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NEIL BLACKSTONE:
The title of this lecture
is "Major Transitions
in the History of Life",
and I am Neil Blackstone at
Northern Illinois University.
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When we think of the vast
sweep of geological time
and the massive changes
that life on Earth and Earth
itself have undergone,
it seems impossible
that anything about
the history of life
could exhibit a simple
repeating pattern.
Yet as remarkable as this may seem,
it may also be the case.
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Indeed, the history of life consists
of a series of major transitions
in which lower-level
biological units
cooperatively banded together to
form higher-level biological units.
First groups of molecules, then
molecules within simple cells,
then simple cells
within complex cells,
complex cells within multicellular
organisms, and even in some cases,
multicellular organisms
within societies.
In the process of these transitions,
life became increasingly complex.
While there is the simplicity
in the repeating pattern,
these major transitions themselves
were not necessarily simple.
In fact, they were
perhaps the greatest
achievements of organic evolution.
In each case, the major
obstacle impeding the transition
was evolutionary conflict.
As lower-level units band
together, conflicts arise.
Some units free ride using group
resources without contributing
their fair share.
These conflicts must be mediated
if a higher-level unit is to emerge.
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Mechanisms of conflict
mediation involve a huge variety
of biological features.
While these mechanisms were
no doubt difficult to evolve,
there remains a conceptual
simplicity in the nature
of conflict mediation.
Rick Michod points out that
mechanisms of conflict mediation
in biology typically decrease
the variation of the lower-level units,
thus decreasing the likelihood
that a selfish lower-level
unit will evolve.
Or increase the variation
among the higher-level units,
thus increasing the likelihood
that a cooperative group will
be favored by natural selection.
Much of the history
of life is the story
of the derivation of these
mechanisms of conflict mediation.
In some sense, much of life
is like a bad marriage or maybe
a good marriage, lots of fighting
among the lower-level units
as 'who should do the dishes and
take out the trash' until mechanisms
to mediate these conflicts evolve
and the higher-level unit emerges.
