Consider the case of
HIV/AIDS, where phylogenies
have been used to identify the
source of the virus, to date the
onset of the epidemic, to detect
viral recombination, to track viral
evolution within a patient, and to
identify modes of potential transmission
(2). Phylogenetic analysis
was even used to solve a murder
case involving HIV (3). Yet “tree
thinking” remains widely practiced
only by professional evolutionary
biologists. This is a particular
cause for concern at a time
when the teaching of evolution is
being challenged, because evolutionary
trees serve not only as tools for biological
researchers across disciplines but also as
the main framework within which evidence
for evolution is evaluated (4, 5).
At the outset, it is important to clarify
that tree thinking does not necessarily
entail knowing how phylogenies are
inferred by practicing systematists. Anyone
who has looked into phylogenetics from
outside the f ield of evolutionary biology
knows that it is complex and rapidly changing,
replete with a dense statistical literature,
impassioned philosophical debates,
and an abundance of highly technical computer
programs. Fortunately, one can interpret