As early humans faced new environmental challenges and evolved bigger bodies, they evolved larger and more complex brains. Large, complex brains can process and store a lot of information. That was a big advantage to early humans in their social interactions and encounters with unfamiliar habitats.
By the time our species, Homo sapiens, emerged about 200,000 years ago, the human brain had swelled from about 350 grams to more than 1,300 grams. In that 3-million-year sprint, the human brain almost quadrupled the size its predecessors had attained over the previous 60 million years of primate evolution.
Human brain size nearly quadrupled in the six million years since Homo last shared a common ancestor with chimpanzees, but human brains are thought to have decreased in volume since the end of the last Ice Age.
Last year, a group of scientists made headlines when they concluded that the human brain shrank during the transition to modern urban societies about 3,000 years ago because, they said, our ancestors' ability to store information externally in social groups decreased our need to maintain large brains.
Our modern civilisation may be the most advanced to ever exist on Earth, but around 100 generations ago, our ancestors had brains that were larger than our own.
According to the “cultural brain hypothesis,” humans evolved large brains and great intelligence in order to keep up with our complex social groups. We've always been a social species, and we may have developed our intelligence in part to maintain those relationships and function successfully in these environments.
In healthy volunteers, total brain volume weakly correlates with intelligence, with a correlation value between 0.3 and 0.4 out of a possible 1.0. In other words, brain size accounts for between 9 and 16 percent of the overall variability in general intelligence.
Brain size has a surprisingly small impact on intelligence and behavior. Key Points: Having an unusually large brain doesn't necessarily make someone a genius, and large-scale research suggests only a slight and tenuous relationship between brain size and intelligence.
Genetic studies have demonstrated that humans are still evolving. To investigate which genes are undergoing natural selection, researchers looked into the data produced by the International HapMap Project and the 1000 Genomes Project.
We moved towards a more energy-rich diet of meat and tubers, and we took a lot of the digestive work away from our bowels by cooking our food before eating it. Our guts can afford to be much smaller than expected for a mammal of our size, and the energy freed up by these shrunken bowels can power our mighty brains.
Extreme swings. Culture, in the form of clothing, fire use and the construction of shelters, has allowed humans to expand into environments that their relatively frail bodies could not otherwise have coped with.
Neanderthals had larger brains than modern humans do, and a new study of a Neanderthal child's skeleton now suggests this is because their brains spent more time growing.
Indeed, to some scientists the find supports the idea that mental abilities associated with modern humans emerged when anatomically modern humans did, about 200,000 years ago, rather than resulting from a genetic mutation cropping up between 40,000 and 50,000 years ago, as others have posited.
Measuring survival under benign conditions, we find that large-brained animals live 22% shorter than small-brained animals and the effect is similar in both males and females.
The average male brain 20,000 years ago, during the late Stone Age, was 1,500 cubic centimeters. Now it's 1,350. In other words, we've lost roughly a tennis ball of brain volume.
They identified a gene, called ARHGAP11B, which is present in our DNA but also in that of most humanoid species like, for example, the chimpanzee. This gene affects the generation and division of brain cells in a specific part of the neocortex.
But even if that common ancestor still existed, the fact that evolution is the result of both random mutation and a process of natural selection imposed by environmental conditions, means it's highly unlikely that it would ever retrace its steps in quite the same way.
We will likely live longer and become taller, as well as more lightly built. We'll probably be less aggressive and more agreeable, but have smaller brains. A bit like a golden retriever, we'll be friendly and jolly, but maybe not that interesting. At least, that's one possible future.
Worldwide there are roughly two new mutations for every one of the 3.5 billion base pairs in the human genome every year, says Hodgson. Which is pretty amazing - and makes it unlikely we will look the same in a million years.
Researchers have previously shown that a person's IQ is highly influenced by genetic factors, and have even identified certain genes that play a role. They've also shown that performance in school has genetic factors. But it's been unclear whether the same genes that influence IQ also influence grades and test scores.
They found that greater height was associated with bigger cortex, which in turn was linked with better cognitive ability. "Even though taller individuals have, on average, bigger brain compared to shorter people, the size of any given individual's brain cannot be determined by their stature alone.
Although scientists have not determined an ideal healthy brain size, a brain that is too small (microcephaly) or too big (macrocephaly) can lead to abnormal cognitive development and lifelong challenges. The human brain reaches maximum size around a person's early 20s, Thompson said.
Though this data might seem to suggest that dogs are twice as intelligent as cats, a direct correlation between larger brain size and increased intelligence has not been conclusively proven. Regardless, dogs' higher neuron count is often viewed as a gauge of their superior intelligence.
Are dolphins smarter than humans? Current tests for intelligence indicate that dolphins do not possess the same cognitive abilities as humans and are thus not the "smarter" species. Like humans, dolphins possess the ability to beneficially alter their surroundings, solve problems, and form complex social groups.
The sperm whale has the biggest brain of any animal species, weighing up to 20 pounds (7 to 9 kilograms). Larger brains don't necessarily make a smarter mammal. But as mammals evolved, many groups, from Primates to Carnivora, have shown independent increases in brain size.