Saturday, June 26, 2010

Microcosmos: Lynn Margulis and Dorian Sagan

Lynn Margulis and Dorion Sagan's Microcosmosis a recapitulation of the history of evolution of microbes and how it affects us. The work that Margulis & Sagan report on also led to an article at that produced a quote I've been using as one of my email signatures.

All sensory cells [in all animals] have in common the presence of ... cilia [with a constant] structure. It provides a strong argument for common ancestry. The common ancestor ... was a spirochete bacterium.

The copyright date is 1986. A lot has been learned about evolution and microbes since then. Even so, this book is a good introduction to the subject; it's very readable and has lots of detail that is still accepted. The story starts with the very beginnings of life on earth, and is always connected to its affect on how our biology works now:

As we examine ourselves as products of symbiosis over billions of yeaaar, the supporting evidence of our multimicrobe ancestry becomes overwhelming. Our bodies contain a veritable history of life on Earth. Our cells maintain an environment that is carbon- and hydrogen-rich, like that of the Earth when life began. They live in a medium of water and salts like the composition of the early seas.

The presentation is ordered chronologically, starting with the formation of stars and planets, proceeding through the cooling of the earth and the formation of the first entities that could reproduce reliably, the invention of sex and the alternative means of exchanging genetic information, and the change in composition of Earth's atmosphere to something that supported oxygen breathers and was toxic to their precursors. That takes us through the first 3.5 Billion years of the history of the earth, and all of the evolution of macroscopic life occupies the most recent 500 Million years. The emergence of cells, multi-cellular life, and then plants and animals follows, but the microbes are still around and still affecting both metabolism and evolution.

Margulis & Sagan provide a very readable introduction to modern microbiology and modern thinking about evolution. There are certainly more recent books that cover the details of the modern understanding in more detail, but this is a good overview and doesn't miss much that's important.

No comments: