>>... the common complaint that "kinds" in the OT is rather
vague at best, not aligning well with modern classification
categories.<<
I think that this principally tells us not to claim that the Bible
provides a limit on the possible extent of evolution in its
use of "kind" or similar terms, as there is no definition of
kind. In contrast, Huse cites Gish as declaring that kinds
are roughly equivalent to a family.
>But I have found that the prime unit of evolution theory,
"species," as in "Origin of the....," is often more than a little
flexible, especially when defending evolution. I mean,
kids, and gullible adults, are told that new resistant
"species" of bacteria are appearing every day, this "proving"
evolution. <
I have not seen the new varieties of bacteria called
species. The application of the term species to bacteria is
indeed problematic. There is a separate nomenclatural
code for bacteria, independent of the codes for plants and
for animals. If you were to try to define species as
reflecting a certain level of genetic differentiation, the
so-called species of bacteria would probably come out
more equivalent to family-level variability in animals.
Morphologically, there are only a limited number of features
available for distinguishing bacterial species, and this
typically requires being able to grow and study colonies. If
it does not like petri dishes, then identifying a species is
difficult. Another problem is that bacteria are promiscuous
in swapping genes. A stray bit of DNA is relatively easily
taken up by a bacterium. Does this count as
interbreeding?
>But, the dictionary definition of species, "
category...comprising related organisms or populations
potentially capable of interbreeding...," fails when
categorizing asexual organisms. The temptation to equate
"strains" and "species" seem a little too hard to resist, or
justify. <
The definition of species is highly debated in biology, and
its application to asexual organisms is especially
problematic. On the other hand, there is some consensus
on recognizing species. A study on an Australian
aboriginal community that relied extensively on shellfish
found that the correlation between what they had separate
names for and what malacologists recognize as distinct
species was very good. Species seem to be real entities,
but how to define them?
Several species definitions are currently in use by
biologists. Although a general underlying idea is genetic
continuity, the details differ. Perhaps the most widely used
is the morphological species concept. Things that look
different are presumed to be different species. What
constitutes a valid difference may be problematic.
However, in many cases, direct testing of reproductive
compatibility is not an option. Extinct organisms do not
interbreed even with members of the same species
anymore. In other cases, it is theoretically possible but not
feasible. Attempting to get every plausible pair of varieties
to reproduce would require a lot of time and money.
The biological species concept is what your dictionary was
aiming at. Organisms that are reproductively compatible
are considered conspecific. However, this leaves open the
question of just how compatible is enough? For example,
in the leopard frogs, it is possible to fertilize eggs of a
female from one region with sperm from a male from
another region. However, the female from one region will
not respond to the croak of a male from another region,
and so in nature the two would never get together. The
Baltimore Oriole and the Bullock's Oriole were
synonymized as one species when occasional
hybridization was observed. However, longer-term studies
revealed that the offspring seemed to not do as well as
pure-blooded individuals, and more recent molecular
studies have even indicated that they are not each other's
closest relative. A horse and donkey can be crossed to
produce a mule, but the mule is almost always sterile. An
indirect way to look at this is to look for distinctive genetic
markers in a population. If it is freely interbreeding with
other populations, we expect to see genetic markers
shared between the populations. If each population has
distinct genetic features, then it looks as though DNA is not
being shared and the groups might be separate species.
However, the amount of interbreeding that is necessary to
produce sharing in genetic markers (and conversely, the
amount of interbreeding that can occur while genetic
differences are amintained) seems variable.
Another concept is the phylogenetic species concept. It
seeks to identify species as evolutionarily distinct entities.
Proponents of this view tend to claim that it is better
because it is phylogenetic and have not done much to deal
with the problem of testing whether one has correctly
recognized evolutionarily distinct entities.
For asexually reproducing organisms within predominantly
sexually reproducing groups, individuals with a common
genetic origin are generally considered conspecific.
Several kinds of animals, including many lizards, some
amphibians and fishes, and assorted invertebrates, can
produce asexually reproducing partheneogenetic
individuals through hybridization between two species.
This offspring is reproductively isolated from either parent,
and so seems to qualify as a new species. Its offspring
are genetically identical to it, except for mutations, and so
seem reasonably identified as conspecific. Other
individuals produced by the same cross (i.e., a male of
species a and female of species b) are morphologically
and physiologically similar, and so are also considered
conspecific. In plants it becomes more complex because
the hybrid often is capable of reproducing sexually with
other hybrids (including its own asexually produced
offspring), and some plants can self-fertilize as well.
However, the hybrid cannot reproduce with either parent,
although in some cases yet another hybrid can be
produced.
>But I have found scientists like to put a spin on the
definition concerning larger critters. I had a heated
discussion a year ago about some new species of fish
supposedly found in Canada. Trying to stifle this
evolutionist's enthusiasm concerning this new proof of
"speciation," I inquired whether this fish could mate with a
member of the species from which it "evolved." I was told
that, for what ever reason, these critters like to stay with
"their own kind." So I suggested trying artificial
insemination. "Oh my goodness, no! Why would anyone
want to do THAT?" was basically the response.<
This gets back to the question of the level of separation
necessary to recognize species. There are fish, shells,
crustaceans, etc. living on either side of Panama that look
very similar, yet the chance of two getting together from
either side in nature is nearly nil. They have been
separated for at least about 2 million years (depending on
how shallow a connection they were willing to cross).
Some are considered separate species, but some are
considered to still represent the same species. If two
individuals theoretically could interbreed, but there is an
uncrossable barrier between them, are they conspecific? If
they theoretically could interbreed, but refuse to do so
because behavioral cues are missing, are they
conspecific? A well-studied example similar to your fish
comes from some fruit flies. They originally lived on
hawthorn berries as larvae, and mating takes place on the
berry. Some have now taken to living on apples instead.
Apples ripen at a slightly different time and take longer to
rot away, so there are a number of changes in habits to
make, in addition to the key factor of looking for mates on
apples instead of on hawthorn berries. At least one
genetic change has been observed as well, and there is a
strong tendency for apple-reared young to mate on apples
and hawthorn-reared young to mate on hawthorns. Are
they two species yet? A more extreme situation develops if
artificial insemination theoretically would work, but
reproduction is physically impossible. For example, if all
dogs except chihuahuas and Great Danes were
eliminated, no Greathuahuas would be produced naturally.
(As is, the varieties of dogs are considered conspecific
because there are so many intermediates.) For practical
purposes, they would be separate species. A different sort
of example comes from mice in isolated valleys in Italy.
They all look like ordinary mice, but many populations have
chromosomal rearrangements. If a mouse from one valley
with one chromosomal configuration mates with a mouse
from another valley with a different chromosomal
configuration, the offspring will probably be infertile
because the chromosomal mismatch prevents gamete
production. Are these separate species?
>What amazes me is, at other sites, of course,
evolutionists tend to try to come off with a rather "fearing
neither man or God" persona, but when it comes to proving
speciation, they seem to claim that if interbreeding is not
achieved through soft music, and a candle-lit dinner, then
the results are unwarranted, illegal, and possibly, invalid.<
The general tendency has been to restrict the definition of
species, so that a lack of interbreeding simply through
behavioral differences is recognized as a species-level
difference. A good example of this can be found by
comparing older and newer field guides to birds. Many of
the old forms now split into two or more species look
similar throughout their range but produce distinctive
songs in different parts of their ranges. Females expecting
one song usually won't respond to the other song.
Except in the case of hybridization producing reproductive
isolation in a single step, speciation will generally be a
process rather than an abrupt event. We see populations
at several different stages of the process, so it is difficult to
draw a precise line as to which ones have truly split and
which ones are not quite there yet.
Dr. David Campbell
Old Seashells
46860 Hilton Dr #1113
Lexington Park MD 20653 USA
bivalve@mail.davidson.alumlink.com
That is Uncle Joe, taken in the masonic regalia of a Grand
Exalted Periwinkle of the Mystic Order of Whelks-P.G.
Wodehouse, Romance at Droigate Spa
---------- Original Message ----------------------------------
From: Woodward Norm Civ WRALC/TIEDM
<Norm.Woodward@robins.af.mil>
Date: Tue, 19 Feb 2002 12:30:31 -0500
>Adrian Teo did an admirable job of trying to defend us
OECs, but this is a
>hard room to please...
>
>But one item that he seemed to be taken to task is the
common complaint that
>"kinds" in the OT is rather vague at best, not aligning well
with modern
>classification categories.
>
>But I have found that the prime unit of evolution theory,
"species," as in
>"Origin of the....," is often more than a little flexible,
especially when
>defending evolution.
>
>I mean, kids, and gullible adults, are told that new
resistant "species" of
>bacteria are appearing every day, this "proving" evolution.
But, the
>dictionary definition of species, " category...comprising
related organisms
>or populations potentially capable of interbreeding...," fails
when
>categorizing asexual organisms. The temptation to
equate "strains" and
>"species" seem a little too hard to resist, or justify.
>
>But I have found scientists like to put a spin on the
definition concerning
>larger critters. I had a heated discussion a year ago
about some new
>species of fish supposedly found in Canada. Trying to
stifle this
>evolutionist's enthusiasm concerning this new proof of
"speciation," I
>inquired whether this fish could mate with a member of
the species from
>which it "evolved." I was told that, for what ever reason,
these critters
>like to stay with "their own kind." So I suggested trying
artificial
>insemination. "Oh my goodness, no! Why would anyone
want to do THAT?" was
>basically the response.
>
>And I hear this rationale over and over...such as claims
that many breeds of
>dog is of a different "species." When they say that a
Chihuahua can no
>longer interbreed with a Great Dane, I ask has it been
tried using
>artificial insemination, with the Great Dane carrying the
litter, of course.
>The answer was the same as above.
>
>What amazes me is, at other sites, of course,
evolutionists tend to try to
>come off with a rather "fearing neither man or God"
persona, but when it
>comes to proving speciation, they seem to claim that if
interbreeding is not
>achieved through soft music, and a candle-lit dinner, then
the results are
>unwarranted, illegal, and possibly, invalid.
>
>I would like any comments about this observation.
>
>Norm Woodward
>Warner Robins Georgia
>
>
>
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