A Layman's Explanation of Why Macroevolution is True

I make every effort to understand the world around to the best of my ability and I trust in the scientific method, a self-correcting process to discovery and study of the observable, natural world. I think science is interesting, but I'm not a scientist. I don't have a degree in biology. I'm just a guy who finds enjoyment in interesting research. Because I'm not scientist, I don't claim the following to be great research--it's merely my best attempt to explain a process (to the best of my knowledge) to somebody who very clearly doesn't understand what it is or how it works. A biologist who goes by @ProtoAtheist on Twitter proofread my work for scientific accuracy. 

First, let's define some of our terms. 

Evolution is a change in allele frequency in a population over time. An allele is an inheritable trait. Evolution is a bona fide fact by any definition of the word "fact." It's been observed in every Genus of life on earth. The theory of evolution is the explanation of why evolution is a fact.

It was once explained to me by a biologist living in New Zealand that the terms "macroevolution" and "microevolution" are not scientific words, but are actually clever terms invented by creationists in a dishonest (and quite lame) attempt to debunk evolution. Since then, I have seen the words used in science vernacular in America, so I assume that science has either adopted the terms over the years, or that the biologist I spoke to has yet to encounter the words in New Zealand.  Nonetheless, since I'm going to use the words here, I'll operationally define them. 

Macroevolution is sometimes defined by creationists as "a change in kind." "Kind" is not a scientific word. In my experience when I ask a creationist to define the word "kind" I'm often given some rhetoric about a kind being a cat, a dog, a giraffe, or a snake. But these would only be examples of kinds, not a definition. When pressed to actually define the word "kind," I've never encountered a creationist who could do so. I'll define "macroevolution" as a change above the species level in the taxonomic tree and over a long period of time, and "microevolution" as a change within a species or small group of a species over a short time.

Microevolution has been observed innumerable times by scientists. Once example came in 2009 when a species of finches in the Galapagos diverged to create a new species of bird. Macroevolution, although an abundance of evidence exists for it, has not been observed, and this is all the ammunition needed by an ignorant creationist, to declare defeat over evolutionary theory. 

The reason macroevolution has never been observed is because most scientists agree that the process would take about 50,000 years (minimally), and, well, nobody has been alive that long to observe it. We can't rely on written history either, because it only goes back about 9,000 years. Nonetheless, scientists, much like a good detective, can gather evidence from a scene and draw accurate conclusions about past events despite not being present at the time the event occurred. The evidence for macroevolution is immaculate, but it isn't the point of this article to espouse the mountains of evidence here.

My point is that microevolution and macroevolution are just different names for exactly the same event. 

If you believe that microevolution is possible, but macroevolution is impossible, my question to you would be "what process stops it?" Name any observed mechanism by which a plant or animal can sustain small (micro) changes over a short period of time but then stop changing over a very long time. 

To state that microevolution is possible but macroevolution is impossible would like saying that you believe it's possible for a sapling to grow to 36 inches but impossible for the sapling to grow to three feet (or if you use the metric system, possible for a sapling to grow to 100 centimeters but impossible for it to grow to one meter). Macroevolution is essentially a long series of microevolutionary changes.

Many small changes occurring over a very long period of time equals one very big change. It's that simple. If you think it's more complex than that, then explain the phenomena that breaks the chain of events.

To illustrate the process of many small changes totaling up to be one big change, imagine that a father takes a photo of his newborn son on the day of his birth, and continues to take a new photo of the boy every single day... for 21 years. 

In fact, you don't have to imagine this to have occurred, because it really happened, and you can watch the time lapse video here: 

Now, you would probably struggle to notice a discernible difference in a random sample of two consecutive photos. What if every photo, instead of being the exact same person taken 24 hours later, actually represented the next generation. The photo taken on day of birth could represent an animal in past time, and the photo taken on Day 2 would be the offspring of that animal, and the photo taken on Day 3 would be the offspring of the one before it (the grandchild of the Day 1 animal), and so on and so forth. Every offspring would look acutely similar to it's parent, and very similar as well to its grandparent and great-grandparents. But they definitely are not identical. We are never exactly the same as we were the day before, and no child is exactly identical to its parent. As we know based on observation, there are means (such as gene mutation, genetic drift, and natural selection) by which successive generations are different from previous generations.

So every photo looks more or less indistinguishable from the one before or after it, but when all the small changes from one photo to the next are added up over a long period of time, we see a very different person in the picture. The newborn infant in the first photo looks nothing like the 21-year old man we see in the last photo.  

If, in our hypothetical analogy, the average age at which this organism breeds is seven years, then 53,655 years would have passed between the first photo and the last (365 days per year, 21 years, 7 years between photos = 365x21x7 = 53,655). Again, it takes a minimum of about 50,000 years for a macroevolution event to occur. 

Once again, the photo analogy is my attempt to explain the process of evolution to somebody who doesn't understand it; and based on the interactions I have every day with people on social media, there is a significant percentage of the population who have no idea what evolution is. If you are one who thinks microevolution can happen but macroevolution is impossible, then please explain to me how there are men who are 72 inches tall, but there is no such thing as a 6-foot tall man.

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