Evolution For Beginners.

How This Book Is Organized.

To help you find information that you’re looking for, this book is divided into five parts. Each part covers a particular aspect of evolution and contains chapters relating to that part.

Part I: What Evolution Is

Look up the word evolution in a dictionary, and you’ll come across a definition that says something about change or maybe change through time. That’s good as far as it goes. But in the context of biology, evolution refers to specific changes — genetic changes — in a group of organisms through time. That concept isn’t so hard to grasp, but you may be surprised by how revolutionary the idea of evolution was in the mid-1800s, when Darwin came up with his theory explaining what could cause such changes (natural selection).
Back then, the concept that species could change over time — even the concept of vast time spans — was foreign and frightening to most people. But facts are facts, evidence has a way of piling up, and the science of evolutionary biology has progressed in the century and a half since Darwin’s major insight.

This part introduces the key principles of evolution by natural selection. And because to grasp the main idea, you need to know a bit about genetics, the part includes a brief discussion of that topic, too. If it makes you feel any better (and it should), reading this short discussion of genetics puts you in the position of knowing more about genetics and heredity than Darwin himself did.

Part II: How Evolution Works

Sometimes, evolution is the result of natural selection. Other times, it’s the result of random factors (genetic drift). Populations have variability; not all the individuals are the same, and sometimes individuals with particular genetic traits leave more descendant than others. That’s evolution in a nut shell: The next generation is genetically different from the last one because not everybody’s genes made it! These changes can have big effects on populations. Sometimes they end up with altered proportions of different variants (more fast cheetahs than slow ones, for example). Sometimes, they lose genetic variation, and sometimes, just sometimes, populations speciate (that is, form a new species).
You can consider this part to be the nuts-and-bolts section of the book, because it explains that biological variation exists, where this variation comes from, and the different ways it can change through time. Plus this is the part where I explain how scientists can watch evolution happen both in laboratory experiments and in nature, as well as how they can use data about species today to come up with strong hypothesis about evolution in the past.

Part III: What Evolution Does

Evolution is no more complicated than genetic changes accumulating through time. Sounds almost boring, yet it’s anything but boring. Because all those changes in the DNA, which you can’t even see (outside a biology lab) influence all the things about living creatures that you cannot only see, but also be amazed by. Look out the window at nature’s diversity: Evolution did that! Evolution has a pretty big impact on lots of things you can observe about life, such as:
Physical characteristics (petal color, length of tail, eye color, and so on) Body shape (number of fins, fingers, limbs, and heads, for example) Sexual selection (who mates with whom, how, and why) Life histories (reproduction and life spans) Social behaviors (competitive, altruistic, and so on)
This part covers ’em all.

Part IV: Evolution and Your World

Two things hold folks’ attention better than anything else: themselves and things that affect them. This part covers both topics, beginning with human evolution to explain where we came from (out of Africa), whether we’re unique among all the animals in creation (it turns out that we aren’t; quite a few other hominid species preceded us, and a couple even shared the Earth with us for a while), and how we continue to evolve.
The remainder of the part delves into antibiotic resistance and the evolution of two scourges: HIV and influenza. Why the shift from the exalted Us to the microbial Them? Because these buggers can and do wreak havoc on humans by evolving so quickly and in response to the very medications we use to fight them. Perhaps you’ve seen on the news that bacteria have “acquired” or “developed” antibiotic resistance. Those are just other ways of saying that these bacteria have evolved resistance to our antibiotics — a problem that we need to stay on top of.

Part V: The Part of Tens

Throughout the book, I spend a lot of time talking about the fossil record and adaptations, explaining what they are and why they’re important to evolutionary study. But in this part, I list the fossils and adaptations that are particularly fun or revealing.
I also include the only response you’re going to find to the challenges people throw at evolution. The purpose of these challenges isn’t to clarify the science of evolution but to promote a particular theology. Unfortunately, the challengers do this by misstating scientific facts, which I clear up in this part.