I’ve been read­ing a fas­ci­nat­ing study of microbes — Dead­ly Com­pan­ions by Dorothy H. Craw­ford, just pub­lished by OUP. Her book shows how bac­te­ria, virus­es and oth­er micro­scop­ic organ­isms have proven them­selves to be mas­ters of evo­lu­tion, deft­ly exploit­ing any oppor­tu­ni­ty cre­at­ed by our chang­ing lifestyles.

Our bod­ies are teem­ing with microbes ‑ 10¹⁴ to be exact; that’s about a kilo­gram in weight. Aston­ish­ing­ly, they out­num­ber our own body cells by 10 to 1. Accord­ing to Craw­ford: “We rel­a­tive new­com­ers to the plan­et emerge from the safe envi­ron­ment of our moth­er’s womb pris­tine, untouched by the infec­tious microbes, but with­in hours our bod­ies are colonised by swarms of them, all intent on liv­ing off this new food source.”

But, hap­pi­ly, they’re not all bad: at least 400 of them help our bod­ies ward off oth­er, dead­ly microbes. Of the mil­lion or so microbes known to sci­ence, only 1,415 cause human dis­eases. Of course, they don’t mean to harm us; our dis­eases are just side-effects of their life-cycles. But ever since Homo sapi­ens evolved, we have been locked in mor­tal com­bat with microbes, our dead­ly com­pan­ions. In fact, Craw­ford argues they have shaped our his­to­ry as a species.

You can read my review of Craw­ford’s excel­lent book in today’s Guardian Review. In the same issue I’ve also reviewed The Portable Athe­ist: Essen­tial Read­ings for the Non­be­liev­er, a won­der­ful anthol­o­gy select­ed by Christo­pher Hitchens, and Bad Med­i­cine: Doc­tors Doing Harm since Hip­pocrates, by David Woot­ton, a con­tro­ver­sial view of the his­to­ry of med­i­cine. Both ide­al Christ­mas stock­ing-fillers! You can read my reviews of these here.