Category Archives: Transhuman News

Genetics research sheds light on a long human relationship

A poison we adapted to tolerate

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Alcohol has been part of human existence for millennia. Alcoholic beverages are an integral part of human culture. Like the wines consumed in Jewish and Christian rituals, these drinks have ceremonial and religious uses. Until the nineteenth century, beer, brandy, rum or grog was the drink of choice for sailors in lieu of stagnant water during long voyages. Alcohol is a social lubricant, an anesthetic and an antiseptic. It is one of the most widely used drugs in the world and has been manufactured since the advent of agriculture nearly 9000 years ago. How is it that this drug an intoxicating poison has become such a part of human existence?

A new study finds that our forebears acquired the capacity to digest alcohol some 10 million years ago, among a common ancestor to humans, chimpanzees and gorillas, and certainly well before we learned to manufacture it. This suggests that alcohol became part of the human diet much earlier than previously thought, and in a manner that had significant implications for the survival of the human species.

Humans carry with them genetic signatures of their ancestral feeding habits. Genetic variants that make new food sources available can provide tremendous opportunities to those who possess them. The ability to consume milk, for example, is due to the lactase persistence variant of a gene which emerged around 7500 years ago among early Europeans. For those lacking the mutation, the lactose in milk is a mild poison, eliciting symptoms akin to those of dysentery. Similarly, the ability to digest alcohol may be a genetic signature of feeding pattern among human ancestors: this alcohol tolerance may have made it possible to eat over-ripe fruit that had fallen to the ground and begun to naturally ferment. Since few animals can tolerate alcohol, this would have provided our ancestors with an abundant food source for which there were few competitors. It may also have contributed to the move towards a terrestrial rather than arboreal existence.

The breakdown of alcohol after ingestion is a complex process that involves a number of different enzymes. Most of the alcohol that is ingested is broken down in the gut and liver. This study focused on the enzyme ADH4 because it is abundant in the gut and plays a major role in preventing ingested alcohol from entering the blood stream. ADH4 from human relatives as distant as the tree shrew were tested for their ability to digest alcohol. The form of ADH4 found in humans, gorillas and chimpanzees was found to be 40 fold more efficient at clearing alcohol than the form found in more primitive species. ADH4 also digests chemicals that plants produce in order to deter animals from feeding upon them. However, with the increase in ability to digest alcohol came a reduced ability to digest many of these other chemicals. This suggests that the food containing alcohol was more important.

While ADH4 is among the most important enzymes for the digestion of alcohol, it is not the only one. Another related enzyme, ADH3, also contributes to the breakdown of alcohol. Women typically have lower activity levels of this enzyme, leading them to have higher blood levels of alcohol then men after taking a high dose of alcohol. And ADH4 is not the only enzyme that may have helped humans adapt to the consumption of alcohol: a variant of a liver enzyme (ADH1B) with high activity in the breakdown of alcohol emerged among East Asian populations during the advent of rice cultivation, perhaps as an adaptation to rice fermentation. (Interestingly, other animals have adopted their own strategies: Using a different enzyme, a member of the tree shrew family is able to consume fermented nectar from palm tree flowers the equivalent of 10 -12 glasses of wine every day without obvious signs of intoxication.)

Because humans rely upon ADH4 as their primary means to digest alcohol, they are also susceptible to hangovers. ADH4 and similar enzymes digest alcohol by converting it into another chemical, acetaldehyde, which causes the skin flushing, headache and other symptoms of overindulgence. The modern consumption of alcohol has been characterized as an "evolutionary hangover," an adaptation to modest levels of alcohol in food sources which left humans prone to alcohol abuse once we learned how to manufacture it in highly concentrated forms. And, in fact, genetic variants of ADH4 have been linked to alcohol and drug dependence, although there are many other genes that may influence susceptibility to alcohol dependency. Regardless of the role ADH4 plays in alcohol addiction, its clear that our complex relationship with alcohol dates back millions of year, and began, in fact, before we were even human.

Robert Martone is a researcher working on neuro-oncology biomarker discovery and development. He lives and works in Memphis TN.

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Our Taste for Alcohol Goes Back Millions of Years

IMAGE:Kai Zhang, Ph.D., is an assistant professor in the Department of Epidemiology, Human Genetics & Environmental Sciences at UTHealth School of Public Health. view more

Credit: UTHealth School of Public Health

HOUSTON - (Feb. 10, 2015) - Houston experienced its hottest summer on record in 2011, resulting in 278 excess emergency department visits per day during the August heat wave, according to research from The University of Texas Health Science Center at Houston (UTHealth) published recently in Environmental Health.

"The 2011 heat wave led to significantly more emergency department visits than would be typical of that period; however, mortality rates did not change much," said Kai Zhang, Ph.D., assistant professor in the Department of Epidemiology, Human Genetics & Environmental Sciences at UTHealth School of Public Health.

For 30 out of 31 days in August, temperatures exceeded 100 degrees in Houston. Emergency department admissions among those ages 65 and older rose by 8.9 percent during the heat wave. Studies have shown that the elderly are especially affected by excess heat.

Previous research has established that heat waves in California and Chicago led to high mortality rates and emergency department visits, especially in Chicago where a heat wave caused 692 fatalities.

"It could be that the mortality rate did not change much in Houston because 98 percent of residents had air conditioning and were acclimated to the hot weather. In Chicago, only 76 percent of residents had air conditioning, which may have been a factor for the number of heat wave-related deaths there," said Zhang.

A health-based heat warning system may help prevent emergency department admissions in the future in Houston, Zhang says. According to the National Weather Service Houston/Galveston office, the criteria used for heat advisories is having two consecutive days with a heat index at 108 degrees or higher, either forecast or observed. Heat index is a combination of temperature and relative humidity.

"These findings could provide insights for local government agencies and communities to design better preparation to reduce adverse health effects of future heat waves," said Charles Begley, Ph.D., co-author of the study and professor in the Department of Management, Policy & Community Health at UTHealth School of Public Health.

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2011 Houston heat wave led to significant rise in emergency department visits

Babies with two fathers or two mothers could soon become a reality Egg and sperm cells can be made using skin from two same sex adults Scientists say technique could be used to create baby two years from now Breakthrough could help infertile or gay couples to have children But concerns have been raised about prospect of 'designer babies'

By Ben Spencer for the Daily Mail

Published: 20:21 EST, 22 February 2015 | Updated: 20:22 EST, 22 February 2015

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Babies with two fathers or two mothers could become a reality after a breakthrough by researchers at Cambridge.

They have shown that it is possible to make human egg and sperm cells using skin from two adults of the same sex.

The development could help men and women who have become infertile through disease or gay couples to have children.

But critics voiced concern, arguing that the breakthrough brings closer the prospect of 'designer babies', in which the looks, character and health attributes of children would be selected by parents.

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Scientists say they can make human egg from skin of two men