Wear patterns on ancient antelope teeth have allowed researchers to reconstruct Europe’s environment 8 million years ago, when the continent’s great apes vanished.
One of those ape species could have given rise to the human lineage, making the circumstances of their disappearance especially interesting.
“Some kind of homogeneity happened around that time,” said anthropologist Gildas Merceron of France’s University Claude Bernard Lyon, co-author of a study published June 2 in the Proceedings of the Royal Society B. “We suspect a uniform environment may be linked to the decrease in great ape biodiversity.”
That apes lived in Europe seems strange today, but the continent 20 million years was warm and wet, well-suited for primates that left Africa after shrinking seas exposed a land bridge between the continents. Within a few million years, Europe hosted more than 100 species of primates, and at least 10 species of great apes.
Climate change ended that geological age. The southern icecap grew, and the Antarctic circumpolar current formed. The Asian monsoon cycle started and Europe cooled. Merceron’s study gives local detail to that big picture.
The researchers analyzed hundreds of deer and antelope teeth found at sites in Germany, Hungary and Greece and dated them to the reign of Europe’s primates and to their extinction. Wear patterns told them what sort of vegetation had prevailed. In Western and Central Europe, ruminants switched from browsing bushes and trees to grazing grasses. In Eastern Europe, the opposite happened, as grazers started to browse.
This slide into woodland homogeneity likely left the apes unable to find food, and perhaps exposed them to predators, suspects Merceron’s team. But some researchers think Europe’s apes didn’t necessarily go extinct. Some may have returned to Africa, and followed an evolutionary course ending in the modern great apes, including Homo sapiens.
“For every aspect that makes us human, there is a time and set of conditions that explains that,” said Rutgers University anthropologist Rob Scott, who was not involved in the study. “This will help explain the sort of conditions that are relevant to the earliest hominids.”
The back-into-Africa hypothesis is controversial, and contradicts the standard narrative of an all-Africa origin for the human lineage. However, there’s a gap in Africa’s great ape fossil record between 14 and 7 million years ago. The Eurasian fossil record is rich at that time.
Among the candidates for an ancestor of humans and other modern great apes are Rudapithecus hungaricus, Anoiapithecus brevirostris and Ouranopithecus macedoniensis. Especially in the face, each has features hinting at those found in known human ancestors. The last of these apes to survive was Ouranopithecus, which lived in Greece and was well-suited to eating nuts and tubers. According to Scott, it’s possible that Ouranopithecus had started to come down from the trees, developing methods of locomotion that eventually turned into bipedalism. “I’d be terribly surprised if they were totally arboreal,” he said.
All this is speculation, but even if Eurasian apes didn’t give rise to humanity, the study embodies an approach that can be applied to African apes, said Scott.
“The field is progressing from the discovery of new taxa, new names to put in our charts, to having enough information to construct larger hypotheses and scenarios,” Scott said. “We want to know, why are we human?”
Source: Wired
