Too dry for a fly
First posted on homepage: 8 January 2007 (GMT+10)
Re-posted on homepage: 20 October 2021 (GMT+10)
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!
Evolutionary theory claims that life arose by a process which is ultimately creative, and virtually without limits.
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; www.trueorigin.org/b_cell_maturation.asp. 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.