Darwin, Then and Now

Posts Tagged ‘use and disuse’

Vestiges  are tauted as evidence for biological evolution based on the Larmarckian concept of “use and disuse” that Charles Darwin reluctantly, yet fully accepted by the 6^th edition of The Origin of Species in 1872.

In the 1^st edition Darwin wrote that“use and disuse seem to have produced some effect” that was later changed to “use and disuse seem to have produced a considerable effect” in the 6^th edition. For Darwin, the importance of “use and disuse” increased from “some effect” to “considerable effect.”

In this series, we are examining the concept that the human appendix is a vestige structure through the process of “disuse.” Vestiges are thought to be biological elements that have lost their function through “disuse.” At issue is—what is the evidence that the process of “disuse” can actually produce vestiges?

In the decade following the publication of the 6^th edition, German biologist August Weismann, at the University of Freiburg, launched the first scientific inquiry to directly challenging Darwin’s theory. Now known as the “Weisman Barrier” in 1883 Weismann cut off the tails of mice from twenty-one generations. Seeing that the twenty-second generation still had tails, Weismann concluded that the evidence contradicted Darwin’s theory of “disuse” and that despite obvious reasons for change in the mice, “continuity” was observed, not new variations.

The concept of the Weismann Barrier became central to the emerging  Modern evolutionary synthesis. “Disuse” alone simply does not result in vestige structures. Ernst Mayr, known as Darwin’s bulldog of the twenty-first century, called Weismann “the second most notable evolutionary theorist of the nineteenth century, after Charles Darwin.”

Evidence from the Weismann Barrier continues to stand unchallenged, now for over 100 years. Even more to the point, after thousands of years of circumcision, “disuse” has failed to any effect on human anatomy. Without scientific experimental evidence demonstrating that “disuse” can result in any biological changes, the concept of vestige as evidence for evolution remains untenetable.

Other known vestige problems for evolution include, 1) the appendix is not found systematically found through nature, even in mammals; 2) “vestige” structures are now known to be functional. These evolutionary contradictions for vestiges continue to undermining evidence for evolution.

In the up-coming posts, we will continue to explore why these last two problems have completely undermined the concept that the human appendix is a vestige structure.

Charles Darwin attempted to avoid the use of the term “vestiges” largely because the term had been associated with the “erroneous” Larmarckian concept of “use and disuse” that was only “veritable rubbish.”

Jean-Baptiste Lamarck (1744 – 1829) was a member of the French Academy of Sciences and was appointed to the Chair of Botany in 1788. When the Muséum national d’Histoire naturelle was founded in 1793, Lamarck was appointed professor of zoology. In 1801, he published Système des animaux sans vertèbres, a major work on the classifications and coined the term invertebrates. Lamarck is thought to be the first use the term biology in its modern sense. Lamarck continued his work as a premier authority on invertebrate zoology.

Darwin did credit “Lamarck as the first man whose conclusions on the subject excited much attention.… In these works he up holds the doctrine that all species, including man, are descended from other species.”

Lamarck’s theory of evolution, which he referred to as “transformism,” was based on the idea that individuals develop new traits during their own lifetimes by “use and disuse” and transmit them to the next generation. Larmack writes – “Progress in complexity of organization exhibits anomalies here and there in the general series of animals, due to the influence of environment and of acquired habits.”

The giraffe served as Lamarck’s classic example of evolution through “use,” acquiring longer necks in successive generations in competition to reach the ever-scarcer leaves higher in the trees. In illustrating Lamarck’s views on adaptation, Darwin wrote, “To this latter agency he seems to attribute all the beautiful adaptations in nature; such as the long neck of the giraffe for browsing on the branches of trees.”

For Darwin, however, this explanation was simply not scientific – “Lamarck, who believed in an innate and inevitable tendency towards perfection in all organic beings, seems to have felt this difficulty so strongly that he was led to suppose that new and simple forms are continually being produced by spontaneous generation. Science has not as yet proved the truth of this belief.”

One of the most eminent pre-Darwinists was Charles Darwin’s own grandfather, Erasmus Darwin (1731–1802). Erasmus discussed his ideas at length in a two-volume work, Zoonomia, published in 1794. Erasmus wrote that “all … have risen from one living filament.”

Erasmus’ book was widely popular in Western Europe- even translated into German, French, and Italian. Erasmus envisioned that the driving force behind species modification was a result of “lust, hunger, and danger.” In line with Greek philosophy, Erasmus envisioned changes by “continuing to improve its own inherent activity.”

Actually how these “improvements” developed was completely unknown to Lamarck and Erasmus—evolution was a philosophy, not a science. The unknown cause of “improvements” is what drove Darwin to discover the underlying laws of nature—scientifically. Writing in the preface of The Origin of Species, Darwin suggests how Erasmus’s work, although “erroneous,” may have influenced Lamarck: “It is curious how largely my grandfather, Dr. Erasmus Darwin, anticipated the views and erroneous grounds of opinion of Lamarck in his Zoonomia.”

For Lamarck, new characteristics are acquired through the process of “use and disuse.” Darwin’s grandfather, Erasmus Darwin, was a Lamarckian evolutionist. Charles Darwin, however, in pursuit of a “scientific theory” of evolution, initially opposed Lamarckian evolution, only granting the theory marginal support.

In a letter written to J. D. Hooker in 1844, Darwin wrote, “Heaven forefend me from Lamarck nonsense of a ‘tendency to progression.’ … But the conclusions I am led to are not widely diff erent from his, though the means of change are wholly so.” “With respect to books on this subject,” Darwin continues, “I do not know any systematic ones, except Lamarck’s, which is veritable rubbish.”

Although attempting to distance himself from Lamarck’s concepts of “use and disuse” and “vestages,” Darwin distain for “use and disuse” eventually waned as causes for the origin of variation required for the actions of natural selection remained Darwin’s largest unsumountable enigma.

Since then, the term, “vestiges” has once again gained prominence over “rudiments,” as has Larmarckian concepts of evolution. The question remains, however, are structures classified as “vestiges” evidence of evolution? Specifically, have vestiges seemingly lost all or most of their original function in a species through evolution?

To address answers to these questions, we will be examining the most popular example of vestiges—the mammalian appendix in the up-coming posts.