Re: Viva Neornithine Birds!

[john bois <jbois@verizon.net>]

David said:
> Of course, not all species are equally susceptible to the various effects
of
> impacts, and I think this is what we are looking at here. Arboreal birds
> will run into trouble when all the trees burn, for example. This --
> exaptation for impact conditions -- seems to be what you have never taken
> into account so far.

Not at all.  All I want are hypotheses for why neornithines.  Previously,
this request was resisted on grounds that extant bird diversity descended
from a single surviving species.  Under this conceptual regime, it made
sense to invoke luck.  However, with more surviving species it is sensible
to delve a little deeper.  Your hypothetical example of  arboreal species
suffering higher extinction rates might be testable...at least it is an
attempt to _explain_.

> > Assuming equal numbers and distribution of neornithines and
> > enantiornithines, the probability is .5 ^10 that they would _all_ be
> > neornithines.
>
> How do you arrive at this number?

For Neo/Enanti pair #1, chance of Neo surviving and not enanti is .5.  Same
with pairs 2 through 10.  Multiply unrelated outcomes for astronomically
small chance of only neos surviving.

> > It's glib because it doesn't require evidence and is, indeed,
untestable.
>
> What? It requires evidence for an impact. It is entirely falsifiable: show
> me that the -- more and more precise -- expectations are _not_ met, and
the
> hypothesis that the impact alone is to blame _is_ disproven. For example,
> show me a steady decline of Enantiornithes across the boundary, or one
that
> reaches 0 right at or even before the boundary, at the same time an
increase
> in neornithine diversity, and show that whatever environmental conditions
> can't be to blame (that's the easiest part).

Two things: 1. Evidence of an impact and mass extinction is not necessarily
evidence for differential survival of neos vs. enantis--unless you can
propose a testable hypothesis for why.  The tyranny of this
bolide-explains-everything is weakened by increased survival and especially,
differential survival of similar species!
2. I agree that hypotheses regarding enanti/neo temporal and geographic
distribution need testing.  And then let ideas follow the data.  Enough of
this umbrella hypothesis.

> > And it's glib because it inspires glib
> > hypotheses (e.g., the fanciful crab-cracking of shore birds).
>
> Never heard of that one.

Feduccia's idea: detritus-eating crabs survive due to abundance of food
remaining; shore birds eat crabs and survive.

> > ...are you arguing against their conclusions, or just gainsaying for
epistemological sport?
>
> You still haven't understood them. That particular claim is _not_ part of
> their conclusions.

 I am not not not claiming that pre-boundary neo survival was an official
Conclusion of this paper.  But, in this informal venue, I believe it is OK
to say that, after a review of the relevant literature, they concluded the
following: "If accurate, despite the vulnerability of such data to
suboptimal rooting, this record undermines early anticipations of K-T
boundary effects in modern orders and an evolutionary timespan in which
major divergences of neornithine lineages would extend through the early and
middle Cenozoic."
I agree that I should have been more careful in my initial post: I should
have said they were reviewing other literature and that the data referred to
was not fossil but molecular data.  I certainly was not trying to mislead.
Let's move on.
Are you arguing against the conclusions of the references they cite?
Specifically, are your anticipations of "boundary effects in modern orders"
undermined?