Gorongosa 2024-FULL-FINAL - Flipbook - Page 77
PA L EO NTOLOGY
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GORONGOSA SP ECIAL
What local Armageddon befell the
organisms on this rock?
Miocene excavation. But, importantly, Lucy was a generalist omnivore,
able to subsist on a variety of nutrients flourishing in her ancient environment. The hominins that would have been common during the Miocene
had a more specialized diet and subsisted on soft fruits and other vegetation common along the water’s edge—a diet Bobe and Carvalho can analyze by examining patterns of wear on the ape’s teeth that they disinterred.
To both Carvalho and Bobe, there is a clear lineage among these earlier
versions of ourselves. About 9 million years ago, the Earth became more
arid, and the rainforests favored by Miocene primates began to shrink. It
is around this time, says Bobe, that the last common ancestor of humans
and chimpanzees was thought to live.
The chimpanzee ancestors—and their preference for ambulating with
four limbs—remained within the moist forests that they still prefer today.
Where in this historic relocation we emerged as a species remains, of
course, the big unknown. At some point, we stepped into a more arid landscape as bipedal primates—but whether this happened when we reached
the savanna or before is an intriguing question. There’s striking evidence
suggesting that the apes from which our species of Homo eventually evolved
were bipedal even before we left the trees.
So, what of these Last Common Ancestors, as the scientific literature calls them in capitalized terms, these theorized transitional species
between us and the chimps we left in the forest?
In Carvalho and Bobe’s telling, they may well sit among the finds at the
Mazamba Formation—all the more present for their absence. It’s a little
like entering a house whose occupants have just left—here is a half-eaten
apple, there an empty cup of coffee with a fresh brown ring at the bottom,
the jackets on the rack by the door still astir.
Amid this hoard of fossils and bones from the Mazamba Formation,
where will Carvalho and her colleagues find imprints of our shared precursors? “The stone tools might be able to tell us,” she says. “Because the
hominins that used them could have left DNA samples in the sediments,
and DNA preserves well in certain conditions like the limestone caves.”
It will be some time before Carvalho can have those sediments
sequenced. But when she does, whose photo might she find?
Charles Digges is an environmental journalist and researcher who edits Bellona.org,
the website of the Norwegian environmental group Bellona.
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