WHERE ARE THE ANCESTOR SPECIES? (not particularly a birding question)

To: Birding-aus <>
Subject: WHERE ARE THE ANCESTOR SPECIES? (not particularly a birding question)
From: John Leonard <>
Date: Mon, 1 Nov 2010 15:16:27 +1100
The problem is we can't usually tell the time-depth of species
sufficiently accurately to determine whether one form or another is
ancestral. (The case of humans and other homonoid species is unique
because the fossil and sub-fossil evidence is subjected to a level of
scrutiny that forms in other genera aren't subjected to, plus we know
human anatomy very well).

For example, take the Corellas, it's a possible scenario to say that
once an ancestral species ranged widely over Australia, but drought
reduced it to three areas, a western refuge, a central refuge and a
south-eastern refuge, from whence emerged the Western Corella, the
Little Corella and the Long-billed Corella. With wetter climates the
central population expanded and is now in contact again with the
Western Corella, and Long-billed Corella.

Is the Little Corella the ancestral species? Or do the Long-billed or
Westerns look more like the ancestor? I remember reading that a fossil
of a Corella type parrot was found at Riversleigh from the Miocene
that looked very like the modern Long-billed. So perhaps the story is
that all Corellas were long-billed before the Pleistocene drying and
we should call the Little the Short-billed Corella and the Western the
Medium-billed Corella!

This is going to be a fascinating thread.

John Leonard

On 1 November 2010 14:55, Ralph Reid <> wrote:
> Greetings all,
> A short poser.
> Given that all existing species (particularly those of the animal kingdom) 
> are descended from a somewhat similar ancestor species, but divergent enough 
> to be considered a separate species; and given that the general definition of 
> a species is that a species of animal does not/cannot interbreed with another 
> separate species (although, admittedly, there are many exceptions - tigers 
> and lions interbreed, horses and donkeys interbreed as just two examples, but 
> with sterile offspring).  Then, by this definition a species must generally 
> have evolved/changed its characte ristics to the extent that members of this 
> species now cannot inter-breed with members of the ancestor species.
> Does this imply that the descendant species (generally being more fitted to 
> exploit a particular environmental niche that the ancestor species) 
> ultimately replace the ancestor species, driving that ancestor species into 
> extinction?
> Or do the two species continue to co-exist side-by-side, possibly each 
> exploiting somewhat different environmental niches, due to sympatric 
> speciation?
> If one considers the genus homo, for example, why are all the previous 
> variants of hominins not continuing to live today alongside homo sapiens?
> So the question arises - are there any known, proven instances of an ancestor 
> species continuing existing with a descendant species?  Are there any known 
> ornithological examples of this?
> Regards
> Ralph Reid
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John Leonard

I want to be with the 99,999 other things.
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