In this my second post in a series addressing some of the common reasons people give for not believing in the Theory of Evolution, I’m going to address what Evolution is, and what it isn’t. If you haven’t already read my other posts on the subject, the whole thing would make a lot more sense if you did. In the first series I cover Natural Selection for the non-scientist in three parts to bring the basics to the non-believer. As a non-scientist myself, I thought I’d be the right person to explain this stuff to others who are not scientific by background. In the first post addressing reasons people give for refusing to believe in evolution, I cover the issue that people have with it being “just a theory.”
If you’re ready to roll on, here’s a question I get asked whenever evolution comes up:
- If evolution is true, where did the very first life forms come from?
Evolution is the change in living organisms over time. This change is caused in several ways, namely through Natural Selection as variations in organisms best suited for the environment they find themselves in survive long enough to reproduce while others less suited do not. These fitter variations of organisms pass on their genetic traits to their offspring, and the process repeats itself over and over again. New species evolve when changes in the organism, either through isolation from their peers or genetic mutation, alter the genetic makeup enough that they can longer produce fertile offspring with their original peers.
Evolution is also caused by Genetic Drift, which is the random mixture of genetic material passed on to offspring. If parents have a small number of offspring, all of their genes will not be reproduced. There’s a chance assortment of chromosomes in the genes that are mixed together to create the zygote. The offspring are not an exact replica of their parents. This process continues from generation to generation with a random mixture of genetic material. Genetic Drift is an important evolutionary topic that I will delve into in a separate post.
So what evolution describes is the reason we have the diversity of life we see on the planet. It lays out the case for how complex organisms like us came into existence from less complex organisms over many generations of adaptations and mutations. Through evolution we can understand how there came to be 40,000 species of snails and 37,500 species of spiders. We can see through the fossil record how species changed over time through subsequent generations over millions of years. The Theory of Evolution allows all of life’s diversity to make sense.
- See chart below
What the Theory of Evolution does not do is address the question of the origin of life. This is a separate, albeit related area of study and I’ve encountered many people who get frustrated when they can’t get a simple answer to perhaps the most important question of all time! It’s important to understand that evolutionary biology is not trying to answer that question! There is no single scientific discipline that is trying to address all aspects of life on Earth. So should you roll your eyes and discount evolution because it doesn’t address your question? Of course not!
The answer to the origin of life on Earth is being sought, and scientists are making serious progress. We now know that RNA, one of the three molecules essential to all forms of life, can be created in the lab with the basic elements and in the same relative conditions that would have existed on the early Earth. It is a major discovery and it brings us one step closer to answering the elusive question.
So understand what the Theory of Evolution is. Once you grasp the concepts, see the fossilized remains of our ancestors, see the similarity in species of plant and animal you see every day, you will come to experience the wonder and power of the Tree of Life.
To get a glimpse of how the first RNA molecules could have formed on Earth billions of years ago, grab a cup of coffee or tea and watch this video.
(A) Pan troglodytes, chimpanzee, modern
(B) Australopithecus africanus, STS 5, 2.6 My
(C) Australopithecus africanus, STS 71, 2.5 My
(D) Homo habilis, KNM-ER 1813, 1.9 My
(E) Homo habilis, OH24, 1.8 My
(F) Homo rudolfensis, KNM-ER 1470, 1.8 My
(G) Homo erectus, Dmanisi cranium D2700, 1.75 My
(H) Homo ergaster (early H. erectus), KNM-ER 3733, 1.75 My
(I) Homo heidelbergensis, “Rhodesia man,” 300,000 – 125,000 y
(J) Homo sapiens neanderthalensis, La Ferrassie 1, 70,000 y
(K) Homo sapiens neanderthalensis, La Chappelle-aux-Saints, 60,000 y
(L) Homo sapiens neanderthalensis, Le Moustier, 45,000 y
(M) Homo sapiens sapiens, Cro-Magnon I, 30,000 y
(N) Homo sapiens sapiens, modern
Hominins courtesy of the Journal of Imaginary Sciences