Joseph Leidy and Charles Darwin
Joseph Leidy, the master describer of nature, and Charles Darwin, Biology's greatest theoretician, met only once. The two were introduced to each other by Richard Owen (1) during Leidy's first visit to Europe in 1848. Both Leidy and Darwin were young and relatively unknown at the time.
In the decades before Darwin published his On the Origin of Species scientists had struggled with a growing body of information at odds with scriptures. Geologists presented compelling evidence that the world was extremely old. Paleontologists revealed past worlds populated by bizarre creatures that no longer existed. Biologists were confronted by similarities between species that begged for answers and variation within species that made no sense.
Leidy was well versed in the emerging conundrum. For instance, in a lecture given to his anatomy students in 1859 —just months before the debut of The Origin of Species— he said:
"The geologist has satisfactorily proved that man and his contemporaries, animals and plants at least in their present form, have existed for a comparatively brief time. They further show that the race of animals and plants of our day were proceeded by a different race which became extinct. But more than this, they have discovered indisputable evidence that many races have existed and become extinct in succession. How the are we to account for this most wonderful appearance and disappearance of organized bodies? Have the latter races been the antecedents of those which preceded them by gradual transformation under a change of conditions in progress for ages or has each been the witness of the independent origin of a race of plants and animals? We can now form no opinion on the matter, though we may dimly see that we are accumulating facts from which our successors may perhaps derive positive opinions in the earliest history of organized beings."
Leidy was one of the first Americans to embrace Darwin's theory of Natural Selection (2). Upon reading On the Origin of Species, Leidy wrote Darwin a letter praising the book for putting light into day:
"I feel as though I had hitherto groped about in darkness and that all of a sudden a meteor flashed upon the skies."
Darwin replied:
"Your note has pleased me more than you could readily believe; for I have during a long time heard all good judges speak of your palaeontological labours in terms of the highest respect. Most paleontologists (with few good exceptions) entirely despise my work; consequently approbation from you has gratified me much. All the older geologists (with the exception of Lyell whom I look at as a host in himself) are even more vehement against the modification of species that are even the palaeontologists."
Leidy soon lobbied for the election of Darwin as a member of the Academy of Natural Sciences of Philadelphia. He succeeded in March 27, 1860. The Academy became the first American scientific institution to recognize Darwin's contributions.
Despite the scientific affinity of these two men, there's no subsequent record of either of them mentioning the other. Nor is there any evidence that they continued their correspondences. We do, however, know that Darwin read Leidy's later monographs.
Leidy embraced Darwin's theory of Natural Selection, but he did mobilize his research efforts to support it. It's unclear whether this was the result of Leidy's reluctance to theorize, his aversion to intense public debates or his firm belief that he best served science by collecting facts. In any case, Leidy continued to believe that life —including humans— evolved from earlier forms.
Websites:
- AboutDarwin.com website:
www.aboutdarwin.com/ - Lucid Cafe's web page on Charles Darwin:
www.lucidcafe.com/lucidcafe/library/96feb/darwin.html
- Michon
Scott's web page on Charles Darwin:
www.strangescience.net/darwin.htm - Talk Origins' online version of The Origin of Species:
www.talkorigins.org/faqs/origin.html
Notes:
- Richard
Owen was the dean of British comparative anatomy and vertebrate paleontology.
Although he was a mentor for the young Charles Darwin, he became a staunch
critic of evolution in general and of Darwin's theory of Natural Selection in particular.
[go back] - Many people think that Darwin
invented the theory of evolution, which essentially is that species evolve (or change over
time) into new species. But in fact, evolutionary change was becoming accepted
by a growing number of scientists, including Leidy. Nonetheless, Darwin's contributions were essential to the scientific acceptance of Evolution during the 19th Century and central to our current understanding of evolutionary biology.
Darwin mustered an immense and compelling body of evidence to demonstrate that evolution happens and that it was the result of "decent with modification". In other words, the living things of the present are modified (or evolved) versions of their ancestors.
The majority of Darwin's peers embraced his arguments for evolution and decent with modification, but most of them were either reluctant or hostile to his contentions that evolution was gradual and that it was primarily caused by Natural Selection. Alternative mechanisms for evolution would proliferate during the second half of the 19th Century and into the next, including Neo-Lamarkism (inheritance of acquired characteristics), Orthogenesis (innately deterministic and directed evolution), and Saltation (dramatic and disjunct evolutionary change within lineages).
Darwin's theory of Natural Selection states that there is variation within populations (and species). Because of this variability, some individuals within the population are better suited for their environment than others. Those that are better suited (or better adapted) will be more successful at reproduction than those that are not. Consequently, the offspring of the better-suited individuals will account for an increased proportion of the next generation. Over multiple generations, the decedents of the better-suited individuals will become the majority of the population and change the nature of that population. In other words, the population evolved.
Darwin didn't understand why populations were variable. But his extensive research and experience demonstrated this to be so. He also didn't understand how offspring inherit characteristics from their parents, but it was clear that they did inherit characteristics from their parents. The mechanisms for variability and inheritance would have to wait several decades for the development of the science of genetics. Even then, many scientists dismissed Natural Selection as an important contributor to evolution. It wasn't until the Evolutionary Synthesis in third and fourth decades of the 20th century that Genetics and Natural Selection were reconciled.
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