DNA analysis of a 90-year-old hair sample reveals that Aboriginal Australians left Africa much earlier than Europeans and East Asians
New research in the journal Science presents a number of firsts for Aboriginal Australians.
The first genome analysis of an Aborigine reveals that these early Australians took part in the first human migration out of Africa. They were the first to arrive in Asia some 70,000 years ago, roaming the area at least 24,000 years before the ancestors of present-day Europeans and Asians. They were also the first to live in Australia, according to DNA results of a 90-year-old hair sample of a young man that link Aborigines to the first inhabitants of this part of the world about 50,000 years ago.
This study, however, is not the first to contradict the popular theory that modern humans came from a single out-of-Africa migration wave into Europe, Asia, and Australia. But it does deal it a huge blow by confirming that Aboriginal Australians took part in the first of two rounds of human relocation.
"Aboriginal Australians descend from the first human explorers," explains lead author and University of Copenhagen professor Eske Willerslev in a news release. "While the ancestors of Europeans and Asians were sitting somewhere in Africa or the Middle East, yet to explore their world further, the ancestors of Aboriginal Australians spread rapidly ... traversing unknown territory in Asia and finally crossing the sea into Australia."
In the gallery below, get an up-close look at the Aboriginal Australian hair specimen behind this landmark study. Then, in the Q&A with co-author and University of California, Berkeley biologist Rasmus Nielsen that follows, learn more about the backstory of this sample, how genome-sequencing works, and the technology that led to these discoveries.
What were your team's key findings, and why are they so significant?
Anthropologists have long been interested in finding out how humans have dispersed. Most agree that modern humans evolved in Africa about 50 to 100 thousand years ago and thereafter spread to the rest of the world. But the consensus stops there.
Some anthropologists believe in the hypothesis of a so-called Southern Route or the idea that Aboriginal Australians descended from an early wave of dispersal of modern humans through Southern Asia. Most other population groups outside Africa are, according to this theory, descendants of a separate, more recent wave of dispersal. But others believe there was only one major wave. It has also been hotly debated if Aboriginals living in Australia today descend from the modern humans we know were in this area 50,000 years ago.
To resolve these debates, we sequenced the genome of an Australian Aboriginal using a 90-year-old hair sample. We analyzed the DNA computationally, and compared it to genomes of individuals from other geographic regions. We found that this individual must have descended from an early dispersal wave different from the one leading to East Asians and Europeans and that humans dispersed in two major waves of migration out of Africa. Our results also confirm that Aboriginal Australians are descendants of the first wave of migrants reaching Australia.
What is the backstory behind this hair specimen?
I was not involved in the acquisition of the hair sample, but I've been told that it's from the Duckworth Laboratory collections at University of Cambridge. It was obtained by one of the most distinguished anthropologists of his generation, Dr. Alfred Cort Haddon, in 1923.
According to Haddon's notes, the sample was obtained at Golden Ridge, near Kalgoorli in Western Australia, and the donor is described as a young man. We have worked together on this with the Goldfields Land and Sea Council, which represents the Aboriginal traditional owners of the Goldfields region, including the cultural -- and, possibly, the biological -- descendants of the individual who gave the original sample.
How does genome-sequencing work?
Perhaps I can explain it using an analogy. The genome has been compared to a book with three billion letters. By sequencing the genome of the Australian Aboriginal individual, we managed to find all the letters in the book. We still don't really understand the language the book is written in, but we can compare it to similar books, or genomes, from other populations to learn about differences and similarities between the populations.
Technically, it's easier now than ever to sequence genomes. You cut the genome into many small chunks. You then feed the chopped-up DNA into a machine that will tell you the identity of all the chunks. Using the analogy of a book, it's like you get a book that has been shredded into many pieces. You then have to figure out how all the pieces fit together. The first time this was done for a human, it was very difficult. But, now that we have other humans to compare to, it's not very hard.
We analyzed DNA from a hair sample we knew was from an individual who could not count both Europeans and Aboriginal Australians among its recent ancestors. We wanted to ensure that the individual was of 100 percent Aboriginal Australian descent.
Could you talk more about the methodology, particularly the technology, your team used?
The type of DNA sequencing I talked about earlier, called Next-Generation Sequencing, has been developed during the past five years or so. It has provided an incredible increase in the amount of DNA sequencing and has allowed us to now routinely sequence the genome of an individual at a very low cost.
There have also been computational advances that allow us to extract information from DNA sequences and infer the history of populations from the DNA more accurately. For this study, we developed a new computational method for estimating divergence times between populations using just a single genome representative from each population.
What are the implications of this study, if any, to present-day Aboriginal Australians?
I'm not sure there are any significant political implications. The rights of Aboriginal Australians will hopefully not be determined by genetic issues or events that happened 50,000 years ago. However, it might be satisfying for the Aboriginal Australian community to know that they have occupied the land for so long.