Finch beaks point to a Creator who provides

Finches have been identified as part of a created kind that has diversified
considerably since the Flood of Noah’s time.1 They
are well known for their variation in beak size and shape. These differences
in beak morphology between various species of finches are associated with differences
in diet. It appears that these differences have played an important role in
allowing birds to fill numerous ecological niches around the world.

Not by chance

Both creationists and evolutionists recognize that finches share common ancestry.
So why are different beak shapes characteristic of different species of finches?
Darwin popularized the idea that variation could be acted on by natural selection
to produce the variations in beak shapes he observed between different species
of finches on the Galápagos Islands. While naturalistic mechanisms may play
some role in producing the patterns we see today, creationists have pointed
out that they are insufficient to account for the variety seen within created
kinds.1

One issue to address is the source of variation. Is it really random, as is
commonly believed, or were creatures designed to be able to vary?
Beaks can vary in three dimensions: length, width, and depth. The morphology
of the beak in an individual adult is determined during its development. Research
on Darwin’s finches is revealing molecular mechanisms that account for
these differences in development. Two distinct developmental phases are responsible
for determining adult beak shape. The details are fascinating and contradict
the assertion that variation is random. Rather, they reveal a purposeful design.

The first step: prenasal cartilage formation

Six different species of Darwin’s finches (Geospiza) were compared
and it was discovered that expression of Bmp4, a gene that plays important
roles during development, was correlated with depth and width in finch beaks.2 The
time, place, and level of expression were all found to be important. The sharp
beaked finch (G. difficilis) has a small symmetrical beak that appears
to be relatively unspecialized; it was used as the reference species. In this
species Bmp4 expression is first detected in the area of prenasal
cartilage formation at embryonic stage 26. By stage 29, the cartilage is apparent
and expression continues in a limited area surrounding it. Ground finches have
deeper, wider beaks. In the species with the greatest width and depth (G.
magnirostris), elevated Bmp4 expression was detected by stage
26. In the other two species of ground finch, elevated expression was detected,
but not until stage 29. The last two species, both cactus finches, had more
pointed beaks and did not show the relative increase in the expression of Bmp4.

Were creatures designed to be able to vary?

The scientists ran several other tests to confirm that Bmp4 is actually
responsible for the differences in beak depth and width. The results highlight
the importance of where in the embryo the increased expression of
this gene takes place. When they artificially increased the level of expression
in a chicken embryo at the appropriate stage of development, the results depended
on where the increase occurred. When it was in the mesenchyme region where
the prenasal cartilage forms, it caused a deeper, wider beak, as is characteristic
of ground finches. When the increased expression was in the nearby facial epithelium,
the beaks were narrower and smaller. Thus, time, place, and degree of gene
expression are all critical factors affecting final beak morphology.

A separate study found that increased calmodulin expression is correlated
with greater beak length.3 Calmodulin
is a ubiquitous calcium-binding protein involved in a variety of calcium-dependent
cell functions. An elongated beak enables cactus finches to probe flowers for
food. Again using local upregulation in a chick embryo’s mesenchyme the
researchers were able to show that it resulted in a longer beak. So, beak length
is regulated separately from depth and width during this stage of development.

The second step: premaxillary bone formation

The premaxillary bone also contributes to the final shape of the beak. It
forms later and appears to be independent of prenasal cartilage formation.4 Another
study was done which found that differences in the expression of several other
genes (TGFβIIr, β-catenin, and Dickkopf-3) were
correlated with differences in beak shape. Increased expression of these genes
was correlated with increased beak length and depth, while beak width remained
relatively unchanged. Again, when and where they were expressed was important.5

Is anyone selecting?

It is apparent that differences in beak shape can result from shifts in gene
expression during the complicated development process. So the next question
is how does a particular beak shape become characteristic of an interbreeding
population (species) of finches? The standard answer is natural selection.
But how can nature select if it has no mind? It cannot. However, the term is
used by biologists to describe a potentially valid biological concept.

It is possible that certain individuals in a population have traits that are
advantageous and allow them to be more successful at surviving and producing
offspring. Others may have traits which hinder their survival and/or their
ability to produce offspring in a given environment. Since those with the advantageous
traits should leave more offspring for the next generation, those traits should
become more common in the population.

One example in finches that seems to fit this concept involves the disappearance
of many adult birds from a medium ground finch (G. fortis) population
following periods of drought.7 A high
adult mortality was recorded, which appeared to be from the loss of a previously
abundant food source. The remaining birds tended to be larger and better able
to exploit the remaining food source.

Evidence of provision

While the explanation seems plausible enough, other factors may be involved.
The most obvious is bird behaviour. If some individuals find an environment
unsuitable, what would stop them from migrating? In this case they could still
have offspring, but they would be living elsewhere. In a similar way, if a
new niche became available, it might be invaded by relatively few individuals
that had traits that fit well with the niche. In this case the high proportion
of those traits is not from less fit individuals dying off early as much as
it is from adapted individuals moving in and founding a population in that
area.8 So both migration and the founder
effect are also plausible explanations for the observation that some traits,
like beak shape, have become characteristic of different populations.

There is evidence that bird behaviour has been involved in shifts in the traits
of Darwin’s finches. After the severe drought, hybridization between
medium ground finches (G. fortis) and common cactus finches (G.
scandens) appears to have restored some of the variability in beak size
that had been lost during the harsh drought conditions.9 This
was helpful as some previous food sources became available again after the
rains returned. In addition to the behaviour of the birds affecting the pattern
of traits in a population, there could also be genetic or epigenetic factors
which affect them (e.g. gene conversion, heritable epigenetic changes, phenotypic
plasticity). Environmental factors could signal common traits to undergo rapid
readjustment, as seen in captive foxes, even after generations of stable traits.10 So,
while ‘natural selection’ may have played a role in some cases,
it is important not to glibly attribute all shifts in traits to it. Doing so
obscures what is really going on.

Which way does the beak point?

It is fascinating to learn about a portion of the complex developmental pathways
that are involved in developing bird beaks. These well-designed networks are
impressive as they coordinate the development of the beak in a way that the
components properly fit so the beak is functional. Even more impressively,
the design does not result in a ‘one-size-fits-all’ beak, but provides
for adjustments so the beak can be useful in a wide variety of habitats. Two
dimensions can be changed in concert with each other (such as width and depth
in the first stage) or independently.

Not only must the beak be able to form, but it must
be properly integrated with the rest of the body so as to be functional.

Though these findings were interpreted within an evolutionary worldview, they
don’t support the conjecture that beaked finches evolved from a beakless
ancestor. Certainly there is evidence that the birds have adapted to different
niches because the shape of the beak can vary between individuals. Changing
the final beak shape requires that all the information for beak formation already
be in place. Not only must the beak be able to form, but it must be properly
integrated with the rest of the body so as to be functional. All this suggests
considerable planning and foresight was involved in the design of beak formation
in birds.

The evidence fits very well in the creation model. Both birds and sea creatures
were created on Day 5. Then, God blessed them and said, “Be
fruitful and increase in number and fill the water in the seas, and let the
birds increase on the earth” (Genesis 1:22 NIV). In learning
about beak development we catch a glimpse of one way God has provided for birds
so the earth can be inhabited (Isaiah 45:18). The harsh realities of death
are recognized as effects of the Fall (Genesis 3; Romans 8:19–22). Yet
in the midst of this, God still provides. He gives birds wisdom so they can
survive (Job 35:11), which is evidenced by their behaviour in finding food
sources and a mate. There are certainly many ways God has provided for them
that we have yet to learn as we continue to study them. What an awesome Creator
we have!

Though often bone is formed on a cartilage template, these two development
phases seem to be independent in this portion of craniofacial development.
Mallarino, R., Grant, P.R., Grant B.R., Herrel, A., Kuo, W.P. and Abzhanov,
A., Two developmental modules establish 3D beak-shape variation in Darwin’s
finches, PNAS108(10):4057–4062, 2011. Return
to text.

In ground finches there was expression in a broader area within the mesenchyme
compared to that of cactus finches. In the large ground finch, expression
also appeared earlier. Return to text.

Darwin, C., Journal of researches into the natural history and geology
of the countries visited during the voyage of H.M.S. Beagle round the world,
under the Command of Capt. Fitz Roy, R.N., 2nd ed., 1845. Return
to text.

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