Too dry for a fly
by David Catchpoole
The rainforest fly Drosophila birchii likes living in, not surprisingly,
rainforests, where the air is humid and everything is nice and moist.
But Australia ’s pockets of tropical rainforest are becoming more fragmented
by land clearing for roads, agriculture and urban development. Increasing penetration
of drier air from outside alters the ‘microclimate’ inside the rainforest—particularly
humidity.
So scientists decided to test Drosophila birchii in the laboratory to see
how quickly this rainforest fly would be able to adapt to a drier environment.1
They exposed flies to a dessication (drying) stress until 80 to 90% had died, and
then bred from the survivors. But the offspring were no better than their parents
at surviving drier-than-normal conditions. With mounting surprise, the researchers
repeated the process—for 30 cycles over 50 fly generations—but still
no increase in dessication resistance.
The astonished researchers thought something must have gone wrong with that particular
batch of D. birchii flies. After all, when the lab tested other species
of Drosophila from less humid environments—D. melanogaster,
D. simulans and D. serrata—they saw a two- to five-fold
increase in dessication resistance.
Even after dry-stressing fresh batches of the flies from four separate rainforest
populations, the researchers noted that ‘the most resistant population lacks
the ability to evolve further resistance even after intense selection for over 30
generations’.
As other evolutionists have commented, this was ‘a complete surprise’.2 For creationists, this is a classic
example of the built-in limits to genetic variation—and therefore
evidence for (biblical) creation!
How so?
Evolutionary theory claims that life arose by a process which is ultimately creative,
and virtually without limits.
When researchers found that a rainforest fly was unable to adapt to drier conditions,
it was ‘a complete surprise’. But why?
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But the Genesis creation account implies that virtually no new genetic information3 has arisen since Creation Week
around 6,000 years ago. Note that God finished creating all the plant and
animal kinds in the first six days (Genesis
2:2–3,
Exodus 20:11 )—that’s the key reason there’s no new
information. So we would expect today’s various Drosophila species
to each carry less genetic variety than the original created kind from which all
Drosophila flies are descended.4
Why? Because natural selection eliminates genes. It cannot create
new ones.
This is most noticeable in extreme environments—e.g. in dry conditions, flies
that lose body moisture too quickly will die out and, without offspring, their genes
will be lost from that population. But in a wet rainforest environment, there’s
no advantage in conserving body moisture; what’s needed is just the opposite—the
ability to withstand high humidity and the rampant diseases which thrive in such
conditions. Hence Drosophila birchii populations have become highly adapted
to life in the rainforest, but it has come at a cost. The price paid for such specialization
is the permanent loss of genetic information useful for survival
in a drier environment.
In contrast, the Drosophila flies from intermediate (less humid) environments,
D. melanogaster, D. simulans, and D. serrata, still contain
sufficient genetic variation to enable the population to adapt to drier conditions.1,5
So, what we have here is not evolution, just natural selection.6,7 Not a creative, limitless process,
but one of culling genes already in existence. Just what we’d expect when
we build our thinking about biology and genetics on what the Bible tells us. That
is, God designed all creatures to reproduce ‘after their kind’ and fill
the whole earth.
References and notes
- Hoffman, A.A., Hallas, R.J., Dean, J.A. and
Schiffer, M., Low potential for climatic stress adaptation in a rainforest Drosophila
species, Science 301(5629):100–102, 2003.
Return to text.
- Roff, D., Evolutionary danger for rainforest
species, Science 301(5629):58–59, 2003.
Return to text.
- There are designed (i.e. created) mechanisms
for generating limited new information under strict cellular control. See, e.g.,
Batten, D., The adaptation
of bacteria to feeding on nylon waste, TJ 17(3):3–5,
2003, and Truman, R.,
The unsuitability of B-cell maturation as an analogy for neo-Darwinian theory. Return to text.
- The ‘splitting’ up of a large gene
pool (represented by a ‘kind’) into smaller ones (‘species’)
adds to the amount of observed variety within the descendants of an original kind.
But each variety has less genetic information than the original population.
Return to text.
- The only way D. birchii could (re-)adapt
to drier conditions would be to reintroduce lost genes by mating with other Drosophila
species from less humid environments. N.B. the intermediate populations would presumably
also be able to adapt to rainforest conditions. Return to text.
- Evolutionists look to mutations as a way to
add new genetic information, but such genetic copying mistakes to date all appear
to be losses of information—not surprising for a random process.
See: Wieland, C., Beetle
bloopers, Creation 19(3):30, 1997.
Return to text.
- Wieland, C.,
Muddy waters—clarifying the confusion about natural selection. Creation
23(3):26–29, 2001. Return to text.
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