Last time I saw a dateable sample (i.e. straight from the crematorium vs. at a mountaintop or waterfall) was about nine years ago, and it was quite chunky. This was from a crematorium in Arizona that was presumably using modern methods. I do recall that there was an episode of a TV show a while back (Dexter?) where someone did an ashes swap and it was discovered because the ashes looked like they were from the 70's, but that could have just been something the writer dreamed up.

You can almost imagine an eccentric subculture rife with debate over the preferences and arguments in favor of the virtues distinctive degrees of granularity in cremated human ashes, not unlike peanut butter varieties.

The defining aspect of the argument being whether you can tell the ashes came from a human, or whether you'd rather not know, or care to think about it.

The show was "six feet under"

Interesting. Maybe someone can chime in on how it would be different from ash at the center of a fire pit?