Extinct ancient human species found
In a cave in the Philippines, scientists have discovered a new branch of the human family tree.
At least 50,000 years ago, an extinct human species lived on what is now the island of Luzon, researchers reported Wednesday. It’s possible Homo luzonensis, as they’re calling the species, stood less than 3 feet tall.
The discovery adds growing complexity to the story of human evolution. It was not a simple march forward, as it once seemed. Instead, our lineage assumed an exuberant burst of strange forms along the way.
Our species, Homo sapiens, inhabits a comparatively lonely world.
“The more fossils that people pull out of the ground, the more we realize that the variation that was present in the past far exceeds what we see in us today,” said Matthew Tocheri, a paleoanthropologist at Lakehead University in Canada, who was not involved in the discovery.
In the early 2000s, Armand Salvador Mijares, a graduate student at the University of the Philippines, was digging at Callao Cave, on Luzon, for traces of the first farmers on the Philippines. Soon, he decided to dig a little deeper.
Researchers on the Indonesian island of Flores had discovered the bones of an extraordinary humanlike species about 60,000 years old. The scientists named it Homo floresiensis.
Some features were similar to ours, but in other ways Homo floresiensis more closely resembled other hominins (the term scientists use for modern humans and other species in our lineage).
Starting about 2.5 million years ago, one lineage of African hominins began to evolve new traits — a flatter face, bigger brains and a taller body, among other features. These hominins were the first known members of our own genus, Homo.
Only later, about 1.8 million years ago, do the first fossils of Homo appear outside of Africa. One common species was Homo erectus, a species that spread to East and Southeast Asia. The youngest Homo erectus fossils, discovered in Indonesia, might be just 143,000 years old.
Human lineage kept evolving in Africa. Homo sapiens emerged about 300,000 years ago, and only 100,000 years ago did humans start leaving the continent.
One hypothesis, then, is that Homo floresiensis evolved from Homo erectus. So here was the question for Philippine archaeologists: Could hominins have reached Luzon as well as Flores?
In 2007, Mijares returned to Callao Cave. As his team dug into the cave floor, the researchers hit a layer of bones.
When Philip Piper, an archaeologist at the University of the Philippines, later sorted through the finds, he noticed one that resembled a human foot bone. It was small, Mijares said, “and there was something weird about it.”
In 2011, on another dig, he and his colleagues found more humanlike fossils, including teeth, part of a femur and hand bones. In 2015, they found two molars, which they dated to at least 50,000 years ago.
All told, the fossils came from three individuals. And they were remarkable. The teeth had a peculiar shape. Some of the front teeth had three roots, for example, whereas those of our species usually have one. And the teeth were tiny.
“These adult teeth are smaller than any hominin known,” said Debbie Argue, a paleoanthropologist at Australian National University, who was not involved in the new study.
The researchers did not find enough bones to estimate how tall Homo luzonensis stood. But they do display their own strange mix of traits. One toe bone, for example, looks nearly identical to those of early hominins living in Africa more than 3 million years ago.
Taken together, Mijares and his colleagues concluded, the evidence pointed to a new species of Homo.
Drawing such a conclusion from a few bones is risky, acknowledged Huw Groucutt, a paleoanthropologist at the Max Planck Institute for Chemical Ecology.
Nevertheless, “I think the argument for a new species does look pretty convincing in this case,” he said.