The study of fossils often helps clarify some important aspect of human history.
But recent research, in which scientists extracted the fossilised remains of South China’s ‘Red Deer Cave People’ from rock some twenty years after they were first discovered, has deepened the mystery of human evolution.
It also points to an exciting new era in human evolutionary studies in South-East Asia, where many human fossil remains are not well dated or their origins are unknown.
Those that have been found in recent years – among them the so-called short-statured ‘Hobbit People’ of Flores in Indonesia – don’t fully support the idea of a neat evolutionary trajectory of modern humans arising in Africa and spreading throughout the world to replace existing species .
There is now evidence that modern humans interbred with both Neandertals and the as yet little known Denisovans as they left Africa.
La Trobe’s Dr Andy Herries is part of team of scientists from six Chinese and five Australian institutions who carried out the excavation and dating at Maludong (Red Deer) Cave, near the town of Mengzi in Yunnan. He is an internationally renowned geoarchaeologist and dating specialist and Head of La Trobe’s Australian Archaeomagnetism Laboratory.
Dr Herries says the Red Deer Cave people, with their mix of Neandertal and early African modern human anatomical features, may be further evidence for this, especially as genetic evidence for potential intermixing of Denisovans and modern people has come from this area of southern China.
Archaic and modern features
He says the fossilised remains of at least three Red Deer Cave people from two sites are between 14,500 and 11,500 years old. Despite their young age in evolutionary terms, they revealed a highly unusual mix of archaic, as well as modern anatomical features.
The team of scientists working on the fossils was led by University of New South Wales Associate Professor Darren Curnoe –and Professor Ji Xueping from Yunnan Institute of Cultural Relics.
The results of their research, published in March in the international on line journal ‘PLoS One’, says the Red Deer People inhabited the region alongside modern-looking people at a time when China’s earliest farming cultures were beginning.
Difficulty with fossil dating
‘These new fossils might be of a previously unknown species, one that survived until the very end of the Ice Age,’ says Dr Curnoe. ‘Alternatively, they might represent a very early and previously unknown migration of modern humans out of Africa, a population who may not have contributed genetically to living people.’
Dr Herries says one of the biggest problems in understanding human evolution in East and South East Asia is that many fossils are found ‘out of context’, which makes it difficult, and often impossible, to assess their age.
In contrast, the Maludong remains are some of the best dated fossils anywhere in the world. They come from a small cave that was filled over a very short period of time. A fourth partial skeleton was found by a Chinese geologist in a cave near the village of Longlin, in neighbouring Guangxi Zhuang.
A new evolutionary line?
The anatomy of Red Deer Cave people has similarities with early modern humans who arose in Africa between 200 and 150,000 years ago, but they also have a mixture of primitive features.
They have prominent brow ridges, a short, broad flat face and nose, and a jutting jaw that lacks a human-like chin. Their brains have modern frontal lobes, yet primitive parietal lobes, the region in the brain which integrates sensory information and helps us manipulate objects.
Teeth and jaws have anatomical features like those that define Neandertals, so it makes it difficult for scientists to decide whether they should be classified as Homo sapiens, as hybrid modern humans and Neandertals, as Denisovans, or as some other unique inter-mixed species .
‘The greatest shock was when we found out how young they were, says Dr Herries.
If the Red Deer Cave people are the remanent of an early migration into Asia from Africa then they survived until at least 13,500 years ago, a warm, wet phase during a period of rapid climate change at the end of the last glacial period.
It was also a time of great ecological change, which saw the demise of megafauna at the site such as the giant red deer which they hunted and cooked. Given the Red Deer Cave people survived the coldest phase of the last glacial period, why did they become extinct? This, says Dr Herries, is a question for future research.
Advent of Asian agriculture
One answer may be that at the same time there was a significant move to making pottery for food storage and gathering wild rice, a step to early farming.
Dr Curnoe speculates such ‘economic’ behaviour by their modern human neighbours may have pushed the Red Deer Cave people to the brink.
While Asia today contains more than half the world’s population, Dr Herries says scientists still know little about how modern humans evolved there after our ancestors settled Eurasia some 70,000 years ago.
Fossils of modern human as old as 40,000 years have been found in Australia, Malaysia and northern China. Modern humans appear to have colonised Australia at least 50,000 years ago, if not earlier. Yet in Asia there is no evidence of them before 40,000 years. Dr Herries says the discovery of the Red Deer Cave people has other implications.
‘Human fossils are very rare. It is often assumed certain stone tools and behaviours can be related to particular species, yet modern humans have been documented using Neandertal technology in Israel.
‘With the occurrence of the Red Deer Cave people in South East Asia and the potential of the Denisovans there as well, it can no longer be assumed that more recent archaeological sites are the product of modern humans and modern human behaviour.’
So assumptions that the region had been empty of our ‘evolutionary cousins’ when the first modern humans appeared are challenged by these new discoveries, throwing the archaeological spotlight once more on Asia.
Tip of iceberg of diversity
‘Historically, Europe and Africa have been the focus of intense international research regarding our human origins,’ says Dr Herries.
‘However, due to Asia’s massive size and rugged terrain it is likely a rich record of fossils is still waiting to be found that will further overturn what we know about our evolutionary history.
‘The Maludong and Longlin remains show that it’s possible for small relict populations of humans from earlier migrations into Asia to survive in remote areas until much later than previously thought.’
As his colleague, research leader Dr Curnoe wrote in an article in ‘The Conversation’, these fossils in East Asia deepen the mystery of human evolution in the region: ‘The existence of multiple populations – probably from different evolutionary lines – paints an amazing picture of diversity; one we had no clue about until the last decade.
‘It’s probably the tip of the iceberg of diversity and the opening of a new chapter in recent human evolution – the East Asian chapter.’ □
● The research paper—Human Remains from the Pleistocene-Holocene Transition of Southwest China Suggest a Complex Evolutionary History for East Asians— published in the journal PLoS One and is available on request.