MISSING LINKS AND DAWN MONKEYS
A fuller consideration of human origins requires us to place our own
evolutionary history within a broader context. Did humans take longer
to evolve our unique characteristics than other living primates, or did
our ancestors simply experience unusually high rates of evolution? For
that matter, how unique are humans with respect to other primates anyway?
Which seemingly “human” traits are ours alone, and which are
shared with various primate relatives? Where do humans lie on the family
tree of all primates, and what does that tree look like? Where do primates
lie on the larger family tree of all mammals? Were there particularly
critical events during the earlier phases of our evolutionary history,
before our own lineage branched away from those leading to chimpanzees
and other living primates? Today, these questions pose far greater scientific
challenges than simply filling in the constantly shrinking gaps in
the human fossil record. Yet, ironically, when most people hear the term
“missing link,” they think of a gap in the fossil record that supposedly
fails to link modern humans with our apelike ancestors. The dirty little
secret of paleoanthropology is that, while there are plenty of missing links,
they don’t occur where most people think they do. They exist farther
back in deep time. Ultimately, this is why I’m at the bottom of a ravine
on the banks of the Yellow River.
The ravine itself is a natural erosional feature, an ephemeral drainage
flowing into the Yellow River from the north. It dissects a relatively flat
plateau, which—like most rural parts of central China—is now under intensive
wheat cultivation. Standing on top of the plateau at the head of
the ravine offers a panoramic view of the surrounding terrain. To the
south, on the far side of the Yellow River in Henan Province, lie rugged
mountains composed primarily of limestone of Ordovician age. Some 450
million years ago—about twice the age of the earliest known dinosaurs—
the rock now forming the crest of this range was deposited in a warm,
shallow sea not unlike that surrounding the modern Bahamas.
evolutionary history within a broader context. Did humans take longer
to evolve our unique characteristics than other living primates, or did
our ancestors simply experience unusually high rates of evolution? For
that matter, how unique are humans with respect to other primates anyway?
Which seemingly “human” traits are ours alone, and which are
shared with various primate relatives? Where do humans lie on the family
tree of all primates, and what does that tree look like? Where do primates
lie on the larger family tree of all mammals? Were there particularly
critical events during the earlier phases of our evolutionary history,
before our own lineage branched away from those leading to chimpanzees
and other living primates? Today, these questions pose far greater scientific
challenges than simply filling in the constantly shrinking gaps in
the human fossil record. Yet, ironically, when most people hear the term
“missing link,” they think of a gap in the fossil record that supposedly
fails to link modern humans with our apelike ancestors. The dirty little
secret of paleoanthropology is that, while there are plenty of missing links,
they don’t occur where most people think they do. They exist farther
back in deep time. Ultimately, this is why I’m at the bottom of a ravine
on the banks of the Yellow River.
The ravine itself is a natural erosional feature, an ephemeral drainage
flowing into the Yellow River from the north. It dissects a relatively flat
plateau, which—like most rural parts of central China—is now under intensive
wheat cultivation. Standing on top of the plateau at the head of
the ravine offers a panoramic view of the surrounding terrain. To the
south, on the far side of the Yellow River in Henan Province, lie rugged
mountains composed primarily of limestone of Ordovician age. Some 450
million years ago—about twice the age of the earliest known dinosaurs—
the rock now forming the crest of this range was deposited in a warm,
shallow sea not unlike that surrounding the modern Bahamas.
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