Evolution, 4th Edition

10 CHAPTER 1

In the eighteenth century, several French philosophers and naturalists sug-

gested that species had arisen by natural causes. The most significant pre-Dar-

winian evolutionary hypothesis was proposed by the Chevalier de Lamarck in

his Philosophie Zoologique (1809). Lamarck hypothesized that different organisms

originated separately by spontaneous generation from nonliving matter, starting

at the bottom of the chain of being. A “nervous fluid” acts within each species, he

said, causing it to progress up the chain. Species originated at different times, so

we now see a hierarchy of species because they differ in age (FIGURE 1.5A).

Lamarck argued that species differ from one another because they have differ-

ent needs, and so use certain of their organs and appendages more than others.

Just as muscles become strengthened by work, more strongly exercised organs

attract and become enlarged by the “nervous fluid.” Lamarck, like most people at

the time, believed that such alterations, acquired during an individual’s lifetime,

are inherited—a principle called inheritance of acquired characteristics. The the-

ory of evolution based on this principle is called Lamarckism. In the most famous

example of Lamarck’s theory, giraffes must have stretched their necks to reach

foliage above them, and so their necks were lengthened. The longer necks were

inherited, and over the course of generations, this process was repeated and their

necks got longer and longer. This could happen to any and all giraffes, so the

entire species could have acquired longer necks because it was composed of indi-

vidual organisms that changed during their lifetimes (FIGURE 1.6A). L a m a rc k ’s

ideas of how evolution works were wrong, but he deserves credit for being the

first to advance a coherent and testable theory of evolution.

Charles Darwin

Charles Robert Darwin (February 12, 1809–April 19, 1882) was the son of an Eng-

lish physician. He briefly studied medicine in Edinburgh, then turned to studying

for a career in the clergy at Cambridge University. He believed in the literal truth

of the Bible as a young man. He was passionately interested in natural history. In

1831, at the age of 22, his life was forever changed when he was invited to serve as

Jean-Baptiste Pierre Antoine de

Monet, Chevalier de Lamarck

Futuyma Kirkpatrick Evolution, 4e

Sinauer Associates

Troutt Visual Services

Evolution4e_01.05.ai Date 10-31-2016

Q: Does Darwin’s version need any red nodes

along the curvy branches?

Complexity

(A) Lamarck’s hypothesis

Time

Form

(B) Darwin’s hypothesis

Time

FIGURE 1.5 Lamarck’s and Darwin’s hypotheses of the history of evolution. (A) Under

Lamarck’s hypothesis, life has originated many times (the red dots). Each lineage that

descends from one of these origins becomes more complex. Thus, organisms range

from recently originated, simple forms of life to older, more complex forms. (B) Dar-

win’s theory of descent with modification, represented by a phylogenetic tree. From a

single ancestor (the red dot), different lineages arise by speciating (splitting) from ex-

isting lineages. Some (such as the more central lineages) may undergo less modifica-

tion from the ancestral condition than others. Darwin supposed that species become

different from each other in various features (“form”), not necessarily becoming more

complex. (A after [1].)

01_EVOL4E_CH01.indd 10 3/23/17 8:43 AM