[Rockhounds] Fossils key to fulfilling Darwin's 160-year-old prediction

[Alan Silverstein]

> Fossils key to fulfilling Darwin's 160-year-old prediction
> December 12, 2018, University of Salford
> https://phys.org/news/2018-12-fossils-key-fulfilling-darwin-year-old.html

Brief and interesting, thanks.  It reminds me, though, of some "mind
blowing" (at least to me) new perspectives I got a while ago, probably
from Dawkins' book, "The Greatest Show on Earth".

Quibbles continue over definitions of today's species.  It's not as
simple as we might have learned in middle school, "successful
interbreeding," given microbial direct DNA exchanges, and
varieties/subspecies, etc.  Even if you're up to speed on all that, it's
still easy to forget that:

- Species morph over time, and not necessarily smoothly.  Consider
  "punctuated equilibrium."

- In almost every case, parents at least theoretically should be able to
  interbreed with their direct offspring!  So when is a new species
  created?  Never suddenly, only after many generations of physical or
  virtual separation and mutation/evolution.

  (It still bugs me how can chromosome count ever change, since it
  cannot happen all at once, but it's a small integral number, and
  mismatches interferes with sexual reproduction.)

- And yet, it should always (except in case of direct DNA exchange) be
  at least theoretically possible to trace members of different species,
  even wildly diverse ones (like cantalopes and chinchillas) to "last
  common ancestors", meaning common parents, of siblings that forked
  forever (for whatever reason) without interbreeding (neither directly
  nor in later generations).

- So, back to fossils:  Nowadays I'm amused by debates over how to
  categorize their species, especially considering that in most cases we
  only have age, locale, and (some) anatomy to go on, but no DNA.
  Definitions of species can be relatively fuzzy, even at a GIVEN time,
  and the tree of life is a tangled mess over the long run.

Cheers,
Alan Silverstein