Researchers can use a new technique to identify the closest relative of an extinct giant ape. The technique provides insight into prehistory in unprecedented detail.
Half a million years ago, Asia had an ape so huge that it made a full-grown male gorilla look like a scrawny teenager.
The ape was about 3 metres tall and weighed up to 600 kg, which is twice the size of a male silverback gorilla.
So far, palaeontologists have only found molars and a few mandible fragments from this long-extinct ape, but now researchers can use a new technique developed in Denmark to determine which species is most closely related to this giant ape.
The discovery indicates that the giant ape is most closely related to an orangutan and that the lineages of this ape and the orangutan diverged up to 12 million years ago.
“We are very excited that we can use this new method to map the lineage between an ape that became extinct 300,000 years ago and its modern relatives based on just a few protein sequences in tooth enamel,” explains an author, Enrico Cappellini, Associate Professor, Section for Evolutionary Genomics, Globe Institute, University of Copenhagen.
The findings have been published in Nature.
Gigantopithecus lived at the same time as our ancestors
The gigantic ape, which very appropriately goes by the tongue-twisting name Gigantopithecus, lived in regions that today span China, Vietnam and Indonesia.
Gigantopithecus lived from 2 million to 300,000 years ago. Some researchers even claim to have evidence that it first became extinct 100,000 years ago.
Nevertheless, this giant ape co-existed with our ancestor Homo erectus, which also lived in these areas at that time.
However, despite its size, Gigantopithecus has not left many traces of its existence. Only a few jawbones and thousands of ancient molars have been found so far.
Nevertheless, one of these molars has been enough for the researchers to determine that the orangutans are the closest living relatives of Gigantopithecus.
“Using the molars, researchers had previously determined that Gigantopithecus was much larger than all modern primates. But researchers could not determine with 100% certainty whether it was more closely related to orangutans or to other modern primates,” says Enrico Cappellini.
The technique is revolutionizing research into prehistory
Enrico Cappellini and colleagues analysed dental enamel from a Gigantopithecus that was 1.9 million years old.
The researchers extracted proteins from Gigantopithecus dental enamel and reconstructed their amino acid sequence by using a technique called mass spectrometry.
They then compared the sequence of dental enamel proteins from Gigantopithecus with those of modern chimpanzees, orangutans, gorillas and humans, which are already known.
Another article in Sciencenews describes the technique, explaining how researchers have used it to map the relationships between modern and long-extinct rhinoceroses.
The researchers examined differences in the amino acid sequences to determine how the various primates are related and found that the orangutan is the closest modern relative to Gigantopithecus.
These two species had the fewest differences in their dental enamel protein sequences. The researchers even determined that the two species diverged 12 million years ago.
“Looking that far back in time is completely unheard of. This was impossible until now, because previously we examined ancient DNA, which degrades much faster than enamel proteins,” says Enrico Cappellini.
Unique opportunity to study subtropical fossils
This is the first time that researchers have been able to investigate and use genetic information from primate fossils that are so old.
So far, researchers had only been able to retrieve genetic information that is 10,000 years old from fossil samples from subtropical environments and almost 700,000 years from fossils from permafrost areas.
The mapping of the lineage of Gigantopithecus thus sets entirely new standards for how far researchers can go back in time and map relationships between species.
This technique could be especially useful in studying humans, because our ancestors often lived in precisely these subtropical environments.
“Our results imply that we can potentially find similar information on the history of human evolution. This is groundbreaking for studies in evolutionary biology,” says another co-author, Frido Welker, a postdoctoral fellow in Enrico Cappellini’s group.
Greater insight into prehistoric humans
Enrico Cappellini elaborates that the lineage of modern humans diverged from our closest living relatives, i.e. chimpanzees and bonobos, about 7 million years ago.
Since then, we have diverged, and our lineage includes many species that have evolved to become us, including Homo heidelbergensis and Homo erectus.
Prehistory has also included species that have been distant cousins to humans, such as Australopithecus (Lucy).
So far, all knowledge about our relationship with these distant ancestors and relatives has been based on morphological studies of skulls and bones.
However, this is qualified guesswork for the vast majority of the numerous species.
“Of the 7 million years of human history, we only have genetic knowledge of the last 400,000 years. With the new technique, we can map a much larger part of human prehistory since we diverged from chimpanzees and can gain completely new insight into where we come from and how we got to where we are today,” explains Enrico Cappellini.
“Enamel proteome shows that Gigantopithecus was an early diverging pongine” has been published in Nature. One co-author is Jesper Velgaard Olsen, Professor and Deputy Director, Novo Nordisk Foundation Center for Protein Research, University of Copenhagen.
