Western scientists first learned about extinct giant ape species Gigantopithecus blacki—the largest primate to ever exist—in 1935 when an anthropologist came across some of its massive molars in Chinese drug stores selling them as dragon teeth. Since then, researchers have identified thousands of teeth and a few partial jawbones from the creature. With these pieces in hand, they’ve tried to fit the bigfoot-like ape into the primate family tree. Without any usable DNA, however, the task has been difficult.
Now, using proteins in dental enamel, researchers report they've finally found how the Gigantopithecus fits into the great ape puzzle, according to a new study published in the journal Nature.
According to a press release, DNA has been key in helping scientists map out the messy relationships between primates and hominids that lived within the past 50,000 years. But in fossils older than that, DNA is very difficult to extract and scientists have only done it successfully in a few rare cases, including in one 400,000-year-old hominin specimen.
Gigantopithecus remains are estimated to be between 300,000 to 2 million years old, placing its reign at some point during the Pleistocene epoch.
No Gigantopithecus DNA has ever been recovered. That’s why an international team of researchers used techniques from an emerging field called proteomics to get molecular information from the Gigantopithecus molar in the new study.
In traditional DNA sequencing, pieces of the DNA molecule are put through a process that copies its sequence of nucleotides and puts them back together into a full genome. The quality and completeness of the genome, however, depends on how well-preserved the original sample of DNA is. Most DNA degrades much more quickly, especially in hot, humid climates.
But in proteomics, researchers more or less reverse-engineer DNA by looking at the proteins preserved in teeth, which last much longer. Because each protein is made up of amino acids, and because each amino acid is encoded by a three-letter DNA sequence, researchers can produce snippets of ancient DNA by analyzing the proteins. Last September, the technique was used to properly place a 1.7-million-year-old species of wooly rhinoceros in its family tree, proving that the method could be used to understand ancient animals.
Researchers applied the protein-mining technique to a 1.9 million-year-old molar from Gigantopithecus found in a Chuifeng cave in China. Gretchen Vogel at Science reports the team dissolved tiny amounts of enamel from the tooth and then analyzed it using mass spectrometry. They were able to identify 500 peptides, or short chains of amino acids, from six different proteins.
Bruce Bower at Science News reports that five of those proteins still occur in extant ape and monkey species. The team compared the accumulated differences in the proteins to those animals, finding that the massive Gigantopithecus is a distant relative of modern orangutans. The two lineages likely diverged from a common ancestor over 10 million years ago.
“Until now, all that was known about this species was based on the morphology of the many teeth and the few mandibles found, typical of a herbivore," study author Enrico Cappellini, an evolutionary geneticist at the University of Copenhagen, says in the press release. “Now, the analysis of ancient proteins, or palaeoproteomics, has allowed us to reconstruct the evolutionary history of this distant relative.”
The success of this technique has big implications for the future of paleoanthropology. Because many of the fossilized remains of ancient hominins come from tropical and subtropical areas, like East Africa, southern Africa and Indonesia, there’s little chance that viable DNA has survived. But the protein trick changes everything.
“Until now, it has only been possible to retrieve genetic information from up to 10,000-year-old fossils in warm, humid areas,” Welker tells Katie Hunt at CNN. “This is interesting, because ancient remains of the supposed ancestors of our species, Homo sapiens, are also mainly found in subtropical areas, particularly for the early part of human evolution. This means that we can potentially retrieve similar information on the evolutionary line leading to humans.”
The team also says that they may be able to look at more than just molars. It could be possible to analyze protein sequences in the bones of apes and hominins that lost their viable DNA long ago.
While the study tells researchers a little bit about Gigantopithecus’s origins, Capellini tells Hunt that it doesn’t shed much light on what the massive ape looked like or how it behaved.