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Re: Sauropodz r kewl WAS: silly conversation on 2012 US presidential race



On Wed, Apr 18, 2012 at 9:33 AM, Anthony Docimo <keenir@hotmail.com> wrote:
>
>
> hoping the paragraph breaks don't vanish again.
>
I believe this is because you sent an email to the list as in a 'rich
text', where it actually only accepts plain text. Rich text messages
show up on the list as just a message saying 'this was rich text and
can't be shown'. Somehow D.M. was able to retrieve it to respond.
>
>
>
>> Date: Wed, 18 Apr 2012 04:35:57 +0200
>> From: david.marjanovic@gmx.at
>> To: dinosaur@usc.edu
>> Subject: Re: Sauropodz r kewl WAS: silly conversation on 2012 US 
>> presidential race
>>
>> > House cats and pumas and fishing c=
>> > ats all have a similarity to one another=2C just like tigers to lions=2C 
>> > bu=
>> > t neither is particularly close to cheetahs=3B thus=2C cheetahs are alone 
>> > i=
>> > n their genus (all their siblings are dead). Similarly=2C field mice have=
>> > extant relatives all over the place=2C cladistically...tuataras=2C aardvar=
>> > ks and pangolins don't. The way I learned it=2C ranks also demonstrate how 
>> > =
>> > distinct something is from everything else.
>>
>> They pretend to do that, too, but they don't. That's because "distinct"
>> has never been quantified.
snip

>all the extant organisms as closely related to the tuatara as mice are related 
>to muskrats

In a way we can do that, we can build a phylogenetic tree with
quantified branch lengths, calculate the length from mice to muskrats,
get a number, and then find all taxa at the same difference from the
tuatara. Now, given two researchers, they'll both produce trees with
different branch lengths and thus get different answers. Hell given
two researchers you'll probably get two different tree topologies too!


> That doesn't sound like a good deal, does it?  Because sometimes things *are* 
> distinct and separate.

I am sure D.M. will respond, but for my part, with living organisms,
we have a species concept that allows us to quantify species; if they
can't interbreed, they're distinct species. If they can fruitfully
interbreed, they're just varieties of the same species.
There is no way to quantify the difference, in a similar way, between
genera or families.

>  I don't need a yardstick to tell me the Atlantic is broader than the 
> Mississipi and the Rhine

But of course you are making a qualitative determination, not a
quantitative one. We can't quantify how much difference is required
between two populations to determine if they are in different genera
(and similarly we have trouble quantifying the the degree of
difference for sub-species distinctions).
>
>
>
>
>> Oh, there have been a few extremely short-lived attempts to define ranks
>> as times of origins of taxa: everything that originated in the
>> Cretaceous would become, I don't know, an order, and so on.

>
>  I believe the technical response is "WTF?"

I think there's some sense to this (even if we ultimately reject it).
Consider the idea that most phyla appeared in the Cambrian. If a
population of lizards separated into two species today, you'd have a
hard time convincing anyone that one of them was a new phyla. So the
differences that make up the phyla represent 'huge' differences that
accumulated over a long period of time, and therefore the phyla
originated in the pre-Cambrian. Orders in the Cretaceous, etc.
Again, not advocating that, but I think that's the idea behind it.

snip



-- 
Robert J. Schenck
Kingsborough Community College
Physical Sciences Department
S332 ph# 718-368-5792
Follow Me on Twitter: @Schenck
KCC Class Schedule on Google Calendar: http://tinyurl.com/mqwlcy