[MrB]

Everybody SING now!
"Welllllll....
the fossils date the rocks
and the rocks date the fossils
and the fossils date the rocks, again!"

[Any Fate But Submission]

So it was a red tide that contaminated the shell fish and wiped out the Neanderthals. The red tide was obviously from human pollution so there you go.

[BroJoeK]

MrB: "Everybody SING now! 'Welllllll.... the fossils date the rocks and the rocks date the fossils and the fossils date the rocks, again!' "

Rocks are dated using:

• radiometrically -- decay rates of about two dozen different radioactive elements and
• and/or geological stratigraphy -- analysis of rock layering, including fossil-bearing layers.

Fossils are dated:

• radiometrically, if they include radioactive materials,
• and/or by reference to previously established ages of geological strata in which they were found,
• by reference to related fossils of previously established ages.

Of course, some of these methods are "derivative" of others, and each has associated difficulties.
But the "gold standard" is radiometric dating, and when several different materials agree, then that's as good as it gets.