Evolution in humans is commonly thought to have essentially stopped in recent times. But there are plenty of examples that the human race is still evolving, including our brains, and there are even signs that our evolution may be accelerating. Comprehensive scans of the human genome reveal that hundreds of our genes show evidence of changes during the past 10,000 years of human evolution. Surprisingly, based on skull measurements, the human brain appears to have been shrinking over the last 5,000 or so years.
When it comes to recent evolutionary changes, we currently maybe have the least specific details with regard the brain, but we do know from archaeological data that pretty much everywhere we can measure — Europe, China, South Africa, Australia — that brains have shrunk about 150 cubic centimeters, off a mean of about 1,350. That's roughly 10 percent," Hawks said. "As to why is it shrinking, perhaps in big societies, as opposed to hunter-gatherer lifestyles, we can rely on other people for more things, can specialize our behavior to a greater extent, and maybe not need our brains as much," he added.
There are signs that human evolution may not only be continuing, but that its rate has even accelerated in recent times. Hawks and his colleagues have found evidence of rapid change, with a host of new mutations originating in the last 40,000 years.
"The ecology of humans has been changing," Hawks said. "The biggest changes have to do with agriculture and its consequences — dealing with a new subsistence pattern that caused people to rely on foods that were never very important before, a radical shift from hunter-gatherer diets. For instance, agricultural populations tend to have more copies of a gene for salivary amylase, which helps them digest starch."
According to a report in New Scientist magazine, Dr Holdcroft and colleagues found that as the woman's body and physiology returned to the non-pregnant state, their brains increased in size. It is possible that their brains were swelling from a normal state but this is unlikely.
The investigators believe that the brain changes are more likely to be the result of changes in the volume of individual cells rather than in the quantity of brain cells, Dr Holdcroft told the magazine. In addition, the team found that the pituitary gland, which lies at the base of the brain, showed the opposite effect - increasing in size during pregnancy, when it is responsible for producing reproductive hormones - and then diminishing in size in the months after pregnancy.
Vegans and vegetarians are the most likely to be deficient because the best sources of the vitamin are meat, particularly liver, milk and fish. Vitamin B12 deficiency can also cause anaemia and inflammation of the nervous system.
The link was discovered by Oxford University scientists who used memory tests, physical checks and brain scans to examine 107 people between the ages of 61 and 87. When the volunteers were retested five years later the medics found those with the lowest levels of vitamin B12 were also the most likely to have brain shrinkage. It confirms earlier research showing a link between brain atrophy and low levels of B12.
For every excess pound piled on the body, the brain gets a little bit smaller. Thats the message from new research that found that elderly individuals who were obese or overweight had significantly less brain tissue than individuals of normal weight. The brains of obese people looked 16 years older than their healthy counterparts while those of overweight people looked 8 years older, said UCLA neuroscientist Paul Thompson, senior author of a study published online in Human Brain Mapping.
Dr Coffey used magnetic resonance imaging technology to measure the brain size of 330 healthy men and women. He noticed varying rates of shrinkage particularly among people in their 60s.
The brain shrinkage and fluid increase were mostly seen in the frontal and temporal lobes, which control thinking, planning and memory.
Dr Coffey also found that women are better at holding on to verbal memories, while men are better at non-verbal skills, like map-reading or putting a puzzle together.
A research team from the National Institute on Aging took MRI brain scans of 1,400 women ages 71 to 89 one to four years after the Women's Health Initiative hormone studies ended. The brains of women who had taken estrogen with or without progesterone were significantly smaller in two areas of the brain, the frontal lobe and the hippocampus, when compared to the women who had taken a placebo. The frontal lobe and the hippocampus are parts of the brain involved in thinking and memory. What's more, loss of volume in the hippocampus is a known risk factor for dementia.
Michael Valenzuela of the school of psychiatry at the University of NSW has revealed that the finding results from an analysis of the brain scans used during the study. The results of the study also add strength to the evidence that mental exercises, like puzzles and new languages, stave off ageing diseases. Valenzuela and his colleagues wanted to determine how mental activity delayed the onset of the degenerative brain diseases, such as Huntington's, Alzheimer's and Parkinson's.
The researchers discovered that, of the 50 subjects, people who had been more mentally active over their lives had a larger hippocampus, an important memory centre in the brain.
Among such subjects, the area shrank at half the rate of those who had lower mental activity over the period of three years.
Brain shrinkage was a normal process in the transition between adolescence and adulthood, when the brain refined its processes, said Associate Professor Chris Pantelis, the centre's co-director. But it appeared that in schizophrenics, this process occurred too quickly, leading to excessive loss of brain in important regions.
The finding suggested the onset of the disease, or its severity, could be slowed down, Prof Pantelis said. "If we can understand the mechanisms that underlie these normal developmental processes, we may to able to develop new ways to tackle the illness," he said.
The scientists made their conclusions after taking brain scans of people soon after the onset of their first schizophrenic episode, and of a control group.
They took similar scans two years later. Comparisons revealed the brains of the schizophrenia sufferers changed twice as fast, resulting in greater loss of brain volume.
Tests on mice fed an Atkins-style diet found they ended up with brains FIVE PER CENT lighter than those on other diets. The areas of the brain responsible for memory were also less developed. Scientists suspect the high-protein low-carbohydrate diets leave brains more vulnerable to Alzheimer's.
At the height of Atkins-mania in 2003 and 2004, around three million Brits were following the diet. It urges people to fill up on meat, eggs and cheese - and to shun carbohydrate-rich items like bread, rice and pasta.
Scientists say the new study suggests that the ravages of dementia "might be slowed or avoided through healthy eating."
Previous research has shown Mediterranean-style diets rich in vegetables, fruit and fish may slow Alzheimer's.
Dr Ellemarije Altena, who led the research, said, "The findings predict that chronic insomnia sufferers may have compromised capacities to assess stimuli.”
For their study, the scientists compared the brains of chronic insomnia patients to normal sleepers. They found that those with severe insomniacs exhibited the most extensive density loss, regardless of how long they had suffered from the disorder.
However, the researchers are not yet able to pin down whether sleeplessness precedes grey matter loss or the other way around.
The new research found that Stress can literally shrink areas of gray matter in your brain, or even kill a person. It also speeds aging and robs memory.
New research at the University of Leicester, found that opposite to popular belief, adversity makes its victims more vulnerable to suggestions and lies, and that stress creates more adversity. Good news is that stress can be reduced. It takes awareness of the problem first though.