[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Microraptor hanqingi, new species from China.

On May 25, 2012, at 3:53 PM, Don Ohmes wrote:

> Do I need to point out (yet again) that if there is no *need* for 
> special equipment, then there is no selective path to adaptation -- and 
> thus "comparing [...] adaptations" is not useful in this context?

If you expect no differences in anatomy, then what are we looking for?  Do you 
propose differences in taphonomy or paleoenvironment?  We only have a handful 
of things that can be used to test predictions.  The roosting in trees model 
seems reasonable, but it is nothing more than a reasonable speculation unless 
you have something we can test.  Again, I actually like the idea - since you're 
the one who pointed it out here, I was hoping you had some suggestions for what 
we'd predict if tree-roosting was indeed important to paravians.  If your 
assertion is, instead, that we'd see no difference in the fossil record between 
a case a fully "terrestrial" origin and a "terrestrial + tree roosting" origin, 
then I'm not sure what is being argued.

> "My model" falsifies the idea that an animal evolving flight in 
> tree-down gliding-first mode will by evolutionary logic show "arboreal 
> adaptations" in its skeleton -- beyond the basic capacity to climb a 
> tree, that is...
> This has implications to those who would, with any rigor, match 
> speculations about the evolutionary path taken by birds as they achieved 
> flight, and the evidence in the fossil record.

So, then is your argument simply that there might have been some arboreal 
activity involved that we will never see in the fossil record?  If so, I'm 
inclined to agree - but then I also don't know what all the arguing is about.

> (Thought experiments are necessary, and highly useful. Ditto scenario 
> building and ranking...)

A bit.  They can be useful in helping us mentally get to hypotheses we can 
test.  But on the whole, I am of the opinion that they are not terribly useful 
on their own most of the time.  I think they are greatly overused and typically 
involve a lot of arm waving.

>> Also, for all of the individuals in the current thread: we should be sure to 
>> give good cause at each step for putting paravians in trees to begin with.
> Why? Is evolution no longer the null hypothesis?

Evolution is expected, but the null hypothesis is the ancestral state.  
Proposing a novel habitat or behavior relative to what is reconstructed for the 
ancestor is, by definition, a form of assertion.  It therefore requires 
support, as per the usual.  Typically, these are so obvious that we don't even 
notice.  In this case, it's not obvious.

> Do we no longer assume, given deep time, and a diverse and numerous 
> clade (Theropodia) -- 1) ghost lineages, 2) a reasonably complete array 
> of ecologically viable lifestyles and 3) optimization to those lifestyles?

We don't assume them; we observe them and/or test for them.  So, we might 
expect that there would be diverse behaviors among theropods.  But any given 
behavioral supposition requires support.  In short, no - we do not assume that 
just because a lifestyle could evolve in a group that it did so.
>> The potentially intuitive nature of arboreal proto-flight does not 
>> constitute good cause.
> Huh?

In other words, just because arboreal origins of flight might make more sense 
to us does not constitute evidence that such actually happened.  The importance 
of arboreal habitats in the origin of avian flight is a question, not a 
starting assumption.  Intuition isn't evidence, and much of what was intuited 
about animal flight in the past has turned out dead wrong.  None of that means 
that trees didn't play in a role in the origin of avian flight, of course.  I 
rather expect they did, personally.  Still, we need to support each step of our 


Michael Habib
Assistant Professor of Biology
Chatham University
Woodland Road, Pittsburgh PA  15232
Buhl Hall, Room 226A
(443) 280-0181