Lagerstatten
The Burgess Shale
September 23, 2009
I.
II.
III.
Before the Burgess Shale (was discovered)
A. Edicarn Fauna of the Vendian time period
B. Precambrian/Cambrian boundary extinction-Snowball Earth
hypothesis
The Burgess Shale
A. History of Important Players
1. Darwin had something to say
2. Charles Dolittle Walcott-Discovered the deposit in 1909 in
the Canadian Rockies of Yoho National Park, BC.
a. He classified the organisms into existing phyla
b. His publications from 1911-1920 described and classified
the fauna. Definitive book after he died (1931)
3. Whittington and Briggs-organized reexamination of the
fossils (60’s)
a. This is the start of the career of Simon Conway Morris as
part of this team.
b. The team classified the fauna into groups that have no
known extant members.
B. The Burgess Shale-get environment and formation from movie.
The ongoing controversy
A. Gould’s insights and marginal contributions
1. Challenging the Iconography of the Cone-the sweep of
anatomical diversity reached its peak right after the initial
diversification of multicellular animals and the later history
of life proceeds by elimination, not expansion.
2. Diversity vs. Disparity-the revision of the Burgess shale
rests upon diversity in its second sense of disparity of
anatomical plans. A surprising trend in evolutionary history
is that a decrease in disparity is followed by an outstanding
increase in diversity within a few surviving designs.
3. If we replayed the Cambrian explosion (one of his favorite
mental exercises is replaying life’s tape), would we get the
same results?
B. Conway Morris replies
1. The evidence does not support the inverted cone of life,
evolution does not reflect a dramatic decline in disparity.
2. Constraints we see in evolution suggest an underlying
predictability, so contingency in individual history has little
or no bearing on biological properties.
Selected References
Conway Morris, Simon. 1998. The Crucible of Creation: The Burgess Shale and
the Rise of Animals. Oxford University Press.
Gould, S.J. 1989. Wonderful Life: The Burgess Shale and the Nature of History.
Norton and Company.
Gould, S.J. 2002. The Structure of Evolutionary Theory. Norton and Company.
Knoll, A. H. 2003. Life on a Young Planet: The First Three Billion Years of
Evolution on Earth. Princeton University Press.
Maynard Smith, J. and E. Szathmary. 1999. The Origins of Life: From the Birth of
Life to the Origin of Language. Oxford University Press.