Biology 5C ~ Lecture 24 ~ Human Evolution

The common ancestor of primates:

-rodent-like ancestors (85-55mya)

-tree shrews and colugos are the closest living relative

Hypothesized characteristics of rodent-like ancestors and primates:

-arboreal lifestyle (tropical forests)
-diversified after the K-T extinction 65mya
-larger brains
-color vision
-shoulder girdle
-dexterous hands

The Great Apes (in order from oldest to youngest):

-Orangutans

-Gorillas

-Chimpanzees and bonobos

-Australopithecus

-Humans and extinct Homo species

The closest relatives among living primates are:

-chimpanzees and bonobos

Hominins:

-Australopithecus
-Humans and extinct Homo species

The traits examined in early Hominin ancestors:

-Ardipithecus ramidus: complete skeleton

-Orrorin tugenensis: femur consistent w/bipedalism

-Sahelanthropus tchadensis: upright posture

-adaptations to support bipedalism

-dental adaptations

-changes in hands and feet

Characteristics of Australopithecus

-small brain, large jaw and teeth, curved fingers from climbing

-extinct close relatives of humans

-obligate bipeds

-some climbing

-smaller than modern humans

-450 mL brains versus 1350 mL brains

When did Australopithecus emerge?

-between 4.2-3.9mya

Who are the members considered members of a single evolving lineage?

-A. anamensis

-A. afarensis

Homo sapiens emerged:

-About 300,000-200,000 years ago in Africa

Major steps in the evolution of early Homo (Homo Erectus):

-Larger size and brain

-Smaller teeth

Major steps in the evolution of early Homo (Homo Habilis):

-unclear relationship to H.erectus (maybe preceded)

Major steps in the evolution of early Homo (Homo floresiensis):

-Short-lived island population

Major steps in the evolution of early Homo (Homo heidelbergensis):

- "archaic H. sapiens"

-Largest brains

Early Homo was about:

-1.8 mya

Paranthropus

-diversified into different reigned populations

What did increased brain size influence?

-increased dependence on meat

-changes in development and maturity

Modern humans did not "evolve from" apes but:

these groups share a common ancestor

Two groups of archaic (premodern) humans and their relationship:

-Neanderthals: emerged around the same time as Homo sapiens in Europe + Western Asia

-Denisovans: emerged in Asia, Australia, New Guinea

Admixture:

-the exchange of genetic material between two or more populations

-previously isolated or diverged populations interbreed

-can "map" genes from different populations

What does admixture tell us about archaic and modern humans?

-That there's gene flow between them

-Hybridization between humans + Neanderthals after leaving Africa

Neolithic revolution:

-A wide-scale transition from hunter/gatherer communities to agriculture and settlement

What did the Neolithic Revolution involve?

-Experimentation with planting and maintaining seed crops

-Management of herd animals

-Settlement into villages and cities

-Development of political and economic elites

Human skin color pigmentation is the result of:

-A trade-off

What are the constraints on the evolution of skin color?

-Vitamin D synthesis requires some UV but too much UV damages folic acid and can cause cancer.

Review: Modern primates evolved from a:

rodent-like ancestor approximately 65 million years ago

Review: Early hominids emerged in:

-Africa from an ancestral primate and adapted over time to bipedalism

Review: Over generations, members of the genus Homo:

-Grew larger and more complex brains

Review: Modern humans evolved:

-rapidly over the last 20,000 years, with increasingly sophisticated communication and tool use