BI SC 002 LECTURE 13—HUMAN EVOLUTION
Draft: December 3, 2010
Our final topic for this semester is also one of our most controversial—the topic of human
To classify a human, first we are an animal, because we consume food for energy.
the animals, we are chordates because we have a spinal cord.
Of the chordates, humans are
mammals, which mean we have body hair, give live births, and nurse our young.
mammals, humans classify as primates because we have ape-like features.
Before we go any further, we must say one thing: just because humans have ape-like features
does NOT mean that humans descended from apes.
It does NOT mean humans descended from
What this means is that humans, apes, and monkeys all have the same
and each descended from this primate.
It is more like humans, apes, and monkeys are
cousins of each other instead of one being the parent/grandparent of the other.
All primates shared a common ancestor millions of years ago.
It is thought that this primate may
have resembled a tree shrew in its size and structure.
About 45 million years ago, there was an
The lemurs and other very small primates split from what was now the
lineage for monkeys, apes, and humans.
About 15 million years ago, the precursors of monkeys
split from our lineage.
About 7 million years ago was the other major split—apes separated from
our lineage, and our line evolved into the
Hominid is the group of classification that includes humans and human-like ancestors.
Characteristics of hominids include bipedalism (the ability to walk upright, probably developed
while our ancestors still lived in the trees), a shorter jaw, less specialized teeth than apes, and a
larger brain size than other primates.
The oldest hominid fossil,
dates to about 7 million years ago and was discovered in eastern Africa.
In fact, most of the
fossils of the earliest hominids were found in East Africa.
It is thought that hominids evolved in