[Taxacom] Madagascar (was: Timetree of Life)

Richard Zander Richard.Zander at mobot.org
Wed May 18 16:32:30 CDT 2011


My answer to perplexing questions about the intransigence of life is statistical (and therefore rocket science). For every normal distribution, there are (usually) two tails of stuff that just does not do what you expect. For every 95% credible interval, 5% is on vacation or at least staring into the middle distance or reading a good novel. 

Apropos of this, it has been pointed out in a book I read that, in casinos with roulette wheels (I would not know about this in person, of course), they often post a list of all the numbers and colors that come up, in order. Apparently due to the nature of chance, the same number or color often comes up many, many times in a row. 

This is a multiple test problem in that if you have 100 numbers, each with a chance it is on vacation some of the time, one of them, if you "test" each and every one, has a great chance of doing the very much unexpected. 

So, horses and camels in the Americas went "on vacation" and never came back, statistically, as a sample of two of a bunch of examined species. 

This is fun stuff to mess around with, but the idea that statistics must rein in bad or untoward behavior of models in evolutionary analysis is something to doubt. Five percent of 95% supported clades, and five percent of all statistical phylogenetic papers, could be horrendously wrong. If you're lucky. Hummmmmm, if 5% of morphological clades or cladograms conflict with molecular clades or cladograms, maybe this is to be expected, statistically? What do you think?

 
* * * * * * * * * * * *
Richard H. Zander
Missouri Botanical Garden, PO Box 299, St. Louis, MO 63166-0299 USA�
Web sites: http://www.mobot.org/plantscience/resbot/�and http://www.mobot.org/plantscience/bfna/bfnamenu.htm
Modern Evolutionary Systematics Web site: http://www.mobot.org/plantscience/resbot/21EvSy.htm



-----Original Message-----
From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Robin Leech
Sent: Wednesday, May 18, 2011 4:08 PM
To: Michael Heads; taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] Madagascar (was: Timetree of Life)

Michael,
That is rather like asking, "Why didn't something evolve this
way or that way?"
It could be:
1.  no opportunity.
2.  events (weather, floods, timing, etc.).
3.  low population when the time was propitious.
4.  any other reason or reasons you can think up.

Just as with people, "Why oh why didn't I take him up
on his offer for PhD studies?"  "Gee, I wish I had studied
more for this exam."

Horses used to be here in North America.  How come it took
the Spaniards to bring them back?  Why did North America
lose both the equids and camelids?  Why didn't they come back?

Robin

here




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