The existence of ancient proteins is no surprise. Evidence of remnants of durable, skeleton-associated proteins such as collagen are not uncommon in the fossil record long before Tyrannosaurus rex. For example, remains of bivalve ligaments are known from the mid-Ordovician, over 400 million years ago. Other durable but pliable organic materials, such as protist resting cysts, are important parts of the Precambrian fossil record, up to 2 billion years old.
David Campbell University of Alabama Tuscaloosa, Ala.
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