554
Chimpanzee Genome
Hominoids
Old world
monkeys
New world
monkeys
Prosimians
Fig. 1
A phylogenetic tree for the anthropoid
primates. The prosimians combine the Lemur
species from Madagascar, the nocturnal Lorises
from South and Southeast Asia and from Africa, and
the Tarsiers from certain islands of Southeast Asia.
Generally, prosimians seem to be more ancestral in
their morphology compared to the other three
groups. The New World monkeys are conFned to
South and Central America and are, with one
exception, the owl monkey, active during the day.
They differ from the third group, the Old World
monkeys typically in having a flat nose and separate
nostrils. Old World monkeys such as rhesus
macaques and baboons are found in Africa as well
as in certain parts of Asia. The hominoids combine
the gibbons (Asia), the orangutans (Asia), the
African apes (gorillas, chimpanzees, bonobos),
and humans.
HYL
GGO
PTR
PPA
PPY
HSA
(a)
HYL
HSA
PPY
GGO
PTR
PPA
(b)
HYL
HSA
PPY
GGO
PTR
PPA
(d)
HYL
HSA
PPY
GGO
PTR
PPA
(c)
Fig. 2
Alternative phylogenies of the hominoids.HYL:gibbons;PPY:orangutans;
GGO: gorillas; PTR: chimpanzees; PPA: bonobos; HSA: humans.
problematic interpretation rendered mor-
phologists unable to conclusively solve the
question of hominoid phylogeny.
In the second half of the twentieth cen-
tury, the expansion of molecular biology
provided a new and presumably more pow-
erful approach to phylogenetic studies.
The genetic distance between species as
reflected in the amount of structural differ-
ences between their proteins and nucleic
acids was introduced as a more objective
measure of their evolutionary relationship.
Under the assumption that the accumula-
tion of such differences behaves like a clock
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