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Early Concepts of Evolution: Jean Baptiste Lamarck
Darwin was not the first naturalist to propose that species changed over time into new species—that life, as
we would say now, evolves. In the eighteenth century, Buffon and other naturalists began to introduce the
idea that life might not have been fixed since creation. By the end of the 1700s, paleontologists had swelled
the fossil collections of Europe, offering a picture of the past at odds with an unchanging natural world. And in
1801, a French naturalist named Jean Baptiste Pierre Antoine de Monet, Chevalier de Lamarck took a great
conceptual step and proposed a full-blown theory of evolution.
Lamarck started his scientific career as a botanist, but in 1793 he became one of the founding professors of
the Musee National d'Histoire Naturelle as an expert on invertebrates. His work on classifying worms, spiders,
molluscs, and other boneless creatures was far ahead of his time.
Change through use and disuse
Lamarck was struck by the similarities of many of the animals he studied, and was
impressed too by the burgeoning fossil record. It led him to argue that life was not fixed.
When environments changed, organisms had to change their behavior to survive. If they
began to use an organ more than they had in the past, it would increase in its lifetime. If a
giraffe stretched its neck for leaves, for example, a "nervous fluid" would flow into its neck
and make it longer. Its offspring would inherit the longer neck, and continued stretching
would make it longer still over several generations. Meanwhile organs that organisms
stopped using would shrink.
Lamarck believed that the long necks of giraffes
evolved as generations of giraffes reached for
ever higher leaves.
Organisms driven to greater complexity
This sort of evolution, for which Lamarck is most famous today, was only one of two mechanisms he proposed. As organisms adapted
to their surroundings, nature also drove them inexorably upward from simple forms to increasingly complex ones. Like Buffon,
Lamarck believed that life had begun through spontaneous generation. But he claimed that new primitive life forms sprang up
throughout the history of life; today's microbes were simply "the new kids on the block."
Lamarck also proposed that organisms were driven from simple to increasingly more complex forms.
Evolution by natural processes
Lamarck was mocked and attacked by Cuvier and many other naturalists of his day. While they questioned him on scientific grounds,
many of them were also disturbed by the theological implications of his work. Lamarck was proposing that life took on its current form
through natural processes, not through miraculous interventions. For British naturalists in particular, steeped as they were in natural
theology, this was appalling. They believed that nature was a reflection of God's benevolent design. To them, it seemed Lamarck was
claiming that it was the result of blind primal forces. Shunned by the scientific community, Lamarck died in 1829 in poverty and
obscurity.
But the notion of evolution did not die with him. The French naturalist Geoffroy St. Hilaire would champion another version of
evolutionary change in the 1820s, and the British writer Robert Chambers would author a best-selling argument for evolution in 1844:
Vestiges of a Natural Creation. And in 1859, Charles Darwin would publish the Origin of Species.
Different from Darwin
In many ways, Darwin's central argument is very different from Lamarck's. Darwin
did not accept an arrow of complexity driving through the history of life. He argued
that complexity evolved simply as a result of life adapting to its local conditions
from one generation to the next. He also argued that species could go extinct
rather than change into new forms. But Darwin also relied on much the same
evidence for evolution that Lamarck did (such as vestigial structures and artificial
selection through breeding). And Darwin wrongly accepted that changes acquired
during an organism's lifetime could be passed on to its offspring.
Lamarckian inheritance remained popular throughout the 1800s, in large part
because scientists did not yet understand how heredity works. With the discovery of genes, it was finally abandoned for the most part.
But Lamarck, whom Darwin described as "this justly celebrated naturalist," remains a major figure in the history of biology for
envisioning evolutionary change for the first time.
Zoological Philosophy
Jean Lamarck (1809)
The environment affects the shape and organization of animals, that is to say that when the
environment becomes very different, it produces in course of time corresponding modifications in
the shape and organization of animals.
If a new environment, which has become permanent for some race of animals, induces new habits in these
animals, that is to say, leads them into new activities which become habitual, the result will be the use of
some one part in preference to some other part, and in some cases the total disuse of some part no longer
necessary.
Nothing of all this can be considered as hypothesis or private opinion; on the contrary, they are truths which,
in order to be made clear, only require attention and the observation of facts.
Snakes have adopted the habit of crawling on the ground and hiding in the grass; so that their body, as a
result of continually repeated efforts at elongation for the purpose of passing through narrow spaces, has
acquired a considerable length, quite out of proportion to its size. Now, legs would have been quite useless to
these animals and consequently unused. Long legs would have interfered with their need of crawling, and
very short legs would have been incapable of moving their body, since they could only have had four. The
disuse of these parts thus became permanent in the various races of these animals, and resulted in the
complete disappearance of these same parts, although legs really belong to the plan or organization of the
animals of this class.
The frequent use of any organ, when confirmed by habit, increases the functions of that organ, leads to its
development, and endows it with a size and power that it does not possess in animals which exercise it less.
We have seen that the disuse of any organ modifies, reduces, and finally extinguishes it. I shall now prove
that the constant use of any organ, accompanied by efforts to get the most out of it, strengthens and enlarges
that organ, or creates new ones to carry on the functions that have become necessary.
The bird which is drawn to the water by its need of finding there the prey on which it lives, separates the
digits of its feet in trying to strike the water and move about on the surface. The skin which unites these
digits at their base acquires the habit of being stretched by these continually repeated separations of the
digits; thus in course of time there are formed large webs which unite the digits of ducks, geese, etc. as we
actually find them.
It is interesting to observe the result of habit in the peculiar shape and size of the giraffe; this animal, the
largest of the mammals, is known to live in the interior of Africa in places where the soil is nearly always
arid and barren, so that it is obliged to browse on the leaves of trees and to make constant efforts to reach
them. From this habit long maintained in all its race, it has resulted that the animal's fore-legs have become
longer than its hind legs, and that its neck is lengthened to such a degree that the giraffe, without standing up
on its hind legs, attains a height of six metres (nearly twenty feet).
Philosophie Zoologique. Paris. 1809.
Translated by H. Elliott, Macmillan Company, London. 1914.
Natural Selection: Charles Darwin & Alfred Russel Wallace
The genius of Darwin (left), the way in which he suddenly turned
all of biology upside down in 1859 with the publication of the
Origin of Species, can sometimes give the misleading impression
that the theory of evolution sprang from his forehead fully formed
without any precedent in scientific history. But as earlier chapters
in this history have shown, the raw material for Darwin's theory
had been known for decades. Geologists and paleontologists had
made a compelling case that life had been on Earth for a long time,
that it had changed over that time, and that many species had
become extinct. At the same time, embryologists and other
naturalists studying living animals in the early 1800s had
discovered, sometimes unwittingly, much of the best evidence for Darwin's theory.
Pre-Darwinian ideas about evolution
It was Darwin's genius both to show how all this evidence favored the evolution of
species from a common ancestor and to offer a plausible mechanism by which life
might evolve. Lamarck and others had promoted evolutionary theories, but in order
to explain just how life changed, they depended on speculation. Typically, they
claimed that evolution was guided by some long-term trend. Lamarck, for example,
thought that life strove over time to rise from simple single-celled forms to complex
ones. Many German biologists conceived of life evolving according to predetermined
rules, in the same way an embryo develops in the womb. But in the mid-1800s,
Darwin and the British biologist Alfred Russel Wallace independently conceived of a
natural, even observable, way for life to change: a process Darwin called natural
selection.
The pressure of population growth
Interestingly, Darwin and Wallace found their inspiration in economics. An English
parson named Thomas Malthus published a book in 1797 called Essay on the Principle
of Population in which he warned his fellow Englishmen that most policies designed to
help the poor were doomed because of the relentless pressure of population growth.
A nation could easily double its population in a few decades, leading to famine and
misery for all.
When Darwin and Wallace read Malthus, it occurred to both of them that animals and
plants should also be experiencing the same population pressure. It should take very
A visit to the Galapagos Islands in 1835 helped Darwin
formulate his ideas on natural selection. He found
little time for the world to be knee-deep in beetles or earthworms. But the world is
several species of finch adapted to different
not overrun with them, or any other species, because they cannot reproduce to their
environmental niches. The finches also differed in beak
full potential. Many die before they become adults. They are vulnerable to droughts
shape, food source, and how food was captured.
and cold winters and other environmental assaults. And their food supply, like that of
a nation, is not infinite. Individuals must compete, albeit unconsciously, for what little food there is.
Selection of traits
In this struggle for existence, survival and reproduction do not come down to pure chance.
Darwin and Wallace both realized that if an animal has some trait that helps it to withstand
the elements or to breed more successfully, it may leave more offspring behind than others.
On average, the trait will become more common in the following generation, and the
generation after that.
As Darwin wrestled with natural selection he spent a great deal of time with pigeon breeders,
learning their methods. He found their work to be an analogy for evolution. A pigeon breeder
selected individual birds to reproduce in order to produce a neck ruffle. Similarly, nature
unconsciously "selects" individuals better suited to surviving their local conditions. Given
enough time, Darwin and Wallace argued, natural selection might produce new types of body
parts, from wings to eyes.
The carrier pigeon (bottom left) and the
Brunner pouter (bottom right) were derived
from the wild rock pigeon (top).
Darwin and Wallace develop similar theory
Darwin began formulating his theory of natural selection in the late 1830s but he went on working quietly on
it for twenty years. He wanted to amass a wealth of evidence before publicly presenting his idea. During those
years he corresponded briefly with Wallace (right), who was exploring the wildlife of South America and Asia.
Wallace supplied Darwin with birds for his studies and decided to seek Darwin's help in publishing his own
ideas on evolution. He sent Darwin his theory in 1858, which, to Darwin's shock, nearly replicated Darwin's
own.
Charles Lyell and Joseph Dalton Hooker arranged for both Darwin's and Wallace's
theories to be presented to a meeting of the Linnaean Society in 1858. Darwin had
been working on a major book on evolution and used that to develop On the Origins
of Species, which was published in 1859. Wallace, on the other hand, continued his
travels and focused his study on the importance of biogeography.
The book was not only a best seller but also one of the most influential scientific books of all time. Yet it took
time for its full argument to take hold. Within a few decades, most scientists accepted that evolution and the
descent of species from common ancestors were real. But natural selection had a harder time finding
acceptance. In the late 1800s many scientists who called themselves Darwinists actually preferred a
Lamarckian explanation for the way life changed over time. It would take the discovery of genes and
mutations in the twentieth century to make natural selection not just attractive as an explanation, but
unavoidable.
On the Tendency of Varieties to Depart Indefinitely from the Original Type
Alfred Russell Wallace (1858)
The Struggle for Existence
The life of wild animals is a struggle for existence. The full exertion of all their faculties and all their energies is required to
preserve their own existence and provide that of their infant offspring. The possibility of procuring food during the least
favorable seasons and of escaping the attacks of their most dangerous enemies are the primary conditions which determine the
existence both of individuals and of entire species.
The numbers that die annually must be immense; and as the individual existence if each animal depends upon itself, those that
die must be the weakest--the very young, the aged, and the diseased--while those that prolong their existence can only be the
most perfect in health and vigor, those who are best able to obtain food regularly and avoid their numerous enemies. It is “a
struggle for existence,” in which the weakest and least perfectly organized must always succumb.
Useful Variations Will Tend to Increase, Unuseful or Hurtful Variations to Diminish
Most or perhaps all the variations from the typical form of a species must have some definite effect, however slight, on the
habits or capacities of the individuals. Even a change of color might, by rendering them more or less distinguishable, affect
their safety; a greater or less development of hair might modify their habits. More important changes, such as an increase in the
power or dimensions of the limbs or any of the external organs, would more or less affect their mode of procuring food or the
range of country which they could inhabit. It is also evident that most changes would affect, either favorable or adversely, the
powers of prolonging existence. An antelope with shorter or weaker legs must necessarily suffer more from the attacks of the
feline carnivora; the passenger pigeon with less powerful wings would sooner or later be affected in its powers of procuring a
regular supply of food; and in both cases the result must necessarily be a diminution of the population of the modified species.
If on the other hand, any species should produce a variety having slightly increased powers of preserving existence, that variety
must inevitably in time acquire a superiority in numbers.
Lamarck’s Hypothesis Very Different from that Now Advanced
The hypothesis of Lamarck—that progressive changes in species have been produced by the attempts of animals to increase the
development of their own organs and thus modify their structure and habits—has been repeatedly and easily refuted by all
writers on the subject of varieties and species.
The giraffe did not acquire its long neck by desiring to reach the foliage of the more lofty shrubs and constrantly stretching its
neck for the purpose, but because any varieties which occurred among its ancestors with a longer neck than usual at once
secures a fresh range of pasture over the same ground as their shorter-necked companions, and on the scarcity of food where
thereby enabled to outlive them.
Name: ______________________________________ Date: ______________ Period: ____
Evolution: Darwin and Lamarck
1.
In Lamarck’s explanation of evolution, he made some assumptions. First was the idea of “use and disuse”. Based on the reading,
provide an example of use and disuse.
2.
Another idea Lamarck had was the idea that acquired characteristics are inherited.
a. Explain what an acquired characteristic is.
b.
Based on the reading, provide an example of the idea that “acquired characteristics are inherited”.
3.
According to Lamarck, what is the role of the environment in evolution?
4.
Darwin and Wallace both understood the idea of population pressure (sometimes called a “struggle for existence”). Explain what
this is and why some animals would survive and some would die as a result of it.
5.
Breeders use artificial selection to produce a desired trait in offspring (ex: a neck ruffle in pigeons). Darwin thought a similar
situation occurs in nature (natural selection). Explain how nature “selects” for certain traits.
6.
What is a variation?
7.
Give a specific example of how a slight variation can affect the survival of an individual.
8.
If a favorable variation exists in a population, what is likely to happen?