The Evolution and Medicine Review

…bridging the gap.

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Where there is smoke there may be human evolution

Researchers at Penn State have discovered a mutation in the gene for the aryl hydrocarbon receptor which would desensitise an individual’s reaction to the aromatic hydrocarbons in smoke from cooking fires, and in meat roasted upon them, and through exposure to burning vegetation in the environment. This would cause these chemicals to be broken down more slowly in the body which, they hypothesise, would present a less toxic burden to body cells. The mutation is ubiquitous in modern humans but was not shared by Neanderthals who, therefore, might have suffered more from respiratory problems associated with smoke inhalation, a range of cancers, decreased reproductive capacity and an increased susceptibility to respiratory viruses.

Smoke tolerance, the researchers say, could have given our immediate human ancestors a competitive edge in a world where the use of fire for heating, ground clearing, and cooking had become widely adopted.

You can find the research paper here in the Journal of Molecular Biology and Evolution and you can read popular accounts of the discovery in Science Daily and at Physorg.

Earliest Human Cancer Found in 1.7-Million-Year-Old Bone

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Micro-CT image showing a osteosarcoma in an ancient toe bone. PHOTOGRAPH BY PATRICK RANDOLPH-QUINNEY, UCLAN

Many thanks to Cynthia Beall for flagging up this interesting Scientific American piece about the discovery of an osteosarcoma in the toe bone of an as yet unidentified hominin discovered in the Swartkrans Cave and dated to around 1.7 million years ago. The source paper is from the South African Journal of Science. Popular accounts of this find – such as the SciAm piece – seem to find it really interesting that cancer has been found in such an old specimen, citing an orthodox view that much cancer is the direct result of modern life-styles typified by obesity, cigarette and alcohol use, and environmental carcinogens. However, while these factors have increased the incidence of cancer, as has relative longevity, it remains the case that cancer will always occur wherever and whenever cells are dividing. That is, after all, why long-lived massive animals like elephants and whales have multiple copies of the tumour suppressor gene p53. Given the acknowledged occurrence of cancer throughout the animal kingdom it should not come as a surprise when ultra-modern 3-D imaging exposes it in our ancestors. As the paper’s authors say in the Abstract: “The expression of malignant osteosarcoma in the Swartkrans specimen indicates that whilst the upsurge in malignancy incidence is correlated with modern lifestyles, there is no reason to suspect that primary bone tumours would have been any less frequent in ancient specimens. Such tumours are not related to lifestyle and often occur in younger individuals. As such, malignancy has a considerable antiquity in the fossil record, as evidenced by this specimen.”

For anyone interested there is another popular piece about this discovery, and a twin discovery of bone cancer in a specimen of Australopithecus sediba, in Physorg which has a link to the second paper in SAJC.

Decoding Human Accelerated Regions

Katherine Pollard, now at the Gladstone Institute, has done most, over the last decade, to research and identify small non-coding regions of the humane genome that have evolved very rapidly since the split from the last common ancestor with chimpanzees. Hence they are called human accelerated regions or HARs. In this superb piece for The Scientist she gives an overview of the field and its history. Pollard, to date, only knows the function of one or two HARs – HAR1, for instance is involved in normal brain development through its role as enhancer to the genes that control brain growth. It is likely that many or most of the HARs already identified will be found to be important because they act as gene regulators and enhancers. As such, far from being junk DNA, they probably have vital roles, not only in what sets us apart from the other higher primates, but in normal human development – and, if things go wrong, human disease processes.

The evolutionary origin of female orgasm

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I must admit to an internal debate on whether or not to post this piece on Meg Ryan Syndrome – otherwise known as female orgasm – until I saw that the second author on the paper in the Journal of Experimental Zoology was Gunter Wagner – a professor at Yale who has already made a number of visionary contributions to reproductive medicine. Wagner and lead author Mihaela Pavlicev have found one dominant theory – that female orgasm arose as a fortunate byproduct of male orgasm that accompanies sperm transfer – unsatisfactory. They have trawled through many mammalian species, from humans and other primates, through a range of mammals including woodchucks, dolphins and Bactrian camels, down to aardvarks and koala bears, to discover which species are typified by induced ovulation, where copulation is needed to trigger ovulation, and which are typified by spontaneous ovulation, where eggs are released at a certain point in every ovulatory cycle regardless of copulation. They then correlated the distance of the clitoris from the copulatory canal with each form of ovulation.

Their main point is that induced ovulation is an ancestral trait where a pronounced copulatory hormonal surge accompanies ovulation and is necessary to command the ovary to release its eggs. This hormonal surge is similar to that experienced by women at the point of orgasm but where it is no longer needed for ovulation to occur. They noticed that induced ovulators tended to have the clitoris positioned inside or very close to the sex canal/vagina because it is essential for copulation to stimulate it in order for the hormonal surge and ovulation to ensue. Spontaneous ovulators are released from this necessity and this is why they found that spontaneous ovulation is associated with increasing distance of the clitoris from the vagina. Which could explain why Meg Ryan’s behaviour in the restaurant was the envy of her fellow female diners – “I’ll have what she’s having!” Orgasm in human females can be a bit of a hit or miss affair because it cannot be guaranteed by penetrative sex.

The publication of the J. Exp. Zoology paper is accompanied by a very readable piece by Nicola Davis in The Guardian newspaper.

Pathogens, the immune system and social behaviour

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Lead author Tony Filiano (left) together with     Jonathan Kipnis

Over thirty years ago, a veterinary scientist from the University of California at Davis – Benjamin Hart – first drew the links between pathogenic infections, the immune response, and behaviour, when he formulated his theory of sickness behaviour. At the onset of a severe infection, he said, an animal or human develops a fever thanks to the action of pro-inflammatory immune messenger molecules called cytokines. The high body temperature, he said, was an evolved adaptation to efficiently fight pathogens but the cytokines that stoke fire in the body are capable of being transported to the brain, either through the bloodstream or by hitchhiking along the vagus nerve, and produce behavioural changes like depression, social withdrawal, loss of appetite and sleepiness that cause the organism to, in effect, hibernate while the infection, and immune attack against it, runs its course. Now, in a fascinating paper in Nature, Jonathan Kipnis and his co-workers provide another compelling story of evolved links between infection, the role of the immune system, and changes in social behaviour.

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What is evolutionary medicine?

is the first of Ten Questions answered  by Randolph Nesse in an essay at http://evmedblog.org

Evolution & Medicine Symposium in Barcelona October 6-7

15TH CRG SYMPOSIUM: EVOLUTION AND MEDICINE. 6-7 OCTOBER 2016, BARCELONA, SPAIN
The conference aims to explore the interplay of evolution and medicine, acting either in our own species or on species directly affecting our well being. We will explore topics in cancer evolution, the emergence of resistance to antibiotics and other drugs, the origin and evolution of pathogens, and the evolutionary influence on our own construction and predisposition to various diseases.

Speakers

Registration (Free until Sept 16) 

Deadly Australian soil bacterium sheds light on infection hypothesis for Alzheimer’s disease.

Burkholderia

Burkholderia pseudomallei www.npr.org

Researchers at Griffith University in Queensland, Australia, are the first to completely document the entire route by which bacteria can get into the brain by passing through the nasal mucosa, traveling up the trigeminal nerve, and entering the brain through the brainstem. James St. John and his colleagues infected mice with the soil bacterium Burkholderia pseudomallei, common in northern Australia and throughout South East Asia. Once sniffed up from rural dust the bacterium can travel to the brain in under 24 hours. The ensuing infection – melioidosis – is related to the disease glanders in horses and cattle and can lie dormant for up to 60 years, but if it erupts it is fatal in up to 50% of cases. These researchers believe the “royal road” they have discovered into the CNS may be shared by other bacteria like Staphylococcus and acne bacterium as well as by Chlamydia, which has been strongly implicated as a causative agent in Alzheimer’s disease.

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Viruses are the most potent drivers of human evolution

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A human T cell (blue) is under attack by HIV (yellow), the virus that causes AIDS.          SciTechDaily

What events have most shaped our human genomes since the split of our ancestors from the ancestors of chimpanzees? What has been the main driving force for human gene evolution? Climate comes to mind; nutrition also; ecology is linked to both. Then there’s social interaction which has driven the evolution of social intelligence. But the one factor that stands out, according to a recent eLIFE paper whose lead author is David Enard from Stanford University, is our interaction with viruses. Viruses have driven over 30% of all the adaptive amino acid changes (non-synonymous mutations) in our genomes, and are the most potent drivers of evolutionary change across mammalian genomes in general.

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New edited volume: Evolutionary Thinking in Medicine

Alvergne, Alexandra, Crispin Jenkinson, and Charlotte Faurie, eds. Evolutionary Thinking in Medicine: From Research to Policy and Practice. Springer, 2016.
(free preview available)

From the publisher’s webpage (Springer.com):
“The aim of this edited book is to provide health professionals, across a wide variety of specialisms, with a targeted access to evolutionary medicine. Throughout the book, the views of both medical and evolutionary scientists on the latest relevant research is presented with a focus on practical implications. The inclusion of boxes explaining the theoretical background as well as both a glossary for technical terms and a lay summary for non- specialists enable medical researchers, public health professionals, policy makers, physicians, students, scholars and the public alike to quickly and easily access appropriate information. This edited volume is thus relevant to anyone keen on finding out how evolutionary medicine can improve the health and well-being of people.”

Download Preface 1 PDF (55.1 KB)
Download Sample pages 2 PDF (181.6 KB)
Download Table of contents PDF (73.8 KB)

 

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