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For about 200 000 years the immune system has kept the human species
alive in spite of the onslaught of bacteria, viruses, toxins and parasites.
The immune system is polymorphic, changing in response to new challenges,
and it contains within its repertoire traces of its invertebrate ancestry.
Its rapid evolution, however, may not be able to keep up with threats posed
by the modern world, explains Avrion Mitchison, a contributor to Life, Death
and the Immune System (Scientific American Library/W. H. Freeman, pp 136,
$16.95, £13.95 pbk). He points out that the relationship between the
immune system and its challenges is ongoing and mutual. But the time our
immune system takes to adjust makes it vulnerable to rapid changes – diseases
spread more quickly in fast-growing cities and by global travel. This fine
set of essays charts what we know about our defence system.