Archive for the ‘Evolution’ Category

Can gorillas find a role in the world?

April 19, 2020

Some 40 million years ago there was a primate which was the common ancestor of all the current great apes. The primates were established first in Africa and Asia and then some found their way, somehow, across the ocean to South and Central America. They were restricted to forest areas and were not to be found in northern climes (Europe, N America, Asia). Great deserts and mountain ranges were a major barrier to their spread. They did not reach Australia even though the body of water to be traversed was shorter than that to S America.

 

Non-human primate range

The appearance of new species of apes was not something that happened across the entire range of the primates. In South and Central America, apes did not evolve. Gibbons and orangutans only appeared in South-East Asia. Gorillas, chimpanzees and the precursors of humans appeared only in Africa.

Knowledge about evolution has exploded in the last century especially now as genetic analysis is getting into its stride. But the common feature with the growth of knowledge is that the questions, too, grow. Why did the ancestors of all apes break away from the parent primate line? What survival advantage led to the gibbons separating from the ancestral ape line to become a separate species? The survival advantages then that caused the speciation of the gorilla ancestors are probably no longer valid now. When a species evolves and a new species appears, the parent species may become extinct, or may well continue down other, separate evolutionary paths. But not all these many paths can be successful. At any given time many of the ongoing evolutionary paths being followed will – and must – be dead-ends leading eventually to the extinction of the dead-end branches. The appearance of every new species must have been because some non-standard individuals, in that place, at that time, exhibited some survival or reproductive advantage over their more “standard” relatives. Clearly the pressures and conditions that caused orangutans and gibbons to appear in SE Asia were not of significance in South and Central America. Neither were the conditions and pressures which caused gorillas and chimpanzees and the species homo to appear in Africa of significance in other parts of the world. Equally the conditions in Africa did not give rise to gibbons or orangutans.

What then were the advantages of being a gorilla – when gorillas evolved – that are now of very little benefit?

The reasons for the splits at A, B, C, D and E are still more a matter of speculation rather than of knowledge.

The current status of a species can only be measured by its numbers. Dinosaurs may once have been of high status and were clearly successful for a long time but – as with every other extinct species – they are all, now, failed species. (Since birds do originate from the dinosaurs then they, at least, represent some very successful current species). If we consider just the surviving ape species (gibbons, orangutans, gorillas, chimpanzees and humans), there is a striking difference in their current status as species.

We have to go back about 40 million years to find a common ancestor. The most striking difference is that which separates humans from all other species – the control of fire. It makes the “fire and cooked meat” theory of human brain development seem very plausible.

Smithsonian Magazine:

Thus, the unprecedented increase in brain size that hominids embarked on around 1.8 million years ago had to be paid for with added calories either taken in or diverted from some other function in the body. Many anthropologists think the key breakthrough was adding meat to the diet. But Wrangham and his Harvard colleague Rachel Carmody think that’s only a part of what was going on in evolution at the time. What matters, they say, is not just how many calories you can put into your mouth, but what happens to the food once it gets there. How much useful energy does it provide, after subtracting the calories spent in chewing, swallowing and digesting? The real breakthrough, they argue, was cooking.

I find watching gorillas (on film) compulsive. When I have seen them in zoos, they are magnificent but deeply tragic figures. They radiate a benign strength which is more than impressive. They are quite intelligent. It is claimed they have an IQ around 40 -50, though applying human IQ tests on them is largely meaningless. Their motor skills develop faster than with human infants and even if some have learned the meaning of some human words, gorillas do not have language. Gorillas are a dying species and, as such, are a failing species. “Conservation” is concerned with the survival and protection of individuals and groups. Though laudable, these efforts only freeze the species within the shrinking habitat they are comfortable with and in the unsuccessful form they have reached.

The gorilla as a species has reached an evolutionary dead-end. I don’t want gorillas to disappear, but to keep them in their frozen, unsuccessful, evolutionary state in zoos or reserves or protected habitats does not seem right either. The conservation practiced today, which makes no provision for the further development of a species, is both unethical and immoral. Other species which adapt and find a role to play in the world of today are not threatened. It is not necessary for a species to find that role within human society as livestock and household pets do. But the survival of livestock and pets is as slaves to humans. Birds and insects remain free of human control but have adapted to varying degrees and continue together with humans. Fish and sea-creatures don’t compete for habitat with humans but do constitute prey. Foxes and rodents and even urban leopards are adapting to continue in freedom and in parallel with humans. It is more difficult for primates. The challenge is to find a way for a species to develop and move forward in the reality of a world dominated by humans. When conservation denies reality and merely tries to go back to some scenario from the past it does no service to any species.

How then can we find a free and meaningful, role for gorillas (or tigers) in a world dominated by humans but which is not an evolutionary cul-de-sac?


 

Apocalypse Now (yet again) or the false god of biodiversity

May 7, 2019

Here we go again.

The UN (who else) has its annual freak-out about a million species being threatened by humans. (There are about a trillion species on Earth). The 6th mass extinction is upon us! The solution is mass suicide by humans! The humans left will be happily dead ever after. Failing that we could have World Government.

When life on earth began, there was no biodiversity. As individual life-forms survived environmental changes, new species were created. Sometimes the parent species survived and sometimes not. Sometimes the new species did not survive further changes. The results of survival we call evolution. As for anything else there is an optimum number of species for any given environment, in any given place at any given time. Too many species is a worse thing than too few. Too few, and new species will always be formed to exploit the available environment. Too many, and every species is miserable.

All invasive species are – by definition – successful species. All endangered species are – also by definition – failing species. “Protecting” failed, but somehow attractive, species is entirely an emotional response by humans but it has no rational purpose. The rational and responsible approach to biodiversity would be to genetically modify failing species to survive or to let them become extinct in a world where they have no place.

Judging by the posts I have been driven to write in recent years, I must find all sanctimonious, self-righteous apocalypse predictions somewhat obscene.

Mass extinctions correct for evolution’s greater than 99% failure rate

Earth has too many failed species and 30% need to go extinct

There was no biodiversity to begin with

Raging biodiversity – “One trillion species on earth”

I just repeat my post from 2018.

The biodiversity myth (or How many species should there be?)

How many species should there be?

In any given environment, even with no change in the environment, natural selection will see to it, given enough time, that the number of species will increase to fill the available space. Competition between species will increase with increasing biodiversity. Species incapable of coping with the competition will restrict themselves to protected niches or disappear. As environment changes, modifications will also follow. As environment changes, species which were once viable may become extinct, continue in a suitable niche or adapt.

As far as we know the earth is the only planet on which life has developed.

……… 

Time and the laws of the Universe were established soon after the Big Bang singularity occurred some 13.8 billion years ago. ………… The earth itself was formed when it congealed about 4.54 billion years ago……. Chemistry between atoms and molecules happened. About a billion years later chemistry became biochemistry. Somehow RNA molecules (the RNA world) appeared. Some of these were replicating molecules. Some of these arranged themselves into single celled organisms. Single celled life began. Around 500 million years ago, complex multi-cellular life took off.

In the 500 million years since there have been at least 10 major extinctions and 5 Great Mass Extinctions. The last one was around 50 million years ago when the large dinosaurs “disappeared” (though that disappearance may have taken many thousands, or even hundreds of thousands, of years). Nevertheless it was the spaces left vacant in the environment which enabled, and were filled by, the mammals and in turn the primates and humans. …..


 

When the encyclopedia in your pocket is wired into your brain

January 20, 2019

All human knowledge is not, yet, available on the web. All the knowledge which is available on the web is not, yet, available to each of us. But all that is available on the web is already available to each of us who has a connected smart phone in a pocket. With every connected smart phone there is an encyclopedia in a pocket.

But using such an encyclopedia is not, yet, instantaneous. It is not yet a part of your brain. It is not just the choice of browser or search engine (e.g. Google) or the repository (e.g.Wikipedia). You still have to search the web. You still have to ask the right question. You still have to discard the advertisements and the fake news and select the relevant information. It takes a little time. By the time you find the right answer the conversation may have moved on to another topic, such that presenting the information you found in your pocket may be embarrassingly irrelevant.

Nevertheless, everyone with a connected smart phone now has an encyclopedia in their pocket. And, I would guess, this encyclopedia will be implanted and connected to the brain within the next 50 years.

We are already in the age of implants.

Currently, implants are being used in many different parts of the body for various applications such as orthopaedics, pacemakers, cardiovascular stents, defibrillators, neural prosthetics or as drug delivery systems. Concurrent with the increased life span in today’s world, the number of age-related diseases has also increased. Hence, the need for new treatments, implants, prostheses and long-term pharmaceutical usage as well as the need for prolonging the life span of the current techniques has increased. 

Implants where thoughts can be used to control computers are already with us. Brain-computer interfaces (BCI’s) which were first thought of in the 1970s are now with us to stay.

image from Frontiersin.org

When drone warfare emerged, pilots could, for the first time, sit in an office in the U.S. and drop bombs in the Middle East. Now, one pilot can do it all, just using their mind — no hands required.

Earlier this month, DARPA, the military’s research division, unveiled a project that it had been working on since 2015: technology that grants one person the ability to pilot multiple planes and drones with their mind.

“As of today, signals from the brain can be used to command and control … not just one aircraft but three simultaneous types of aircraft,” Justin Sanchez, director of DARPA’s Biological Technologies Office, said, according to Defense One.

….. Back in 2016, a volunteer equipped with a brain-computer interface (BCI) was able to pilot an aircraft in a flight simulator while keeping two other planes in formation — all using just his thoughts, ….. In 2017, Copeland was able to steer a plane through another simulation, this time receiving haptic feedback — if the plane needed to be steered in a certain direction, Copeland’s neural implant would create a tingling sensation in his hands.

We cannot yet, at will, without noticeable delay, mentally call for and access some particular information from the entire store of human knowledge.  But it is no longer science fiction to imagine people with an implant which has all the abilities of a mobile, smart phone. It will be an implant where the input/output interface would no longer require the use of fingers or the reading of a physical screen. Your thoughts (and perhaps also sub-vocalisations) would be sufficient to trigger the appropriate questions to the web. The answers would be projected onto your eyes or enter your brain subliminally. Humans would have to become far more practiced not only at distinguishing between interfacing with the external world and internally connecting with the web, but also with mental multi-tasking in a way never required before.

Maybe not in 10 years but surely within 50.


 

And then came counting

August 25, 2018

Origins of human cognitive development go back a lot longer than was once thought. Our first bipedal ancestors who came down from the trees more than 5 million years ago, had  already some concept of “more” and “less” and  perhaps even of rudimentary numbers upto 3 (as rhesus monkeys have today). Genetic analysis of ancient bones is showing that the origin and development of modern humans needs to be taking the Neanderthals and the Denisovans into account and perhaps has to go back at least to the time of a common ancestor from over 1 million years ago. Just considering the last 200,000 years is no longer enough.

I have no doubt that the mastery of fire, the eating of cooked meat, the growth of the brain and, above all, the increased need for cooperation were interconnected and drove human cognitive development. Whether developments happened in one place and spread or happened at many places, perhaps at many times, will always be a matter of speculation. But it is not so difficult to come up with a not implausible time-line of the key developments which gave us first counting and then tallying and arithmetic and geometry and now complex number theory. The oldest evidence we have of counting are tally-sticks from over 50,000 years ago. But counting surely started long before that.


Related:

What led humans to counting and when?

The origins of base 60


 

Invasive species and opposing natural selction

June 1, 2018

Sweden is planning to declare the mouflon to be an invasive species. It would then be politically acceptable to eradicate the species.

“The mouflon (Ovis orientalis orientalis group) is a subspecies group of the wild sheep (Ovis orientalis). Populations of O. orientalis can be partitioned into the mouflons (orientalis group) and the urials (vignei group). The mouflon is thought to be one of the two ancestors for all modern domestic sheep breeds.” – Wikipedia

 

I find much of “conservation” sanctimonious, hypocritical and illogical.


 

Extinction is normal

April 17, 2018

Living things evolve, dead things can be remembered but extinction is normal.

I have no objection to expressions of regret, but I find the hand-wringing and sanctimonious claptrap about the extinction of species, languages and cultures illogical and without thought. I don’t miss the dodo or any of the dinosaurs. I don’t miss Latin or Sanskrit (even though I had to sit through boring lessons in both). It is only a natural course of development that isolated Amazonian tribes have disappeared as their members have joined the rest of the world. I don’t miss the cannibalistic cultures which have disappeared. The recent splurge of nonsense about the “death of the last known male, northern white rhino” was a case in point. It may be a matter of some regret that this particular individual died a natural death, but the end of an unfit sub-species of rhino is not an event requiring the mawkish sentimentality that flooded the media.

Extinction is normal.

Species evolve to survive or they go extinct. Languages evolve and they die when they are of no use to anyone anymore. Cultures evolve and merge with other cultures or they try to remain separate as a distinct, (often racial) identity by isolation and inevitably they die out. The cultures that disappear don’t survive because they are not viable in the world they live in. Regret is one thing, but trying to artificially protect non-viable species, languages or cultures or peoples by putting them in a “zoo” is mawkish and irrational and, ultimately, unethical. Keeping backward tribes isolated to “preserve” their cultures and freezing them into backwardness (by preventing them from merging or being absorbed by the world) is immoral. Freezing individuals from unfit species in a zoo, and neither helping them to evolve nor allowing the species to go extinct, is immoral. Preserving dead languages is of academic interest and does not prevent the extinction of languages which no longer serve a useful purpose.

To the best of our knowledge there are about 7,000 languages recognised today. Depending upon when language began (between 50,000 and 200,000 years ago) between 90 and 99% of all languages are now extinct. Written languages are much younger of course. An extinct language is a matter of history. Some languages evolved and produced versions still in use today. Others did not. We know about some of these because they developed writing and left some records which have survived. Languages die a natural death when they stop being used. Of course there is nothing wrong in speakers of dying languages trying to revitalise them. Governments have sometimes tried to promote particular languages (French, Hindi), and sometimes to suppress some (Welsh, Sami). Languages have been invented (Esperanto or Klingon). Most of these attempts of artificially creating, protecting or suppressing language are futile. The ultimate arbiter of language (and of grammar and of spelling) is usage.  The real question should not be whether a language is “endangered” and should be protected but whether a language serves any useful purpose. If it does, it will survive. If it does not, it should not survive. Endangered languages should be recorded for history and allowed to die in peace.

We don’t know how many species are alive today. Estimates have ranged from 10 million to 14 million, of which over 86 percent have not yet been described. A 2016 study even concludes that Earth currently has 1 trillion species. Whatever the actual number, what is known is that over 99% of all species that ever existed are now extinct. By the time a failing species is formally considered to be endangered, it is almost irrelevant to the ecological system it is embedded in. Tigers, as an example, are restricted only to areas of captivity (whether zoos or reserves). Even in some reserves where they are nominally free, the species is of no great significance to the bio-system. A species may well be going extinct because it is losing habitat to humans, but that in itself is a failure of that species. Some species are adapting to man, but where conservationists intervene to “protect” species they always do so by freezing the species into some form of captivity. They never try to help that species to adapt genetically to survive in its new environment. This form of conservation may be emotionally satisfying for humans but is of little consequence in the sustainable survival of the endangered species. Evolution produces far more failed species than successful ones. The detritus of evolution needs to be cleaned out from time to time. A mass extinction is one way to muck out the evolutionary stables. Currently there are too many species surviving and around 30% probably need to be washed away into extinction.

As with language and species there is much energy and misguided thinking expended in the protection of “indigenous peoples” and outdated, non-viable cultures. Much of this “protection” is about “freezing” these humans and their cultures into unsustainable conditions in what are effectively human zoos or reserves.

There are approximately 370 million Indigenous people in the world, belonging to 5,000 different groups, in 90 countries worldwide. Indigenous people live in every region of the world, but about 70% of them live in Asia.

The long term survival of tribes and indigenous peoples is by them joining or being absorbed by the mainstream or of reaching a critical mass such that they can have an autonomous survival. Genetic isolation (or genetic purity as practiced by some groups) is not sustainable in the long term. The Sentinelese are still apparently in the “stone-age” and both isolated and captive. Is it better (for whom?) to allow them to remain isolated and doomed or to bring them into the mainstream which would effectively eliminate them as a separate but backward culture?

Extinction is normal for peoples, languages, cultures and for species. To struggle against extinction is just a part of survival and also normal. But when extinction does occur, it may be a matter of regret and even of sorrow, but it is normal and morally neutral. But “conservation” by freezing language or culture or species or peoples into a “failed” condition is immoral.


Related:

Evolution is indifferent to species survival

Conservation denies tigers a future as a species

There was no biodiversity to begin with


 

Life exists as a succession of identities

November 18, 2017

Life is an abstract concept manifested as living things. The thread of life has no discernible beginning.

Life – to be life – must be manifested in an entity capable of reproduction. The elements displaying life either continue or come to an end. The thread is carried as a possibility by every sperm and every egg but the sperm and egg cannot themselves reproduce. Most of these possibilities come to an end before the two combine. If – and only if – a sperm and egg do combine, then life continues as, and within, a unique identity created by that combination. It is the creation of the identity – at conception – which continues life. About one in 300 billion sperm survives to combine with about one in 200 eggs to create an identity. It is a unique genetic identity. That identity, first as a fetus may end before birth. Or it may continue after birth as a child. It may grow to be an adult human and give rise to further sperm or eggs before itself coming to an end. When that identity qualifies to be considered a human entity and protected by society is a choice for the societies and the individuals concerned. Most societies start assigning the identity some rights and protections before birth but only after about 20 weeks of life as a fetus.

There is little doubt, however, that a unique genetic identity is created at conception, whether in a test tube or in a womb. At what stage of development that identity achieves consciousness and then self-awareness is not certain but almost certainly only after a rudimentary brain has formed. That would be some weeks after conception but probably some little time before birth. At what point that identity is to be afforded legal “rights” is then a matter for the surrounding society to determine.

Until the identity reaches birth – whether by natural or by artificial means – it has no options and no choices to exercise. Whether self-aware or not, its existence is in the gift and the power of others. It starts acquiring choices and freedoms of action only after birth, as allowed or constrained by its own development and the rules of the society it finds itself in.

Life then only exists as a succession of identities.

To trace the beginning of life would require going back from identity to identity to the specific cells some 3.7 billion years ago. A collection of sperm and eggs may contain the elements for life to continue but do not in themselves constitute life. The beginning of an identity is not the beginning of life. But the act of conception brings a unique identity into being and it is surely the beginning of a specific new life.

Life may be continuous as a concept but can only be realised and manifested as a succession of unique, discrete identities.


 

Evolution is indifferent to species survival

November 11, 2017


 

Early hominins left Africa 6 million years ago

September 3, 2017

A foot print found in Crete is probably that of an early hominid and was made 5.7 million years ago.

The single Out-of-Africa theory sometime around 70,000 years ago is already obsolete. It was more likely to have been multiple hominin crossings out of Africa into both Europe and Asia. The expansion of homo sapiens sapiens is more likely to have been in  at least two waves out of Africarabia.  Homo erectus appeared around 2 million years ago while homo sapiens appeared about 1 million years ago.  Homo sapiens sapiens then split from homo sapiens neanderthalensis around 600,000 years ago. So the footprint found is that of a human ancestor after the split with chimpanzees (c. 8-9 million years ago), after the beginning of bipedalism but well before homo erectus appeared.

image from physorg

The paper is

Gerard D. Gierlińskia et al., Possible hominin footprints from the late Miocene (c. 5.7 Ma) of Crete? Proceedings of the Geologists’ Association, 2017 DOI: 10.1016/j.pgeola.2017.07.006

As the Uppsala University  press release puts it:

….. Ever since the discovery of fossils of Australopithecus in South and East Africa during the middle years of the 20th century, the origin of the human lineage has been thought to lie in Africa. More recent fossil discoveries in the same region, including the iconic 3.7 million year old Laetoli footprints from Tanzania which show human-like feet and upright locomotion, have cemented the idea that hominins (early members of the human lineage) not only originated in Africa but remained isolated there for several million years before dispersing to Europe and Asia. The discovery of approximately 5.7 million year old human-like footprints from Crete, published online this week by an international team of researchers, overthrows this simple picture and suggests a more complex reality. …….

The new footprints, from Trachilos in western Crete, have an unmistakably human-like form. This is especially true of the toes. The big toe is similar to our own in shape, size and position; it is also associated with a distinct ‘ball’ on the sole, which is never present in apes. The sole of the foot is proportionately shorter than in the Laetoli prints, but it has the same general form. In short, the shape of the Trachilos prints indicates unambiguously that they belong to an early hominin, somewhat more primitive than the Laetoli trackmaker. They were made on a sandy seashore, possibly a small river delta, whereas the Laetoli tracks were made in volcanic ash. …….

…… During the time when the Trachilos footprints were made, a period known as the late Miocene, the Sahara Desert did not exist; savannah-like environments extended from North Africa up around the eastern Mediterranean. Furthermore, Crete had not yet detached from the Greek mainland. It is thus not difficult to see how early hominins could have ranged across south-east Europe and well as Africa, and left their footprints on a Mediterranean shore that would one day form part of the island of Crete.

‘This discovery challenges the established narrative of early human evolution head-on and is likely to generate a lot of debate. Whether the human origins research community will accept fossil footprints as conclusive evidence of the presence of hominins in the Miocene of Crete remains to be seen,’ says Per Ahlberg.

Abstract

We describe late Miocene tetrapod footprints (tracks) from the Trachilos locality in western Crete (Greece), which show hominin-like characteristics. They occur in an emergent horizon within an otherwise marginal marine succession of Messinian age (latest Miocene), dated to approximately 5.7 Ma (million years), just prior to the Messinian Salinity Crisis. The tracks indicate that the trackmaker lacked claws, and was bipedal, plantigrade, pentadactyl and strongly entaxonic. The impression of the large and non-divergent first digit (hallux) has a narrow neck and bulbous asymmetrical distal pad. The lateral digit impressions become progressively smaller so that the digital region as a whole is strongly asymmetrical. A large, rounded ball impression is associated with the hallux. Morphometric analysis shows the footprints to have outlines that are distinct from modern non-hominin primates and resemble those of hominins. The interpretation of these footprints is potentially controversial. The print morphology suggests that the trackmaker was a basal member of the clade Hominini, but as Crete is some distance outside the known geographical range of pre-Pleistocene hominins we must also entertain the possibility that they represent a hitherto unknown late Miocene primate that convergently evolved human-like foot anatomy.


 

Manliness has more than halved in western men since 1973

July 26, 2017

There is a new paper, a meta-review, receiving much attention.

The manliness of western men has more than halved between 1973 and 2011. It reports a significant ongoing decline in sperm concentration and sperm counts of Western men. It seems that “between 1973 and 2011, the researchers found a 52.4 percent decline in perm concentration, and a 59.3 percent decline in total sperm count, among men from North America, Europe, Australia and New Zealand ….  In contrast, no significant decline was seen in South America, Asia and Africa.”

Being a meta-review this study does not shed light on the causes of this drastic decline in the manliness of western men. It speculates that this may be due to chemicals or lifestyle or smoking or obesity or pesticides or some other factor. This speculation is just speculation and smoking or pesticide use would have caused stronger effects in Asia. They are quite right, however, in not following the sheep and including global warming as a possible cause. However they seem to be ignoring some other relevant factors.

I am inclined to think that the decrease of manliness among western men sounds more like a psychological reaction to political trends. Western society just values “manliness” much less than it used to. So other factors which probably need to be considered include:

  1. the increase of gender ambiguity
  2. the decrease in men’s social status
  3. the decline of political leadership in the west,
  4. the spread of political indecisiveness,
  5. the decline of corporal punishment in schools,
  6. the decline of femininity

It stands to reason that if gender difference is eliminated then sperm count and concentration will also decline. It follows that eliminating gender difference will result in the elimination of reproduction and species extinction.

Hagai Levine et al. Temporal trends in sperm count: a systematic review and meta-regression analysis. Human Reproduction Update. DOI: 10.1093/humupd/dmx022

MedicalXpress writes:  ….. between 1973 and 2011, the researchers found a 52.4 percent decline in perm concentration, and a 59.3 percent decline in total sperm count, among men from North America, Europe, Australia and New Zealand ….  In contrast, no significant decline was seen in South America, Asia and Africa. ….. The study also indicates the rate of decline among Western men is not decreasing: the slope was steep and significant even when analysis was restricted to studies with sample collection between 1996 and 2011. ….. 

While declines in sperm count have been reported since 1992, the question has remained controversial because of limitations in past studies. However, the current study uses a broader scope and rigorous meta-regression methods, conservatively addresses the reliability of study estimates, and controls for factors that might help explain the decline such as age, abstinence time, and selection of the study population.

“Given the importance of sperm counts for male fertility and human health, this study is an urgent wake-up call for researchers and health authorities around the world to investigate the causes of the sharp ongoing drop in sperm count, with the goal of prevention,” said Dr. Hagai Levine, the lead author and Head of the Environmental Health Track at the Hebrew University-Hadassah Braun School of Public Health and Community Medicine, in the Hebrew University of Jerusalem’s Faculty of Medicine.

The findings have important public health implications. First, these data demonstrate that the proportion of men with sperm counts below the threshold for subfertility or infertility is increasing. Moreover, given the findings from recent studies that reduced sperm count is related to increased morbidity and mortality, the ongoing decline points to serious risks to male fertility and health.

“Decreasing sperm count has been of great concern since it was first reported twenty-five years ago. This definitive study shows, for the first time, that this decline is strong and continuing. The fact that the decline is seen in Western countries strongly suggests that chemicals in commerce are playing a causal role in this trend,” Dr. Shanna H Swan, a professor in the Department of Environmental Medicine and Public Health at the Icahn School of Medicine at Mount Sinai, New York.

While the current study did not examine causes of the observed declines, sperm count has previously been plausibly associated with environmental and lifestyle influences, including prenatal chemical exposure, adult pesticide exposure, smoking, stress and obesity. Therefore, sperm count may sensitively reflect the impact of the modern environment on male health across the lifespan and serve as a “canary in the coal mine” signaling broader risks to male health.

It also follows that western men pose less of a risk to women looking for promiscuity, but that western women who wish to have children have a better chance with men having a higher level of manliness.


 


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