Science isn’t for those with fragile egos.
Those who hope to find evidence of human supremacy, proof that Homo sapiens stands atop the pinnacle of nature, will be bitterly disappointed. To the contrary, science has delivered one demotion after another. The more we learn, the more we find that we’re just one part of nature, not unique or above it.
A case in point: One of the most distinctive human traits is tool use. At least, we used to think so—until more careful observation showed that other animals make and use tools too.
Brainy primates
Chimpanzees turn twigs into probes to fish yummy ants and termites out of their mounds. They use stones as a hammer and anvil to crack nuts. They even shape branches into crude spears to hunt monkeys.
Orangutans have been observed using sticks to fish for insects, to scoop honey from beehives, to extract seeds from prickly fruit, and to catch fish. Capuchin monkeys also know the hammer-and-anvil trick for nuts and hard fruits.
These brainy primates raise the question of when tool use appeared in the human lineage. Our ancestors have likely been using sticks as fishing rods and rough stones for pounding for millions of years, just like our primate cousins. Since these simple tools don’t fossilize, we can’t know for sure.
Purpose-made stone tools are a different story. Tools like these are made by knapping: strategically bashing one rock against another to chip off flakes, shaping the target rock into the desired form. With this method, you can make handheld hammers to crack nuts, crush bones to get at the marrow, and pound tough plants into pulp. You can also make cutters to carve meat and cut hides for clothing.
The patience, forethought and planning that goes into this activity requires a quantum leap above and beyond what other animals can do. To many archaeologists, this is the stamp of humanity. Best of all, these artifacts are durable and readily distinguished (by experts) from natural rocks, so they can be seen in the archaeological record.
The oldest known tools are knapped stones from a site in Kenya called Lomekwi 3. Based on radiometric dating of the volcanic ash layers they were found in, they’re 3.3 million years old.
However, as far as we know, the genus Homo is only about 2 million years old. This means that either human precursors are older than the fossil record lets on, or some earlier, more primitive hominid made them. Either way, the identity of these toolmakers has been a subject of spirited debate.
Now a paper in the journal Science pours gasoline on the fire.
Big brains or big jaws: a false dichotomy?
The paper’s authors discovered hundreds of stone tools at Nyayanga, Kenya that are as much as 3 million years old, almost as ancient as the Lomekwi site. What’s more, there’s proof these tools were used. They unearthed hippopotamus and bovid bones covered in cut marks, the telltale sign of prehistoric butchers.
By itself, this fits in with previous discoveries. It’s what the authors say next that raises some eyebrows:
Paranthropus molar KNM-NG 77316 from the excavation 3 hippopotamid butchery site is a clear association of a hominin fossil with artifacts, raising the possibility that Paranthropus made and/or co-opted stone tools.
“Expanded geographic distribution and dietary strategies of the earliest Oldowan hominins and Paranthropus.” Thomas W. Plummer et al., Science, 9 Feb 2023, vol. 379, issue 6632.
Paranthropus. Paranthropus?!
Of all the primitive hominds, Paranthropus isn’t what you’d think of when you picture a tool-user. They hail from a lineage known as the robust australopithecines. Their skulls are heavily built, with a large sagittal crest—a ridge of bone that anchors massive jaw muscles, used for chewing tough food—and broad, flat teeth suited for grinding. These are gorilla-like traits, and indeed, their brains were similar in size to modern gorillas.
Conventional wisdom states that Paranthropus was a dead end in the hominid family tree. According to this thinking, they specialized in powerful jaws and grinding teeth, so they could chomp their food raw.
Meanwhile, our ancestors in the genus Homo took a different path. We evolved big brains instead of big jaws, giving us the intelligence to invent tools and fire so we could cook our meals. This made our food easier to digest, unlocking more calories with less chewing. (Imagine how much more effort it would be to choke down a raw potato, compared to eating a baked one.)
That strategy won out, which is why we dominate the planet today—even though our shrinking jawbones cause problems with our now-vestigial wisdom teeth.
Branches and thorns
If Paranthropus hominids were the Nyayanga tool-makers, it could upend our thinking about intelligence and the role it played in human evolution. Why did Paranthropus die out, if they were as smart as us? What were our big brains even for, if not to give us a technological edge over our extinct cousins?
We already knew that human evolution was complex and many-branched, more like a tangled bush than a linear march of progress. But even taking that into account, we keep stumbling across new and thorny mysteries.
That’s a good thing, because nothing is more exciting in science than an unsolved mystery. It’s an opportunity for discovery, a chance to learn something new and unexpected. If we’re fortunate, this paper will spur more exploration to answer these questions. Who knows what other wonders are still buried in our ancestral African home, awaiting their turn to be discovered?