Animals are amazing. They come in many varieties, and can be classified in groupings that can easily be seen. One of the first thing a child learns is the difference between a bird and a fish and a snake. These categories are unmistakable. How is it that life is aligned in such distinct categories?
You may think that all things can be similarly characterized, but that is not true. For instance, Carl Linnaeus, after establishing the modern groupings in plants and animals in his 1735 book,
Systema Naturae, set out to do the same thing for rocks. Everyone could see that the groupings for animals were correct. But the rocks? He could not seem to find anything that people would agree on. Oh, one could classify rocks by mineral content, or depth of the formation, or apparent process in making the rocks, or apparent age, but each grouping leads to a completely different arrangement. He could find no grouping that all could agree was the correct one.
He had not had this problem with animals. Everybody could see that snakes, sharks, birds and mammals were distinctly different groupings. And one could subdivide the mammals into primates, rodents, carivora (cats, bears, dogs, etc.), and other groups. All could see those subgroups were real. And one can readily learn to tell which of those groups each mammal belongs to. The carnivora could be further divided into groups like Canidae (dogs, wolves and foxes), Felidae (cats), and Ursidae (bears). And even young children can readily tell if an animal should be grouped in a cat family, a dog family, or a bear family. The cat family can be further subdivided into over 40 different species such as lions, tigers, and bobcats. And the major groups like birds and mammals can be grouped together with all other animals with backbones to form the vertebrates, and the vertebrates can be combined with sea squirts and lampreys to form the chordates, and the chordates can be combined with starfish to make the Deuterosmoes, which are distinct from the larger group of animals called the Protosomes (insects, worms, etc.).
An interesting tidbit here is that the Protoosomes all eat with the hole that forms first in the embryo, using the second hole that develops to expel waste. But the Deuterosomes (us vertebrates and our kin) have it backwards, eating with what most animals would call the anus and sending waste out the end that most animals would call the mouth. So we find a clear distinction here. One group universally treats the first hole that forms as the mouth, and the other universally uses that same hole for expelling waste. This is no trivial difference. And again one wonders why it is that all sharks, birds, humans, and starfish would use one end to eat with, while all worms and insects walk in a direction that we would consider backwards, and eat with what we would consider the wrong end.
If one can examine the details, it is easy to distinguish between eating with the front end or eating with the back end. It is easy to distinguish having a backbone and not having a backbone. The groups are unambiguous.
We see multiple layers of groupings. Chimpanzees, for instance are part of a line that branches off in 40 different places from lines that lead to other living things. Starting with a group that includes all life, we find that all plants go their own way to make their own group, then later all the Amoebozoans, then the fungi, and on up through to the Protosomes which branch off to eat with what us dignified folks would consider to be the wrong end, and others branch off later to be distinct from the chordates, and some of the chordates branch off later without being vertebrates, and some vertebrates branch off without being descendents of the first tetrapods, and some of the tetrapod descendents branch off without becoming mammals, etc. in 40 different layers of branching, before the chimpanzees branch off from humans and then finally the bonobos to form their own group. And each of the groups that branches off forms its own tree of branching life forms.
This is what we refer to as a nested hierarchy. It is not simply sorting by size or some other characteristic. It is groups within groups within groups, all the way down. See figure below.
See also diagram at
29+ Evidences for Macroevolution: Phylogenetics .
Try doing that with rocks. You can't. Try doing that with chemical elements. You can't. Try doing it with mountains, planets, lakes, or streams. You can't. And again, the question is why?
Try doing that with vehicles. You can't. I hear the objection already. Many here have claimed that you can. They will probably respond to this post with a picture showing perhaps cars, light trucks and heavy trucks arranged in what looks like a nested hierarchy. But the arrangement is a simple arrangement based basically on one category, hauling capacity. Which brings up an interesting question. What is the definition of the truck? Look it up. A truck is a vehicle that hauls a lot of cargo. A heavy truck is a vehicle that hauls more than a light truck. Ok, so if we arrange vehicles by cargo capacity, we find small cargo capacity (cars), medium cargo capacity (pickups), and high cargo capacity (heavy duty trucks). Sure, you will see features that, almost by definition, are needed in bigger and bigger vehicles and so tend to exist in larger vehicles as one goes along. All this does is sort on one variable, cargo capacity. Now lets add in all the variables in which vehicles vary: air conditioning, make and model, engine type, fuel, brand of spark plugs, type of brakes, type of sound system, etc. Now give me a breakdown, please, that groups vehicles in all these categories in a single nested classification system that is readily accepted by all. You may think a beat-up '57 Chevy pickup should be classified with an '18 Ford F-150, but others would say that is closer the the '57 Bel Air.
There are only a few things that can be grouped in a clear, objective, readily accepted nested hierarchy. These include languages and manuscripts of old books. They share the same trait. They are all reproduced with changes from some previous reproduction with changes. Reproductions of reproductions tend to keep the changes in the line of ancestry that led to that copy. Where you see a clear, unambiguous, objective nested hierarchy of many layers, that is strong evidence you are dealing with something that has been reproducing with changes.
And so it is that nested hierarchies are evidence that things have descended with change from a common source. For living things, that means evolution. See
29+ Evidences for Macroevolution: Part 1 .
I conclude that nested hierarchies are evidence for evolution.