Freaks of Nature – What Anomalies tell us about Development and Evolution

; Oxford 2009, kt., Abb. Many of the most striking developmental anomalies have evolved into
some of the most striking species characteristics (e.g., limbless humans,
limbless snakes). (key idea Body, brain, and behaviour are shaped through
development, not programmed before development). We take for granted how easily
we can adjust to an anomalous body when we are allowed to "grow" into
it. Key examples: Johnny Eck, the two-legged goat, Faith the two-legged dog
(key idea: developmental flexibility). Some of the most devastating anomalies —
e.g., two-headedness, cyclopia — can arise from a mutation or an environmental
factor during development. Freaks are not necessarily mutants (key ideas
epigenesis, gene-environment interchangeability). Anomalies provide a stark
contrast to "intelligent design" and a note of caution to
"evolutionary design." They bring us closer to the gears and
mechanisms of development, and the options available to evolution.  Debates over whether Barack Obama is
"black" recall similar discussions concerning the nature of sex.
Nature often offers ambiguities, and it is the human inability to grasp
ambiguity that leads us to force natural products into human categories. But
anomalies won't go away so easily, because they are an integral part of nature.