|MadSci Network: Earth Sciences|
There are two ways to date old footprints. The easiest way is to simply date the mud or ash that the footprint was formed in, but you need the cooperation of the owner of the foot. If the person who made the print happened to do so in volcanic ash, or another medium that is directly dateable, you're home free. You can use any of several isotopic techniques (such as Uranium-Lead or Argon-Argon) or scintillation techniques to date the footprint directly. There are several assumptions which have to be made, but the "true" date can often be determined with great accuracy. The second way is to date rock strata above and below the footprints (using the same techniques as above) to get a "date range." Thus the age of the prints has to be at least as old as the rock under them (because the rock under the prints had to have been laid down BEFORE the prints were made), and the prints have to be older than the rock deposited on top of them. Of course, because the prints are now exposed, finding and dating rock strata "above" the prints can be a problem, but usually there are remnants of "complete" rock stratigraphy (in the local stratigraphic area of interest), so this is usually not a big problem (however, finding suitable rock for DATING, either above or below the region of interest, can be quite a challenge). For more information, go to
for a great "anthropological resources" page. Also,
has lots of stuff on paleontology, with information about stratigraphy (and good pics of fossils). Later! (If your mother ever said "Questions are food for the Brain," she was ABSOLUTELY RIGHT!) By the way...the "aquatic ape" theory? There is NO solid evidence of an aquatic phase in the lineage of ANY primate, to my knowledge. Two years or so ago, Dr. Richard Leaky (in a presentation to the public in Los Alamos, New Mexico), said the same thing. The aquatic ape theory is BUNK, in my opinion.
Try the links in the MadSci Library for more information on Earth Sciences.