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Scientists are alarmed by shrinking of the human brain

Scientists are alarmed by shrinking of the human brain


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A study published earlier this year confirmed what scientists have long believed to be the case – the human brain is shrinking. For more than 7 million years the hominid brain has grown increasingly bigger, almost tripling in size. But for the last 10,000 years, the human brain has been shrinking at an alarming rate and no one really knows why. New research has attempted to answer this question by examining size changes in specific regions of the brain.

The study published in the American Journal of Physical Anthropology was carried out by a team of Chinese researchers who looked at over 500 endocasts from the past 7,000 years. Endocasts are moulds of brains created from the imprints on the inside of the skull. They are an invaluable resource when studying human evolution, allowing us to track how our brain has evolved over the past few million years. The results confirmed what has long been suspected – our brains are getting smaller.

It was in 2010 when researching a skull that belonged to a Cro Magnon man that scientists first discovered the brain of our ancient ancestor was significantly larger than humans today. This has been replicated time and again and it can now be said that the human brain has decreased from 1,500 cubic centimetres (cc) to 1,350cc, irrespective of gender and race. If we continue on this path, we will end up having the same-sized brain as Homo Erectus, an ancient human species which had a brain of 1,100 cc.

Does a smaller brain mean less intelligence?

Scientists have been debating for many years about whether a smaller brain means less intelligence, and no agreement has been reached. To clarify, it is not simply the size of the brain that is relevant here, but the size of the brain in relation to body size, referred to as the Encephalization Quotient (EQ). Research has found a close relationship between intelligence and EQ.

Over millions of years, the hominid body has been shrinking but the worrying fact is that our brains are shrinking faster than our bodies. Does this mean human beings are getting dumber, or are smaller brains not necessarily bad?

The human brain is shrinking faster than the shrinkage of the body. Image credit: Superscholar.org

Many scientists have argued that bigger doesn’t always mean better. Duke University anthropologist Brian Hare says "the decrease in brain size is actually an evolutionary advantage" because it could indicate we're evolving into a less aggressive animal. For example, the common chimpanzees have bigger brains than bonobos, but they are less likely to resolve issues through teamwork because they're more aggressive.

Other proponents of the ‘bigger isn’t better’ hypothesis have argued that our ancestors had a larger visual cortex because good vision was necessary for survival. But as social support increased, vision became less important. Those with smaller visual cortexes had more resources available for social regions of the brain, thus increasing chances of survival.

However, the findings of the new study conducted in China are not consistent with these theories because the results indicated that it was not one particular area of the brain that was shrinking – the whole brain has been getting smaller. If the hypothesis about the visual cortex was correct, we should see shrinkage only in that region of the brain.

The one exception is the frontal lobe, which actually seems to be increasing in size. The frontal lobe is the region of the brain responsible for speaking, comprehending the speech of others, reading and writing. It is possible that we are doing a lot more of that now – at least the reading and writing part – compared to our ancient past.

While plenty of hypotheses have been put forward to justify the shrinking of the human brain, there remain many who are less optimistic. The authors of a study published in 2012 maintained that humans lost the evolutionary pressure to be smart once they formed agricultural settlements.

"A hunter-gatherer who did not correctly conceive a solution to providing food or shelter probably died, along with his/her progeny, whereas a modern Wall Street executive that made a similar conceptual mistake would receive a substantial bonus and be a more attractive mate. Clearly, extreme selection is a thing of the past," the researchers wrote in the journal article published in the journal Trends in Genetics.

More than 4,000 years ago, great civilizations existed around the world and the ancient inhabitants built incredible buildings and cities with great precision and beauty, often with astronomical alignments that we are only just beginning to realise. Nowadays, technology has taken over, rendering our need to apply skill, creativity, and memory virtually redundant. Instead of memorising navigational routes we switch on our ‘sat navs’ and rather than storing phone numbers and addresses in our memory banks, we have them all to hand on our iPhones and Blackberries. Our technology is evolving rapidly, but sadly it seems that we are not.


A brief history of the brain

IT IS 30,000 years ago. A man enters a narrow cave in what is now the south of France. By the flickering light of a tallow lamp, he eases his way through to the furthest chamber. On one of the stone overhangs, he sketches in charcoal a picture of the head of a bison looming above a woman’s naked body.

In 1933, Pablo Picasso creates a strikingly similar image, called Minotaur Assaulting Girl.

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That two artists, separated by 30 millennia, should produce such similar work seems astonishing. But perhaps we shouldn’t be too surprised. Anatomically at least, our brains differ little from those of the people who painted the walls of the Chauvet cave all those years ago. Their art, part of the “creative explosion” of that time, is further evidence that they had brains just like ours.

How did we acquire our beautiful brains? How did the savage struggle for survival produce such an extraordinary object? This is a difficult question to answer, not least because brains do not fossilise. Thanks to the latest technologies, though, we can now trace the brain’s evolution in unprecedented detail, from a time before the very first nerve cells right up to the age of cave art and cubism.

The story of the brain begins in the ancient oceans, long before the first animals appeared. The single-celled organisms that swam or crawled in them may not have had brains, but they did have sophisticated ways of sensing and responding to their environment. “These mechanisms are maintained right through to the evolution of mammals,” says Seth Grant at the Wellcome Trust Sanger Institute in Cambridge, UK. “That’s a very deep ancestry.”

The evolution of multicellular animals depended on cells being able to sense and respond to other cells – to work together. Sponges, for example, filter food from the water they pump through the channels in their bodies. They can slowly inflate and constrict these channels to expel any sediment and prevent them clogging up. These movements are triggered when cells detect chemical messengers like glutamate or GABA, pumped out by other cells in the sponge. These chemicals play a similar role in our brains today (Journal of Experimental Biology, vol 213, p 2310).

Releasing chemicals into the water is a very slow way of communicating with distant cells – it can take a good few minutes for a demosponge to inflate and close its channels. Glass sponges have a faster way&colon they shoot an electrical pulse across their body that makes all the flagellae that pump water through their bodies stop within a matter of seconds (Nature, vol 387, p 29).

This is possible because all living cells generate an electrical potential across their membranes by pumping out ions. Opening up channels that let ions flow freely across the membrane produces sudden changes in this potential. If nearby ion channels also open up in response, a kind of Mexican wave can travel along a cell’s surface at speeds of several metres a second. Since the cells in glass sponges are fused together, these impulses can travel across their entire bodies.


Brain development is surprisingly similar between humans and other primates

Credit: Pixabay/CC0 Public Domain

What makes the human brain special? It's not the time it takes to mature, according to new research. Scientists report the human frontal cortex, the part of the brain involved in higher-level thinking and reasoning, follows a developmental trajectory similar to that of other primates including chimpanzees and macaques.

"We find no evidence that frontal cortex maturation is unusually extended in humans," said Christine Charvet, Ph.D., assistant professor at Delaware State University and the study's lead author. "Overall, our studies converge to demonstrate a surprising level of similarity in brain structure and development between humans and other studied primates."

Charvet will present the research at the American Association for Anatomy annual meeting during the Experimental Biology (EB) 2021 meeting, held virtually April 27-30. Some of the findings were recently published in the Proceedings of the Royal Society B.

Charvet and colleagues integrate data on gene expression, brain structure and behavioral markers to comprehensively analyze brain development across species. While previous researchers have applied these approaches in isolation, each approach has limitations, so combining them provides a more complete picture. The researchers used their integrated approach to compare frontal cortex development in humans and chimpanzees. In total, they had acquired 137 time points from 44 days after conception to 55 years of age.

"It's only by merging information across scales of biological organization that we can conclusively say how old a chimpanzee is in human days," said Charvet. In addition to chimpanzees, the team applied similar methods to analyze brain development in mice and macaques, a type of monkey. As expected, the researchers found that mouse brains mature at a much faster rate than human brains, but humans and macaques showed similar patterns of development.

These comparisons offer a reference point that scientists can use to compare ages and better understand how our brains differ from those of other animals. In addition, Charvet says the integrated approach can help researchers map brain circuitry to gain insights into human evolution.

"Integrating across scales of biological organization expands the repertoire of tools available to study biological programs in human evolution and opens new avenues to study connections in health and disease," said Charvet.

The research will be incorporated into a website that catalogues brain development and relative biological ages of a variety of mammalian species.


Farming to blame for our shrinking size and brains

A fossil of modern humans, dating back 160,000 years. Photo © 2000 David L. Brill, Brill Atlanta

(PhysOrg.com) -- At Britain's Royal Society, Dr. Marta Lahr from Cambridge University's Leverhulme Centre for Human Evolutionary Studies presented her findings that the height and brain size of modern-day humans is shrinking.

Looking at human fossil evidence for the past 200,000 years, Lahr looked at the size and structure of the bones and skulls found across Europe, Africa and Asia. What they discovered was that the largest Homo sapiens lived 20,000 to 30,000 years ago with an average weight between 176 and 188 pounds and a brain size of 1,500 cubic centimeters.

They discovered that some 10,000 years ago however, size started getting smaller both in stature and in brain size. Within the last 10 years, the average human size has changed to a weight between 154 and 176 pounds and a brain size of 1,350 cubic centimeters.

While large size remained static for close to 200,000 years, researchers believe the reduction in stature can be connected to a change from the hunter-gatherer way of life to that of agriculture which began some 9,000 years ago.

The fossilized skull of an adult male hominid unearthed in 1997 from a site near the village of Herto, Middle Awash, Ethiopia. The skull, reconstructed by UC Berkeley paleoanthropologist Tim White, is slightly larger than the most extreme adult male humans today, but in other ways is more similar to modern humans than to earlier hominids, such as the neanderthals. White and his team concluded that the 160,000 year old hominid is the oldest known modern human, which they named Homo sapiens idaltu. Image © J. Matternes

While the change to agriculture would have provided a plentiful crop of food, the limiting factor of farming may have created vitamin and mineral deficiencies and resulted in a stunted growth. Early Chinese farmers ate cereals such as rice which lacks the B vitamin niacin which is essential for growth.

Agriculture however does not explain the reduction in brain size. Lahr believes that this may be a result of the energy required to maintain larger brains. The human brain accounts for one quarter of the energy the body uses. This reduction in brain size however does not mean that modern humans are less intelligent. Human brains have evolved to work more efficiently and utilize less energy.


Behind glass cases, Harvard’s Peabody Museum of Archaeology displays ancient tools, weapons, clothing, and art — enough to jar you back into the past.

But the venerable museum offered a jarring moment of another sort in its Geological Lecture Hall last month (March 20). Paleoanthropologist Leslie Aiello delivered a late-afternoon talk on diet, energy, and evolution. It was jolting to see her, slight and matronly, stand before a story-high screen filled with images of rugged early hominids on a savannah, gathered around fallen game.

Then again, Aiello — as one of her admirers put it — is the “alpha female” among anthropologists who make a study of human origins. She co-wrote the widely used text “An Introduction to Human Evolutionary Anatomy” (Academic Press, 1990), based on the idea that the fossil record offers clues to how early hominids looked, moved, and even ate.

Aiello — a professor for three decades at University College, London, and now president of the Manhattan-based Wenner-Gren Foundation for Anthropological Research — was in Cambridge to deliver the 2008 George Peabody Founder’s Lecture.

Introducing Aiello was Daniel E. Lieberman, a professor of biological anthropology at Harvard and a proponent of the idea that upright walking and long-distance endurance running set early humans on their novel evolutionary path.

He held up a well-thumbed copy of Aiello’s book and said, “Her CV is so long, it’s hard to know where to start.” But two seminal ideas stand out, said Lieberman. One is that in evolutionary terms, big human brains — with enormous energy requirements — are inversely proportional to gut size.

This idea — called the Expensive Tissue Hypothesis (ETH) in Aiello’s co-authored 1992 paper — argues that around 1.5 million years ago early humans began to eat more meat, a compact, high-energy source of calories that does not require a large intestinal system.

A second seminal idea posited by Aiello and another colleague is that increased brain size meant higher reproductive costs for females — who, over time, compensated in part by increasing in size at a greater rate than males of the genus Homo. (Homo erectus females had a 64 percent larger body mass than earlier hominids males of the species — though still larger than females — were larger than their earlier male counterparts by only 45 percent.)

In her lecture, Aiello revisited ETH to see how scientifically robust an idea it was after more than 15 years of academic scrutiny.

The idea is still viable, she said, but in an era of better testing technology and accelerating scholarship on human origins, ETH has theoretical competitors explaining the evolution of bigger brain size.

For one, some scientists say that walking upright — “bipedalism” — is the most important way to support larger brain size. (Upright hunters and gatherers were more efficient than their quadripedal counterparts.) Others say that the key to supporting big brains is the smaller muscle mass of hominids compared to apes.

And still other scientists have pointed out that ETH doesn’t hold true for all animals, including birds and bats.

Said the modest Aiello, “we’re much further along in understanding energy tradeoffs and evolution than 15 years ago.”

But for whatever reason, she said, “encephalization” — the tendency of some species to evolve larger brains — is the third stage that led humans to civilization. (One earlier stage is bipedalism. The oldest is “terrestriality,” the movement of early hominids from canopied forests — rich in lower-calorie foods — to savannahs, where small game, carrion, and insects supplemented a plant-based diet.)

Around 1.5 million years ago there was “a lot going on” in evolutionary terms, said Aiello. Hominid habitat changed, along with the size of early human craniums (larger) and jaws (smaller).

But growing brain size presented a metabolic problem. A gram of brain tissue takes 20 times more energy to grow and maintain than a gram of tissue from the kidney, heart, or liver, she said. Gut tissue is metabolically expensive too — so as brains grew gut sizes shrank.

It’s likely that meat eating “made it possible for humans to evolve a larger brain size,” said Aiello. Early human ancestors probably consumed more animal foods — termites and small mammals – than the 2 percent of carnivorous caloric intake associated with chimpanzees.

The social implications of increased meat eating were interesting, said Aiellio. In most primates, there’s no food sharing between females and offspring, she said. But the difficulty of getting meat led to cooperative food sharing among early humans, strengthening the bond between a female and her offspring.

Increased meat eating also likely led to an increased division of labor between the sexes, said Aiello. The males would hunt and provide the females — faced with more intensive motherhoods — would raise the hominid young, who were dependent longer than ape infants.

But is there evidence in the fossil record for a transition to what Aiello called “a high-quality animal-based diet”?

Briefly, yes. For one, animal bones from 2.5 million years ago showed cut marks thought to be from the earliest stone tools. And earlier species of early hominids had strong jaws and molar-like teeth later species were more like modern humans, with weaker jaws, smaller faces, and smaller teeth.

There are other of bits of evidence pointing to meat eating by early humans, said Aiello. “My favorite are the tapeworms.”

Parasite historians — yes, there are some — say that hyenas and early humans were infected by the same type of tapeworms, which suggests they shared booty from scavenged carrion. (Such analysis is possible because of “isotopic ecology,” the study of microscopic traces of food-related isotopes in both fossils and living creatures.)

Our human ancestors were not wholly carnivores — “that would be silly,” said Aiello, who does not argue that meat-eating caused bigger brains — just that it made bigger brains possible.

About 1.5 million years ago, she said, “there was a definite dietary change to foods of high nutritional value [that were] easy to digest.”

Better food sources and the social changes they engendered accelerated our human ancestors toward civilization. “Whatever was happening here,” said Aiello of the highest branch in the primate tree, “Homo erectus got it right.”


Brain Facts Update: Myths Debunked

Rapid advancements in neuroscience mean that information gets outdated fast.

This is one reason that there’s a lot of misinformation and myths floating around about the brain.

New evidence has shown that these commonly accepted brain “facts” are not true.

32. You’ve probably heard that attention spans are getting shorter.

And that the average person’s attention span is shorter than that of a goldfish.

This “fun but alarming” fact turns out to not be true.

There’s no evidence that human attention spans are shrinking or that goldfish have particularly short attention spans either. (43)

33. The popular myth that we use only 10% of our brains is flat-out wrong.

Brain scans clearly show that we use most of our brain most of the time, even when we’re sleeping. (44)

34. There is no such thing as a left-brain or right-brain personality/skill type.

We are not left-brained or right-brained we are all “whole-brained.” (See #33)

35. In spite of what you’ve been told, alcohol does not kill brain cells.

What excessive alcohol consumption can do is damage the connective tissue at the end of neurons. (45)

36. The “Mozart effect” has been debunked.

While listening to certain kinds of music can improve memory and concentration, there’s nothing unique about listening to Mozart. (46)

37. You may have heard that we have more brain cells than there are stars in the Milky Way, and while this is a beautiful sentiment, it is not an accurate one.

Best-guess estimates are that we have 86 billion neurons while there are 200-400 billion stars in the Milky Way. (47)

38. It’s often said that there are 10,000 miles of blood vessels in the brain.

In fact, that number is closer to 400 miles — still a substantial amount. (48)

39. Contrary to the prevailing medical belief, having high total cholesterol is not bad for your brain. (See #5)

In fact, your brain consists of fat and cholesterol, and having high cholesterol has been found to actually reduce your risk of dementia. (49)

40. Until recently, it was a “fact” that you were born with a set level of intelligence and a number of brain cells that could never be changed.

But it has since been discovered that your brain has the capacity to change throughout your lifetime due to a property known as brain plasticity.

The brain can continue to form new brain cells via a process known as neurogenesis. (50)

Think more clearly, learn faster, and remember more.

Dr. Pat | Be Brain Fit


Modern Man’s Shrinking Brain


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For millions of years the hominid brain has grown increasingly bigger. But for the last 10,000 years, the human brain has been shrinking at an alarming rate and no one really knows why.

The Ups and Downs of Brain Size

For the past 800,000 years, brain size has increased at a rate of about 7cc every 10,000 years. But in the past 10,000 years, brain size has decreased by 150cc. That’s over 200,000 years of brain growth lost in just 10,000 years.

The Ups and Downs of Body Mass

Body mass changed with the brain size at a rate of 1 kilogram of body mass for every 4.3cc of brain size. In the past 10,000 years, body mass has decreased by 5 kg. That’s 30,000 years of growth lost in just 10,000 years. This means our brains are shrinking faster than our bodies. If our brains shrank as slow as our bodies, we would have an extra tennis ball worth of brain matter. If our bodies shrank as fast as our brains, we would be about 4’ 6” tall and weigh 64 lb.

The Ups and Plateaus of EQ

Does this mean we are dumber?

Scientists have found a close relationship between intelligence and the encephalization quotient, or EQ. It is the ratio between actual brain mass and predicted brain mass for an animal of a given size. The formula for mammals looks like this: EQ=E/0.12 P2/3 , where E = brain mass, and P = body mass. Throughout hominid history, EQ has consistently risen. But for the past 20,000 years, eq has remained the same.

So What’s the Big Idea?

No one really knows for sure why our brains are shrinking but following are some proposed ideas.…

Around 800,000 years ago the earth started experiencing climate fluctuation which coincided with fast brain growth. Cold weather is survived by bigger bodies and therefore bigger brains. Warming trends in the past 20,000 years have favored smaller bodies and therefore smaller brains.

The advent of agriculture led to unhealthy grain-heavy diets (lacking protein and vitamins). Body sizes and brain sizes responded. Those with more energy hungry grey matter in their heads would die off, lacking nutrition.

Social Complexity

As complex societies emerged, those with smaller brains could survive with the help of others. A higher survival rate allowed smaller brains to populate the gene pool. Increased population density leads to increased division of labor. When population is sparse, brains grow because you need to know more to survive. With the division of labor you do not have to know as much. Mistakes in judgment are less likely to be fatal in more supportive societies.

The brain constitutes 2% of the human body, but it uses 20% of the body’s resources. The larger the brain, the more fuel it takes to formulate thoughts. As gene pools grow, the most efficient populations excel.

Domestication

As violence and aggression is bred out of domesticated animals, they lost brain mass. Animals that remain juvenile longer are easier to domesticate (like humans). Bonobos have brains 20% smaller than chimps. They act like juvenile Chimpanzees, and consequently function as domesticated chimps.

Common characteristics of domesticated animals include:

• More striking range of coloration and hair types

The History of Brain Sizes

Sahelanthropus tchadensis
Lived: 7 – 6 (6.5 mean) mya
Brain Size: 282cc – 500cc (350cc mean)

Ardipithecus ramidus
Lived: 4.35 – 4.45 (4.4) mya
Brain Size: 300cc – 350cc (325cc)

Australopithecus afarensis
Lived: 3.85 – 2.95 (3.11 mean) mya
Brain Size: 387cc – 550cc (445.8cc mean)
Brain Weight: 435g
EQ: 2.2
Body Weight: 42 kg
Body Height: 151 cm

Australopithecus africanus
Lived: 3.3 – 2.1 (2.7 mean) mya
Brain Size: 400cc – 560cc (461.2cc mean)
Brain Weight: 450g
EQ: 2.5
Body Weight: 41 kg
Body Height: 138 cm

Paranthropus aethiopicus
Lived: 2.7 – 2.3 (2.1 mean) mya
Brain Size: 400cc – 490cc (431.8cc mean)
EQ: 3.4
Body Weight: 38 kg
Australopithecus garhi
Lived: 2.5 mya
Brain Size: 450cc
Brain Weight: 445g

Homo habilis
Lived: 2.4 – 1.4 (1.8 mean) mya
Brain Size: 509cc – 687cc (609cc mean)
Body Weight: 32 kg
Body Height: 100 – 135 cm
Paranthropus boisei
Lived: 2.3 – 1.2 (1.7 mean) mya
Brain Size: 475cc – 545cc (508.3cc mean)
Brain Weight: 515g
EQ: 2.7
Body Weight: 34 – 49 kg
Body Height: 124 – 137 cm

Australopithecus sediba
Lived: 1.977 – 1.98 (1.9785 mean) mya
Brain Size: 420cc – 450cc (435cc mean)
Homo rudolfensis
Lived: 1.9 – 1.8 (1.865 mean) mya
Brain Size: 752cc – 825cc (788.5cc mean)
Brain Weight: 735g
EQ: 5.1
Body Weight: 46 kg

Homo erectus
Lived: 1.89 – 0.14 (.72 mean) mya
Brain Size: 727cc – 1390cc (990cc mean)
EQ: 5
Body Weight: 40 – 68 kg
Body Height: 145 – 185 cm

Homo ergaster
Lived: 1.8 – 1.3 (1.7 mean) mya
Brain Size: 750cc – 848cc (800.7cc mean) 850g
EQ: 4.5
Body Weight: 58 kg
Paranthropus robustus
Lived: 1.8 to 1.2 (1.5 mean) mya
Brain Size: 450cc – 530cc (493.3cc mean)
Brain Weight: 525g
EQ: 3
Body Weight: 40 – 54 kg
Body Height: 100 – 120 cm

H. e. georgicus
Lived: 1.7 mya
Brain Size: 650cc – 780cc (715cc mean)

Homo antecessor
Lived: 1.2 – 0.8 (1 mean) mya
Brain Size: 1,000cc – 1,150cc (1075cc mean)

Homo e. soloensis
Lived: 0.55 – 0.143 (.347 mean) mya
Brain Size: 1013cc – 1251cc (1144.6cc mean)

Homo heidelbergensis
Lived: 0.7 – 0.2 (0.339 mean) mya
Brain Size: 1165cc – 1450cc (1268cc mean)
EQ: 5.3
Body Weight: 51 – 62kg
Body Height: 157 – 175cm

Homo s. neanderthalensis
Lived: 0.2 – 0.028 (0.081 mean) mya
Brain Size: 1172cc – 1740cc (1420cc mean)
EQ: 5.5
Body Weight: 65 kg
Body Height: 164 cm

Homo s. sapiens
Lived: 0.2 – present (0.044 mean) mya
Brain Size: 1090cc – 1775cc (1457cc mean)
EQ: 7
Body Weight: 64 kg

Homo s. idaltu
Lived: 0.16 mya
Brain Size: 1450cc
Homo floresiensis
Lived: 0.095 – 0.013 (0.054 mean) mya
Brain Size: 426cc
EQ: 3.6
Body Weight: 30 kg
Body Height: 106 cm

H.s. erectus “Cro Magnon”
Lived: 0.03 – 0.02 (0.025 mean) mya
Brain Size: 1590cc – 1730 (1660cc mean)
Body Height: 166 – 171cm

Modern Human
Brain Size: 975cc – 1499cc (1350cc mean)
EQ: 7.44
Body Weight: 58kg
Body Height: 165 – 175cm


What should we believe?

Both Carroll and Rovelli are master expositors of science to the general public, with Rovelli being the more lyrical of the pair.

There is no resolution to be expected, of course. I, for one, am more inclined to Bohr's worldview and thus to Rovelli's, although the interpretation I am most sympathetic to, called QBism, is not properly explained in either book. It is much closer in spirit to Rovelli's, in that relations are essential, but it places the observer on center stage, given that information is what matters in the end. (Although, as Rovelli acknowledges, information is a loaded word.)

We create theories as maps for us human observers to make sense of reality. But in the excitement of research, we tend to forget the simple fact that theories and models are not nature but our representations of nature. Unless we nurture hopes that our theories are really how the world is (the Einstein camp) and not how we humans describe it (the Bohr camp), why should we expect much more than this?


Back pain linked to shrinking brain

BACK pain has a mysterious link with brain damage. Brain scans have shown that patients with chronic lower back pain have lost grey matter from two brain areas. Scientists are not yet sure whether this is the cause of back pain or the result, but the finding could lead to new drug treatments for backache that target the brain rather than the back or spine.

The discovery was made by Vania Apkarian of Northwestern University in Chicago, when he and his colleagues scanned the brains of 26 patients who had suffered lower back pain for at least a year. Some &hellip

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Increasing brain size

Because more complete fossil heads than hands are available, it is easier to model increased brain size in parallel with the rich record of artifacts from the Paleolithic Period (c. 3.3 million to 10,000 years ago), popularly known as the Old Stone Age. The Paleolithic preceded the Middle Stone Age, or Mesolithic Period this nomenclature sometimes causes confusion, as the Paleolithic itself is divided into Early, Middle, and Late (or Upper) periods. Hominin brain expansion tracks so closely with refinements in tool technology that some scholars ignore other factors that may have contributed to the brain’s increasing size, such as social complexity, foraging strategies, symbolic communication, and capabilities for other culture-mediated behaviours that left no or few archaeological traces.

Throughout humanevolution, the brain has continued to expand. Estimated average brain masses of A. afarensis (435 grams [0.96 pound]), A. garhi (445 grams [0.98 pound]), A. africanus (450 grams [0.99 pound]), P. boisei (515 grams [1.13 pounds]), and P. robustus (525 grams [1.16 pounds]) are close to those of chimpanzees (395 grams [0.87 pound]) and gorillas (490 grams [1.08 pounds]). Average brain mass of H. sapiens is 1,350 grams (2.97 pounds). The increase appears to have begun with H. habilis (600 grams [1.32 pounds]), which is also notable for having a small body. The trend in brain enlargement continued in Africa with larger-bodied H. rudolfensis (735 grams [1.62 pounds]) and especially H. ergaster (850 grams [1.87 pounds]).

One must be extremely cautious about ascribing greater cognitive capabilities, however. Relative to estimated body mass, H. habilis is actually “brainier” than H. rudolfensis and H. ergaster. A similar interpretive challenge is presented by Neanderthals versus modern humans. Neanderthals had larger brains than earlier Homo species, indeed rivaling those of modern humans. Relative to body mass, however, Neanderthals are less brainy than anatomically modern humans. Relative brain size of Homo did not change from 1.8 to 0.6 mya. After about 600 kya it increased until about 35,000 years ago, when it began to decrease. Worldwide, average body size also decreased in H. sapiens from 35,000 years ago until very recently, when economically advanced peoples began to grow larger while less-privileged peoples did not.

Average capacity of the braincase in fossil hominins
hominin number of fossil examples average capacity of the braincase (cc)
Australopithecus 6 440
Paranthropus 4 519
Homo habilis 4 640
Javanese Homo erectus (Trinil and Sangiran) 6 930
Chinese Homo erectus (Peking man) 7 1,029
Homo sapiens 7 1,350

Overall, there were periods of stagnation and elaboration in stone tool technology during the Paleolithic, but, because of variations over time and between locations as well as the possibility that plant materials were used instead of stone, it is impossible to link brain size with technological complexity and fully human cognitive capabilities. Moreover, in many instances it is impossible to identify assuredly the hominin species that commanded a Paleolithic industry, even when there are associated skeletal remains at the site.

The unreliability of brain size to predict cognitive competence and ability to survive in challenging environments is underscored by the discovery of a distinctive human sample, dubbed H. floresiensis, in a limestone cave on Flores Island, Indonesia, in 2004. The diminutive H. floresiensis had brains comparable in mass to those of chimpanzees and small australopiths, yet they produced a stone tool industry comparable to that of Early Pleistocene hominins and survived among giant rats, dwarf elephants, and Komodo dragons from at least 38 kya to about 18 kya. If they are indeed a distinct species, they constitute yet another archaic human (in addition to H. neanderthalensis, the Denisovans [known from remains from Denisova Cave in Russia], and perhaps H. erectus) that lived contemporaneously with modern humans during the Late Pleistocene.


Watch the video: The human brain is shrinking according to scientists (October 2022).

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