420 Marc Ereshefsky
not think that number would greatly increase given his assumption of how much of
the world had been explored. With not too much difficulty, a biologist could mem-
orize all the names and taxonomic positions of genera in a kingdom. Once those
names and positions were memorized, a biologist would know the classification
of each species in a kingdom by reading the generic name in a species’ binomial
name. Linnaeus’s binomials, thus, served as guides for memorizing the taxonomic
positions of species in a kingdom.
Binomials may have served their intended purpose in Linnaeus’s time when it
was assumed that there was approximately 300 plant genera and 300 animal genera
and those numbers would not increase greatly. The problem is that Linnaeus did
not envision the extent of biodiversity in the world, and so he grossly underesti-
mated the number of genera in the world. Conservative estimates put the numbers
of plant genera in the tens of thousands. Estimates for animal genera are in the
tens of thousands as well. Given these numbers, there are too many generic names
in a kingdom to memorize. As Mayr [1969, 334] writes, “a generic name no longer
tells much to a zoologist except in a few popular groups of animals.” Binomials
have lost their original motivation: they do not serve as guides for memorizing
the classification of all the species in a kingdom. Nevertheless, biologists are still
required to assign a species both a generic and a specific name. The binomial rule
remains in place even though it fails to achieve its original aim.
One might wonder if the continued use of the binomial rule is problematic.
Though the original motivation is gone, there seems no harm in incorporating a
generic name in a species name. However, the use of binomials has its costs. The
binomial rule can place a biologist in the awkward position of having to assign a
species to a genus before having the proper empirical information for making that
assignment. The binomial rule, in other words, can lead to hasty classification.
Recall that the binomial rule requires that a species be assigned to a genus before
it can be named. But in some situations, a biologist lacks the proper information
for assigning a species to a genus. In such situations, if a biologist wants to name
a newly discovered species, she must assign that species to a genus on the basis
of insufficient information. This is no small problem. Cain [1959, 242] writes
that “the necessity of putting species into a genus before it can be named at all
is responsible for the fact that a great deal of uncertainty is wholly cloaked and
concealed in modern classification.” Thus, the use of the binomial rule is not so
innocuous. It causes biologists to assign species to genera without having sufficient
data.
There are further problems with the Linnaean rules of nomenclature, and these
involve not just Linnaeus’s binomial rule but also other Linnaean rules. Many of
these rules of nomenclature were introduced by taxonomists in the 20thCentury.
For example, one rule is that the names of taxa have rank-specific endings that
indicate the Linnaean rank of a taxon. For example, the suffix —idaein the names
‘Hominidae’ and ‘Tipulidae’ indicate that such taxa are families. The suffix —ini
shows that Hominini is a tribe. The inclusion of rank-specific endings in the names
of higher taxa causes further problems with the Linnaean hierarchy.