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Study details Peking Man's teeth
by Brooks Hays
Washington (UPI) Feb 1, 2018

Study reveals secrets of DNA mutation
Washington (UPI) Feb 1, 2018 - According to new research, some mutational DNA bases are able to avoid detection by the body's natural defense systems and incorporate themselves into the human genome.

The DNA base pair formed by guanine and thymine, a mutational mismatch, are able to shape-shift so they blend in with the rest of the DNA ladder, or helix.

"When these two bases form a hydrogen bond by accident, at first, they don't fit quite right," Zucai Suo, professor of chemistry and biochemistry at Ohio State University, said in a news release. "They stick out along the DNA helix, so normally it's easy for the enzymes that replicate DNA to detect them and fix them."

And normally, they do get caught and the mismatch is rectified. But sometimes, the base pair can change shapes before detection, avoiding the attention of genetic repair mechanisms.

"They're bad guys, but they pretend to be good guys to survive," Suo said.

This common form of DNA mutation is responsible for disease, the aging process and the experimental adaptations that drive evolution.

All genetic coding is formed by four bases: adenine, thymine, cytosine and guanine -- or A, T, C and G. All healthy base pairs are either A-T or C-G. Any combination besides A-T and C-G is considered a mutation.

G-T is the most common mutation found in human DNA. A G-T mutation occurs once for every 10,000 to 100,000 base pairs. There are 3 million base pairs in the human genome. So every genome has anywhere from 30,000 to 300,000 G-T mutations.

To better understand how G-T pairs form and disguise themselves, Suo and doctoral student Walter Zahurancik inserted the duo into a DNA strand using a DNA-replicating enzyme. The researchers froze the chemical reactions driving the mutation process at different time intervals to study the details of the mutational mechanism.

They found the enzyme can efficiently pair the two bases, but they form an odd-shaped molecule. However, in just a fraction of a second, the bases can rearrange themselves and successfully snap into play in the DNA helix.

A-T and C-G base pairs fit because they're shaped in ways that compliment one another. When they pair, they're very energy efficient. Mutational pairings are not and must alter themselves to overcome this energy barrier.

That's what happens when G-T pairs form -- they become just efficient enough to pass muster and avoid detection.

Scientists believe their findings -- detailed this week in the journal Nature -- can help researchers better understand the factors that cause DNA mutations.

"An interesting question is: What determines the mutation rate in a living organism," said Duke University researcher Hashim M. Al-Hashimi. "From there, we can begin to understand the specific conditions or environmental stressors that can elevate errors."

Scientists have for the first time analyzed the only original remains of Peking Man, the Homo erectus specimen discovered in China in the 1920s.

In a paper, newly published in the journal Scientific Reports, scientists with the National Research Center on Human Evolution in Spain detailed six fossilized teeth belonging to Peking Man.

Peking Man was originally recovered from a fossil-rich Middle Pleistocene site called Zhoukoudian. During the Second World War, most of Peking Man and other fossils recovered from Zhoukoudian were lost while being shipped from China to the United States.

Later, six teeth were recovered, but the remains haven't been analyzed until now.

"Since they were lost, for research on the fossil humans found at the site during the 1930s, plaster replicas of very poor quality have been used, as well as the descriptions and sketches that the researcher Franz Weidenreich left us," CENIEH researcher Bermúdez de Castro said in a news release.

Peking Man was first classified as a Sinanthropus pekinensis specimen. But the discovery of additional teeth in the 1950s helped scientists correctly identify Peking Man as belting to Homo erectus.

Peking Man lived some 750,000 years ago. And many scientists have interpreted much of modern human history in Asia as deriving from Peking Man's ancestry.

"All the human fossils found in what we call the Far East and in the current islands of Indonesia have been attributed systematically to Homo erectus," de Castro said.

However, variation among hominin fossils found throughout China suggests the evolution of Homo erectus and its relatives wasn't so straightforward.

The latest analysis of Pekin Man's teeth revealed similarities between fossils found at Zhoukoudian and other Middle Pleistocene sites in China. But the research also points to differences between the dental structures of Peking Man and Homo erectus.

Scientists hope their work will help researchers more accurately position Peking Man within the context of hominin species in Africa, Asia and Europe, and offer new insights into the evolution of early humans in the Far East.

Genome study reveals history of human populations in Northern Europe
Washington (UPI) Jan 30, 2018 - According to new genomic analysis, Scandinavia was settled by human populations migrating along both a northern and southern route.

Scientists were able to trace historic waves of migration into Northern Europe by analyzing DNA samples collected from the remains of 38 different people. The remains included humans living in Scandinavia between 7,500 and 500 BC.

The findings -- published this week in the journal Nature Communications -- suggest the arrival of agriculture was late to Northern Europe.

While agriculture was firmly established throughout Central Europe some 7,000 years ago, the first Neolithic farmers and pastoralists didn't arrive in Scandinavia until between 6,000 to 5,300 years ago.

Previous genomic studies have revealed two distinct populations of hunter-gatherers living in Europe during the Mesolithic, between 10,000 and 5,000 BC: a western group centered around present-day Hungary and an eastern group from Russia.

The latest analysis suggests the early people of Scandinavia can trace their roots to both populations.

"Eastern hunter-gatherers were not present on the eastern Baltic coast, but a genetic component from them is present in Scandinavia," Johannes Krause, director of the department of archaeogenetics at the Max Planck Institute for the Science of Human History, said in a news release. "This suggests that the people carrying this genetic component took a northern route through Fennoscandia into the southern part of the Scandinavian peninsula. There they genetically mixed with western hunter-gatherers who came from the south, and together they formed the Scandinavian hunter-gatherers."

Despite the establishment of farming practices throughout Central Europe by around 5,000 BC, hunting, gathering and fishing remained the sole means of subsistence in Northern Europe until the arrival of agriculture around 4,000 BC.

The new data suggests Scandinavia's first farmers came from Central Europe. Along with new tools and techniques, these agriculturalists brought genetic roots that can be traced back to the Anatolian farmers, who first migrated from the Near East to Europe some 8,200 years ago.

Surprisingly, hunter-gatherers living in the Eastern Baltic region did not mix with the earliest migrant farmers. The groups coexisted for several millennia. The hunter-gatherers began to mix with nomadic pastoralists of the Pontic-Caspian steppe around 2,900 BC.

"Interestingly, we find an increase of local Eastern Baltic hunter-gatherer ancestry in this population at the onset of the Bronze Age," said lead study author Alissa Mittnik, a researcher at the Max Planck Institute. "The local population was not completely replaced but coexisted and eventually mixed with the newcomers."


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Evolving sets of gene regulators explain some of our differences from other primates
Cold Spring Harbor NY (SPX) Jan 30, 2018
Today, biologists add an important discovery to a growing body of data explaining why we're different from chimps and other primate relatives, despite the remarkable similarity of our genes. The new evidence has to do with the way genes are regulated. It's the result of a comprehensive genome-wide computational analysis of multiple individuals across three primate species - human, chimpanzee and rhesus macaque. The researchers focused on regulatory DNA elements are called gene enhancers and promot ... read more

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