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Hello,
Can someone brief me on what the Theory of Evolution is about and its stance vs Church teaching? I know some Catholics believe Catholicism and Evolution are compatible, and I may be along that line too because God can create the world via science. But I just find it hard to believe we evolved from apes.
Evolution is the phenomenon of allele drift over time. What is an allele? My example will be oversimplified, but let’s say that there is a gene for eye color. For that gene, there could be the blue eye allele, the brown eye allele, the hazel eye allele, the green eye allele, and perhaps more. The gene is the location/what it controls, and the allele are all the variants that fit into that slot. An example of allele drift would be if in the year 1900, 80% of the population had brown eyes and 20% had blue eyes, and then in the year 2,000 only 70% had brown eyes and 30% had blue eyes. There is a change in the frequency of the brown and blue eye alleles in a population over 100 years. That is allele drift. It doesn’t occur in an individual, but in a population. The allele frequency in the example above is different in the ancestor population from 1900 than it is in the descendant population in 2000.
Evolution isn’t any different from this, but instead of one gene, consider we have millions. We tend to use the word “evolution” when there have been significant allele drifts such that if we compared the ancestor population to the descendant population a million years later (or five or ten or a hundred million years), we might be dealing with two populations that look and behave significantly different. In fact, if they look different enough, or if there have been significant changes in behavior, or if certain mutations in prior ancestors which were once rare are then distributed more widely by allele drift, we might call them different species. That is just a man-made category to designate the difference (a giraffe is obviously a different thing than an elm tree, but our
genus species designations are man-made categories to try to capture these differences). Consider also: perhaps you have one ancestor population, and then the continents drift apart such that the ones living on one side have no interaction with the ones living on the other, the allele drift in one population can be different than the allele drift in the other, such that they take different divergent paths in the alleles that affect their phenotypes. Other factors that could isolate the two are, for example, a mountain range rising up over millions of years, and one side of the mountain range catches all the rain, and the other side has its rain clouds blocked by the mountains, making the environments on either side become different.
Allele drift has random factors to it (meiosis cell division, which sperm fertilizes the egg, etc…), and in large populations random chance tends to even out and allele frequencies tend to remain fairly steady. When the sample size is smaller, one could see fast swings caused by the randomness.
