One of the subjects that has interested me as of late is that of Convergent Evolution. This is a process of living organisms that have developed similar (and often almost identical) traits to that of other, completely unrelated species. This is in contrast to Divergent Evolution, where related species develop different traits.
One of the best examples of this parallel phenomenon is the recently-extinct marsupial Thylacine (see above photo), verses the distinct but very similar family of Canidae (which includes foxes, wolves, and modern dogs). The modern Thylacine is thought to have appeared about 4 million years ago in Australia and New Guinea, with the oldest known ancestor appearing 23 million years ago. This is in contrast to the much older canids, which date back some 40 million years. Since the Thylacine filled the same ecological niche as the wolves and dogs of the Northern Hemisphere, they developed many similar traits. Both the male and female Thylacine had pouches, one of only two species of marsupials to develop this feature in both sexes. Although there are occasional reported sightings of the Thylacine to this day, officially they have been considered extinct since the 1930’s.
The big cats also have unrelated friends on the tree of life. Thylacosmilus is another interesting marsupial example of convergent development, this time alongside the saber-tooth tiger. Koalas have developed fingerprints, much like those of humans. The Sugar Glider is the marsupial version of the placental flying squirrel. The Hummingbird of the Americas is similar to the Sunbird of Asia. These and other examples provide interesting fodder for study in completely independent development of similar features amongst unrelated species.
From a theological perspective, it is of great curiosity that a divine Creator would have designed two distinct versions of basically the same animal, with each version appearing only in geographically isolated parts of the world. In the case of design, why this deliberate act of parallel creation and then physical separation for the mere sake of variety?
However, in the case of evolution and natural selection, the examples of convergently-evolved animals we see make perfect sense. Two competing species living in the same environment and relying on the same food sources will typically breed or evolve the weaker group out of existence. This is one of the major driving factors of speciation in the first place. We can agree that the act of evolution produces many common traits in many distinct orders and species which are needed to survive (digestive systems, light collection, olfactory and auditory systems, motor functions, etc). It then makes sense that the natural workings of evolution would, in many cases, result in two or more similar living iterations that evolved entirely separate from each other when isolated by vast distances of impassable land or water.
All this makes me wonder, that if life has arisen on some other planet, while working within similar favorable environmental qualities and the boundaries of evolution, whether those lifeforms would somewhat resemble the ones we see here on Earth, with only minor differences based on their own unique living conditions. I doubt we will ever really discover the answer to such questions, at least in our lifetimes, but the question is an interesting one at least. One could speculate, based the evidence of convergent evolution we see around us, that life outside of our known world would indeed appear quite similar to our own.
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