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?
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