In 1758, Carl Linnaeus attempted to discover the “natural” system of classification God had used to organize his various creations. But he discovered something that startled him.
He found that the various organisms he classified were not related as the Bible or other Creationists asserted. Instead, he classified them in a hierarchical order that evolution would find simple to explain. However, he could not explain it.
Linnaeus challenged scientists of the time to explain. To no avail, as the theory of evolution as we know it did not yet exist back then.
In his system, you get a branching hierarchy of groups of organisms that very much suggests a hierarchy of ancestors. From which descendant species and groups of organisms branched off from earlier ones.
He discovered that chimpanzees, gorillas, orangutans, gibbons and humans were both in the same family as Hominidae. If you cluster these apes with the Old and New World Monkeys, lemur and bush babies, you get the order Primate.
Include the Primate order with cows, whales, horses, bats, lions to get the class Mammalia.
If you group Mammalia with fishes, birds, reptiles and amphibians to get the sub-phylum Vertebrata. Then if you jump a few steps and lump the Vertebrata in with sponges, corals, molluscs and you get the kingdom Animalia.
We still classify organisms according to a similar hierarchical pattern. With a few refinements here and there and with the addition of a few levels. As well as other changes. However, the general hierarchy he laid down is somewhat intact.
On what basis? Based on the development of distinguishing characteristics.
For instance, mammals are a subset of animals. Everything that has the distinguishing characteristics of this group of animals is a mammal. Within mammals are further groups.
Groups such as marsupials, mammals which typically rear their young in a pouch; monotremes, egg-laying mammals which also feed their young via milk and placentals, mammals which rear young.
And all these groups have subgroups. With each group and subgroup being defined based upon the distinguishing features of that group.
So no, taxonomists do not arbitrarily define these groups by drawing lines on paper. Despite what Creationists like to claim. They define groups based on distinguishing characteristics of different types of organisms.
Where is the evidence for evolution? In the hierarchical relationships between organisms. Relationships that show that species and groups developed from populations of earlier groups.
Which clearly indicates groups of organisms branching off from earlier organisms in a pattern which is only consistent with evolution and nothing else.
Only evolution explains this. How so?
Evolution results in organisms branching into species with differing characteristics. And those species branch off into species with still different characteristics.
And so on until we get a successive tree of related organisms with groups branching off from earlier groups.
Nothing else could explain this branching tree pattern of organisms. Especially given what we know about molecular biology.
Which shows that these animals are indeed genetically related according to these taxonomical relationships.
The fossil record also supports this hierarchy of creatures. So, we know that we have this taxonomy largely right.
Evolution is a truly remarkable theory. How many other theories have compelling evidence that you can literally dig out of the ground? And then mount on your wall! Not very many!
Paleontologists have brought us some of the best known and compelling evidence of evolution. Suppose that we had no evidence for evolution other than the evidence provided by fossils. We would still be entitled to consider evolution proven beyond any reasonable doubt.
As we dig deeper into the Earth, we are digging further into the past. Deeper layers of Earth contain earth laid down further and further into the past. As we dig deeper and uncover increasingly older fossils, we see a clear pattern.
The further back in time we go we find increasingly more primitive forms of life. And we see fewer and fewer of the organisms we now know came later in history.
Not only that, we find many fossils which are clearly of groups of beings which are ancestral to the groups we have today.
If we dig in earth laid down around 3 billion years ago, all we find are simple single-celled organisms such as bacteria. If we dig in earth laid down about 750 million years ago, the only animals we find are primitive animals such as sponges. We then find evidence of the first chordates arriving around 61o million years ago.
And as we go forward in time from the very oldest days of the Earth, we find entire groups of organisms coming into being as developmental offshoots of early groups.
We find species within groups becoming more and more advanced. And sometimes branching off into sub-groups of their own. In other words, we see evidence of changing heritable characteristics over time.
All of this clearly indicates that evolution is happening.
We can also study transitional fossils which show species which have the essential traits of one group of beings. As well as the traits of a descendant group.
That is, fossils which show one species evolving into another!
Despite what Creationists would have us believe; we have an abundance of such fossils. As a result, we know how whales evolved from land mammals.
We know some of the steps taken by the evolution of the first land animals. That is not all, we also have fossils showing how some dinosaurs are becoming birds (while remaining dinosaurs)!
We have excellent transitional fossils of dinosaurs with relatively few bird-like features but which were able to fly. Dinosaurs with very bird-like features. And very primitive birds which retain a few non-avian dinosaur features.
We have excellent fossil records of human species that are gradually walking more and more upright and becoming taller. And generally becoming more and more like our own species of humanity, homo sapiens.
We have the fossil record of land mammals which spent more and more time in the water. Until their descendants adapted to aquatic life. They lost their back limbs almost entirely, leaving only vestigial hind limbs and became whales!
The fossil record is excellent evidence of evolution all by itself.
But the next article will discuss even more evidence! You can find that article here.