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Response to Orenstein's "explanation" of mammal success.
Ron Orenstein says: "...in some ways mammals were MORE diverse
before the K/T than after...But that diversity was still
diversity among small ratty, shrewy, or squirrely things."
Then perhaps we agree on this. My difficulty is with what I see
as the standard Gouldian claim that mammals were "almost
surely...small and insignificant...restricted, and unendowed with
consciousness" (in _Dinosaur in a Haystack_). Just as we cannot
know (just yet, anyway) whether mammals were significant, we also
can't know, or even "almost surely" know, that they were
_insignificant_. Yet this is the prevailing paradigm. And
though you may disown it, you shouldn't claim the same for
Pharris and Rowe, as in: "what we all are saying." Pharris also
believes mammals were insignificant. Again, this is pure
Anyway, Archibald's find says more about the increased
_quality_ not the quantity of diversity, i.e., innovations in the
mammals stock were making the clades of today. And the viability
which these innovations subsequently demonstrated creates a
_greater_ probability of their increased significance in the pre-
Ron infers that my arguments are "either fallaciously reasoned or
based on inadequate consideration of the facts." Furthermore, he
likens himself to a "referee in a journal."
Firstly, this is not a journal. Secondly, a referee would
presumably be free of bias. You may believe yourself so, but you
argue fallaciously in order to bolster the beliefs you hold. Here
are some examples.
1. You use extinct creatures to show the viability of non-
mammalian open-niche life-styles as in your response to my claim
that we see (today) no big ground-laying birds, lizards, turtles,
and snakes: "there WERE big open-country lizards...[terrestrial]
crocs lasted until fairly recently...As for birds, don't forget
Diatrymids, Phorusracids, and Dromornithids..."
2. You argue the applicability of a general rule with
insignificant exceptions as in your response to my claim that
"bird eggs can be hidden in out-of-the-way places" and "lizards
are small and can hide their eggs well": "These are gross
overgeneralizations. What about ostriches, for example? Komodo
Ron, there is _one_ big ground-laying bird in all of Africa.
One in South America. One or two only, in Australia. The Komodo
dragon is named after one of the three small islands it lives on
(with a total range less than a quarter of Rhode Island). And it
is threatened, among other things, by introduced mammals. The
general rule, then, applies: mammals do better in the big-animal,
open-field niche than egg-layers. (Ron's comments here were in
another post but I bring them up because he referred to the
Komodo in a similar context in this one.)
3. You use a non-example, albeit parenthetically, to lend weight to your
arguments against an example, as in your response to my claim (I
think) that egg laying in the open-field is a liability: "By the
way - there are actually more species of birds, and more species
of reptiles (sensu lato), alive today than there are species of
mammals..." So what! There are more beetles, more atoms of
water, more lots of things around today than mammals. We are
only arguing about the niche the dinosaurs used to live in. In
those niches, with VERY FEW EXCEPTIONS, mammals today dominate.
And when you subtract your above irrelevant and fallacious
arguments, I'm not sure you have much left.
So now I try to pin you down to making your own explanation of
the overwhelming success of a life style you still don't fully
admit. I almost gave you the three possible choices for this
success, i.e., chance, intrinsic worth, and "don't know". Lo and
behold you went for all three.
1. "Don't know": "...the fact that an adaptation exists does NOT
mean that we can assess its contribution to fitness -
particularly overall fitness - in prehistoric ecosystems."
In other words, just because live-bearing is very
successful today (presumably because it has _some_ advantages), I
can't make inferences about its value at _any_ time. Your view
is too restrictive. Of course we can't know the precise
implications of the various tactics, but we ought to be able to
make inferences. They may be right or they may be wrong. But
reasonable inferences may be good guides to future research.
Blanket statements such as "we cannot assess" are unhelpful to
2. Chance: "To some degree the answer may be, in Stephen Jay
Gould's sense, Why not mammals? Or, mammals, because it wasn't
something else. The luck of the draw, in other words."
This is sophistry when applied to mammalian success. There are
an infinite number of possible niches even in the open field.
There are many geographical locations around the world. There
have been an infinite number of opportunities for other
strategies to take hold. But, ultimately, this has not happened.
Again, one in Africa, one in South America, and one or two in
Australia. The likelihood that this result happened by chance
alone is practically zero. Yes, small random changes in initial
conditions lead to profound effects later. My argument is that
these changes happened _before_ the K/T, and their effects were
so profound that they, in part, led to the extinction of the
dinosaurs. The Cenozoic is just a playing out of this inevitable
plot line. In the period 100 mya to today, the mammals triumphed
not because of chance but because of their intrinsic abilities!
3. Intrinsic worth: "...the chief cards in the mammalian pocket
were related to niche flexibility - and these may have included
dental structure, small size, endothermy or any combination of
these or other factors."
First of all "any combination of these or other factors" is
legalese. It is an answer that works for just about _any_
complex ecological question. But it is of not much use in answer
to the question: What specific advantages did mammals have over
other creatures which enable (and enabled) them to dominate the
open-field niche of today?
So what we are left with, in response to my request for A DEEPER
EXPLANATION of the reasons for mammal domination in the open-
field is not much. Niche flexibility? Birds are incredibly
diverse and flexible in the niches they exploit. Lizards are
found throughout the world, in almost all biomes. They are also
very successful creatures, as are snakes, and turtles. Small
size? All of these groups have many small members among their
number! These characteristics, by themselves, say nothing about
mammalian success since other groups, groups which are
_unsuccessful_ in the open-field, also possessed them!
I'm not sure about teeth. Obviously this and jaw structure
had something to do with it. But what, and to what extent? I
really don't see how a ferocious Phorusracid, for example, with
its bone-crushing jaws could have been bested by _any_ small
mammal, no matter how finely its teeth were put together (unless
of course egg-gnawing ability were involved!). But they went the
way of all other open-field pretenders. And this is another
major problem with your argument. After all, compared to the
big birds, mammals were "insignificant". Yet they too became
extinct. Don't tell me, I know. PHORUSRACIDS WERE DONE IN BY
ANOTHER BOLIDE SMART BOMB, presumably programmed to keep those
cursed open-field egg layers out of business!
Endothermy? Important for sure. But, again, birds had that
advantage as well.
So far, in my solicitation of explanations for the decidedly
non-random distribution in favor of mammals in the open-field of
today, the only thing that is unique to mammals is teeth.
Archibald's 2mm tooth looms large indeed!
Ron says that mammals were generalists and had not gone "down
roads of specialization that it would be extremely difficult to
retrace." As such they were more able to step into the niches
made available by the dinos exit. But birds were generalists,
too and did, in fact, step into those niches before mammals. Ron
uses snakes as an example and suggests that they could not be
herbivores because of "early specialization" (for carnivory, I
presume). But this is silly. Any snake worth the title has a
long, thin body. Why? So it can hide down holes. Why? Because
a selective pressure existed to make this a viable strategy to
resist predation. Having adapted for laying low, carnivory was
the only option since herbivores must forage longer. Now, if you
kill off everything else and make available a great range of
niches, some of them _would_ evolve into herbivorous species.
But they would also evolve more mobile shapes and they then
wouldn't be snakes anymore. Obligatory carnivory in snakes is
strictly due to a lack of available niches. Look also at the
marine iguana of the Galapogos. It is a vegetarian among
predominantly carnivores, lizards I mean. Yet it has adapted
Ron wonders what "the advantages of altriciality" are that are
allowed by mammalian milk. He believes the additional time spent
in the helpless state would have a "certain cost." I believe the
security of a well hidden and less frequently visited nest, den,
burrow, or marsupium (remember the window of insecurity is
smaller in live birth than egg laying) allowed a period of
relatively less predation for additional offspring development.
Look at humans. We are helpless, our offspring prolong
immaturity so that the incredibly complex finished product can
have time to be completed. Have you heard about the Indigo
bunting whose babies are trained, or learn within the nest to
recognize the pattern of stars by which they will navigate when
they fly (this was in a Scientific American, if I recall)!!! I
believe species will "opt" for altriciality if possible simply
because their is a selective advantage to having more time for
development. Why else would most ground-laying birds be
precocial and tree-laying birds be altricial (To keep the babies
from falling out of the nest? I don't think so. The pattern is
the same for mammals if you compare burrowers to grazers.)
Finally, I would like to apologize publicly for spelling