Page 28 - Introduction to Paleobiology and The Fossil Record

PALEONTOLOGY AS A SCIENCE 15

simpler, forms of life were recognized after alization of course – knowledge probably
1960 by the use of advanced microscopic varies group by group: some are probably
techniques, and some aspects of the fi rst 3000 much better known than others.

million years of the history of life are now All fields of paleontological research, but
understood (see Chapter 8). especially studies of macroevolution, require
quantitative approaches. It is not enough to
look at one or two examples, and leap to a
Macroevolution
conclusion, or to try to guess how some fossil
Collecting fossils is still a key aspect of modern species changed through time. There are many
paleontology, and remarkable new discoveries quantitative approaches in analyzing paleon-
are announced all the time. In addition, pale- tological data (see Hammer and Harper
ontologists have made dramatic contributions (2006) for a good cross-section of these). At
to our understanding of large-scale evolution, the very least, all paleontologists must learn
macroevolution, a field that includes studies simple statistics so they can describe a sample

of rates of evolution, the nature of speciation, of fossils in a reasonable way (Box 1.3)
the timing and extent of mass extinctions, the and start to test, statistically, some simple
diversification of life, and other topics that hypotheses.

involve long time scales (see Chapters 6
and 7).
Studies of macroevolution demand excel- Paleontological research
lent knowledge of time scales and excellent Most paleontological research today is done
knowledge of the fossil species (see pp. by paid professionals in scientifi c institutions,
70–7). These two key aspects of the fossil such as universities and museums, equipped
record, our knowledge of ancient life, are with powerful computers, scanning electron
rarely perfect: in any study area, the fossils microscopes, geochemical analytic equipment,
may not be dated more accurately than to the and well-stocked libraries, and, ideally, staffed
nearest 10,000 or 100,000 years. Further, our by lab technicians, photographers and artists.
knowledge of the fossil species may be uncer- However, important work is done by ama-
tain because the fossils are not complete. Pale- teurs, enthusiasts who are not paid to work as
ontologists would love to determine whether paleontologists, but frequently discover new
we know 1%, 50% or 90% of the species of sites and specimens, and many of whom
fossil plants and animals; the eminent Ameri- develop expertise in a chosen group of fossils.
can paleontologist Arthur J. Boucot consid- A classic example of a paleontological
ered, based on his wide experience, that 15% research project shows how a mixture of
was a reasonable figure. Even that is a gener- luck and hard work is crucial, as well as the

Box 1.3 Paleobiostatistics

Modern paleobiology relies on quantitative approaches. With the wide availability of microcomput-
ers, a large battery of statistical and graphic techniques is now available (Hammer & Harper 2006).
Two simple examples demonstrate some of the techniques widely used in taxonomic studies, fi rstly
to summarize and communicate precise data, and secondly to test hypotheses.
The smooth terebratulide brachiopod Dielasma is common in dolomites and limestones associated
with Permian reef deposits in the north of England. Do the samples approximate to living popula-
tions, and do they all belong to one or several species? Two measurements (Fig. 1.10a) were made
on specimens from a single site, and these were plotted as a frequency polygon (Fig. 1.10a) to show
the population structure. This plot can test the hypothesis that there is in fact only one species and
that the specimens approximate to a typical single population. If there are two species, there should
be two separate, but similar, peaks that illustrate the growth cycles of the two species.

Continued