Sorry for the long delay since my last post; I've been hella busy. This post is going to be a long one.

I promised that we would talk about phylogenetic systematics (the method that most modern paleontologists use to determine the evolutionary relationships of organisms, as well as name groups of species). However, phylogenetic systematics is structured around evolution and common descent (unlike Linnean taxonomy, which was invented by a creationist, even though it illustrates evolution quite nicely; we’ll get back to that later). Therefore, it makes sense to talk about evolution before getting into phylogenetic systematics.

This first blog in the evolution series is really about creationism, and SOME of the reasons why the vast majority of paleontologists and biologists do not consider it a viable alternative to evolution as a way of explaining life in the modern world and the fossil record…or even a type of science. Other aspects of the scientific rejection of creationism are discussed in great detail by AronRa in his marvelous series of YouTube videos on “the Foundational Fal . . . More

Last time, we introduced the nested classification of Linnaean taxonomy originally created in the mid-18th century by Christian creationist Carl Linnaeus. Using this classification system, we established that human beings are not only animals, but vertebrates…even if we completely avoid saying the word “evolution” and just look at our overall anatomy. Vertebrates, you make recall, are eukaryotes (they have cells with a nucleus), animals (mobile multicellular eukaryotes which eat the cells of other organisms), eumetazoans (animals with organized tissues), bilaterians (eumetazoans with bilateral symmetry), deuterostomes (bilaterians in which the opening for the anus develops before that for the mouth), chordates (deuterostomes which have a notochord, pharyngeal pouches, and a tail), craniates, and vertebrates (chordates with an internal skeleton protecting the brain and spinal chord).

Vertebrates include things that we call "fish," as well as amphibians (like frogs and salamanders), "reptiles" (like lizards, snakes, and crocodiles), mammals, and birds. However, several types of "fish" lack a couple of features possessed by most: notably jaws and a . . . More

Sorry about the delay. The last couple months have involved some major changes and frenetic activity, and this post also expanded considerably in scope from what I originally had in mind, evolving (if you will) from a straightforward explanation of Linnaean taxonomy to an extremely detailed answer to the question "how do we know that we are descended from apes?" Since the post was so gigantic, I've split it in half. Here is part one. Read it, get some sleep, the next will be up in a couple days. I have one or two posts on taxonomy I want to do after this one, and then we should move right into evolutionary theory.

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The first scientist to call human beings animals and primates was a Christian creationist.

Carl Linnaeus (1707-1778) was a Swedish biologist, and like most Western natural scientists of his time, he was a Christian who believed all life was divinely created by God, more or less in its present form (he suggested that there might be little changes due to hybridization). He was also the inventor of what is usually called "Linnaean taxonomy" (remember that " . . . More

A genus is a group of very similar species (the plural is genera). The practice of naming genera and species is called alpha taxonomy. When we name a species, we say both the genus and species names together. For Tyrannosaurus rex, “rex” is the actual species. “Tyrannosaurus” is a genus (notice that both words are italicized; genera and species names can also be underlined). This means that you could have a bunch of closely related species which are all grouped under Tyrannosaurus. In fact, there is a form from Mongolia called Tarbosaurus bataar, which lived just a few million years before Tyrannosaurus rex, and which is almost identical to it. Some paleontologists think should be considered a species of Tyrannosaurus: Tyrannosaurus bataar. It is acceptable to give the genus name as just the first letter followed by a period, for example T. rex (but not as T-rex, T-Rex, as it is sometimes given). So, we could say that there are two species of Tyrannosaurus: T. rex and T. bataar.

Unfortunately, we are even vaguer on how to recognize a genus as how to recognize a species. As with the morphological species concept, it is pretty much based on similarity. But how similar? The genus Tyrannosaurus belongs to a group of theropods (meat-eating dinosaurs) called tyrannosaur . . . More

Tom Holtz, a well-known expert on tyrannosaurs, recently posted a blog entitled "What Should Everyone Know About Paleontology?" It is worth checking out.

The next few posts will discuss the subjects of taxonomy and systematics. In biology and paleontology, the word “taxonomy” refers to a system of naming living organisms, and (more importantly for this discussion), figuring out how to classify them (group them together). “Systematics” is a broader subject which includes taxonomy, but also considers the evolutionary relationships and history of organisms.

The word “species” refers to one of the most fundamental groups of living things. Intuitively, it isn’t hard to grasp more or less what a species is: a group of living things that are the exact same “kind” of thing. Apples are one species, oranges are another. Humans are one species, chimpanzees are a different species. However, saying that all humans are the same “kind” of thing is a little vague; what exactly does that mean?

There are several different definitions which have been proposed for species, but I’ll just mention a couple here. The “biological s . . . More

In the last two blogs (click here for Part I and Part II), we've been talking about ways of determining the relative ages of sedimentary rocks and fossils (e.g. species A lived some time before species B), without determining their exact numeric ages (in thousands, millions, or billions of years). This is referred to as "relative age dating." If we start applying numeric ages, we are talking about "absolute age dating." The main method by which this is done is called radioisotopic dating. Explaining how radioisotopic dating works is going to require that I hop around a bit between subjects, but it will all come together in the end.

Just to give a little basic physics recap, an atom is made up of three types of particles: protons, neutrons, and electrons. The number of protons determines the type of atom (and element); for example, an atom of potassium (K) always has 19 protons, which is its "atomic number". The number of neutrons only changes the mass of the atom; atoms with the same number of protons but different numbers of neutrons . . . More

In the last blog, I discussed the Law of Superposition. Layers of sedimentary rocks, or strata, are stacked in vertical sequences, with the oldest layers being on the bottom, and getting younger as we go up through the layers. Remember that the study of the sequence of layers of strata is called lithostratigraphy, and the study of the sequence of fossils in these same layers is called biostratigraphy. Both of these studies were pioneered in the early 19th century by a British geologist named William Smith, who was one of the very first to figure out that you could identify the same sequences of rocks and fossils in different parts of England (an excellent book about Smith and his life is The Map That Changed the World by Simon Winchester). Smith was primarily interested in the economic benefits of these observations, and was able to use his knowledge of the sequence of rocks and fossils, and how they were distributed across England, to inform land owners whether or not they could find coal or building stone on their property. What Smith did not fully appreciate during his lifetime was that he had also figured out the primary methods that . . . More

Sorry about the delay since my last post. I've got a series of blogs about the evolution of dinosaurs and closely related reptiles that I want to do, but as I started writing it, I realized that I ought to do a series of blogs giving a little background into how paleontologists know what they know about the history of life first, and also about what exactly dinosaurs are and how they fit into the big picture of life. So, first things first. Also, I AM paying attention to questions that people ask in the comments section, and will try to cover them (eventually).

This first blog is about how we put events in the history of life in order. Imagine a novel being written in collaboration by a bunch of different authors. Some of them are writing about characters, some about settings, some about specific events which occur in the plot...but they are writing in isolation, and no one has any idea how these people, settings, and events are ordered. What happened first? Did the characters go to Paris after their trip to Mars, or before? Did the schizophrenic dog kill his owner before or after his affair with the monkey? This stuff is important. Everyone is just writing their own pages, but until someone takes all the pages and put them in order, there is no story.

Fo . . . More