The snail-like tracks are about one millimeter
wide and several centimetres long. Experts think whatever
made the marks probably died out in an evolutionary dead-end and
never evolved to be any modern day critter. They seem to have moved
on a slime-like cushion which preserved the grooves. Yuck.
Paleontologist Stefan Bengtson, of
the Swedish Museum of Natural History, says the sandstone bearing
the tracks is at least 1.2 billion years old, possibly as much as 2
billion - but says the lower end of the time range makes more