Human Evolution
Part I - Primates
“To understand the story of evolution,
we must understand both our ancestors
and our relationships to our closest
living kin.” (Holt - Modern Biology – ch 17)
Humans are members of the mammalian
order of Primates.
“As you can see, many
of our behaviors and
characteristics are
similar to those of other
primates, and some
are uniquely human.”
Biologists classify primates into two major groups: strepsirrhines and
haplorhines. Present day strepsirrhines are small primates that include,
among others, the lemurs and aye-ayes. Most strepsirrhines have large
eyes and are nocturnal.
aye aye found in Madagascar
The remaining living primates are members of a
group called haplorhines.
The group consists of tarsiers and the
anthropoids, the humanlike primates.
Anthropoids include hominids and Old and New
World monkeys. In turn hominids include apes
and humans.
ANTHROPOID PRIMATE: (monkeys, gibbons,
orangutans, chimpanzees, gorillas & humans)
Kingdom – Animalia
Phylum – Chordata
Subphylum – Vertebrata
Class – Mammalia
Order - Primate
PRIMATE CHARACTERISTICS
(prosimian primates – resemble early forms such as lemurs, & tarsiers.)
“Primates
have grasping
hands, acute
vision, and
large brains.”
“ Primate parents provide extended periods
of intense care for their young, and many
primate species live in complex social
groups.”
Primates have movable fingers
and toes, and most have
flattened nails rather than
claws. (In some species,
the feet are
grasping
or
prehensile.)
Unlike most mammals, primates have color
vision. They have front-facing eyes, and
overlapping fields of vision.
tarsier
This gives primates depth perception, a
useful trait for an animal that moves by
swinging or jumping from branch to
branch. (An adaptation for life in the
trees.)
Anthropoids have well-developed a well
developed collar bone, rotating shoulder
joints, and partially rotating elbow joints.
Anthropoids have opposable thumbs
which results in increased precision of
the hands.
Nonhuman anthropoids have an
opposable big toe.
All anthropoids have a similar dental
formula, or number and arrangement
of teeth.
Compared with other primates
anthropoids have a large brain
relative to their body size.
Of all the Anthropoid species, the chimpanzees may be
the most closely related to man. Their DNA has a high
degree of similarity. “Now that scientists have decoded
the chimpanzee genome. We know that 98% of our
DNA is the same.”
This similarly suggests
That humans and
chimpanzees may have
shared an ancestor
less than 6 million
years ago.”
Characteristics
of Humans:
Humans are bipedal—that is that they have the
ability to walk on two legs. This is a uniquely
human trait among mammals. Chimps can only
walk in a bipedal fashion for a short period of time.
The cup-shaped pelvis supports the internal organs
during walking. The human spine has two curves resulting
in an = “S” shape that allows for upright posture.
(compared to the “C” shape in chimps)
The center of gravity is located higher in the
chimpanzee body than in a human body. The chimp has
more weight in the upper trunk,
whereas humans have
more weight in the
lower limbs.
Pelvic shape, muscle shape
and attachment, and the
fact that human knees are
straight rather than bent,
are factors that enable
humans, and not chimps,
the ability of prolonged
bipedal movement.
The human foot, has shorter toes than apes,
which are aligned with each other. This may
be seen as an additional bipedal adaptation.
The human jaw is more rounded than the Ushaped ape jaw. It does not protrude as an
ape’s jaw.
The enlargement of the human brain has
resulted in a more vertical face than in apes.
The human brain has extensive areas
devoted to the production and
understanding of speech.