Only in the Light of Evolution

The following also appears at For the Sake of Science. Presented here is that version rather than the version for the physical copy of Without Apology.

By Michael Hawkins

We should see fossils in a certain order if evolution is correct. They should go from simple to more complex overall, and the fossils we see in the most recent strata should resemble extant life much more than the fossils we see in old strata.

We should also see changes within lineages. We should be able to observe instances of gradual change in species that eventually leads up to either current species or at least to the time of extinction for these species.

Here’s a simple timeline of life’s history. Click it.

What the evidence shows is gradual change. First we find simple bacteria which survived off energy from the Sun, then we see more complicated cells known as eukaryotes arise. (You are a eukaryote.) Next we see a slew of multi-cellular animals arise. They’re still simple, but much more complex than the original bacteria. A few million years later more complicated life arrives. Early (and simple) plants begin to take hold. Soon the fossil record begins to show more plant complexity with low-lying shrub such as ferns, then conifers, then deciduous trees, and finally flowering plants. Gradual changes occur in the oceans and fresh waters which lead to fish and then tetrapods (Tiktaalik comes to mind).

One of my favorite fossils is trilobites. They’re extremely common due to their hard bodies. In fact, even their eyes are well-preserved because of their hard mineral make-up. I personally recall entering touristy-stores seeing countless fossils of these guys in the mid-west to the west (which, unsurprisingly, was once a shallow sea). This image shows the different lineages of this organism. Studies show that the ‘rib’ count has changed over time in each individual species, often without regard to how the other species changed. Going back further, there is less and less divergence in each species. Eventually, as evolution predicts, they all meet at a common ancestor.

So naturally the next step is to find fossils which show more significant changes. Let’s take birds and reptiles. They hold similarities between each other, both morphologically (certain shapes and structures) and phylogenetically (genetic sequence). A good hypothesis is that they came from one common ancestor. If this is true, the links between birds and its ancestors and reptiles and its ancestors should lead to the same point. They do. Dinosaurs are the ancestors of both. The links between birds and dinosaurs are so incredibly well established that I’d prefer to not go over them in detail. But for starters, some dinosaurs sported feathers and claws and had the same proteins for the feather-making process as extant birds. The links between reptiles and dinosaurs is easier just on intuition, so I’ll leave it at that for now.

Other transitional fossils include the already mentioned Tiktaalik. A view of the history of life can be see here. This shows the change in head and neck structure. Recent research on long-ago discovered Tiktaalik fossils has shown the importance in the gradual bone changes in the neck. These changes – a hallmark of evolution – were important to the ability to turn its head. This is a hallmark because natural selection only modifies what already exists. This is precisely what happened.

Going further with this example, evolution makes predictions as to how early fish evolved to survive on land. If there were lobe-finned fish 390 million years ago and obviously terrestrial organisms 360 million years ago (which is what the fossil record shows), then if scientists are to find transitional fossils, they should date in between that time frame. There should be an animal that shows both features of lobe-finned fish and terrestrial animals. Tiktaalik is that animal. It has fins, scales, and gills, but it also has a flat, salamander-like head with nostrils on top of its nose. This is a good indication that it could breathe air. Its eyes were also placed there, indicating that it swam in shallow waters. Furthermore, it was lobe-finned, but shows bones (which eventually evolved into the arm bones you used to get out of bed today) that were able to support its weight to prop itself up. And of course, it dates to 375 million years ago.

Next, evolution says the fossil record should show recent fossils being more closely related to extant species than are early fossils. This is precisely what happens. Sixty million years ago there were no whales. Fossils resembling modern whales only show up 30 million years ago. So, again, evolution makes a predication: if transitional fossils are to be found, they will be within this gap. And so it is.

We begin with Indohyus. It was an artiodactyl. This is important because extant whales have vestigial bones which indicate that they came from this order: scientists expected to find this because, again, evolution predicted it. It should be of no surprise that this fossil dates to about 48 million years ago, right in the predicted gap. From here there is a gradual evolution shown in the fossil record which leads up to modern whales.

Only in the light of evolution 3

Once again I am following a chapter in Jerry Coyne’s Why Evolution is True.

There is a pattern within Life that can be seen on oceanic islands. Species which are present are often endemic – only found in that one location. The species common to continents, on the other hand, are often not present on these islands.

In 1703, Alexander Selkrik was part of a plundering group that sailed to the Juan Fernandez archipelago, a few hundred miles off the coast of Chile (pretentiously pronounced “chill-a” by people not from Chile who like to pretend they’re so full of culture). He was voluntarily marooned on one of the islands (Mas a Tierra). He remained there for over four years. He hunted goats and utilized other species introduced by earlier sailors. Little did Selkrik know, his island (now named Alejandro Selkrik Island) was full of these foreign species.

On the island are five species of birds, 126 species of plants, a fur seal, and various insects which are entirely unique to the location. Equally notably, there’s a lot missing from the island. There are no native amphibians, reptiles, or mammals. Islands throughout the world show this same pattern.

Creationism wholly fails to explain the distribution of species – biogeography. It is only in the light of evolution that any logically tenable solution is found. Species are spread across the globe in patterns which follow the movements of the continents. For instance, plants which have a clear common ancestor are explained by the fact that Earth once was composed of a supercontinent known as Gondwana. It split into several sections. This divided species which had already split from one another, causing more adaptation (or extinction). One must believe in tremendous coincidences to just wave this away. That is, the evidence (the biggest foe of the creationist) says plate tectonics caused the movement of the continents which corresponds perfectly to the distribution of species. There is no other plausible explanation.

When observing the world’s biogeography, it is obvious that Australia needs some explanation. Why is it dominated by marsupial mammals while lacking so much in placenta mammals? Better yet, why is the rest of the world lacking in marsupial animals (except for the Virginia opossum)? The answer is in evolution. The animals on Australia show their common ancestry with animals elsewhere by their Class: they are mammals, just as tamarins are mammals. However, they show their divergence and evolution with key differences. Notably, the birthing process and raising of young differs drastically.

Now here’s a prediction that all this makes. Marsupials are found as early as 80 million years ago. Interestingly, they are not found at this time in Australia, but instead North America. With their evolution, they spread to South America about 40 million years ago. About 10 million years later, they’re in Australia. This means there was a connection of land from South America to Australia. The evidence bears this out. Geologists know South America was connected to Antarctica. That in turn was connected to Australia – actually, it was more like a cobble of connection; these continents were all part of Gondwana, deep in the Southern Hemisphere. So, to get from South America to Australia, marsupials must have passed over what is now Antarctica. Prediction: There should be fossils dating between 30 and 40 million years in Antarctica.

It shouldn’t surprise you to learn that, yes, there are marsupial fossils in Antarctica. And yes, they date from 35 to 40 million years in age. Again, a person has to believe in tremendous coincidence to reject this evidence. Geologists independently concluded that Gondwana existed and how it separated, and at roughly what times this all happened. Biologists then concluded that, if evolution is true, marsupial fossils must be presented in a particular location. They were right. Only in the light of evolution does this make sense.

Coyne goes on to explain islands, which I may address in the future. For now, I will leave the evidence at this point. The tremendously short attention span of people – creationists and rationalists alike – forces my hand.