In the late Miocene, Africa changed.
The forests that had clothed the continent
From coast to coast in the green and deranged
Abundance of the tropical experiment
Began to shrink—the climate cooled,
The rainfall lessened, and the eastern
Rift Valley's tectonic uplift pooled
A rain-shadow that worsened
Year by year—the western slopes
Kept their forest, kept their rain,
But the eastern side abandoned its hopes
Of canopy and opened to the plain.
The grassland came—the savanna's vast
And open invitation to the herbivore
And the predator—and the forecast
Of the forest's retreat closed the door
On one kind of primate life and opened
Another.
And here the family split.
In the shrinking forests, one lineage deepened
Its commitment to the arboreal knit
Of the canopy: Panos—the chimpanzee—
Stayed in the trees that remained,
The forest's child, the refugee
Who maintained and retained
The old way—the knuckle-walking ground-traverse
Between one patch of forest and the next,
The tool-use culture that was the universe
Of the chimpanzee's intellect:
Termite-fishing with a carefully
Selected and stripped twig, nut-cracking
With a hammer-stone, the carefully
And culturally transmitted tracking
Of techniques from mother to child—
For the chimpanzee has culture: different
Populations carry the compiled
And locally transmitted, different
Tool traditions that are learned,
Not inherited in the genes—
The Taï Forest chimps have earned
The nut-cracking art, and the routines
Of Gombe's chimps include the fishing-probe
That Taï chimps have never learned—
The chimpanzee's cultural wardrobe
Is the closest thing to what we've earned
In any other living species.
And Panos hunted—cooperatively,
Strategically, the capriccios
Of the red colobus monkey taken actively
By coordinated teams: the driver
Who flushed the prey, the blocker
Who closed the escape, the survivor's
Rush to the kill—the shocker
Of primate-on-primate predation, the meat
Shared afterward in the political
Economy of the chimpanzee's elite
Whose access to the analytical
Distribution of protein was the currency
Of alliance and of rank.
But on the other side of the urgency
Of the shrinking forest, another branch drank
From a different cup: the ones who walked
Into the grassland.
Not yet human—
Not by millions of years—but the ones who balked
At staying in the trees, the acumen
Of whose bodies was beginning to shift:
The pelvis tilting, the spine straightening,
The foot's arch developing, the gift
Of the upright posture, the awakening
Of a body designed for the open ground.
Sahelanthropos—the oldest face
Of the human lineage yet found—
Seven million years in the embrace
Of the Sahel's ancient lakeside clay:
A skull whose foramen magnum's position
Beneath the braincase told the display
Of the upright head—the transition
Had already begun.
And Ardipithos—
"Ground ape"—whose skeleton showed
The halfway house: still grasping toes
For climbing, but a backbone that bestowed
The possibility of upright walking—
Not yet committed, not yet fully
Bipedal, but already talking
To the savanna's open woolly
Grassland with the first tentative steps
Of the vertical primate.
Honor the great split—the two
Directions that the African ape attempts
And the two results: Panos, who
Stayed in the forest and became the closest
Living relative of the human line—
And the other one, the boldest
Of the primates, who crossed the line
Between the forest and the open ground
And began the longest walk
That any primate has ever found:
The walk toward language, toward talk,
Toward fire and art and the question
That only one species has ever asked—
But that is the next chapter's digestion,
And the great split's story is the unmasked
And ancient divergence: the forest chose one,
The grassland chose another,
And neither knew what would be done
With the choice—only that each brother
Walked a different way into the future.