[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: more dinosaur extinction stuff
Regarding the pineal gland theory:
1) If you look long enough for a consistent anatomical difference
between any arbitrary Group A and Group B, you WILL find one. It just
stands to reason that you will because there are countless dozens,
hundreds, or even thousands of possible differences. This is just
like going through the roster of a losing World Series team until you
find an ex-Cub, and then declaring that the team lost BECAUSE of the
Cubs' curse (yeah, I know, it's supposed to be three Cubs).
Therefore, one should be really cautious about the "fact" that
dinosaurs all had anatomical feature X or Y "proving" that that was
the cause of their extinction.
2) The K-T extinction was not just a DINOSAUR extinction, it was
GLOBAL MASS EXTINCTION. The current best estimate is that 70 - 76% of
ALL marine animals went extinction at the K-T. This is nothing to
sneeze at, and I'm sure it has nothing to do with pineal glands.
Furthermore (and more to the point), "mammals, lizards, fish, birds
etc" DID suffer an extinction at the K-T. For example, the mammals
lost about 1/3 of their genera and 1/2 of their species. My friend
down the hall has data showing a similar global extinction for
crocodylians. Birds have virtually no record in this interval, and we
can argue about teleosts, amphibians, squamates, and turtles some
other time. Dinosaurs weren't the only large vertebrates going
extinct at the K-T: so did the icthyosaurs and the plesiosaurs (not
to mention the pterosaurs).
3) As I've argued before, it's just ecological common sense/general
knowledge that when the going gets rough, large body size is a
serious handicap. Large animals have small populations, slow rates of
intrinsic population increase, and generally high rankings on the
trophic "scale"; those are very serious drawbacks in the face of a
catastrophe. In other words, the meek DID inherit the Earth, and
that's just what any community/population/conservation ecologist
In summary, I think we should hold off on speculating about dinosaur
extinctions until someone can disprove the body size hypothesis
combined with the standing null hypothesis - that dinosaurs,
plesiosaurs, ichthyosaurs, pterosaurs were just a few petty little
groups (which is exactly what they were from the perspective of
global diversity) that got unlucky at the K-T, losing all of their
diversity instead of "just" half or more like the mammals.