Scientists
are excited about finding hybrid sharks off the coast of Australia.
Lead researcher, Jess Morgan, said of the discovery, “This is
evolution in action.” You can read the article (here)
but here's the gist of the story:
The
Australian black-tip shark can live only in tropical waters. The
common black-tip shark (described as the Australian black-tip's
“cousin”) can live in more temperate water. Scientist have found
about 57 specimens of hybrids (the offspring of a mating between different species) of the Australian black-tip and common black-tip. The hybrids can live
in the cooler waters. One spin that article suggested is that
hybridization is helping the Australian black-tip adapt to “climate
change.” That's fodder for another post.
Anyway,
is this an example of “evolution in action”? If by “evolution”
one simply means “change,” then this is certainly an example of
change. However, there is no “evolution” of the type that could
change a bird into dinosaur. The article is very interesting and
there's a lot we can learn here. But for the sake of the
creation-evolution debate, this article demonstrates a few things in
particular.
First,
it's another good example of the equivocal use of the word
“evolution.” Any “change” identified in nature is touted as
“evolution in action” which serves to embolden evolutionists.
When I say I don't believe in “evolution” (the descent of all
species from a common ancestor), I'm chided for denying something
they claim has been observed.
Second,
this highlights the subjective meaning of the term “species.”
Species
is typically defined as “a
group of organisms capable of interbreeding and producing fertile
offspring.”1
This
definition is, at best, ambiguous. At worst, it's useless. The
Australian black-tip and the common black-tip can obviously
interbreed (as evidenced by this finding). Why are they different
species? Polar bears (Ursus
maritimus)
and grizzly bears (Ursus
arctos horribilis)
can hybridize (and have done so in the wild) yet they are different
species. The gray wolf (Canis
lupus)
can hybridize with the coyote (Canis
latrans).
Hybridization is so common among flora and fauna that I really don't
see how this definition of species endures. Evolutionists often
demand that creationists provide a rigorous definition of the term
“kind.” This is rather hypocritical of them since they cannot
present a rigorous definition of the term “species.” Also,
evolutionists sometimes define “macro-evolution” as “change
that occurs at or above the level of species.”2
That
term too is rather useless since evolutionists can't seem to pin down
what a species is. In other words, how can we know that change has
occurred “at or above the level of species” if we don't even know
what a species is?
Thirdly,
this finding is a better example of the creationist model. Both the
common black-tip and Australian black-tip belong to the same “kind.”
Each species merely possess different combinations of traits that
were already present in the ancestral population. It's obvious that
the common ancestor of both species was more robust and could likely
tolerate a wider range of temperatures. Natural selection is a
process that tends to eliminate traits which aren't suited to a
particular environment and the modern species of Australian black-tip
have become specialized and adapted to more tropical waters.
I
wrote about this very subject in my post “Were
there Fish on the Ark?” All the things discussed in this
recent article are consistent with the post I had written nearly a
year ago. In that post, where I focused on the adaptation of modern
fish species to their environments, I also mentioned the Biblical
concept of “kind” and the creationist explanation of speciation.
It all comes into play in this new finding. I'm even tempted to say,
“This is creation in action!”
Specific sorts of change in nature are called "evolution:" specifically, change in the frequency of inheritable traits in populations of living things. It is all very well to complain that scientists do not distinguish between changes you consider minor and changes you consider major, but it does not help the matter when creationists refuse to use biological terms as biologists use them.
ReplyDeletePolar bears and brown bears, or Australian and common black-tip sharks, are considered separate species because they maintain (largely) separate gene pools: even though they can interbreed, they do so so rarely, under normal circumstances, that they remain, for the most part, two distinct, identifiable sorts of animals (you don't have one continuous blur with no discernable dividing line between polar and brown bears; you have distinct types with a few crosses).
Species can be separated by behavioral traits (such as who they prefer to mate with) in addition to, or in place of, traits that make it biologically impossible or at least difficult to interbreed.
Why do you say that this hybridization between species is better explained by the "creation model?" On either view, the two shark species (or the two bear species) share a recent common ancestor, and have not evolved mechanisms (behavioral -- "premating" -- or genetic -- "postmating") that prevent interbreeding absolutely. The only reason you give is that you assume that the two species each possesses part of the genetic traits of the common ancestral population, as though "mutations" were some weird fringe idea dreamed up by Darwinists and not an observed fact of nature.
Take pet hamsters, for example: the entire pet hamster population is descended from a single pregnant female captured early in the 20th century. Nearly all their obvious variation is the result of mutations that have taken place and been cultivated in captivity. There is no reason to suppose that every allele in the two shark species was present in the ancestral population (and I don't even think the "creation model" requires that there be, as long as new alleles can be declared not to have "added information," or to have lost as much as they added, if, e.g. a mutation enhanced one trait at the cost of another).
One other point: it is fairly pointless to decry the imprecision with which species are defined and demarcated, when "kinds" have the same problem. If evolution is true, species must have fuzzy boundaries, at least in time, if not in space.
If creationism is true, "kinds" must have fixed and identifiable boundaries; there ought to be obvious and unmistakable demarcations between them. Creationist disagreements on whether, e.g. the Trinil skullcap (the type specimen of Homo erectus) is of the human kind or some nonhuman ape kind, or whether bears and dogs are the same kind, suggest that "kinds" are not so obvious as the creation model would imply.
Steven J,
ReplyDeleteYou said, “Specific sorts of change in nature are called "evolution:" specifically, change in the frequency of inheritable traits in populations of living things. It is all very well to complain that scientists do not distinguish between changes you consider minor and changes you consider major, but it does not help the matter when creationists refuse to use biological terms as biologists use them.”
I wouldn't say I'm complaining as much as I am highlighting evolutionists' abuse of the word “evolution.” To a layman, “evolution” has a specific meaning. Scientists might have a more technical meaning. So when a scientist says “this is evolution in action,” it's confusing to the layman what the scientist means. Hence, I point out that this has nothing to do with the kind of change that could turn an ape into a person.
You said, “Polar bears and brown bears, or Australian and common black-tip sharks, are considered separate species because they maintain (largely) separate gene pools: even though they can interbreed, they do so so rarely, under normal circumstances, that they remain, for the most part, two distinct, identifiable sorts of animals.”
I've heard that definition as well but it's also rather arbitrary. By this definition, hamsters in KY are a different species than hamsters in IL because they are geographically separated and cannot easily interbreed. Humans who become marooned on an island would also technically be a different species than humans on the mainland.
You said, “Why do you say that this hybridization between species is better explained by the "creation model?" On either view, the two shark species (or the two bear species) share a recent common ancestor, and have not evolved mechanisms (behavioral -- "premating" -- or genetic -- "postmating") that prevent interbreeding absolutely.”
The term “species” is a largely invented term that has only marginal utility. The term “kind” is far more objective. According to the creation model, species are simply various combinations of traits within a kind. After the Flood, “kinds” of animals spread out into the world and became adapted to various environments. Thus “species” were born. Such is the case for the Australian black-tip shark which became adapted to the tropical waters of its environment. So to find that the Australian black-tip can successfully mate with the common black-tip is not a surprise to the creationist.
To claim this is “evolution” at all is somewhat generous. It would be like saying a KY hamster mating with an IL hamster is “evolution in action.”
...continued...
You said, “The only reason you give is that you assume that the two species each possesses part of the genetic traits of the common ancestral population, as though "mutations" were some weird fringe idea dreamed up by Darwinists and not an observed fact of nature.”
ReplyDeleteUnlike dino-to-bird evolution, mutations are real and observed. However, they aren't relevant to this example. There were no new features involved. Two “species” of sharks hybridized. It's about as ho-hum as two breeds of dogs having pups. If the sharks grew feathers, I might conceded your theory is possible.
You said, “If evolution is true, species must have fuzzy boundaries, at least in time, if not in space.”
That's a rather novel argument. Evolutionists use a vague definition of species and then claim their theory must be true because species have fuzzy boundaries.
You said, “If creationism is true, "kinds" must have fixed and identifiable boundaries; there ought to be obvious and unmistakable demarcations between them. Creationist disagreements on whether, e.g. the Trinil skullcap (the type specimen of Homo erectus) is of the human kind or some nonhuman ape kind, or whether bears and dogs are the same kind, suggest that "kinds" are not so obvious as the creation model would imply.”
If future generations found fossils of a Chihuahua and a Mastiff, they might believe them to be different species. Though there may be enough similarities that we might suspect they are the same “kind,” we could not be sure if all we have are bones to examine. It's not practical to apply fertility tests between every known species. In the case of fossils, it's impossible.
Thanks for visiting. God bless!!
RKBentley
A point: the first use of "species" in more or less the modern, biological sense was by John Ray, in the late 17th century; he assumed that "species" were the same as "created kinds" and were immutable. The term was popularized by the (creationist) taxonomist Carolus Linnaeaus a century later, who identified many species still recognized as "species" today. The term was not invented by evolutionists, and has been found useful by taxonomists even of creationist leanings.
ReplyDeleteNote that the point of "reproductive isolation" is that separate species remain separate even when they have the opportunity to interbreed: Australian aborigines were reproductively isolated from Englishmen for thousands of years, but did not remain so once they were no longer geologically isolated. In contrast, wolves and coyotes, or polar and brown bears, tend strongly to choose mates of their own species even when they have the opportunity to interbreed. "Species" describes a real aspect of typical behavior (sometimes, of course, speciation involves the sheer inability to interbreed: see, e.g. the evening primrose Oenothera lamarckiana and its chromosome-doubled descendant O. gigas).
You seemed unimpressed that evolutionary theory implies that there cannot be a rigorous and universally applicable definition of "species." It also implies that there cannot be such a definition of "kind," at least for "kinds" that are not uncomfortably huge (Darwin was not willing to commit himself to common ancestry beyond the phylum level, e.g. common ancestry for humans and hagfish, but not necessarily for humans and hyacinths; modern biologists mostly accept that all known life shares common ancestry).
You have not addressed my point that the boundaries of "kinds" are not obvious and well-defined, especially when we take fossil forms into account. There really ought not be cases (as there really are) where reasonably complete skulls exist that some creationists insist are fully-formed humans and others insist are fully-formed non-human apes.
Steven J,
ReplyDeleteI had started writing this, saved it in Word, got distracted, then completely thought I had published it. It's a weird feeling to think you had done something then realize you hadn't.
Anyway, you said, “A point: the first use of "species" in more or less the modern, biological sense was by John Ray, in the late 17th century; he assumed that "species" were the same as "created kinds" and were immutable. The term was popularized by the (creationist) taxonomist Carolus Linnaeaus a century later, who identified many species still recognized as "species" today. The term was not invented by evolutionists, and has been found useful by taxonomists even of creationist leanings.”
I may have been a little cavalier in saying that the term species has only marginal utility. I truly don't object to the word and have used it many times on my blog. I merely want people to recognize that it is more of an invented term of convenience. Creationists recognize species as variations within a kind. When two species hybridize, it fits perfectly within the creation model. It annoys me when evolutionists tout it as “evolution in action.” By the way, it also annoys me when evolutionists recklessly ask, “How could Noah fit millions of species of animals on the Ark?”
And before you comment, remember this: it's my blog so I get to complain about things that annoy me.
You said, “You have not addressed my point that the boundaries of "kinds" are not obvious and well-defined, especially when we take fossil forms into account. There really ought not be cases (as there really are) where reasonably complete skulls exist that some creationists insist are fully-formed humans and others insist are fully-formed non-human apes.”
In the world of taxonomy, a kind would be closest to the term “family.” It is rather large and differences within a kind can be considerable. Did you know, for example, that domestic cows can hybridize with bison? A fertility test is a certain method of determining if different species are in the same kind. However, if I only had fossils of cows and bison, a fertility test is not possible. I might see the similarities between the two but there isn't an “obvious and well-defined” indicator that would tell me they are the same kind.
Thanks for visiting. God bless!!
RKBentley