Category Archives: Human Evolution

পৈশাচিক নেক্রোফিলিয়া বা শবাসক্তি (পর্ব-১)

প্SPN_Necrophiliaরত্নতত্ত্বে অধ্যয়ন করতে গিয়ে আমরা অতীত রাজা রাজড়াদের নানা ধরণের অবাক করার মতো খেয়াল খুশির পরিচয় পাই। এর মধ্যে অদ্ভুদ কিছু বিষয় যেমন মানুষের চিত্তকে বিচলিত করে তেমনি কিছু বিষয় আছে যেগুলো শুনলে ঘৃণায় মুখ বিকৃত করতে হয়। আমার একটা অভ্যাস আছে অবসর সময়টুকু বেশিরভাগই কাটাই হয় বই পড়ে কিংবা নেটে ব্রাউজিং করে যেখানে প্রত্নতত্ত্ব আর ইতিহাসই কেন্দ্রে থাকে। আর প্রত্নতত্ত্ব বিষয়ে ভর্তি হওয়ার পর থেকেই এটা আমাকে এতটাই টানে যে আমার লেখাপড়ার গণ্ডিটা অনেকটা প্রত্নতত্বের মধ্যেই কিভাবে যেন আটকে গেছে। জা. বি প্রত্নতত্ত্ব বিভাগে তখন তৃতীয় বর্ষের মাঝামাঝি পড়ি এমনটা হবে। একটি সংবাদপত্রে ফিচার লেখার প্রস্তাব পেয়ে মিশরীয় মমির কিছু ছবি দেখছিলাম। ফিচার লেখার তুলনায় আমার অনুসন্ধিৎসু চোখ নিবদ্ধ হয় একটি বিশেষ বিষয়ের প্রতি। তখন ঐ প্রবন্ধ শেষ করার কাজ অনেক পিছিয়ে যায়। আমি ভাবতে থাকি অন্য বিষয় নিয়ে। Continue reading পৈশাচিক নেক্রোফিলিয়া বা শবাসক্তি (পর্ব-১)

Advertisements

Discoverer of the Tomb of Tutankhamun: Howard Carter

It may simply have been the luck of the draw, but no one has probably furthered the interests of Egyptology, and indeed the world’s archaeological focus on Egypt more than Howard Carter. His discovery of the tomb of Tutankhamun has inspired almost a century of Hollywood movies, books and media attention for this greatest of all living museums we call Egypt. While Howard Carter’s find of the mostly intact tomb of a pharaoh may have been lucky, it was the result of a dedicated career in Egyptology and the culmination of consistent exploration. Continue reading Discoverer of the Tomb of Tutankhamun: Howard Carter

Natural selection and the driving of female orgasms

Women orgasm more readily during sex with a handsome partner, a study of heterosexual couples has found, with researchers concluding the female orgasm may be linked to an evolutionary urge to produce ‘quality’ offspring. However, other experts in the field say that the jury is still out on the evolutionary function of the female orgasm. In a joint study by anthropologists and psychologists at Pennsylvania State University, 110 heterosexual couples were asked to report details about their sex lives, who orgasmed and how often. Women with partners who rated high on the handsome scale reported orgasming more frequently than their less fortunate sisters. “We found that objective measures of the quality of women’s mates — men’s attractiveness and masculinity — significantly predicted the women’s orgasms,” the researchers wrote in their paper, which was published in the journal Evolution and Human Behavior. 


Passing on healthy genes 

Assuming that female orgasm aids in conception, the researchers concluded that women may have evolved to orgasm more readily with attractive partners so as to pass on their healthy genes to offspring. 

“Thus, possible conception-promoting correlates of female orgasm may be especially effective and/or likely when copulation occurs with masculine males,” the authors wrote. 

Brendan Zietsch, a Postdoctoral Research Fellow at University of Queensland who has researched the female orgasm, said the study provided strong evidence that sexy men were more likely to produce orgasms in their female mates – but that this was not necessarily linked to natural selection. 

“I do not find it compelling support for this evolutionary function of female orgasm. I would guess that men also orgasm more readily having intercourse with an especially sexy woman, but few would argue that this indicates that the function of male orgasm is to choose the best mate,” he said. 

“My point is that arousal being related to both partner sexiness and orgasm frequency is compatible with numerous possible evolutionary explanations of female orgasm.” 

He pointed out that the study also found no link between frequency of female orgasm and the man’s facial structure in cases of non-reproductive sex – such as orgasm during foreplay – but that this may be because more masculine, dominant men might spend less time on non-coital sex than other men. 

“I think we are a long way from understanding the evolutionary function of female orgasm, if indeed it has a function,” he said. 

Coital orgasm not constant

Dr Maciej Henneberg, Professor of Anthropological and Comparative Anatomy at the University of Adelaide and an expert on evolution, said the study relied too heavily on self-reporting. 

“The authors’ own findings are that only about half of women (52%) experience coital orgasm. This means it is not a constant feature. Their measures of “genetic quality” of males are purely speculative (appearance, facial asymmetry),“ he said, pointing out that the study may have underestimated other features women may find attractive in men, such as their social or psychological qualities. 

One cannot assume that function of female orgasm is to aid conception nor place too much emphasis on the idea that the human libido is driven by the urge to procreate, he said. 

“Most of human sexual intercourse is for reasons unrelated to fertility. Moreover, the ability to conceive in humans is low. It takes a persistent copulation every other day for three months to achieve conception, on the average.” 

“All this leads to the conclusion that humans use sexual intercourse for bonding and pleasure, rarely for conception,” said Dr Henneberg. 

“We are unusual amongst animals in this respect. Only dolphins, pygmy chimpanzees and maybe chimpanzees use sex for social contacts. Other mammals copulate only when a female is fecund (can conceive) and the intercourse takes a short time. We can do it for hours!” 

Author: Sunanda Creagh | Source: The Conversation [July 20, 2011

Appearence of Human being in Asia

Stone artifacts unearthed at Georgia’s Dmanisi archaeological site, 90 kilometers southwest of Tbilisi, suggest that early man may have gotten his start in Eurasia and then migrated to Africa, an international team of scientists contends. 

The team’s findings, published in the June 6, 2011 print edition of the Washington, DC-based scientific journal PNAS (Proceedings of the National Academy of Sciences), hold that “Eurasia was probably occupied [by early humans] before Homo erectus [the species from which a straight line of evolution to modern humans begins — ed] appears in the East African fossil record.” 

The sediment in which the artifacts, crude stone tools, were found is “almost 70,000 years older “ than the 1.85 million-year-old early human fossils, also found at Dmanisi, that date as Eurasia’s earliest homo erectus, Reid Ferring, a professor of geoarcheology at the University of North Texas and a member of the research team, told EurasiaNet.org. The sediment is located “several meters below” that earlier find, he said. 

No human fossils have been found next to the tools, but the researchers believe that the artifacts — stones sharpened for cutting — belonged to humans more primitive or from the same era as Dmanisi’s 1.85-million-year-old homo erectus (known as “homo georgicus”). The artifacts will be kept at the Georgian National Museum run by team member Davit Lordkipanidze, a prominent archaeologist-anthropologist who discovered homo georgicus. 

The evidence has prompted the Dmanisi researchers to consider the strong possibility that some more primitive form of human evolved in Africa, came to Eurasia, and there evolved into homo erectus. 

“For a long time, everyone assumed that homo erectus evolved from homo habilis [1.44 million to 2.3 million years], but later it appeared that homo erectus and homo habilis lived side by side in Africa for hundreds of thousands of years, so one cannot evolve into another and both survive,” Ferring said. “That raises the question where homo erectus came from.” 

“Very importantly, the Dmanisi fossils are just barely homo erectus. They are the most primitive of homo erectus . . . very small-brained, very short people,” he continued. “Most of the skulls in Dmanisi have a brain size of 600 cubic centimeters, while the first homo erectus found in Africa is almost 850 cubic centimeters; more than one-third bigger.” 

Researchers on the ground in Dmanisi also do not rule out the possibility that Eurasia’s homo erectus may have evolved in parallel with homo erectus in Africa. 

Ferring describes homo erectus as the “first cosmopolitan” human, with an apparent penchant to travel. The hominid is believed to have spread quickly from Eurasia to China, Southeast Asia and Europe. 

The possible reasons for such a move may not be immediately clear, but, to the homo erectus of the time, territory was territory, one American anthropologist noted. 

“Remember, it would not have been obvious to the hominins they were leaving Africa. There were no signs saying ‘You are leaving Africa now — come and visit us again!'” George Washington University Professor of Human Origins Bernard Wood joked to the weekly journal Nature. 

While few doubt the importance of the Dmanisi find for the study of human evolution, some observers caution that only new human fossils could warrant a conclusion in favor of the hypotheses of the Dmanisi team. Ferring acknowledges that “very aggressive surveys” are needed to find “even older fossils,” but underlines Georgia’s potential role in providing answers to key questions about human evolution. 

“Once again the answers may come from the Caucasus, “ he said. “We may even say maybe from Georgia.” 

Author: Giorgi Lomadze | Source: Eurasianet [June 10, 2011]

Does climate change seriously threaten to wipe out the human species if left unchecked?

Countdown to doomsday 

On January 14 of this year, the Bulletin of the Atomic Scientists moved the hands of its Doomsday Clock one minute further from midnight (it’s now six minutes to midnight), encouraged, it was announced, by the “progress seen around globe in both key threat areas: nuclear weapons and climate change”. 

First published in 1947, the bulletin was founded by scientists, engineers and other experts involved in the Manhattan Project. The clock continues to serve as a metaphorical countdown to the apocalypse – the annihilation of humanity – set for midnight. 

Today, the bulletin’s Board of Sponsors, comprising no less than 18 Nobel Laureates, almost every one of them a physicist or chemist, sets the hands of the clock based on their reading of “threats to the survival and development of humanity from nuclear weapons, climate change, and emerging technologies in the life sciences”. 

They’ve a much wider brief now, a longer list of threats, and, I guess, more reasons to be pessimistic. 

Extinction-prone apes 

Around 500 million years ago, animal life was almost non-existent on Earth. Today, biologists recognise up to 6 million animal species. 

Humanity – Homo sapiens – is just one among the 4,500 living mammal species; and some understanding of where we might be headed can be gleaned from where we’ve been – our evolutionary journey. 

Our starting point as a group of two-footed, small-toothed, weakly-muscled, brainy “have-a-chat” apes is the ancestor we share with living chimpanzees some 7 million years ago. 

(The two chimpanzee species are endangered, incidentally, because of the environmental destruction caused by us, their closest cousin). 

Our evolutionary group – the hominins – diversified quickly after the split from the human-chimp ancestor, and through its multiple evolutionary iterations natural selection produced 25 or 30 two-footed ape species – undoubtedly with more to be found as anthropologists discover more fossils.

All of these are now extinct, except us. 

Those 7 million years represent only the last couple of minutes on a 24-hour clock of Earth’s 5 billion year history. The culling of 30 species to 1 in this short timeframe, or a more than 95% loss of hominin biodiversity, is worse than the worst mass extinction episode recorded in the fossil record: the Permian event some 250 million years ago. 

But these mass events obscure the fact that, in the history of life, extinction has been a dominant theme, a continuous process. Evidence from the last 600 million years shows roughly one-third of existing animal species going extinct every 10 million years. 

Seen in this context, the rate of extinction in the human evolutionary tree is striking, about three times faster than normal. This strongly suggests that we hominins are a highly extinction-prone mammal. 

The blame game 

Why the dramatic loss of hominin diversity? What caused all these species to disappear? These are difficult and complex questions, but the answer may in part centre on the dramatic changes in climate that provided the backdrop for much of our evolution. 

The last half million years or so in particular represent an episode of especially severe climate fluctuation, with intensely cold periods followed by warm phases, flip-flopping between the two on timescales of hundreds or thousands of years – in short, the worst bit of the 2.6 million-year Ice Age or Pleistocene Epoch. 

The archaeological record of Europe suggests that vast areas were largely emptied of hominins during cold phases only to be recolonised during warm periods. 

Hominins, pre-dating our own species, were living in Europe at latitudes as high as 53° north by 700,000 years ago. 

The 53rd parallel runs from the United Kingdom east through the Netherlands, Germany, Poland, Belarus, Russia, Kazakhstan, China (Inner Mongolia), United States (Alaska), Canada and Ireland.
Many places at this latitude today experience temperatures as low as -40° Celsius. But the climate at that time was Mediterranean in character. Soon after, the planet plunged into another cold phase lasting 100,000 years, with vast areas of Europe covered by ice. 

The tyranny of chance 

Biologists have identified various intrinsic features of mammal species that increase their chances of extinction. They include traits such as: 

  • large body size
  •  narrow ecological breadth (i.e. specialist feeders)
  •  low abundance, or sparse numbers of individuals, in the landscape as well as fluctuation in population over time. 

Hominins are large mammals. Estimates of mass and stature for many Ice Age species would easily qualify them for spots on the front row of a rugby team … and that’s just the females! 

Large mammals are slow to mature and reproduce, and normally have one offspring at a time. While many extinct hominins were, like our own species, omnivorous, those living in cold climates relied heavily on animal food, as have recent hunter-gatherers such as the Inuit. This represents a narrowing of dietary niche on a par with many carnivores. 

Estimates of population size from this period are remarkably low, with perhaps only 5,000 individuals in warm phases, plummeting to 1,000 or less during the cold stages, probably for the whole of Europe. 

If around today, these individuals would be part of an endangered species, vulnerable to rapid extinction. And all of this applied to our own species as well for all but the last little bit of our brief evolutionary history. 

Evolutionary game-changer 

Around 10,000 years ago, something unprecedented occurred that altered the course of our evolution: we invented farming. This massive change in dietary, social and economic behavior, a cultural shift known as the Neolithic Revolution, shaped the future course of our own, and the planet’s, evolution in remarkable and unpredictable ways. 

It resulted in anatomical, physiological and genetic changes that massively altered our evolution. 

Our domestication of plants and animals, and the large-scale clearing of land, altered the history of many others as well. It paved the way for a rise in infectious disease, and social changes such as occupational specialisation, writing, standing armies and empires, long distance trade, money and markets. 

But the most profound shift of all was an explosion in human population, the result of greatly improved food security resulting in a dramatic lowering of infant and childhood mortality. 

In Europe, from a base of perhaps only 5,000 Ice Age hunter-gatherers, the take-up of farming from approximately 8,000 years ago sharply increased population growth to an estimated rate of 3% per annum, from a long-term average of zero. 

This is roughly three times today’s global annual growth rate. From a population of less than 100,000 people worldwide, we have grown in less than 10,000 years to almost 7 billion. 

Moments lost in time 

Seen in its broadest context, the history of life on Earth soberly demonstrates that the vast majority of organisms that ever lived, perhaps 99% of them, no longer do. It also shows that mammal species normally last 1-2 million years before extinction inevitably bumps them off. 

Yet, unlike most mammals, including our dozens of extinct hominin cousins, we have escaped the vulnerabilities of a small and massively fluctuating population. 

The simple, but profound act, of growing our own food delivered us the food security that ensured most of our children survived and our population grew. 

In effect, farming gave our species level assurance that the biological isn’t always inevitable. The odds have shifted to such a degree that we may now be, with or without climate change, extinction-proof. 

Author: Darren Curnoe | Source: The Conversation [June 06, 2011]

Neanderthals’ last stand possibly found

A Neanderthal-style toolkit found in the frigid far north of Russia’s Ural Mountains dates to 33,000 years ago and may mark the last refuge of Neanderthals before they went extinct, according to a new Science study. 

Photographs of a large side-scraper from Byzovaya. Tools like this one suggest the site was occupied by Neanderthals some 33,000 years ago [Credit: Ludovic Slimak]

Another possibility is that anatomically modern humans crafted the hefty tools using what’s known as Mousterian technology associated with Neanderthals, but anthropologists believe that’s unlikely. 

“We consider it overwhelmingly probable that the Mousterian technology we describe was performed by Neanderthals, and thus that they indeed survived longer, that is until 33,000 years ago, than most other scientists believe,” co-author Jan Mangerud, a professor emeritus in the Department of Earth Sciences at the University of Bergen and the Bjerknes Centre for Climate Research, told Discovery News. 

Most anthropologists believe modern humans began to replace Neanderthals starting around 75,000 to 50,000 years ago. Project leader Ludovic Slimak said the study suggests “that Neanderthals did not disappear due to climate shifts or cultural inferiority. It is clear that, showing such adaptability, the Mousterian cultures can no longer be considered as archaic.” 

Slimak, a University of Toulouse le Mirail anthropologist, Mangerud, and their colleagues made the determinations after analyzing hundreds of stone artifacts and remains of woolly rhinoceros, reindeer, musk ox, brown bear, wolf and polar fox unearthed at a site called Byzovaya in the western foothills of the Polar Urals. Dates were obtained for sand at the site as well as for some of the bones, many of which “have cut marks that indicate processing by humans,” according to the researchers. 

The tools attributed to the Neanderthal’s Mousterian style (named after the site of Le Moustier in southern France, where they were first identified) were mostly flakes, which the scientists recreated by banging a hard hammer on select stones. It’s therefore likely that the original creators of the tools used a similar manufacturing method. The preserved flakes could have been used to make two-sided scrapers, perhaps for hunting, removing meat from bones, or working with animal hides. 

Modern human tool-crafting methods associated with the Upper Paleolithic (between 40,000 and 10,000 years ago), on the other hand, “were generally focused on the production of what we call blade or bladelet technologies,” Slimak said. The Byzovaya hominins did not apparently make such “blades,” which were often crafted from organic materials like bone and ivory. So Slimak’s team argues that Neanderthals likely made the Byzovaya tools. 

Even though Neanderthals may have disappeared from other locations throughout Europe and Asia, Slimak argues they likely persisted in this remote area near the Arctic Circle. Since conditions in the region were harsh even then, Slimak believes only strong individuals existing in a well-ordered, savvy group could have survived there. 

The Neanderthals may have been gradually absorbed into the population of anatomically modern humans via interbreeding and replacement. As Mangerud explained, “Probably modern humans ousted the Neanderthals.” 

Slimak likens this to what happened to earlier populations from the Americas. 

“In a bit more than 500 years, what will remain of the traditional native societies in America? Just imagine what will remain of these impressive cultures, or their territories, during the next millennium,” he said. 

Recently another study concluded that Neanderthals might have died out earlier than thought and not interacted much with our species, but Neanderthal expert Erik Trinkaus told Discovery News that study “says nothing about possible late Neanderthals in the periphery of cul-de-sacs of western and northern Europe,” and therefore does not discount this latest finding. 

Trinkaus, a professor of physical anthropology at Washington University in St. Louis, thinks the Neanderthal-attributed tools from Russia are “very interesting in terms of people being that far north during the Middle Paleolithic.” 

Author: Jennifer Viegas | Source: Discovery News [May 12, 2011]

Neanderthals died out 10,000 yrs earlier than previously thought

Previous studies had suggested that the most recent Neanderthals died around 33,000 years ago. But using the most up-to-date dating techniques, scientists have dated the remains of two infants of the archaic species to around 40,000 years ago. 


Carbon-dated Neanderthal remains from the foothills of the Caucasus Mountains have suggested that Neanderthals had died out before modern humans arrived. 

The remains are almost 10,000 years older than expected. They come from just one cave in western Russia, called Mezmaiskaya, but bones at other Neanderthal sites farther west could also turn out to be more ancient than previously thought, said Thomas Higham, a palaeoanthropologist at the University of Oxford, UK, and a co-author of a study. 

The implication is that Neanderthals and humans might never have met in Europe, said Higham’s team. 

“I don’t believe there were regions where Neanderthals were living next to modern humans. I just don’t find it very feasible,” said Ron Pinhasi, an archaeologist at University College Cork in Ireland and lead author of the latest study. 

Carbon dating of stone tools characteristic to humans and Neanderthals, as well as their physical remains, has previously given the impression that the first humans to reach Europe, between about 40,000 and 30,000 years ago, shared the continent with Neanderthals long established there. 

However, carbon dating of bones older than about 30,000 years is skirting the limits of the technology, because by that age nearly all of the radioactive carbon has decayed, said Higham. 

The study was published this week in the Proceedings of the National Academy of Sciences. 

Source: ANI [May 10, 2011]

New research suggests right-handedness prevailed 500,000 years ago.

Right-handedness is a distinctively human characteristic, with right-handers outnumbering lefties nine-to-one. But how far back does right-handedness reach in the human story?  

Researchers have tried to determine the answer by looking at ancient tools, prehistoric art and human bones, but the results have not been definitive. 

Now, David Frayer, professor of anthropology at the University of Kansas, has used markings on fossilized front teeth to show that right-handedness goes back more than 500,000 years. He is the lead author (with colleagues in Croatia, Italy and Spain) of a paper published this month in the British journal Laterality. 

His research shows that distinctive markings on fossilized teeth correlate to the right or left-handedness of individual prehistoric humans. 

“The patterns seen on the fossil teeth are directly and consistently produced by right or left hand manipulation in experimental work,” Frayer said. 

The oldest teeth come from a more than 500,000-year-old chamber known as Sima de los Huesos near Burgos, Spain, containing the remains of humans believed to be ancestors of European Neandertals. Other teeth studied by Frayer come from later Neandertal populations in Europe. 

“These marks were produced when a stone tool was accidentally dragged across the labial face in an activity performed at the front of the mouth,” said Frayer. “The heavy scoring on some of the teeth indicates the marks were produced over the lifetime of the individual and are not the result of a single cutting episode.” 

Overall, Frayer and his co-authors found right-handedness in 93.1 percent of individuals sampled from the Sima de los Huesos and European Neandertal sites. 

“It is difficult to interpret these fossil data in any way other than that laterality was established early in European fossil record and continued through the Neandertals,” said Frayer. “This establishes that handedness is found in more than just recent Homo sapiens.” 

Frayer said that his findings on right-handedness have implications for understanding the language capacity of ancient populations, because language is primarily located on the left side of the brain, which controls the right side of the body, there is a right handedness-language connection. 

“The general correlation between handedness and brain laterality shows that human brains were lateralized in a ‘modern’ way by at least half a million years ago and the pattern has not changed since then,” he said. “There is no reason to suspect this pattern does not extend deeper into the past and that language has ancient, not recent, roots.”

Archaeology Of Humankind 
The University of Kansas [April 18, 2011]

Mitochondrial DNA and the mysteries of human evolution

The earliest humans are silent witnesses: they testify only through their bones and tools. But modern humans carry within their tissues a different kind of evidence. DNA serves as a lineal history, a family album, a passport that bears the marks of both origin and journey. Mitochondrial DNA (mtDNA) is inherited only from the mother. 

DNA analysis can tell us a lot about the movements of early humans between continents [Credit: Mopic/Alamy]
Every few generations, a random mutation creeps into this familial signature. So comparison of two samples of mtDNA will show degrees of kinship and ancestral origin. Conversely, the Y chromosome – a twisted rope composed entirely of DNA – is inherited by males from the father. Random infrequent changes once again provide a way of estimating the number of generations back to a shared ancestor. 

The evidence of DNA reveals that all humans are very closely related. A Scot, a Japanese and an Australian Aborigine are far more closely linked by family inheritance than any three chimpanzees from different African groups. 

DNA research suggests that all surviving humans are descended from one woman who lived perhaps 200,000 years ago. Research also shows that the story begins in Africa, home to the greatest variation in human DNA, and therefore the oldest location. Accordingly the woman was promptly dubbed “the African Eve”. 

Not surprisingly, people of the same ethnic and linguistic group turn out to be genetically more closely related to each other than to the rest of the planet, but the same research shows a great deal of mixing of populations as well. 

Studies of telltale markers in the DNA sequence have been used to reconstruct the journeys of ancient human groups around the globe, and not just ancient humans. Along the way from East Africa to Easter Island, early human voyagers picked up fellow travellers such as the stomach ulcer bug Helicobacter pylori. This bacterium also carries a DNA signature of its origins. 

In 2009, it delivered an answer to one of the great mysteries of the human migration: all the settlers on the islands of Polynesia and Melanesia carried stomach bugs that their ancestors could only have picked up in Taiwan. So that became the jumping-off point for the colonisation of the Pacific. 

Long before agriculture, metalwork, settlement, writing, nationality and the idea of history, long before formal territorial identity or ethnic tradition, all humans had a scrapbook, a set of passport stamps that are now beginning to reveal some twists in the great human journey. 

The beginning remains a mystery. But the blood and flesh of humans and chimpanzees holds a molecular story-so-far, a cryptic chemical summary of the 6m-year human thriller. 

DNA is a new way of telling: the secrets of its decryption exposed in less than one human lifetime. As they read it, the characters on the latest page are beginning to see what must have happened in the earlier chapters. There is more to come. 

Author: Tim Radford 

From The Guardian/UK [April 25, 2011]