Another amusing example comes to us from LiveScience.com. It started off as a somewhat minor annoyance reported in July, 2005 (Footprints in Mexico Create Scientific Stir). From that article:
British scientists claimed on Tuesday to have unearthed 40,000 year-old human footprints in central Mexico, challenging previous studies that put the arrival of the first humans in the Americas at about 13,500 years ago.
"We think there were several migration waves into the Americas at different times by different human groups.''
In a follow up story in November, 2005 (Controversial Footprints: Earliest Man or Modern Machine?), the “stir” had become a full blown “controversy.” It seems someone had the bright idea of dating the volcanic ash the footprints had been made in. The results put a whole new kink in their theory:
Using palaeomagnetic analysis—a technique that looks at the Earth's magnetic field during past geologic time—and a radioactive dating technique called argon-argon, the team concludes the ash is actually 1.3 million years old [italics in original].
“Humans are not thought to have even been around 1.3 million years ago. According to most scientific estimates, modern humans didn't begin appearing in Africa until about 200,000 years ago.”
If the markings really are footprints, then it would mean one of two things: either humans appeared much earlier than previously thought or the footprints were made by an early ancestor of humans like homo erectus.
After visiting the site, Renne believes the markings are not really human footprints at all, but rather impressions left by machines or animals that have passed through the quarry in recent times.
"You have to remember this is a public area," Renne said in a telephone interview. "Vehicles drive across it, you can see tire tracks on the surface. There are cows and other animals grazing nearby."