Archive for Medical Hypotheses
Global Warming Reduces Fertility
Posted by: | CommentsIcebergs melting, sea levels rising, islands disappearing, tropical temperatures in Yorkshire, vineyards in Scotland … there’s no end to the changes being predicted due to the effects of global warming. But could one of its most significant effects already be happening and have gone unnoticed? Is global warming to blame for the worldwide drop in fertility and birth rates?
According to research by a team at Columbia University College of Physicians and Surgeons, New York and Columbia-Presbyterian Medical Center, the evidence points that way: “The results of our analyses are consistent with the underlying premise that temperature change affects fertility and suggests that human fertility may have been influenced by change in environmental temperatures,” they say.
There is no doubt that fertility has declined in the industrialized world and, to a lesser extent, in developing countries. While social and economic changes may account for some of the change, it does not explain it all. Nor does it explain why other research is consistently finding that the sperm count is going down in a number of countries.
The New York team say the decline is real, and that by 2040 some nations will have negative population growth – in other words, their populations will fall.
In their research, the team used birth data from 19 countries for the last century and compared these with figures from the National Aeronautics and Space Administration (NASA) on global air temperature changes over the same period. The results show that in each of the 19 countries there was a marked decline in the birth rate over the century. In the USA, the birth rate dropped from 30 births per 1,000 people to 10 over the course of the century. A similar drop was found in most industrialized countries. Over the same period temperatures went up. “We found a remarkably strong inverse relationship between changes in temperature and birth rates in all 19 countries,” they say. Even when they took into account social, cultural and economic changes, the link with temperature persisted.
The researchers say that a number of studies have suggested a link between fertility and temporary temperature changes. For example, in hot countries, fertility varies with the seasons, with sperm counts lowest in the summer and highest in the winter. Laboratory research has confirmed that increases in scrotal temperature can reduce fertility.
“Our analysis leads us to believe that long-term changes in air temperature could influence human fertility,” say the researchers. “Similar to transient environmental temperature change, long-term environmental temperature change may mediate fertility by changes in sperm counts. It is certainly possible that as a result of global air temperature changes, sperm counts may have fluctuated, thereby affecting birth rates.”
They add, “If the relationship we found between temperature change and fertility is correct, then a drop in global temperatures may actually result in an increase in human fertility.”
The Reason for Chins
Posted by: | CommentsThey come in all sorts of shapes and sizes, and some are bigger than others. Some stick out while others recede, a few have dimples and many have spots, but by and large, the chin is a universal feature that is unique to modern man.
But what’s it for? Ancient man and Neanderthals didn’t have one, and the first chin did not appear until the arrival of Homo sapiens. So what’s the evolutionary purpose of a chin? Ears, nose, eyes, lips, even eyebrows and eyelashes all have obvious functions, but chins?
Until now, there have been two main theories. The first is that it has no function at all, it just happened, a sort of evolutionary structural blip, while the second suggests it helps with the chewing of food. The problem with the second theory is that the chin emerged at a time when the use of teeth for ripping raw food was not increasing, and may in fact have been declining.
To investigate other theories, dentists at Otago University, Dunedin, New Zealand constructed three-dimensional models of a human mandible with and without a chin and measured all the forces and angles that are experienced by the jaw in everyday use. They looked at the loading on muscles and bones from various activities to see what could have led to the evolution of the chin. Their research showed that when a tongue contracts at a 45-degree angle in a mandible without a chin, there are increased stresses and strains concentrated at exactly the point where the chin would be.
It’s known that bone can change shape in response to stress, so it is possible that the chin evolved over time in response to changing stresses and pressures from the tongue. But what was so different about the tongue of modern man compared to all those who had gone before? They all had tongues, so what was special about Homo sapiens? The answer is simple – speech.
The researchers say it’s thought that language first made its appearance among our common ancestors 50,000 years ago, which coincides with the emergence of the human chin. With the development of speech came a new repertoire of movements of the tongue and lips, generating different strains and stresses in the mouth and jaw which, say the researchers, resulted in the adaptive changes of bone to form the chin.
The tongue is designed for fast contraction and its rapid acceleration during speech generates highly repetitive forces at the area now occupied by the chin.
“We conclude that the forces generated during speech rather than those generated during mastication, shaped the chin of anatomically modern humans,” say the researchers. “We propose that strong, repetitive contractions of the tongue … demanded by the newly acquired facility of spoken language in modern humans, resulted in an adaptive remodelling of the chin.”They add, “This provides a new perspective on the generation of the chin and importantly suggests that its appearance may be related to the development of the human language.”
The Purpose of Ear Wax
Posted by: | CommentsHuman ancestors once lived in a watery habitat. That’s why, say supporters of the theory, most other land mammals have no conscious control over their breathing, while humans do. The voluntary control we have is, they say, comparable to that of semi-aquatic mammals which need to inhale air before they dive.
Over the years the theory has been attacked as unscientific and too vague, and even ridiculed. But according to research in Belgium, modern humans have many rudimentary characteristics that support the theory. Noses, for example, are perfecdy designed to stop water getting into the lungs while swimming, and hair is ideally aligned for swimming. And why do we have many more fat cells than land animals of a similar size? Could it be residual blubber from our seagoing days?
What’s more, says the research report, many common diseases and conditions may have their origins in our aquatic or semi-aquatic past, including sleep apnoea, acne, alopecia, dandruff, rhinophyma, myopia and osteoarthritis.
Take arthritis and varicose veins, for example. Most of us will suffer at some time from degenerative joint disease or osteoarthritis, and one in three adults will get varicose veins. Could it be that these disorders were less common in a watery habitat and that we suffer because there is no longer a counter-pressure of surrounding water?
And look at asthma. It’s unknown in apes, but according to the research, seals have broncho-constriction while diving, and deep-diving mammals close the bronchi completely during diving.
Then there is short-sightedness. In myopia the eyeball is too long, and at first sight there doesn’t seem to be any obvious advantage to it. But according to the research, closer scrutiny suggests a maritime link. Whales, seals and penguins are all nearsighted outside the water because they need the best vision for use in water. Thus myopia, it’s argued, is an adaptation to the different refractive power of water.
Obesity too has links to a previous watery life. According to the research, all sea mammals are thick-bellied, and in an aquatic habitat, the complications of obesity would have been far less because the fat would be supported by water.
And then there’s ear wax. When it’s wet it absorbs water and swells, and can block the ear canal. So when semi-aquatic man went into the water, any ear wax would swell and keep out infections, but man would not have lost hearing because the wax would have conducted sound waves.
“The abundance of ex-aquatic features and ex-aquatic diseases in man is an indication for a rather recent semi-aquatic phase in our evolutionary history,” says the report. “The ancestors of Homo erectus — perhaps no longer than two million years ago – were highly aquatic.”
Taking the Elevator for a Natural Birth
Posted by: | CommentsOn the face of it there did not seem to be a rational explanation. Out of 198 pregnant women with labour difficulties admitted to the hospital, 42 improved dramatically, gave birth spontaneously and naturally, and no longer needed the caesarean section they had been about to have.
Since their arrival in the hospital, all the women had been given conventional treatment for a difficult labour, but all had failed to respond. Then, for no apparent reason, they each gave birth naturally minutes before surgery was due to be carried out. Many of them gave birth either on the way to or just inside the operating theatre, and each had a normal vaginal delivery before any attempt at a caesarean was made.
Investigations by the researchers showed that these sudden, unexpected natural births often occurred while the patients were being transferred from the labour room to the operating theatre, which are on different floors of the hospital.
None of the patients had received any medication before being taken to the operating theatre which could explain the sudden change, so the researchers at Shiraz University of Medical Sciences, Iran looked for another explanation, particularly factors that were common to the women. What they found was that all of the women who had given birth naturally had travelled to theatre in the hospital elevator.
One of the causes of a difficult pregnancy is that the foetus’s head may be in an awkward position for a natural delivery, and the researchers suggest that the sudden movement of the elevator and the force of gravity may have changed the position of the foetus. That change in pressure, it’s argued, gave the foetus an opportunity to move to a better position, leading to a spontaneous, normal delivery.
“The elevator can give the power to the foetus to have a rotation of the head to a more proper position for the rest of the labour,” say the researchers. “We propose this possibility, that the sudden thrust of the elevator and the force of gravity had an impact on the position of the foetus and gave the foetus the opportunity to change to a better position which was proper for the rest of the vaginal delivery process.”
The Date You Will Die Can Be Calculated
Posted by: | CommentsThe only certainty in life is death. But exactly when that moment comes varies widely among individuals, countries and races. In Botswana, for example, the average lifespan is around 35, while in affluent Andorra it’s in the mid-eighties. Lifespan also varies widely among families living in the same country and from the same race and culture. While the average lifespan in the UK is in the seventies and eighties, some families have members who live well into the nineties, while other families struggle to survive to retirement age.
Is it all down to luck or is it genetic inheritance that determines our sell-by-date? And if the date of our death is fixed, is it possible to find out when it will be?
Yes, according to research at Gifu University, Japan, the date can, in theory, be calculated, and the formula itself is quite simple. It’s called total immediate ancestral longevity (TIAL) and all you have to do is add up the ages at death of your six last relatives -mother, father and maternal and paternal grandparents – and divide the total by six.
That gives you your likely lifespan at birth. The only snag is that while the likely date of death may be pencilled into your DNA, it is also influenced by what you do during your life. Smoke 50 cigarettes a day and any genetic edge for longevity is likely to go up in smoke. What’s more, you may reduce the life expectancy of future generations of your family. But eat a good diet, exercise regularly and avoid unsavoury activities, people and substances and you may live longer than your blueprint suggests.
To test the accuracy ofTIAL, the researchers calculated scores for eminent scientists, including Charles Darwin, Albert Einstein and Irene Joliot Curie.
The TIAL scores for Einstein, Darwin, Curie were 390, 378, and 372 respectively, all considerably lower than the 477 of Jeanne Calment, the French woman who died in 1997 at the oldest authenticated age of 122 years and 164 days
The report says that since Darwin and Einstein exceeded their adjusted TIAL, nearly 14 per cent of their lifespan may have been the result of a good environment. In the case of Irene Curie, her father, Pierre, died in an accident at the age of 46, and her mother, Marie, also had a premature death at the age °f 66 due to excessive workplace radioactive exposure. Irene Curie’s TIAL score is 62 years. But she died four years short of that, at the age of 58 years, also due, at least in part, to excessive radioactive exposure.
The message from the report is that TIAL will tell you how long you will live if you have an average lifestyle. Live well and you will eke out a few more years, but pick up bad habits and you’ll lose years.
“TIAL score is a convenient and easily quantifiable longevity parameter which anyone interested in determining his or her longevity can use to estimate a tentative number,” says the report.
Jet Lag Triggers Mental Illness
Posted by: | CommentsThousands suffer the symptoms of jet lag every day. Insomnia, fatigue, lack of concentration, indigestion, memory problems, irritability and exhaustion are all experienced by those who travel at speed across three or more time zones, especially when the flight is eastbound.
Jet lag is caused by disruption of the body’s circadian rhythm or “body clock” which is involved in the timing of routines like eating and sleeping. For most people, the symptoms disappear in hours or at most a few days … or do they?
According to researchers at the Hebrew University and Hadas-sah Medical School, Israel, there may be a more sinister side to jet lag. They say the possibility of a connection between jet lag and psychiatric disorder seems to have been underestimated and suggest it could trigger existing or new cases of affective disorders, a group of conditions that include depression, anxiety disorder, panic attacks and various phobias. It might also be involved in schizophrenia.
“There is strong evidence relating affective disorders with cir¬cadian rhythm abnormalities,” they say. “It can be hypothesized that in predisposed individuals jet lag may play a role in triggering exacerbation or even de novo affective disorders. Furthermore, we propose the possibility that psychosis and even schizophrenia can be elicited by jet lag.”
There are, they say, a number of examples of psychotic symp¬toms occurring during long-distance trips, including cases of transit paranoid reaction, a condition blamed on changes of envi¬ronment, unfamiliar surroundings, the presence of strangers and a sense of isolation.
Results from an analysis of 359 people referred for psychiatric examination from Kennedy International Airport show that around 38 per cent had symptoms of paranoid schizophrenia, while others had manic depressive psychosis, psychotic depressive reaction and neuroses. Other research has, say the researchers, shown differences in levels of depression between east- and west¬bound travellers.
Just how jet lag triggers new episodes of mental illness or even the illness itself is not clear, but the hormone melatonin could be the villain.
Secreted by the pineal gland deep inside the brain, melatonin is a key player in the regulation of the circadian rhythm and helps the body know when it is time to sleep and when to wake up. In synthetic form, as a supplement, it’s widely used in some coun¬tries to combat the symptoms of jet lag itself.
But changes to the circadian rhythm and melatonin secretion abnormalities have also been linked to a number of mental disor¬ders, say the researchers, and they cite studies suggesting that abnormal melatonin metabolism may be directly related to schiz¬ophrenia. It’s also suggested that sleep deprivation affects mela¬tonin production and may be linked to mania.
Birthmarks Are Proof of Reincarnation
Posted by: | CommentsWhen researchers began investigating children who claimed to remember a previous life, the findings themselves bordered on the supernatural. Among those children who also had phobias, the cause of the fear was nearly always found to be the same as the mode of death they claimed to have witnessed in a prior existence. A child who claimed to remember a life that ended in drowning, for example, was more likely to have a phobia of being immersed in water. In fact, the researchers found that 6 out of 10 children who remembered a death by drowning had a phobia of water. A similar trend was found for snakes and guns.
There are many reports of children talking about a previous life, but relatively few have been investigated in any detail. Where there has been any kind of inquiry, the main method, says the report from a researcher at the University of Virginia, has been interviews with parents or carers of the child and with people connected with the deceased person concerned, backed up by postmortem reports.
According to the Virginia research, in the majority of cases investigated – 67 per cent of 856 cases in one series – the dead person who had been named by the child could be identified, and the facts of their life and death matched the child’s statements.
The report says that many disorders or abnormalities seen in medicine and psychology cannot be fully explained by genetics and environmental influences. As examples it cites phobias in early infancy, gender identity disorder, differences in temperament seen soon after birth and unusual birthmarks.
The report suggests that what it calls the hypothesis of previous lives can explain a number of these phenomena which defy more rational explanation.
Take phobias. In 387 children who claimed to remember a previous life, phobias occurred in 141 (36 per cent) of them. In many cases, say the researchers, the child developed the phobia before he or she had spoken about a previous life. In one study, 56 per cent of parents were not able to explain how their child had developed a phobia of water.
The report says that many children who claim to remember a previous life also have birthmarks that correspond to the position of wounds in the life apparently remembered. Out of 895 cases investigated, from nine different countries and cultures, 309 (35 per cent) had such birthmarks. The site of the birthmarks and wounds or other marks on the body of the deceased was verified by post-mortem reports.