New 'molecular clock' aids dating of human migration history

Jun 04, 2009

Researchers at the University of Leeds have devised a more accurate method of dating ancient human migration - even when no corroborating archaeological evidence exists.

Estimating the chronology of population migrations throughout mankind's early history has always been problematic. The most widely used genetic method works back to find the last common ancestor of any particular set of lineages using samples of (), but this method has recently been shown to be unreliable, throwing 20 years of research into doubt.

The new method refines the mtDNA calculation by taking into account the process of - which researchers realised was skewing their results - and has been tested successfully against known colonisation dates confirmed by , such as in Polynesia in the Pacific (approximately 3,000 years ago), and the Canary Islands (approximately 2,500 years ago).

Says PhD student Pedro Soares who devised the new method: "Natural selection's very gradual removal of harmful gene mutations in the mtDNA produces a time-dependent effect on how many mutations you see in the family tree. What we've done is work out a formula that corrects this effect so that we now have a reliable way of dating genetic lineages.

"This means that we can put a timescale on any part of the particular family tree, right back to humanity's last common maternal ancestor, known as 'Mitochondrial Eve', who lived some 200,000 years ago. In fact we can date any migration for which we have available data," he says.

Moreover, working with a published database of more than 2,000 fully sequenced mtDNA samples, Soares' calculation, for the first time, uses data from the whole of the mtDNA molecule. This means that the results are not only more accurate, but also more precise, giving narrower date ranges.

The new method has already yielded some surprising findings. Says archaogeneticist Professor Martin Richards, who supervised Soares: "We can settle the debate regarding mankind's expansion through the Americas. Researchers have been estimating dates from mtDNA that are too old for the archaeological evidence, but our calculations confirm the date to be some 15,000 years ago, around the time of the first unequivocal
archaeological remains.

"Furthermore, we can say with some confidence that the estimate of humanity's 'out of Africa' migration was around 60-70,000 years ago - some 10-20,000 years earlier than previously thought."

The team has devised a simple calculator into which researchers can feed their data and this is being made freely available on the University of Leeds website.

More information: The paper is published in the current edition of the American Journal of Human Genetics.

Source: University of Leeds (news : web)

Explore further: Bacteria 'hotwire their genes' to fix a faulty motor

add to favorites email to friend print save as pdf

Related Stories

History-hunting geneticists can still follow familiar trail

Dec 19, 2006

As the world's first explorers branched away from humanity's birthplace in east Africa some 65,000 years ago, distinct mutations accumulated in the DNA of each population, essentially providing a genetic trail for modern ...

Early human populations evolved separately for 100,000 years

Apr 24, 2008

A team of Genographic researchers and their collaborators have published the most extensive survey to date of African mitochondrial DNA (mtDNA). Over 600 complete mtDNA genomes from indigenous populations across the continent ...

Long lost sisters

May 15, 2008

The human race was divided into two separate groups within Africa for as much as half of its existence, says a Tel Aviv University mathematician. Climate change, reduction in populations and harsh conditions may have caused ...

Mitochondrial 'bottleneck' cracked

Jan 27, 2008

Scientists have shown for the first time how a particular family of diseases are passed down from mother to child and how this can lead to the severity of the disease differing widely. The research, funded by the Wellcome ...

Scientists say early Americans arrived earlier

Mar 20, 2008

A team led by two Texas A&M University anthropologists now believes the first Americans came to this country 1,000 to 2,000 years earlier than the 13,500 years ago previously thought, which could shift historic timelines.

Recommended for you

Malaria transmission linked to mosquitoes' sexual biology

19 hours ago

Sexual biology may be the key to uncovering why Anopheles mosquitoes are unique in their ability to transmit malaria to humans, according to researchers at Harvard T. H. Chan School of Public Health and University of Per ...

Intermediary neuron acts as synaptic cloaking device

20 hours ago

Neuroscientists believe that the connectome, a map of each and every connection between the millions of neurons in the brain, will provide a blueprint that will allow them to link brain anatomy to brain function. ...

Skeleton of cells controls cell multiplication

20 hours ago

A research team from Instituto Gulbenkian de Ciencia (IGC; Portugal), led by Florence Janody, in collaboration with Nicolas Tapon from London Research Institute (LRI; UK), discovered that the cell's skeleton ...

New study shows safer methods for stem cell culturing

Feb 25, 2015

A new study led by researchers at The Scripps Research Institute (TSRI) and the University of California (UC), San Diego School of Medicine shows that certain stem cell culture methods are associated with increased DNA mutations. ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.