“250-million-year-old bacteria”
How does anyone know it’s not only 249 million years old?
(A million years is a long time; they can’t guess any closer than that? What if it’s only 235 million years old? Fifteen million years is a long time. They can’t guess any closer than that?)
If they can be off by 15 or 20 million years, then how do we know this isn’t all just guesswork? (read: speculation)?
A million years is a long time, but not compared to 250 million years, a difference of 0.4 of a percent. Even 15 million years would only be a 6% error. That's still a pretty decent measurement.