PART 8 OF 10
Response on the issues to:
"Science or science?" and "Darwin on Trial"
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SECTION #2
THE SUPPOSED INABILITY OF MICROEVOLUTION (EVEN IN PRINCIPLE) TO
EXPLAIN
MACROEVOLUTIONARY "LEAPS"
For the most powerful demonstration that microevolution can or could give
rise to the macroevolutionary changes seen in the fossil record, one
actually does not need to go much further than the known record of
transitional forms, such as are documented in Kathleen Hunt's detailed
literature review covered just previously. There are numerous examples of
gradual transition sequences that, by the time the end of the sequence is
reached, demonstrate significant anatomical changes in form from the
beginning to the end of the sequence, in stepwise fashion.
The most dramatic and well-documented example demonstrating
macroevolutionary changes through gradual transition is the transitional
sequence from reptiles to mammals. At the link
http://www.talkorigins.org/faqs/faq-transitional/part1b.html, Hunt says:
This is the best-documented transition between vertebrate classes. So
far this series is known only as a series of genera or families; the
transitions from species to species are not known. But the family
sequence is quite complete. Each group is clearly related to both the
group that came before, and the group that came after, and yet the
sequence is so long that the fossils at the end are astoundingly
different from those at the beginning. As Rowe recently said about
this transition (in Szalay et al., 1993), "When sampling artifact is
removed and all available character data analyzed [with computer
phylogeny programs that do not assume anything about evolution], a
highly corroborated, stable phylogeny remains, which is largely
consistent with the temporal distributions of taxa recorded in the
fossil record." Similarly, Gingerich has stated (1977) "While living
mammals are well separated from other groups of animals today, the
fossil record clearly shows their origin from a reptilian stock and
permits one to trace the origin and radiation of mammals in
considerable detail." For more details, see Kermack's superb and
readable little book (1984), Kemp's more detailed but older book
(1982), and read Szalay et al.'s recent collection of review articles
(1993, vol. 1).
In Darwin on Trial on pp.77-79, Johnson manages to dismiss the entire
reptile-to-mammal transitional sequence with his usual casuistry and
ignorance of the evidence--claiming that because the exact
species-to-species transitions are not yet known, and that BECAUSE (!)
there are so many possible lines of ancestry, evolutionists have been
forced into the position of postulating that mammals could only have
evolved via a mish-mash of multiple lines of ancestry rather than through a
direct sequence as evolutionary theory would require. As the above
indicates, Johnson just simply doesn't know his evidence because he doesn't
care to look too closely, and he is so facile with his arguments, he even
fakes himself out.
Within the mammalian line, especially the closer one gets to the present
where more fossils are able to be recovered, one can begin to see more
fine-grained sequences, including the finest-grained possible: direct
species-to-species transitions. To cite just a few examples from the fossil
record of early primates given by Hunt (this one at the link
http://www.talkorigins.org/faqs/faq-transitional/part2a.html):
Early lemur-like primates: Gingerich (summarized in 1977) traced
two distinct species of lemur-like primates, Pelycodus frugivorus and
P. jarrovii, back in time, and found that they converged on the
earlier Pelycodus abditus "in size, mesostyle development, and every
other character available for study, and there can be little doubt
that each was derived from that species." Further work (Gingerich,
1980) in the same rich Wyoming fossil sites found species-to-species
transitions for _every_step_ in the following lineage: Pelycodus
ralstoni (54 Ma) to P. mckennai to P. trigonodus to P. abditus, which
then forked into three branches. One became a new genus, Copelemur
feretutus, and further changed into C. consortutus. The second branch
became P. frugivorus. The third led to P. jarrovi, which changed into
another new genus, Notharctus robinsoni, which itself split into at
least two branches, N. tenebrosus, and N. pugnax (which then changed
to N. robustior, 48 Ma), and possibly a third, Smilodectes mcgrewi
(which then changed to S. gracilis). Note that this sequence covers at
least three and possibly four genera, with a timespan of 6 million
years.
...And here are some transitions found by other researchers: Rose & Bown
(1984) analyzed over 600 specimens of primates collected from a 700-
meter-thick sequence representing approximately 4 million years of the
Eocene. They found smooth transitions between Teilhardina americana
and Tetonoides tenuiculus, and also beween Tetonius homunculus and
Pseudotetonius ambiguus. "In both lines transitions occurred not only
continuously (rather than by abrupt appearance of new morphologies
followed by stasis), but also in mosaic fashion, with greater
variation in certain characters preceding a shift to another character
state." The T. homunculus - P. ambiguus transition shows a
dramatic change in dentition (loss of P2, dramatic shrinkage of P3
with loss of roots, shrinkage of C and I2, much enlarged I1) that
occurs gradually and smoothly during the 4 million years. The authors
conclude "...our data suggest that phyletic gradualism is not only
more common than some would admit but also capable of producing
significant adaptive modifications."
Though there are in fact numerous examples of known transitional fossils
which add up to macroevolutionary change, as detailed in Kathleen Hunt's
literature review cited above--which puts the lie to creationist claims
there aren't any at all--it is nevertheless true there are also many gaps
in the fossil record. When expectations that the fossil record was not
going to support the idea it should be completely full of gradualist
transitional sequences, evolutionary biologists realized the existence of
gaps or rapid transitions was as real as the existence of gradual
transitional forms, and had to be explained too. This led to the
development of the theory of Punctuated Equilibrium, discussed further
below.
Now of course, Phillip Johnson contends that in having proposed (a)
punctuated equilibrium, and/or (b) that microevolutionary changes *can* add
up to macroevolution even in relatively short geological timespans,
evolutionists are welshing and "changing their story." But that is exactly
what good science is: recognizing when a theory is not complete enough or
accurate enough to explain the evidence adequately, scrapping what doesn't
work, and reformulating it so it does face the additional facts and attempt
to adequately explain them. First Johnson faults scientists for not facing
the evidence; then when they do exactly what he is asking and reformulate
evolutionary theory to better account for it, he complains that they have
"changed their story"! What does this lawyer want? He can't have it both
ways. It has been two-and-a-half decades now--since 1971 or 1972 when
Eldrege and Gould initially proposed the theory of "punctuated
equilibrium"--that the fact of "gaps," or "sudden" or "rapid" transitions
has been squarely acknowledged.
In addition to general punctuated equilibrium theory, however, there have
now been two or three recent developments depicting how macroevolution can
in fact, and/or in theory, take place as the cumulative result of
microevolutionary changes. (One common misunderstanding about P.E. is to
assume that it is intended as a complete replacement for gradualistic
scenarios, which is not the case--it's merely a modification extending and
refining the explanatory power of earlier neo-Darwinism. P.E. theory in
fact does not depend on "jumps," as it says nothing about the mechanisms
about which rapid speciation might occur. What it does say is that
speciation is most likely to occur in a certain way [rapidly among small
populations in fringe geographic areas], but that speciation is still
gradualistic even if rapid.) These recent developments are:
- In a recent landmark experiment on isolated islands in the Caribbean,
macroevolutionary changes were observed occurring in the time span of only
14 years in Anolis lizards newly introduced to the islands. The experiment
confirmed predictions made ahead of time as to what changes would be
observed in the lizards in response to the differing environments on a
number of separate islands the lizards were introduced to. Specifically,
leg length changed in response to branch diameters of the vegetation
existing on the islands--longer legs were more efficient on wider-diameter
limbs and evolved in response; shorter legs conferred a survival advantage
on smaller-diameter vegetation on islands where they evolved.
The changes in leg length and structure were in some cases on the order of
2000 darwins (a measure of evolutionary change in form or function),
compared to instances of slower change (around 1 darwin or so) often seen
between species in the fossil record, making this a truly macroevolutionary
event. And the fact that such macroevolution has now been observed *within*
a species shows that macroevolution is *not* a phenomenon restricted only
to speciation events--as the creationists sometimes seem to tend to assume
for their arguments to hold water. (Johnson's beliefs occasionally seem to
rest on this assumption in "Darwin on Trial.") [The peer-reviewed article
on the lizard experiments is: Losos, et al (1997) "Adaptive differentiation
following experimental island colonization in Anolis lizards." Nature, vol.
387, no. 6628, 5/1/97. Also see the N.Y. Times article of 5/1/97 by
Nicholas Wade, "Lizard experiments show evolutionary change can occur
quickly," for a plain-English summary of the study.)
- In the case of the evolution of the eye--one of the classic examples of
macroevolutionary complexity which creationists say could not have happened
except through some supernatural macroevolutionary event--a recent computer
analysis and simulation based on plugging in known features of
microevolutionary mutation and biological factors such as cellular mobility
and receptivity to light--resulted in a plausible sequence of events for
how the eye could have evolved. In fact, the simulation suggested that it
is unlikely the eye would _not_ have evolved given the known factors used
in the computer model.
In the case of the fish eye--using conservative assumptions--the simulation
generated a stepwise sequence depicting how the fish eye could have evolved
gradually (with useful survival traits at each partial step along the way)
in 364,000 generations, which amounts to less than 500,000 years in the
fish-eye model. This is a relatively small slice of time geologically
speaking, thus showing that "sudden" evolution in terms of the fossil
record could in fact be very gradual, and easily explainable via step-wise
processes at the molecular and cellular level. While this is of course at
present a theoretical model, it still easily refutes the creationists'
objections that no one even has a plausible _theory_ for how macroevolution
in such a case as the eye could have taken place. [Source: See Mark
Vuletic's "Frequently Encountered Criticisms in Evolution vs. Creationism:
Revised and Expanded," at http://www2.uic.edu/~vuletic/cefec.html#4.2,
which contains over 60 references to the scientific literature throughout.]
- Science reporter for the Washington Post, Boyce Rensberger, also mentions
the following regarding the evolution of the eye at the link
http://www.washingtonpost.com/wp-srv/interact/longterm/horizon/010897/evolutn.ht
m - How Science Responds When Creationists Criticize Evolution:
...biologists have vindicated Darwin by discovering many examples of
primitive eyes among various species, ranging from the simplest eye
spots of a few light-sensitive cells through progressively more
complex forms to the complete, highly sophisticated mammalian eye.
Together, these discoveries show how a series of many cumulative steps
could create a human eye. In fact, biologists now know that eyes arose
and evolved independently at least 40 times.
- There are also now at least a few known single-gene mutations that
directly control features of "macroevolutionary" form. Biologist Kenneth
Miller of Brown University mentions a few in his online debate with Phillip
Johnson at http://www.pbs.org/wgbh/nova/odyssey/debate/. In response to
Johnson's assertion that no microevolutionary mechanisms have been shown
capable of producing the macroevolutionary changes necessary to account for
changes in the fossil record, or major changes in form, Miller notes:
...a number of well-understood mechanisms, including single gene
mutations, produce changes that qualify as macroevolution. These
include heterochronic mutations that alter structures by changing
growth rates, homeotic mutations that change the identities of whole
body parts, and paedomorphosis, which converts juvenile stages
directly to adult ones. Indeed, the most recent issue of Science (Nov.
15 [1996], page 1082) reported that a single gene controls tunicate
tail formation. [Tunicates are marine animals such as sea squirts. --
Ward] Mutate it, the tail is lost. Restore it, tail comes back. Just
another example of a genetic mechanism producing macroevolutionary
change.
As we've seen above, there is very strong fossil and genetic evidence that
micromutation can indeed lead to macromutations. A related question is the
claim by David Wolfe in his "Science or science" statement that: "The
Darwinian creation of species is no more observable than supernatural
creation by God. Natural selection exists, but no one has evidence it can
accomplish anything remotely resembling the creative ability to form a new
species." In refutation of this, we offer the following:
SPECIATIONS THAT HAVE BEEN DIRECTLY OBSERVED
OR CAN BE DIRECTLY INFERRED FROM RECENT CIRCUMSTANTIAL EVIDENCE
- Two new plant species (T. mirus and T. miscellus) have evolved from a
common ancestor in the Tragopogon genus in the Idaho/Washington region
within the last 50 to 60 years. Chris Colby discusses this briefly at
http://www.talkorigins.org/faqs/evolution-research.html), as does Joseph
Boxhorn <[log in to unmask]> at
http://www.talkorigins.org/faqs/faq-speciation.html.
- A number of new plant species have been produced experimentally in the
laboratory in this century, including Evening Primrose (1905), Kew Primrose
(1912), and Raphanobrassica (1928) (a cross between radish and cabbage).
(Listed by Joseph Boxhorn at the above link).
- Stephanomeira malheurensis, a new plant species in Oregon arose in the
wild via mutation from Stephanomeira exigua, which contained 5
morphological differences (in certain characteristics of form), as well as
observed chromosomal differences.
The next two examples are available (along with the scientific references)
at http://www.talkorigins.org/faqs/speciation.html.
- The Faeroe Island house mouse was observed to speciate rapidly within 250
years after being brought to the island by man.
- Recent circumstantial evidence strongly indicates that five new species
of cichlid fishes arose approximately 4000 years ago in Lake Nagubago after
becoming isolated from the original parent species.
- Artificial selection has produced several new plant species of the genus
Brassica containing huge differences in form--ones with which we are all
very familiar: broccoli, cauliflower, cabbages, kale, and brussel sprouts.
These all originated from just one species of wild mustard.
(See http://www.infidels.org/library/modern/mark_vuletic/denton.html - A
Critique of Michael Denton's "Evolution: A Theory in Crisis," for the
scientific reference on this one.)
- In experimental conditions simulating the "founder effect" (where
population "bottlenecks" or die-offs occur in nature, which when followed
by a new increase in numbers is one process thought to drive the formation
of new species), a species of worm (Nereis acuminata) gave rise within 28
years to new descendant species that proved unable to reproduce with the
parent form (thus meeting the definition of new species). (Source:
"Frequently Encountered Criticisms in Evolution vs. Creationism: Revised
and Expanded at http://www2.uic.edu/~vuletic/cefec.html#4.2, which contains
references to the scientific literature for each example cited.)
For a more complete listing of observed speciations in the natural world
plus other observed experimentally in the lab, including the scientific
references, see the two following links:
- http://www.talkorigins.org/faqs/faq-speciation.html - The Observed
Instances of Speciation FAQ, by Joseph Boxhorn.
- http://www.talkorigins.org/faqs/speciation.html - Some More Observed
Speciation Events, by Chris Stassen, James Meritt, Anneliese Lilje, and L.
Drew Davis.
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SECTION #3
SINCE EMBRYOLOGICAL DEVELOPMENT OF ORGANISMS BEFORE BIRTH DOES
NOT RETRACE
THEIR SPECIES' HISTORICAL EVOLUTIONARY DEVELOPMENT LIKE EARLY
DARWINISTS
SAID, EVOLUTION IS SUPPOSEDLY THEREBY INVALIDATED.
THE EMBRYOLOGY ARGUMENT - A "STRAW MAN"
Where the argument from embryology is concerned, which Johnson cites in
"Darwin on Trial" as evidence against evolution, there is not much that can
be said except it is puzzling why Johnson even included it in the book at
all (or David Wolfe in his "Science or science?" essay) because it has been
decades since anybody seriously thought that embryological development of
organisms prior to birth ought to _exactly_ recapitulate their species'
evolution as seen in the fossil record.
All evolutionists say is that later evolutionary forms have inherited--as
they have in other of their features--an embryological developmental
pattern from earlier ancestors which has been modified. They also point out
that embryology can demonstrate how vestigial structures may be retained
from earlier stages of evolution and reformed or put to different uses as
the animal develops. And while it is certainly true that scientists may
sometimes use time-lapse photography of embryological development as a
compelling visual aid to give some feel for the relatedness of different
species' forms and how one could have "morphed" or developed into another,
to suggest evolutionists still believe the old "embryology" chestnut that
"ontogogeny [exactly] recapitulates phylogeny" is one of the oldest straw
men in the books.
Johnson strays far off-target in attempting to make big hay of the fact
that the PBS show Nova displayed such embryological sequences in
introductory links on the website that contains his online debate with
biologist Kenneth Miller at http://www.pbs.org/wgbh/nova/odyssey/debate.
His misplaced emphasis also seems based on the misunderstanding of assuming
that the embryological developmental sequence of animals can only be
changed by mutations that are tacked onto the _end_ of the previously
existing embryological sequence, which if it were the only route for
changes, could indeed plausibly cause it to mirror the species' past
evolutionary as it unfolded in the past. But as we now know, that is not
how it happens. In fact, mutations can, do, and have introduced changes
into the embryological developmental sequence of species at any given point
in the sequence--not just the end of it--making the embryological
development of any given animal suggestive of its early evolution at times,
but at other times not.
So while early evolutionists initially thought that the development of
embryos ought to mimic the evolutionary tree of progression for the species
the embryo belongs to, it has been long, long time now that this theory has
been scrapped. (Miller has a very brief summary at the above link.) It is
creationists who stick themselves with this old idea, not evolutionists.
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SECTION #4
CREATIONISTS SAY THAT MOLECULAR GENETICS DOES NOT GIVE US THE
ABILITY TO
IMPUTE COMMON ANCESTORS ANY MORE THAN DO OTHER PHYSICAL
FEATURES--IT'S JUST
ANOTHER WAY OF CLASSIFYING ORGANISMS BASED ON THEIR FORM, IN THIS
CASE
THEIR GENETIC "FORM."
Recent molecular genetics techniques now enable biologists to determine the
amount of "genetic distance" between currently living species. (It is also
just now beginning to allow us to actually look at surviving DNA from
ancient fossilized creatures if any remaining viable DNA is present, though
this has been very rare so far.) This information can then be used to
reconstruct family trees of past genealogical evolutionary relationships
from a completely independent source _other_ than the fossil evidence. As
it has turned out, the picture from the molecular evidence agrees with the
fossil record very closely with only very minor differences.
Since genetic molecular sequences are the actual physical pieces of
organisms (with occasional mutations, which give rise to the "genetic
distance" between organisms) that are handed down from one generation to
this next--a process which can be directly observed in the
laboratory--molecular evidence provides the strongest evidence possible
that the genealogical relationships imputed by the fossil record actually
occurred, short of being able to go back in a time machine and actually
observe them.
That the pattern of past genealogical relationships suggested by the
molecular genetic evidence agrees so closely with what the fossil record
says, with only very minor differences, is considered by scientists to be
spectacular confirmation of the evolutionary genealogical relationships as
judged by the fossil record. In other words, here is an overwhelming
example of confirmation of earlier predictions by a completely separate
line of evidence--one of the prime criteria for what constitutes "science."
In "Darwin on Trial," however, Phillip Johnson dismisses modern molecular
genetic evidence's ability to determine geneaological relationships on the
grounds that he thinks these molecular genetic similarities between
organisms are no different in principle than the comparative differences we
also see in an organism's adult physical form (such as what we see as the
fossil evidence.) This bald assertion of course ignores the fact that while
the characteristics of form preserved in the fossil record are not directly
handed down, adult form *does* develop from the molecular genetic sequences
that *are* directly handed down from parent organism to child--_which_is_a_
_process_known_to_occur_based_on_first-hand_observation_in_the_laboratory_.
To therefore assume that the process of inheritance is *not* how the
genetic similarities and differences observed between different organisms
came about in the first place is one of the most perverse twists of logic
possible. Only by arbitrarily postulating an untestable assertion that a
supernatural being, using genetic sequences as nothing more than an
"artist's palette of painting material," so to speak, in whimsically
creating the range of species we see in the fossil record as we see today,
is Johnson able to philosophically justify dismissing the overwhelming
confirmation of the fossil record by molecular biological evidence.
The extreme whim and arbitrariness of creationists in lodging objections to
points like this can be seen in the fact they don't object to many other
similar areas of biology where exact causation may be just as unknown as
the macroevolutionary changes that cause creationists to go so bug-eyed.
For instance, as biologist Kenneth Miller points out in his on-line debate
with Johnson at http://www.pbs.org/wgbh/nova/odyssey/debate/, no one yet
knows what force causes chromosomes to move apart when cells divide, yet
creationists do not jump all over the unknown details here, and infer that
only the intervening hand of some supernatural force or being must be
responsible. Likewise, how and why an embryo can seemingly miraculously
differentiate from a small clump of cells after fertilization into an
immensely complex organism prior to birth is not something for which they
seem to feel it is necessary to resort to the supernatural for explanations
either.
Creationists do not say it is "materialist philosophy" in these cases to
assume biological mechanisms underlie events even if research has not yet
proceeded to the point it can actually point them out with
super-reductionist precision. Why then do they have such trouble with
"unseen" genealogical relationships in the fossil record? Just because we
cannot "go back" in the past and see things with our own eyes as they
unfolded at the time does not mean we cannot "go back" with other
techniques that reveal the factual history.
There is also a second way in which the modern genetic evidence even more
powerfully demonstrates evolutionary genealogical relationship than by
measures of genetic distance alone. This route examines the phenomenon
sometimes called "plagiaristic copying" of genetic errors that occasionally
occur when genes are duplicated. The way this is usually explained is by
way of analogy to how plagiariam of manuscripts is often detected:
If a plagiarist in copying a manuscript also copies telltale signs or
errors in the manuscript--that the plagiarist is not aware are actual
errors--exactly as they occurred in the manuscript (i.e., unrecognized
typographical errors, or errors of fact, such as incorrect addresses or
phone numbers which when copied have been known to trip up plagiarizers
putting out directories without researching the information for themselves)
then the existence of these errors in the plagiarized copy is considered by
the courts as sufficiently powerful to establish the fact of plagiarization
beyond any doubt. The reasoning is that nobody would purposely copy errors
if they actually knew they were errors--and the fact the same exact errors
exist in the plagiarized copy indicates they had to have been reproduced by
copying the original.
END PART 8
--Ward Nicholson <[log in to unmask]>
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