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| Shared Idea |
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| Cuckoo Egg Mimicry
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| According to the pattern followed in science, evolution is a theory, not a law. This does not make it any less solid. Like laws, theories are backed by extensive evidence and each theory or law is subject to change, should new evidence be found. The predominant difference is that laws can be observed directly; theories can only be observed indirectly. The atomic theory deals with items and occurrences too small to be seen, even with the most powerful microscope. The Big Bang Theory deals with things that happened in the distant past, when our universe was born. The theory of evolution deals with factors that span periods of time that are too long to be watched directly by us. The pertinent time period is far greater than a human lifespan.
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| In The Genetic Book, Richard Dawkins addresses multiple examples that support the Darwinian theory of evolution. Chapter 10 deals with direct evidence involving cuckoo birds. 59 of the 141 species of cuckoos lay their eggs in the nests of other birds. Those birds then feed and raise the cuckoos, thereby sustaining this parasitic species.
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| The egg of the cuckoo mimics the coloration and pattern of the hosting bird, perhaps being slightly larger. They hatch before the other nestlings and gain most of the food brought by the parental bird. In some cases, they even push the other eggs or nestlings out of the nest, guaranteeing that they receive more food to ensure their survival. Prior to reading Dawkins' book, I had never stopped to think about how the cuckoo was able to lay eggs that matched the pattern of the host bird’s eggs. Therein lies the related evidence supporting the theory of evolution.
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| In mammals, the sex genes of the parents are either XY (male) or XX (female). The gene gained from the father determines the gender of the offspring. In the case of birds, the male birds carry ZZ genes and the female birds carry ZW genes. That means that the gene gained from the mother determines the gender of the offspring!
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| This is where the evidence supporting the theory of evolution comes into play. The cuckoos grew up in foster nests. They never actually saw their parents. The male cuckoo mates indiscriminately with female cuckoos. The female, however, will lay its eggs in the nest of the species of her foster parents. Her eggs will thus match the pattern of the eggs of the foster parents. The female carries on her W gene the genetic traits that determine the pattern of the appropriate foster parent egg while also determining the offspring's gender. This means that she will lay her eggs in the nests of birds who were her foster parents. Her eggs will therefore match the other eggs laid in the same nest.
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| Herein lies the Darwinian trait of the survival of the fittest. If the cuckoo egg did not mimic the image of the host eggs, it would be rejected by the foster parent. Over time, the synchrony of the two factors is critical for the cuckoos to survive. This is therefore one more strong example of the validity of this theory!
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