When it comes to matters like infectious disease and the environment, evolution cannot and must not be ignored.

(DISCLAIMER: This article is not about science versus religion. People of all religious persuasions can accept and have accepted evolution.)

When I first heard that creationists were going to be distributing 100,000 copies of The Origin of Species at select campuses, including my own, I thought "Great! I can finally replace the copy that disappeared when I moved to Australia." Of course, Darwin's book is available at Project Gutenberg, so I could just print the thing out myself if I wanted to, but the free copies appear to have a nice binding and would look pretty good on my bookshelf.

Who doesn't like things that are free?

Of course, nothing is ever truly free (tanstaafl): this edition of Darwin's famous book now comes with a 50-page introduction "written" by Ray Comfort, in which he explains why evolution is a giant lie perpetrated by Those Who Must Not Be Named. Undaunted, I thought about different uses for the introduction, including keeping it as a historical curiosity, or finding creative ways to make better use of it.

But then there is L'Affaire des Chapitres Manquants – the expurgation of Chapters 11 through 13 and Darwin's original introduction, for example. So the people who are trying to ruin the Origin's 150th birthday party are playing the same old game of selective reasoning and argumentation. It also means that the opus as presented and promoted by Comfort and Kirk Cameron (by the way, Alan Thicke, you failed as a TV dad) is incomplete and therefore of little use to me.

Universities are meant to be bastions of free speech, and those who are distributing these books are well within their rights to do so, although the alleged plagiarism in the aforementioned introduction sets the bar a bit (check that, a lot) below the standard we expect from our students. Anyway, our students are smart enough to make up their own minds, so have at it.

We can sit and laugh about intelligent design over a peanut butter and banana sandwich (no pineapples, thanks, I can't figure them out), but there is a very serious side to this as well. Intelligent design is intended as the "thin end of a wedge" that is ultimately meant to separate science from public policy. So this is a good opportunity to point out just how important evolution is. By giving a couple of short examples largely drawn from the world of tiny things where I typically work, I aim to illustrate the fundamental importance of evolutionary theory (yes, the scientific theory), and the implied consequences of working in ignorance of evolution.

A good place to start is with infectious disease. As the H1N1v influenza pandemic circles the globe and makes people sick, we must remember that this novel variant arose through several rounds of genetic reassortment – the reshuffling of genes from several distinct strains, and then some amount of time spent accumulating new mutations in swine hosts. Of these accumulated mutations, some will have no impact on the virus at all, while others will determine whether the variant is mostly harmless or a ruthless killer.

Shifting our attention to bacteria, antibiotics have had a huge impact on the treatment of infectious disease. But bacteria are fighting back by evolving new ways to defeat or sidestep antibiotics, and passing resistance genes from one species to another.

If you're a fan of syllables, you'll love the bacterium Dehalococcoides ethenogenes. Another good reason to like it is because it can break down some of the toxic things we dump into our environment, including PCEs. The key to efficient biological tertiary waste water treatment is a humble bug called Accumulibacter phosphatis. Waste water treatment and other important industrial processes rely on the ability of one or more microbial players to break down our nasty by-products, many of which are completely new to the environment. We've been defecating for millennia, but the waste water treatment reactor is a completely new habitat, and microbes have adapted to it through evolutionary means. The outcome of many of the changes that are coming in our world will depend on how the microbes adapt and react to new ecological challenges and opportunities.

But enough about bacteria; let's talk about us for a minute or two. More specifically, let's talk about our close relatives the choanoflagellates, single-celled organisms that are almost certainly the closest living relatives of multicellular animals. They're ecologically important because of who they eat (bacteria) and who eats them (krill), but they're also important because they like to team up when certain kinds of bacteria are around. Why should we care about this? Because it appears that many of the mechanisms they use to clump up are very similar to the ways in which our cells stick together. So if we want to understand more about how our cells work together to do the remarkable things they do, we can look to these beautiful microorganisms for clues. And guess what? It's a lot easier and cheaper to grow 1,000,000 choanoflagellates than it is to grow 1,000,000 lab rats.

The story of how different life forms came to be, how they work, and where they are going, is at heart an evolutionary one. To ignore evolution is to deny the relationships that bind all living things together, and to squander an opportunity to learn things that are as true for salmonella or the platypus as they are for us. Beyond this, if we pretend evolution doesn't exist, then we will fail to recognize the potential that is locked up in today's living things, and will be unable to deal with the consequences tomorrow.

So if a copy of the adulterated Origin should fall into your hands – hopefully an almost-complete "second edition" with missing chapters restored, – then you will have scored a free copy of a landmark text that is central to all of biology. Hurray! However, glued to Darwin's opus will be 50 pages of willful ignorance that has been discredited many times. While the temptation might be to treat this as harmless inanity, when it comes to teaching the truth and making important decisions about public health and the environment, evolution must be on the agenda.

It may not surprise you to learn that "Why Evolution Matters" has been used as a title for other works in the past; many of these are worth reading too.

Thanks to John Archibald and Dennis Wong for their suggestions on an earlier transitional form of this article.