If you train intensively at long-distance running, you’ll find it easier to climb stairs or ride a bike. The running will boost your aerobic fitness and strengthen your leg muscles, providing benefits that transfer to other activities. Does our brain work in the same way? If we train ourselves on a specific mental task, do we become sharper across the board?
There’s a multi-million dollar industry that would like you to believe the answer is yes. Best-selling “brain training” games like Brain Age purport to give your brain a “the workout it needs” through a combination of word puzzles, number problems, Su Doku and more. Unfortunately, there is little good evidence that these games improve anything beyond performance on a specific task.
There are exceptions. Susanne Jaeggi from the University of Michigan has found that a simple exercise called an “n-back task” could increase the “fluid intelligence” of elementary and middle-school children (well, some of them; more on this later). It’s the latest of a series of studies showing that practicing at a single task can lead to a broader intellectual boost.
Fluid intelligence is a broad concept that includes abilities like abstract reasoning, solving new problems, spotting patterns and drawing inferences, rather than relying on knowledge, skills or experience. The n-back task isn’t meant to train all of these. Instead, it is meant to improve working memory – the ability to hold and manipulate pieces of information in our head. A good working memory is essential for problem-solving and reasoning, so Jaeggi reasoned that training the former would improve the latter, in the same way that building a runner’s fitness improves their cycling.
Ever since there have been IQ tests, people have debated what they actually measure. Is it “intelligence”, is it an abstract combination of mental abilities, or is it, as Edwin Boring said, “the capacity to do well in an intelligence test”? Regardless of the answer, studies have repeatedly shown that people who achieve higher scores in IQ tests are more likely to do well in school, perform well in their jobs, earn more money, avoid criminal convictions, and even live longer. Say what you like about the tests, but they have predictive power.
However, Angela Lee Duckworth from the University of Pennsylvania has found that this power is overrated. The link between our IQs and our fates becomes muddier when we consider motivation – an aspect of test-taking that is often ignored. Simply put, some people try harder in IQ tests than others. If you take this into account, the association between your IQ and your success in life becomes considerably weaker. The tests are not measuring intelligence alone, but also the desire to prove it.
At first glance, the African elephant doesn’t look like it has much in common with us humans. We support around 70-80 kg of weight on two legs, while it carries around four to six tonnes on four. We grasp objects with opposable thumbs, while it uses its trunk. We need axes and chainsaws to knock down a tree, but it can just use its head. Yet among these differences, there is common ground. We’re both long-lived animals with rich social lives. And we have very, very large brains (well, mostly).
But all that intelligence doesn’t come cheaply. Large brains are gas-guzzling organs and they need a lot of energy. Faced with similarly pressing fuel demands, humans and elephants have developed similar adaptations in a set of genes used in our mitochondria – small power plants that supply energy to our cells. The genes in question are “aerobic energy metabolism (AEM)” genes – they govern how the mitochondria metabolise nutrients in food, in the presence of oxygen.
We already knew that the evolution of AEM genes has accelerated greatly since our ancestors split away from those of other monkeys and apes. While other mutations were reshaping our brain and nervous system, these altered AEM genes helped to provide our growing cortex with much-needed energy.
Now, Morris Goodman from Wayne State University has found evidence that the same thing happened in the evolution of modern elephants. It’s a good thing too – our brain accounts for a fifth of our total demand for oxygen but the elephant’s brain is even more demanding. It’s the largest of any land mammal, it’s four times the size of our own and it requires four times as much oxygen.
Goodman was only recently furnished with the tools that made his discovery possible – the full genome sequences of a number of oddball mammals, including the lesser hedgehog tenrec (Echinops telfairi). As its name suggests, the tenrec looks like a hedgehog, but it’s actually more closely related to elephants. Both species belong to a major group of mammals called the afrotherians, which also include aardvarks and manatees.
Goodman compared the genomes of 15 species including humans, elephants, tenrecs and eight other mammals and looked for genetic signatures of adaptive evolution. The genetic code is such as that a gene can accumulate many changes that don’t actually affect the structure of the protein it encodes. These are called “synonymous mutations” and they are effectively silent. Some genetic changes do, however, alter protein structure and these “non-synonymous mutations” are more significant and more dramatic, for even small tweaks to a protein’s shape can greatly alter its effectiveness. A high ratio of non-synonymous mutations compared to synonymous ones is a telltale sign that a gene has been the target of natural selection.
And sure enough, elephants have more than twice as many genes with high ratios of non-synonymous mutations to synonymous ones than tenrecs do, particularly among the AEM genes used in the mitochondria. In the same way, humans have more of such genes compared to mice (which are as closely related to us, as tenrecs are to elephants).
These changes have taken place against a background of less mutation, not more. Our lineage, and that of elephants, has seen slower rates of evolution among protein-coding genes, probably due to the fact that the duration of our lives and generations have increased. Goodman speculates that with lower mutation rates, we’d be less prone to developing costly faults in our DNA every time it was copied anew.
Overall, his conclusion was clear – in the animals with larger brains, a suite of AEM genes had gone through an accelerated burst of evolution compared to our mini-brained cousins. Six of our AEM genes that appear to have been strongly shaped by natural selection even have elephant counterparts that have gone through the same process.
Of course, humans and elephants are much larger than mice and tenrecs. But our genetic legacy isn’t just a reflection of our bigger size, for Goodman confirmed that AEM genes hadn’t gone through a similar evolutionary spurt in animals like cows and dogs.
Goodman’s next challenge is to see what difference the substituted amino acids would have made to us and elephants and whether they make our brains more efficient at producing aerobic energy. He also wants to better understand the specific genes that have been shaped the convergent evolution of human and elephant brains over the course of evolution. That task should certainly become easier as more and more mammal genomes are published.
Reference: PNAS doi:10.1073/pnas.0911239106
More on elephants:
For many animals, living with others has obvious benefits. Social animals can hunt in packs, gain safety in numbers or even learn from each other. In some cases, they can even solve problems more quickly as a group than as individuals. That’s even true for the humble house sparrow – Andras Liker and Veronika Bokony from the University of Pannonia, Hungary, found that groups of 6 sparrows are much faster at opening a tricky bird feeder than pairs of birds.
After ruling out several possible explanations, the duo put the speedy work of the bigger flock down to their greater odds of including boffin birds. Individual sparrows vary greatly in terms of their skills, experiences and personalities. Larger groups are more likely to include the sharpest bird brains, or several diverse individuals whose abilities complement each other.
Wild animals constantly encounter new, unfamiliar and challenging situations and the ability to adapt to them more quickly may give social species an edge over loners. The problem-solving advantages of groups have been demonstrated in humans. Three people, far from being a crowd, solve intellectual tasks faster than pairs or individuals, even if they were the smartest of the sample. There has been much less research on other animals, although scientists have certainly found that large groups of birds or fishes find food faster and more efficiently than smaller groups.
But Liker and Bokony’s sparrow experiments are the first to show that large animal groups outperform smaller ones at problem-solving tasks where they have to invent new techniques. House sparrows are a good choice for a study like this. They are very social birds that live in flocks of anywhere from a few individuals to a few hundred. They are opportunists that use their relatively large brains to find food in all sorts of new environments.
In the Goualougo Triangle of the Republic of Congo, a chimpanzee is hungry for termites. Its prey lives within fortress-like nests, but the chimp knows how to infiltrate these. It plucks the stem from a nearby arrowroot plant and clips any leaves away with its teeth, leaving behind a trimmed, flexible stick that it uses to “fish” for termites.
Many chimps throughout Africa have learned to build these fishing-sticks. They insert them into termite nests as bait, and pull out any soldier termites that bite onto it. But the Goualougo chimps do something special. They deliberately fray the ends of their fishing sticks by running them through their teeth or pulling away separate fibres – just watch the chimp on the right in the video below.
The result is a stick with a brush-like tip, which is far more effective at gathering termites than the standard model. This population of chimps has modified the typical design of the fishing stick to turn it into a better tool. They truly are intelligent designers.