george knapp here with the story. >> you ever have the feeling you were switched at birth, because yous birthday but he's recently learned he has no idea when he was born. the response to the first story we did was off the charts. phones ringing off the hook. there were inquiries from cnn, nbc, abc, everywhere. everybody wanted in on this story. >> it's a mystery once with believed solved. now the fbi is revisiting a half century old case. >> his name, his parents, his background. none of it was true. >> a bizarre mystery nearly 50 years in the making. the story was first reported by our las vegas -- >> it was like overnight, the whole country just erupted with this story. >> we're following this morning, a strange twist in a 50-year-old cold case. the fbi in 1964 -- >> i told paul, look, i got a feeling we're going to help you solve this. (patrick) it took a few years, i started to notice that i couldn't go as long. (renee) every half a block i'm stopping to try to catch my breath. (ray) if it's under 20 degrees out, i can't go outside my house because it feels like i'm inhaling broke

george knapp explains. >> footprints left in mud.hat is now white sands national park have caused a stir in scientific circles. the prints nicknamed ghost tracks are an estimated 23,000 years old, meaning people were in north america much earlier than previously thought. the ghost prints are the latest in a string of discoveries that are pushed back the estimates of when and how people arrived in the americas this ancient mummy found in a desert cave in the great basin sat in a museum's storage room for half a century before carbon dating revealed it to be the oldest human remains found on the continent. 5,000 years older than the mummies of ancient egypt spirit cave man as he was known set off heated debates about whether science should do further testing or return the remains to indigenous tribes. we don't believe dna. >> testing should be done or need testing should be we it's ancestors spirit cave man like kennewick man and hundreds of other human remains stashed in museums. >> for science and governments to re evaluate the ethic