An alarming message about deodorant use and breast cancer began circulating on the Internet in the 1990s, spread via e-mail and message-board postings. It continues to resurface now and again and causes a great deal of concern about the safety of items many of us use every day. So let's take a look at the evidence.
How long have sharks been in existence? A: Geological records show that modern shark species have existed for between 201 million and 174 million years. Earlier fish species similar to sharks existed as early as between 419 million and 359 million years ago.
Each shark can produce up to 30,000 teeth over the span of their life. These teeth consist of dentine and enamel which does fossilize in the ocean. There are ways to determine how old these teeth are. That has lead to significant evidence of how long sharks have been around.