A number of science media sources are weighing in:
Hayes and her team analyzed the DNA of 1,217 people from southern Africa who represent a particularly important and poorly studied slice of human genetic diversity. By using that DNA to create a family tree, the team calculated that anatomically modern humans originated in the Makgadikgadi wetlands about 200,000 years ago. They then stayed put for about 70,000 years, before climatic changes allowed some of them to venture outward to other parts of Africa, and eventually to other continents.
But her claims are proving controversial, and other researchers I contacted were either skeptical or outright mad. The study, they noted, is based on just a sliver of DNA from living people, and doesn’t account for the rest of the genome, DNA from ancient human specimens, fossils, or stone tools and other cultural artifacts—all of which suggest that humans arose much earlier, and in a variety of locations.Ed Yong, “Has Humanity’s Homeland Been Found?” at The Atlantic
From the Australia-based Institute where Vanessa Hayes works:
A study has concluded that the earliest ancestors of anatomically modern humans (Homo sapiens sapiens) emerged in a southern African ‘homeland’ and thrived there for 70 thousand years.
The breakthrough findings are published in the prestigious journal Nature today.
The authors propose that changes in Africa’s climate triggered the first human explorations, which initiated the development of humans’ genetic, ethnic and cultural diversity.
“It has been clear for some time that anatomically modern humans appeared in Africa roughly 200 thousand years ago. What has been long debated is the exact location of this emergence and subsequent dispersal of our earliest ancestors,” says study lead Professor Vanessa Hayes from the Garvan Institute of Medical Research and University of Sydney, and Extraordinary Professor at the University of Pretoria.
“Mitochondrial DNA acts like a time capsule of our ancestral mothers, accumulating changes slowly over generations. Comparing the complete DNA code, or mitogenome, from different individuals provides information on how closely they are related.” This study provides a window into the first 100 thousand years of modern humans’ history.
In their study, Professor Hayes and her colleagues collected blood samples to establish a comprehensive catalogue of modern human’s earliest mitogenomes from the so-called ‘L0’ lineage. “Our work would not have been possible without the generous contributions of local communities and study participants in Namibia and South Africa, which allowed us to uncover rare and new L0 sub-branches,” says study author and public health Professor Riana Bornman from the University of Pretoria.
“We merged 198 new, rare mitogenomes to the current database of modern human’s earliest known population, the L0 lineage. This allowed us to refine the evolutionary tree of our earliest ancestral branches better than ever before,” says first author Dr Eva Chan from the Garvan Institute of Medical Research, who led the phylogenetic analyses.
By combining the L0 lineage timeline with the linguistic, cultural and geographic distributions of different sublineages, the study authors revealed that 200 thousand years ago, the first Homo sapiens sapiens maternal lineage emerged in a ‘homeland’ south of the Greater Zambezi River Basin region, which includes the entire expanse of northern Botswana into Namibia to the west and Zimbabwe to the east.Media Release, “The homeland of modern humans” at Garvan Institute of Medical Research
Others wonder how they can be so sure:
As NewsHour notes, mitochondrial DNA tells only a fraction of humans’ history, and scientists are not universally convinced by the paper’s conclusions. Speaking with The Guardian, the University of Pennsylvania’s Sarah Tishkoff took issue with the limited genetic sample. “How can they know that there aren’t old lineages in other regions if they’re not included in the study?” she says.Kerry Grens, “The First Modern Humans Came from What Is Now Botswana: Study” at The Scientist
Accusations of “storytelling” are flung at the authors:
The study revives a long-simmering debate about exactly where in Africa modern humans emerged, and it has drawn sharp criticism from several scientists. They point out that although all humans alive today have mitochondrial DNA passed on from a common ancestor—a so-called Mitochondrial Eve—this is just a tiny fraction of our total genetic material. So even if the proposed founder population described in the new study is the source of our mitochondrial DNA, many others likely contributed to today’s genetic pool.
“The inferences from the mtDNA data are fundamentally flawed,” Mark Thomas, an evolutionary geneticist at the University College London, says via email, adding that in his view, the study amounted to “storytelling.”Maya Wei-Haas, “Controversial new study pinpoints where all modern humans arose” at National Geographic
One is tempted to wonder, how would “storytelling” differentiate the Garvan team from many other human evolution researchers?
See also: We could have come from two parents
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