Environments without oxygen are excellent for the preservation of soft parts: no oxidation, no decay by aerobic bacteria. Such conditions are common … - Stephen Jay Gould

"I remember when we found the first population of living Cerion agassizi in central Eleuthera. Our hypothesis of Cerion's general pattern required that two predictions be affirmed (or else we were in trouble): this population must disappear by hybridization with mottled shells toward bank-interior coasts and with ribby snails toward the bank-edge. We hiked west toward the bank-interior and easily found hybrids right on the verge of the airport road. We then moved east toward the bank-edge along a disused road with vegetation rising to five feet in the center between the tire paths. We should have found our hybrids but we did not. The Cerion agassizi simply stopped about two hundred yards north of our first ribby Cerion. Then we realized that a pond lay just to our east and that ribby forms, with their coastal preferences, might not favor the western side of the pond. We forded the pond and found a classic hybrid zone between Cerion agassizi and ribby Cerions. (Ribby Cerion had just managed to round the south end of the pond, but had not moved sufficiently north along the west side to establish contact with C. agassizi populations.) I wanted to shout for joy. Then I thought, "But who can I tell; who cares?" And I answered myself, "I don't have to tell anyone. We have just seen and understood something that no one has ever seen and understood before. What more does a man need?

Thus, when we tackle the greatest of all evolutionary questions about human existence—how, when, and why did we emerge on the tree of life; and were we meant to arise, or are we only lucky to be here—our prejudices often overwhelm our limited information. Some of these biased descriptions are so venerable, so reflexive, so much a part of our second nature, that we never stop to recognize their status as social decisions with radical alternatives—and we view them instead as given and obvious truths.

Arthropods and vertebrates share some broad features of general organization - elongated, bilaterally symmetrical bodies, with sensory organs up front, excretory structures in the back, and some form of segmentation along the major axis. But the geometry of major internal organs could hardly be more different... Arthropods concentrate their nervous system on their ventral (belly) side as two major cords running along the bottom surface of the animal. The mouth also opens on the ventral side, with the esophagus passing between the two nerve cords, and the stomach and remainder of the digestive tube running along the body above the nerve cords. In vertebrates, and with maximal contrast, the central nervous system runs along the dorsal (top) surface as a single tube culminating in a bulbous brain at the front end. The entire digestive system then runs along the body axis below the nerve cord.