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Author Topic:   Land Mammal to Whale transition: fossils Part II
mick
Member (Idle past 4986 days)
Posts: 913
Joined: 02-17-2005


Message 25 of 288 (231626)
08-09-2005 7:23 PM
Reply to: Message 21 by randman
08-09-2005 7:06 PM


Re: Yet another warning.
randman writes:
If you have not done an analysis of how many transitional forms should appear in a theorized evolutionary sequence
Hi randman, strictly speaking no analysis is required; the number of transitional forms is equal to the number of generations between the the extinct ancestor and the extant species.
randman writes:
and then an analysis of how many such fossils should appear in the fossil record and have been discovered
See here for one example of how it has been modelled
added in edit: here's a relevant section from the cited paper:
quote:
Existing statistical methods designed to account for incompleteness
of the fossil record typically use the size and distribution of gaps
within observed stratigraphic ranges of lineages to estimate the size
of the temporal gap between the oldest fossil and the LCA of the
lineages12. Although these methods are useful for species already
known from the fossil record, they are inappropriate for estimating
the time of the LCA of higher taxonomic groups because they
cannot account for species not preserved at all10,12. Our method for
estimating the temporal gap uses an estimate of the proportion of
species from the group actually preserved in the fossil record and the
shape of its diversification curve. The speciation model we use is the
non-homogeneous Markov branching process13,14 (Fig. 1).
We have developed a computational approach for estimating the
length of the temporal gap between the oldest known fossils and the
LCA of a taxonomic group, as well as an estimated confidence
interval (see Methods). We use as input the number of extant
species, the mean species lifetime, the ages of the bases of the
relevant stratigraphic intervals, the numbers of fossil species found
in those intervals and the relative sizes of the sampling intensities in
each interval. Estimates of the absolute values of the sampling
intensities may also be found (see Methods, equation (6)). This
gives an estimate of the proportion of species that existed in an
interval that were found as fossils.
So in fact your accusations are unwarranted as the analyses you say are not carried out, in fact, are!
mick
This message has been edited by mick, 08-09-2005 07:27 PM

This message is a reply to:
 Message 21 by randman, posted 08-09-2005 7:06 PM randman has replied

Replies to this message:
 Message 26 by Yaro, posted 08-09-2005 7:39 PM mick has not replied
 Message 27 by Omnivorous, posted 08-09-2005 8:43 PM mick has not replied
 Message 103 by randman, posted 08-13-2005 1:55 AM mick has not replied

  
mick
Member (Idle past 4986 days)
Posts: 913
Joined: 02-17-2005


Message 199 of 288 (233403)
08-15-2005 12:18 PM
Reply to: Message 197 by randman
08-15-2005 11:57 AM


Re: Boney species
randman writes:
comparing the changes for the current whale suborders to the changes that would need to have occurred to transition a land mammal to a whale in 10-15 million years, the current whale suborders have shown remarkable stasis
hi randman,
first, the transition from land mammal to aquatic mammal took at least 50 million years, not 10-15 (you are out to a factor of 5, so can we grant archaeocetes five time more "transition" than exists between contemporary species of aquatic mammal?)
second, the radiation of archaeocetes includes all whale-like mammals (i.e. dolphins too) not just true whales. Compare the right whale to the hump-backed dolphin:
right whale
dolphin
That ain't "remarkable stasis".

This message is a reply to:
 Message 197 by randman, posted 08-15-2005 11:57 AM randman has replied

Replies to this message:
 Message 202 by randman, posted 08-15-2005 12:45 PM mick has replied

  
mick
Member (Idle past 4986 days)
Posts: 913
Joined: 02-17-2005


Message 224 of 288 (233532)
08-15-2005 8:15 PM
Reply to: Message 202 by randman
08-15-2005 12:45 PM


Re: Boney species
randman writes:
The reason I ask is that Pakicetus is a fully and solely land mammal dated to 52 million years ago
okay, I said 50 million years, you said 52. That's a level of inaccuracy I can live with.
not sure where you got your original 10-15 from though...made up?
mick

This message is a reply to:
 Message 202 by randman, posted 08-15-2005 12:45 PM randman has replied

Replies to this message:
 Message 225 by randman, posted 08-16-2005 12:17 AM mick has not replied
 Message 226 by NosyNed, posted 08-16-2005 1:16 AM mick has not replied

  
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