Re: [asa] donkey and horse

Such examples do reflect the great range in degree of limitations on
hybridization and corresponding difficulties in deciding exactly what
constitutes separate species. There are also more philosophical
issues relating to how one defines species, the question of how one
applies definitions to asexually reproducing forms, etc. The fact
that there is a continuum rather than sharp lines matches much better
with the expectations of evolution than of separate creation.

Examples: Frogs in which you can place a female from one population
and a male from another in a bucket of water and get tadpoles, but the
female would never come find the male herself because she expects a
different croak than the one he makes. Baltimore and Bullock's
orioles, lumped for a time when fertile hybrids were found and then
split again when the hybrids were found to be at a disadvantage
relative to either parent. In fact, they do not appear to even be
each other's closest relative. It may be a natural example of coming
into contact after separation.

Over time, barriers of some sort to breeding are expected to develop.
If hybridization is frequent and counterproductive, such barriers are
expected to develop rapidly; if not, such barriers may be very slow to
develop but are expected eventually on the basis of random changes in
DNA and in traits associated with reproductive compatibility.

A complicating factor comes from recent human-caused changes in
distribution (both from habitat changes and from transporting species
to different places). Species that evolved in isolation and had no
need to develop barriers to hybridization are now in contact and
responding in various ways.

Hybridization is very common in plants. Often (in plants and in
animals) it can lead to the production of a new species that can't
brred with either parent but can reproduce itself.

> I note that YECs want great changes before they will consider something evolving. There are, I believe, something like 800 species of fruitflies in the Hawaiian Islands. They apparently do not interbreed naturally, the usual mark of a good species. But Creationists KNOW that all creatures breed after their kind, though the phrase means "of all sorts," so this example doesn't count.<

There are additional complications here. I've seen it cited in YEC
context as proof that maybe species can evolve, but not new genera.
However, the reason that all the Hawaiian fruit flies are lumped into
Drosophilia despite their vast diversity and often drastic changes is
that they turn out to be more closely related to the offical type
species of Drosophilia than are a lot of the ordinary-looking fruit
flies in other parts of the world. Rather than make everyone change
the names of their lab fruit flies, the entomologists have decided to
recognize lots and lots of subgeneric groupings.

> You may want to consider the statement attributed
> to a backwoods sage: "It ain't the things that we don't know that gets us into trouble. It's the things we know for sure that ain't so."

I think Josh Billings has been cited as a source for that, though the
wording I recall was closer to "better to be ignorant than to know
things that ain't so".

-- 
Dr. David Campbell
425 Scientific Collections
University of Alabama
"I think of my happy condition, surrounded by acres of clams"
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