Human EvolutionPart 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 orprehensile.)

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 organsduring walking. The human spine has two curves resultingin an = “S” shape that allows for upright posture. (compared to the “C” shape in chimps)

The center of gravity is located higher in thechimpanzee body than in a human body. The chimp hasmore weight in the upper trunk, whereas humans have more weight in thelower limbs. Pelvic shape, muscle shapeand attachment, and thefact that human knees arestraight 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 U-shaped 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.