Welcome to Earth

Some other customer reviewers treat this book as if it was a horror novel by Stephen King, and both the title and the back matter certainly give that impression. "Imagine a world where the parasites control the minds of their hosts, sending them to their destruction...where parasites steer the course of evolution, where the majority of species are parasites. WELCOME TO EARTH".

In reality, Carl Zimmer's "Parasite Rex" is a perfectly serious, popular science book about parasites and their impact on evolution. Zimmer, and presumably the scientists he interviewed, believe that the majority of species are parasites, and that parasites might be the driving force of evolution. Apparently, this hasn't always been the scientific consensus. For a long time, parasites were seen as degenerate organisms, organisms that had "devolved" rather than evolved. This was connected to a misinterpretation of Darwinism as "progressive" evolution. Since parasites didn't seem "progressive", they were considered evolutionary dead ends. Sometimes, the political analogies were pretty transparent: parasites were a metaphor for human welfare cheats (and welfare states).

Today, scientists know that parasites aren't "degenerate". Quite the contrary. They are perfectly well adapted to their respective environments, and their life-cycles and behaviour are incredibly complex, which implies that they have been evolving for a very long time. "Parasite Rex" takes this reasoning one step further, arguing that co-evolution between parasites and their hosts has been a prime feature of all evolution, and that the parasites are the most dynamic part of that process. In effect, the course of evolution, perhaps even human evolution, is steered by...the parasites. They are the movers and shakers of planet Earth.

Zimmer also believes that many natural scientists haven't faced the implications of this yet. Many studies of population dynamics and animal behaviour are made without taking into consideration that parasites might affect the populations, and even their behaviour, in dramatic ways. Zimmer wants biologists to place parasitology, and parasite-host interaction, centre stage.

But the most disturbing aspect of the book is, of course, philosophical.

If evolution is a blind process steered by parasites, where on earth does that leave us?

Perhaps that's why some people think "Parasite Rex" is so scary...