advance of the past 25 years was the discovery this year by Mary Schweitzer and Jennifer Wittmeyer of soft, flexible blood vessels and cells in the cortical bone of a Tyrannosaurus rex femur. Regardless of whether or not these soft tissues have been altered, their occurrence suggests that

some of our previous notions concerning the processes of fossilization are in need of revision. The discovery has significant implications for the next 25 years of paleontology in that our investigations to elucidate the biology of extinct organisms will focus more and more on paleobiomole-

JACK HORNER,
CURATOR OF PALEONTOLOGY,
MUSEUM OF THE ROCKIES, MONTANA STATE UNIVERSITY

cular studies and genetic engineering. The re-creation of a look-alike of an extinct organism is likely to be the next most important development.


xpeditionary paleontologists now collaborate with geneticists in ways that we never would have dreamed of 25 years ago. The uncovering of deep similarities in major genes in diverse organisms, including flies, fish, chicken, and mice, is profound for paleontologists because it enables us to look at key evolutionary transitions in a whole new way. The discovery of new fossils and the analysis of the function of these major genes together tell us about the origin of structures as complex and fundamental as heads, limbs, brains, and sense organs. In the next 25 years, the most important development in our field will lie in understanding how genes build bodies and how these genes evolve to produce the evolutionary patterns that we see in the fossil record. The big evolutionary steps will be bridged by these new understandings of genetic mechanisms.

NEIL SHUBIN, PROFESSOR AND CHAIRMAN, DEPARTMENT OF ORGANISMAL BIOLOGY AND ANATOMY, UNIVERSITY OF CHICAGO

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