iar forms. Fossils were merely freak resemblances to plants or animals. Na- 

 ture could make rocks of any shape, like crystals, or like a leaf, or a queer bird, 

 or an old shoe — why not? Perhaps nature had tried out various forms before 

 deciding on the kinds to be produced in quantity; fossils were the experi- 

 mental models that had been rejected. Leonardo da Vinci (1452-1519), the 

 great artist and engineer of the time of Columbus, took them to be the remains 

 of ancient life. 



The great objection to da Vinci's view was that many mountain fossils 

 obviously resembled sea animals. How could sea-shells and the bones of ocean 

 fish get up into the mountains? Da Vinci's view is today supported by 

 vast numbers of facts. And today we know that in the course of millions of 

 years the surface of the earth in any region may have been alternately under 

 the floor of the ocean and high up in the mountain levels. 



Students of fossil structures naturally tried to classify them and to com- 

 pare them with existing plants and animals. Many resemblances were found 

 between the organisms of the past and the organisms of the present, but also 

 marked differences. Assuming that the relative ages of fossils correspond to 

 their relative positions in the layers of rocks, we find that forms that are 

 intermediate between the most ancient and the most recent are also inter- 

 mediate in structure (see illustration, p. 443). One of the best examples is 

 seen in the horse and his probable ancestors (see illustration opposite). Similar 

 series of fossils have been worked out for the elephant in Africa, for various 

 fishes in England and elsewhere, and for many lines of birds and reptiles in all 

 parts of the world. A remarkably complete series was found in Germany, 

 showing successively different types of snails, leading down to the forms 

 existing today. 



Pickled Fossils Since the time of Cuvier, who founded the science of 

 comparative morphology, scientists have been "reconstructing" ancient life 

 forms from fossil fragments. In many cases there are only fragments of skele- 

 tons, sometimes only fragments of bones. Reconstructions are necessarily 

 based on inference, since there is no way of "proving" the guesses as to how 

 these ancient plants and animals really looked. But early in this century 

 John C. Merriam (1869- ), an American paleontologist, found a remarkable 

 collection of complete skeletons of animals that must have lived from fifty to a 

 hundred thousand years ago. Near the present site of Los Angeles an old 

 "tar hole" at Rancho La Brea was being worked for asphalt. Almost daily the 

 workers observed that chickens, squirrels, and various other birds and small 

 mammals would get entrapped in this brea, or tar. And as these animals 

 struggled to escape, they attracted larger predatory mammals, which in turn 

 would also be swallowed up in the asphalt. 



The workers, digging deeper and deeper, would bring out, with the asphalt, 

 remains of old trees (which made very good firewood) and thousands upon 



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