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Chook Evolution Rate Questions Domestication Rate and Human Migration

Posted: October 30th, 2015 | Author: | Filed under: Applied Science, Engineered Life, Genetics | Tags: , , , , | Comments Off on Chook Evolution Rate Questions Domestication Rate and Human Migration

Chicken evolution rate challenges timings of domestication and human migrationChickens are evolving faster than previously thought, according to new research that challenges ideas of when they were domesticated and may have implications for human migration.

The findings, published in journal Biology Letters, are based on a genetic analysis of a chicken population that can be traced back over 50 generations.

The international team of researchers sequenced 12 mitochondrial genomes – DNA generally thought to be passed down from the mother to their offspring – in a well-known population of White Plymouth Rock chickens.

Previous chicken research – March 2014 – has been used to gauge human events in history, notably that Christopher Columbus beat Polynesians to South America ::::

Chicken evolution rate challenges timings of domestication and human migration

Two lineages of the White Plymouth Rock chicken – a small-sized chicken and a 10-times larger chicken – have been bred separately for 50 years. The researchers found the rate of mutation since the two lineages split was up to 30 times the rate assumed for birds.

Previously, the mutation rate in birds was generally thought to be about 1 per cent per million years. DNA changes by 1 per cent every million years in birds,” study co-author Associate Professor Simon Ho of Sydney University said.

Pinpointing the rate of mutation is important for working out when chickens were domesticated.

“In our pedigree study, we estimated a rate of at least 4 per cent per million years, but perhaps up to 30 per cent per million years.” Dr Ho said. “Our estimate of when chickens were domesticated depends on knowing the mutation rate of DNA. If we use an incorrect mutation rate, then our estimates of the timing of chicken domestication will be very wrong.”

He said that this had been a problem in domestication studies of other animals such as dogs and cattle.

The researchers also found that in one case, mitochondrial DNA had been passed down from a father to its offspring.

“In all of these cases, new mutation rates have shown us that domestication occurred much more recently than originally believed,” Dr Ho said. “We’ve shown that it doesn’t always pass from mother to offspring and it can mutate much more quickly than we thought.” Dr Ho said.

Dr Ho said the study findings may change our understanding of bird evolution. “The understanding of evolution is based on mitochondrial DNA,” he said.

Chicken timing has implications for human migration The research also has implications for our understanding of human migration, Dr Ho said.

“Chickens are one of the animals used as a proxy for human migration and especially colonising the Pacific, because humans carried chickens across the Pacific,” he said.

Associate Professor Jeremy Austin of the Australian Centre for Ancient DNA at the University of Adelaide said the new molecular clock has the potential to “dramatically alter” the timing of when both chicken domestication and human migration events occurred in the Pacific.

The new data gives a better estimate of when things happened in the recent past.

“Having this new estimate means we are much more likely to get a more accurate picture of exactly when things like chicken domestication happened,” said Dr Austin, who was not involved in the research.

Dr Austin and his team are currently studying mitochondrial DNA to understand the translocation of chickens into the Pacific.

“We may be able to apply this new rate to our data and see whether the dates for the original chickens in the islands and SE Asia and their movement out into the South Pacific correlates well with radiocarbon dating of human remains along that translocation route.” Dr Austin said. “We’ve always argued that chickens were more likely to be the animals transported first.”

The new data would help his team test whether chickens were part of the initial migration or came later.

“That’s important for understanding the whole archaeological history of the colonisation of the Pacific,” Dr Austin said. “Did humans carry living food items with them on those initial voyages or did they just go out blind and live off the land?”

Chicken DNA 'Suggests Columbus Was First' to America

unRELATED!? Chicken DNA ‘Suggests Columbus Was First’ to America

Research published in March 2014 on the DNA of ancient bones from domesticated chickens confirms Columbus beat Polynesians to South America, say researchers. However, not everyone is convinced by the new findings published this week in Proceedings of the National Academy of Sciences.

In 2007, Dr Alice Storey (then a PhD student at the University of Auckland) and colleagues reported in PNAS that a 600-year-old chicken bone from Chile had a rare genetic mutation also found in ancient bones from the Pacific.

They argued the findings supported the idea that Polynesians made it all the way to South America before Columbus.

But in 2008, Professor Alan Cooper from the Australian Centre for Ancient DNA at the University of Adelaide and colleagues challenged this idea. They said the mutation identified by Storey was actually a common genetic sequence from European chickens.

This so-called “KFC” gene could therefore not be used to link South America and Polynesia, argued Cooper and team.

Now, Cooper and colleagues say the genetic sequence identified by Storey and team must have resulted from contamination of the ancient Polynesian bones by modern chicken DNA.

After analysing the mitochondrial DNA of 37 ancient chicken bones from the Pacific, including six samples from Rapa Nui (Easter Island) used by Storey, Cooper and colleagues say they have found no evidence of the KFC gene at all.

“We found instead this quite distinct Pacific genetic signature — with four particular markers — that we only find in the Pacific and seems to be in all of the ancient Polynesian birds,” says Cooper.

He says this is the true DNA fingerprint of chickens brought across the Pacific by the Lapita Polynesian people.

“You don’t see this Pacific sequence in South America in modern chickens,” he says.

Cooper says the findings suggest the Polynesians went as far east as Rapa Nui (Easter Island) and no further.

Original Findings Defended

However Storey, who is now a consulting archaeologist in British Colombia, Canada, stands by her original findings.

She says a major flaw in Cooper and colleagues’ paper is that much of their argument is based on mitochondrial DNA from modern chickens.

“In chickens in particular we know that mitochondrial DNA doesn’t tell us anything about the past,” says Storey.

“People move around chickens all the time,” she says. “Modern chicken DNA is this huge hodge podge mix of stuff.”

While one expects to see ancestral lineages in both ancient and modern DNA, Storey says looking at modern chicken DNA is like taking samples at a central Sydney rail station at rush hour and expecting to learn about how humans came to Australia.

“You might get some Aboriginal DNA but it’s not going to tell you much about the Aboriginal settlement of Australia,” she says.

Storey insists that understanding the movement of Polynesians requires looking at preferably nuclear DNA, from chickens prior to 1600, when Europeans started moving them around the Pacific.

Storey also says she and colleagues originally identified two genetic signatures in ancient Polynesian chicken bones.

While both are found in modern domestic chickens, Storey says Cooper and colleagues excluded one as contamination, but not the other.

“You can’t pick and choose which contamination you like and which one you don’t,” she says. “If you are going to exclude one you have to exclude them both.”

Storey points to other evidence to support contact between Polynesians and South America prior to Columbus.

For example, says Storey, a sweet potato known as ‘kumala’ in South America shows up in the Pacific (where it is known mainly as ‘kumera’) before European contact.



CHRONIC! Australia to Legalise Cannabis

CHRONIC! Australia to Legalise CannabisAustralia’s Government has announced it will legalise the growing of cannabis for medicinal purposes.

Health Minister Sussan Ley says the Government wants to give people suffering from debilitating illnesses access to all of the most effective medical treatments, including medical cannabis.

The minister said she had been moved by stories of people who get relief from the currently restricted drug, sometimes legally imported but not always. However, Ms Ley said the legalisation was only about medicinal cannabis, not recreational use.

“This is not a debate about legalisation of cannabis. This is not about illicit drugs. This is not a product you smoke. This has nothing to do with that,” Ms Ley said. “Most commonly the product is an oil or a tincture that you put on your skin.”

A progressive government in Victoria looks to have that state as the nation’s first onboard, the state Government plans to embark on a cannabis cultivation trial, based on the recommendations of a report by the Victorian Law Reform Commission :: Read the full article »»»»


unRELATED! Scientists Discover New Volcanic Eruption Trigger

Scientists Discover New Volcanic Eruption TriggerScientists say they’ve found a new way to predict when a volcano is about to erupt. Simply; after a measurable pressure drop occurs within a volcano’s internal plumbing, an eruption is likely to follow.

This pressure drop can potentially be used by volcanologists to predict a catastrophic eruption. The researchers say the importance is quite significant, particularly if you are part of a community that lives next door to a volcano, or an airline company mapping flight routes.

The study is hoping to engineer early warning systems so that people can be told with a huge degree of confidence when to get out of the way.

Lead author Dr Janine Kavanagh from the University of Liverpool said with more than 600 million people worldwide living near a volcano at risk of eruptive activity, it is more important than ever that triggering mechanisms are made more accurate. This previously unrecognised trigger could also alleviate the “headache” volcanic eruptions cause civil aviation by providing early and accurate warnings to authorities when they should divert aircraft.

“There is also a strong economic incentive to understand the causes of volcanic activity as demonstrated in 2010 by the eruption of Eyjafjallajökull, Iceland, causing air-traffic disruption across Europe for more than a month, and an estimated $A2.5 billion loss in revenue to the airline industry :: Read the full article »»»»


The Kernel

RELATED! Scientific World Stunned at Accuracy of Australian Aboriginal Legend

Scientific World Stunned at Accuracy of Australian Aboriginal Legend

The scientific community is stunned by research which backs an Australian Aboriginal legend on how coastal palm trees got to Central Australia. Tasmanian ecologist Professor David Bowman did DNA tests on palm seeds from the outback, and his conclusion is startling :: Read the full article »»»»

RELATED! Researchers Transplant Bionic-heart Into Sheep

Researchers Transplant Bionic-heart Into SheepMedical and engineering specialists say they are on the cusp of a breakthrough after successfully transplanting a bionic heart into a sheep.

The bionic heart was designed by Brisbane engineer Dr Daniel Timms in 2001 while he was studying at the Queensland University of Technology.

It contains a spinning disc with small blades on each side that pump blood around the body and lungs, without a traditional pulse.

The bionic heart can last at least 10 years and could help bridge the gap between patients requiring heart transplants and the number of donor hearts available.

The team, made up of Queensland and international researchers, said the device was a significant advance on other designs that were large, prone to wear, or could only pump on the left or right side. It is expected to be ready for human trials within three years :: Read the full article »»»»




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source: university.sydney/acad
source: biology.letters/pdf
source: pnas/abc
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