Chemistry Reference
In-Depth Information
11
Biomineralization and Evolutionary History
Andrew H. Knoll
Department of Organismic and Evolutionary Biology
Harvard University
Cambridge, Massachusetts, 02138 U.S.A.
INTRODUCTION
The Dutch ethologist Niko Tinbergen famously distinguished between proximal and
ultimate explanations in biology. Proximally, biologists seek a mechanistic understanding
of how organisms function; most of this volume addresses the molecular and
physiological bases of biomineralization. But while much of biology might be viewed as
a particularly interesting form of chemistry, it is more than that. Biology is chemistry
with a history, requiring that proximal explanations be grounded in ultimate, or
evolutionary, understanding. The physiological pathways by which organisms precipitate
skeletal minerals and the forms and functions of the skeletons they fashion have been
shaped by natural selection through geologic time, and all have constrained continuing
evolution in skeleton-forming clades. In this chapter, I outline some major patterns of
skeletal evolution inferred from phylogeny and fossils (Figure 1), highlighting ways that
our improving mechanistic knowledge of biomineralization can help us to understand this
evolutionary record (see Leadbetter and Riding 1986; Lowenstam and Weiner 1989;
Carter 1990; and Simkiss and Wilbur 1989 for earlier reviews).
Figure 1
. A geologic time scale for the past 1000 million years, showing the principal time divisions
used in Earth science and the timing of major evolutionary events discussed in this chapter. Earlier
intervals of time—the Mesoproterozoic (1600-1000 million years ago) and Paleoproterozoic (2500-
1600 million years ago) eras of the Proterozoic Eon and the Archean Eon (> 2500 million years ago)—
are not shown. Time scale after Remane (2000).
