Because no vertebrate has an odd number of limbs, having three limbs is considered a “forbidden phenotype”, i.e. a body structure that cannot happen. However, some animals can use other body parts as well as their limbs to help them move around. Researchers at noted that some parrots use their beaks to help them climb trees, so they set up an experiment to see if the birds were if they were simply using their beaks as stabilisers or if they were actively using their heads to propel themselves up, effectively using their head as a third limb.
The research team used high speed video cameras to study birds moving a up a runway, which the scientists could set at different angles from completely horizontal to 90 degrees. The researchers also analysed how much force was generated by the bird’s legs and its head and tail if these contacted the runway during the climb.
When the angle of the runway was at 45 degrees or higher the birds used their beaks to help ascend the slope. When climbing the vertical runway the force generated by the head in order to use the beak to help climb was equal to the forces generated by the legs. Therefore, the parrots were using their heads as third limb to propel themselves up. No extra force was directed through the tail, indicating it was only used as a stabiliser if it made contact with the runway during the climb.
Melody Young, who led the study commented that this behaviour must have evolved over many years. She explained: “Although many birds climb vertically, so far, parrots are the only birds known to engage the head as a third limb. This behaviour seems to have necessitated neuromuscular changes over time, including neck flexors that generate additional force and modifications to spinal neural circuitry.”
References: PhysOrg 19 May 2022; Proceedings of the Royal Society B: Biological Sciences 18 May 2022, doi: 10.1098/rspb.2022.0245.
Editorial Comment: The comment about neuromuscular changes brings up a problem for evolutions – it is not enough to develop a new body structure in order to turn one kind of living thing into another. It also requires changes to brain, spinal cord, nerves and muscles in order to use it. The new structure and neuromuscular control have to be built in together. What would make a parrot try to use its head this way if it didn’t already have the muscles and nervous system control to do so? It makes far more sense that the Creator of tree climbing parrots equipped them with all these features from the beginning.
The same applies to other animals that defy the “forbidden phenotype” and use another body part to work with their paired limbs. Many tree-dwelling mammals, such as monkeys, have prehensile tails that are strong and enable them to grip branches and propel themselves through trees. However, the favourite example for us Downunder is the kangaroo, which uses its strong tail effectively as a fifth limb. See our item Five Legged Kangaroo Walk here.
Creation Research News 1 June 2022
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