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Creation 42(4):23, October 2020

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Rails derail Darwinism

Loss of flight is not evolution

by

Image: Charles J. Sharpfig-1
Figure 1. The White-Throated Rail (Dryolimnas cuvieri)

A recent paper on a bird called the White-Throated Rail (Dryolimnas cuvieri, fig. 1) has shown evidence for the repeated loss of flight in this flying species on several small islands in the southwest Indian Ocean near the islands of Madagascar and Mayotte, over an alleged 340,000 years or so.1 This has given rise to several flightless subspecies on these islands, listed in table 1.

One of these, the Aldabra Rail (Dryolimnas cuvieri subsp. aldabranus), found on the Aldabra atoll (island reef) in Seychelles, is the last remaining flightless rail in the Indian Ocean. Fossil evidence indicates that the flightless rails on that island actually went extinct previously, then an essentially identical flightless species re-emerged. This was as a result of more of the flying rails arriving on the island, then once more losing flight. The researchers concede that this happened “in 20,000 years or less”—a blink of an eye in evolutionary terms.2

What is special about this group of birds is that the loss of flight capabilities seems to have occurred several times, and rapidly. The specific conditions for this include the lack of both land predators and competitors for food.

Loss of flight is not evolution!

The authors of this paper claim that flightlessness has “evolved” several times.1

But despite such descriptions, this does not qualify as a demonstration of evolution. Flightlessness is a loss, not a gain. No new structure is being developed as would be required if flying creatures had evolved from non-flying ones; rather, function has been lost.

When the flying birds first arrived at the relatively underpopulated island, there was no pressure on them to escape from predators by flying away from them. Therefore, birds with mutations damaging their wings were not selected against, because they did not suffer in terms of predation or finding less food.

In addition, it is known that loss of flight in both birds and insects is more common on small windy islands. In such an environment, those suffering the effects of a flight-destroying mutation actually have a selective advantage over the flighted variety. Flying birds are more likely to be blown away in storms, never to return, so they can no longer contribute genes to that population.3 Also, the flightless creatures did not have the added energy cost of maintaining the muscles and nerves required for flight-capable wings.

This is a case of devolution, not evolution. The actual generation of genes (and the associated structures) responsible for flight has never been observed or demonstrated. Furthermore, the rapidity of flight loss in these birds is in contrast to the popular notion that millions of years are required for significant biological changes to take place.4

Tables

Table 1. List of flying (volant) and flightless rail species in the southwest Indian Ocean

Species Flight capacity Location Extinct?
Dryolimas cuvieri cuvieri Volant Madagascar & Mayotte No
Dryolimas cuvieri aldabranus Flightless Aldabra No
Dryolimas cuvieri abbotti Poorly volant Assumption Extinct by 1937
Dryolimas augusti Flightless Mascarenes Extinct 17th cent.
Dryolimas sp. Flightless Mauritius Extinct

References and notes

  1. Hume, J.P. and Martill, M. Repeated evolution of flightlessness in Dryolimnas rails (Aves: Rallidae) after extinction and recolonization on Aldabra, Zoological J. Linnean Society, 2019. Return to text.
  2. Katz, B., How evolution brought a flightless bird back from extinction; smithsonianmag.com, May 13, 2019. Return to text.
  3. See Flightless insects on windswept islands: Even a defect can be an advantage sometimes, Creation 19(3):30, 1997. Return to text.
  4. Catchpoole, D. and Wieland, C. Speedy species surprise, Creation 23(2):13–15, 2001. Return to text.

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