This page represents rather old work.
Newman has written a book Modeling Extinction with Richard Palmer,
an early draft of which can be found here
or at adap-org/9908002.
A Mathematical Model for Mass Extinction
Introduction
Of all the species that have lived on the Earth
since life first appeared here 3 billion years ago, only about one in a
thousand is still living today. All the others, the vast majority, became
extinct, typically within ten million years or so of their first
appearance. This large extinction rate has had an important influence on
the evolution of life on Earth - the population and repopulation of an
ecological niche by species after species allows for the testing of a much
wider range of survival strategies than the slower process of phyletic
transformation by which a species gradually adapts its morphology and
behavior to its surroundings. This in turn has contributed greatly to the
current level of biodiversity on the planet. There is nothing however to
suggest that the species alive at present are special in any way.
Presumably they too will become extinct within the next ten million years or
so, and make way for successors themselves.
The importance of extinction to the development of life leads us to some
crucial questions about the process, the most fundamental of which is this:
is extinction a natural part of the evolution process, or is it simply a
chance result of occasional catastrophes besetting either single species
(such as diseases) or larger groups of species (such as changes in the
salinity of the sea, or changes in the climate)? Many talented thinkers have
offered arguments on either side of this debate. We suggest that the truth
lies somewhere between the two opposing points of view, and present a model
demonstrating how the evolution process might interact with environmental
stresses to produce a distribution of extinctions very similar to that seen
in the fossil record. A detailed writeup of the model is
here. For the moment we just present the main
results.
Extinctions
We find a sporadic series of extinctions with long periods of stability
separated by bursts of extinction activity:
We find a power-law distribution of extinctions sizes within our model. The
power law has a measured exponent of -2.0. Here's a log-log picture of the
distribution:
Last modified: May 20, 1994
Mark Newman,
newmme@lassp.cornell.edu and
Bruce Roberts,
bwr@lassp.cornell.edu