There is a very common hang-up people have about evolution. They understand that the theory says that current organisms are descended from earlier organisms, but cannot process the fact that these ancestors can look so completely different. To make my point, first try fulling accepting this fact:
…a study revealing that sea sponges share almost 70 percent of human genes.
That’s a hard one for most people to come to terms with, as it is so far removed from our ideas about ancestry.
But whether you like it or not, it’s true. Skirting this ancestry, and the implications of evolution in general, produces the common misconception that there is some “transitional species” between each recognizable species we see today. Of course there are ancestors that are genetically, morphologically, physiologically, transitional between species; a species of feathered dinosaur is physiologically transitional between dinosaurs and birds, for example, but this is not what the misconception is. Many people don’t agree with the fact of evolution because they think it impossible that species alive today are descended from earlier (very different) species.
Rather than follow the science that clears up the issue, evolution deniers like Creationists use the misconception and make two mistakes about the progression of life: first they assume that every species that is alive today has always been alive, so their ideas about what should be transitional to what is clearly warped. Second, they imagine the tree of life to look like a straight line, with bacteria morphing all the way to humans in an upward progression of complexity.
Assuming that every animal species alive today is the only species to ever exist is just plain ignorance, just go to a museum and look at the fossils for proof. Furthermore, assigning humans a special place at the top of Mount Evolution is misinformed and unwarranted. Evolution does not have a will, nor does it select for higher complexities of life, it only selects what works. It may be hard to wrap you head around, but a sea slug is more evolved than you are.
Creationist-like ideas about ancestry, stemming from the mistake that the only species that exist are the ones alive now, are highlighted by the picture below:
This confusion of different ancestral lines cannot be reconciled other than to say that it is a false argument. No biologist, biology textbook, etc., has ever said that evolution works this way. It arises from plain ignorance of the theory.
A (very) rough idea of how evolution has progressed looks something like this:
If you wish to join me for a bit of science, this evolution confusion can be reconciled.
A gradual change
Many creationists often demand a “missing link” between apes and humans. However, between apes and humans, there was no distinguishable “missing link” that was half-human-half-ancestor, as I believe the creationists require. This is not how evolution works. Small changes, caused by random mutations, the beneficial of those mutations being passed on to subsequent generations, altered the species gradually, over millions of years until Homo sapiens was distinguishable.
Let me give you an example:
You can barely tell the visual or genetic differences between a mother and her daughter. Both are remarkably similar, but with small changes appearing in the daughter due to the random assortment of genetic mutations. Now consider a mother-daughter chain, with each mother standing next to her daughter, with that daughter being a mother to the next, etc. At any single point along the mother-daughter chain, there will not be a daughter standing next to her mother who is a different species. But if you compare the beginning of the chain to the end of it, you can see there have been subtle changes over the generations. With a long enough chain, over thousands or millions of years guided by evolution, these small changes can accumulate and become big changes.
For an even better example, read the text in the graphic below, paying special attention to the color of the text.
And it’s just that simple. It’s elegant, it’s logical, and, most importantly, it is backed up by numerous lines of evidence and has eluded disproof for over almost 200 years (certainly not from lack of trying). It is the best explanation we have to explain the diversity of life.