Tag Archives: brain

The Evolutionary History of the Brain

The development of the human brain is intricately linked with almost every moment of our evolution from sea-dwelling animals to advanced, social primates. That is the the overwhelming theme from New Scientist‘s brief history of the brain.

The engaging article ends with a look at the continued evolution of the human brain (“the visual cortex has grown larger in people who migrated from Africa to northern latitudes, perhaps to help make up for the dimmer light”), and this on why our brains have stopped growing:

So why didn’t our brains get ever bigger? It may be because we reached a point at which the advantages of bigger brains started to be outweighed by the dangers of giving birth to children with big heads. Or it might have been a case of diminishing returns.

Our brains are pretty hungry, burning 20 per cent of our food at a rate of about 15 watts, and any further improvements would be increasingly demanding. […]

One way to speed up our brain, for instance, would be to evolve neurons that can fire more times per second. But to support a 10-fold increase in the “clock speed” of our neurons, our brain would need to burn energy at the same rate as Usain Bolt’s legs during a 100-metre sprint. The 10,000-calorie-a-day diet of Olympic swimmer Michael Phelps would pale in comparison.

Not only did the growth in the size of our brains cease around 200,000 years ago, in the past 10,000 to 15,000 years the average size of the human brain compared with our body has shrunk by 3 or 4 per cent. Some see this as no cause for concern. Size, after all, isn’t everything, and it’s perfectly possible that the brain has simply evolved to make better use of less grey and white matter. That would seem to fit with some genetic studies, which suggest that our brain’s wiring is more efficient now than it was in the past.

Others, however, think this shrinkage is a sign of a slight decline in our general mental abilities.

via @mocost

Our Amazing Senses

As neuroscientist Bradley Voytek points out, “we’re used to thinking of our senses as being pretty shite”, and this is mostly thanks to the plethora of animals that can see, hear, smell and taste far better than we can. “We can’t see as well as eagles, we can’t hear as well as bats, and we can’t smell as well as dogs”, he concludes… and that seems to be the consensus on every nature documentary I’ve ever watched.

However our brain is a magnificent construction (and our senses are equally as wondrous), and so Voytek tries to reverse this idea by explaining just how sensitive and amazing our senses really are:

It turns out that humans can, in fact, detect as few as 2 photons entering the retina. Two. As in, one-plus-one. It is often said that, under ideal conditions, a young, healthy person can see a candle flame from 30 miles away. That’s like being able to see a candle in Times Square from Stamford, Connecticut. Or seeing a candle in Candlestick Park from Napa Valley.*

Similarly, it appears that the limits to our threshold of hearing may actually be Brownian motion. That means that we can almost hear the random movements of atoms.

We can also smell as few as 30 molecules of certain substances. […]

These facts suggest that we all have some level of what we’d normally think of as “super human” sensory abilities already.

But what the hell? If I can supposedly see a candle from 30 miles away, why do I still crack my frakkin’ shin on the coffee table when it’s only slightly dark in my living room?

It may not surprise you to hear that the answer to that question is attention.

* For the Europeans among you, that’s more than a fifth longer than the Channel Tunnel‘s underwater section (or Hyde Park to Stansted Airport for the Londoners).

Social Cognition and Staving Off Dementia

A longitudinal study of health and mental lucidity in the aged—focusing on the huge retirement community of Laguna Woods Village south of Los Angeles—is starting to show some results.

From studying members of the so-called ‘super memory club’ (people aged 90+ with near-perfect cognitive abilities) it is being suggested that not all mental activities are equal when it comes to staving off dementia, and social intereactions may be vastly more important that previously thought.

The researchers have also demonstrated that the percentage of people with dementia after 90 does not plateau or taper off, as some experts had suspected. It continues to increase, so that for the one in 600 people who make it to 95, nearly 40 percent of the men and 60 percent of the women qualify for a diagnosis of dementia.

So far, scientists here have found little evidence that diet or exercise affects the risk of dementia in people over 90. But some researchers argue that mental engagement — doing crossword puzzles, reading books — may delay the arrival of symptoms. And social connections, including interaction with friends, may be very important, some suspect. In isolation, a healthy human mind can go blank and quickly become disoriented.

via Mind Hacks

The Infant Brain, Redux

An interesting follow-up if you enjoyed reading about the development of the infant brain last week: Seed Magazine interviews Alison Gopnik, asking about her research and “why everything we think we know about babies is wrong“.

Seed: You describe children as being “useless on purpose.” What do you mean by that?

AG: It’s related to one of the basic things that came out of our research: Why do children exist at all? It doesn’t make tremendous evolutionary sense to have these creatures that can’t even keep themselves alive and require an enormous investment of time on the part of adults. That period of dependence is longer for us than it is for any other species, and historically that period has become longer and longer.

The evolutionary answer seems to be that there is a tradeoff between the ability to learn and imagine — which is our great evolutionary advantage as a species — and our ability to apply what we’ve learned and put it to use.

The article also mentions how Gopnik believes “Freud’s and Piaget’s conceptions of young children’s theory of mind are wrong”. A recent (correlative) study has shown that she may be correct.

Development of the Infant Brain

Looking primarily at the research of Alison Gopnik, Jonah Lehrer looks at the development of the infant brain.

Gopnik argues that, in many respects, babies are more conscious than adults. She compares the experience of being a baby with that of watching a riveting movie, or being a tourist in a foreign city, where even the most mundane activities seem new and exciting. “For a baby, every day is like going to Paris for the first time,” Gopnik says. “Just go for a walk with a 2-year-old. You’ll quickly realize that they’re seeing things you don’t even notice.”

via Mind Hacks, which itself has a word of caution about the claim that babies have more neurons than adults.