Understanding through Discussion


Welcome! You are not logged in. [ Login ]
EvC Forum active members: 78 (8908 total)
Current session began: 
Page Loaded: 05-23-2019 9:57 PM
25 online now:
DrJones*, JonF (2 members, 23 visitors)
Chatting now:  Chat room empty
Newest Member: WeloTemo
Post Volume:
Total: 851,966 Year: 7,002/19,786 Month: 1,543/1,581 Week: 365/393 Day: 89/99 Hour: 0/3


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   Transitional forms in existence today
Dr Jack
Member (Idle past 244 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 5 of 62 (623683)
07-12-2011 2:34 PM
Reply to: Message 1 by peter1985
07-12-2011 11:17 AM


How would you know?

Go back a few hundred million years and look at the fauna flopping around and you'll see all sorts of thins, including an unremarkable semi-amphibious fish with legs - Tiktaalik roseae. It'd be a bit unusual but you can't recognise it as a transitional between bony fish and Tetrapods until you know that tetrapods are going to become a big thing and what features end up defining the group.

Pop back to the time of Archaeopteryx and it'll appear as one of a number of flying dinosaurs, sharing some features with its close relatives and having a few novel features. It isn't until you've seen a modern bird that you can identify those features as a patchwork of features of theropods and birds.

It might be that, in the future, otters become fully aquatic and displace the cetaceans at which point a future scientist would look back and point out the remarkable patchwork of features that otters have, and their clearly transitional nature. But until we know what life will be like in the future we cannot identify transitionals.


This message is a reply to:
 Message 1 by peter1985, posted 07-12-2011 11:17 AM peter1985 has not yet responded

  
Dr Jack
Member (Idle past 244 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 17 of 62 (623764)
07-13-2011 7:15 AM
Reply to: Message 16 by Percy
07-13-2011 6:48 AM


Saying "All Species are Transitional" is equivocation
All species are transitional. Both Gould and Dawkins are aware of that and would have no reason to contradict what they believe to be true.

It's kinda true that many species are transitional - obviously not all, because any species that goes extinct is not - but it's a broader meaning of the word 'transitional' than the one being discussed. In general usage, when we talk about transitionals without context what we're talking are transitionals specifically between distinct higher taxonomic groups.


This message is a reply to:
 Message 16 by Percy, posted 07-13-2011 6:48 AM Percy has responded

Replies to this message:
 Message 38 by Percy, posted 07-14-2011 7:18 AM Dr Jack has not yet responded

  
Dr Jack
Member (Idle past 244 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 35 of 62 (623865)
07-14-2011 4:18 AM
Reply to: Message 34 by Portillo
07-14-2011 4:12 AM


Re: All Species are Transitional
All transitional forms are fully formed creatures. There aren't any "part formed" creatures in evolutionary theory.
This message is a reply to:
 Message 34 by Portillo, posted 07-14-2011 4:12 AM Portillo has not yet responded

  
Dr Jack
Member (Idle past 244 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 47 of 62 (623984)
07-15-2011 4:51 AM
Reply to: Message 43 by Taq
07-15-2011 12:36 AM


Fist of pedantry
For example, the platypus lays leathery eggs and uses a cloaca like a reptile. The platypus also has fur and mammary glands like mammals do.

The Platypus is a mammal, so you either mean Theria (marsupials + placental mammals) or other mammals.


This message is a reply to:
 Message 43 by Taq, posted 07-15-2011 12:36 AM Taq has responded

Replies to this message:
 Message 54 by Taq, posted 07-15-2011 3:09 PM Dr Jack has not yet responded

  
Dr Jack
Member (Idle past 244 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 59 of 62 (624126)
07-16-2011 5:58 AM
Reply to: Message 52 by Dr Adequate
07-15-2011 2:57 PM


Re: Interpretation
I think it's worth noting that most transitional fossils aren't strictly speaking actually transitionals between the groups they're transitional between. We have no way of knowing whether a fossil is in the direct line of ancestry or a side branch closely related to that direct line.

The existence of the transitionals we find confirms the existence of the direct transitionals, but they are likely not to be those direct transitionals themselves.

So the real tree probably looks a bit like this:

Dinosaurs---->Bird transitional--->Birds
\
-->Archaeopteryx

rather than like this:

Dinosaurs---->Archaeopteryx--->Birds

This represents an additional layer of interpretation, but - as Dr A has explained - such interpretation is not arbitrary.


This message is a reply to:
 Message 52 by Dr Adequate, posted 07-15-2011 2:57 PM Dr Adequate has responded

Replies to this message:
 Message 60 by pandion, posted 07-17-2011 2:31 AM Dr Jack has not yet responded
 Message 61 by Dr Adequate, posted 07-17-2011 3:52 AM Dr Jack has not yet responded

  
Newer Topic | Older Topic
Jump to:


Copyright 2001-2018 by EvC Forum, All Rights Reserved

™ Version 4.0 Beta
Innovative software from Qwixotic © 2019