The Science Book

75

See also: Jan Swammerdam 53 ■ John Ray 60–61 ■ Jean-Baptiste Lamarck 118 ■ Charles Darwin 142–49

EXPANDING HORIZONS

In 1735, Linnaeus produced a
classification in a 12-page booklet
that grew into a multivolume 12th
edition by 1778 and developed the
idea of the genus into a hierarchy
of groupings based on shared
physical characteristics. At the top
were three kingdoms: animals,
plants, and minerals. Kingdoms
were divided into phyla, then
classes, orders, families, genera,
and species. He also stabilized the
naming of species by using a two-
part Latin name, with one name
for the genus and another for a
species within that genus, as in
Homo sapiens—Linnaeus was the
first to define humans as animals.

God-given order
For Linnaeus, classification
revealed that “nature does not
proceed in leaps and bounds”
but rather in its God-given order.
His work was the fruit of numerous
expeditions across Sweden and
Europe in search of new species.
His classification system paved the
way for Charles Darwin, who saw
the evolutionary significance of its

“natural hierarchy,” with all species

in a genus or family related by

descent and divergence from a

common ancestor. A century after

Darwin, German biologist Willi

Hennig developed a new approach

to classification, called cladistics.

To reflect their evolutionary links,

this groups organisms into “clades”

with one or more shared unique

characteristics, which they have

inherited from their last common

ancestor and which are not found

in more distant ancestors. The

process of classification by clades

continues to this day, with species

reassigned new positions as fresh,

often genetic, evidence is found. ■

Carl Linnaeus Born in 1707 in rural southern

Sweden, Carl Linnaeus studied

medicine and botany in the

universities of Lund and Uppsala,

and earned a degree in medicine

in the Netherlands in 1735. Later

that year he published a 12-page

booklet called Systema Naturae,

which outlined a system of

classification for living organisms.

After further travels in Europe,

Linnaeus returned to Sweden in

1738 to practice medicine before

being appointed professor of

medicine and botany at Uppsala

University. His students, most

famously Daniel Solander, traveled

the world collecting plants. With

this vast collection, Linnaeus

expanded his Systema Naturae

through 12 editions into a

multivolume work, more than

1,000 pages long, encompassing

more than 6,000 species of

plants and 4,000 animals. By the

time he died in 1778, Linnaeus

was one of the most acclaimed

scientists in Europe.

Key works

1753 Species Plantarum

1778 Systema Naturae,

12th edition

Nature does not

proceed by leaps

and bounds.

DNA is used to

map evolutionary

relationships.

Linnaean classification

groups like with like.

Cladistic classification

groups organisms with a

common ancestor.

For Linnaeus, the

order of life reflects

God’s creation.

The order of life reflects

evolution over time.