By Contributor
updated 7/26/2011 8:33:08 PM ET 2011-07-27T00:33:08

Brains are larger in those who live farther from the equator — in order to help them see better, researchers now suspect.

Scientists have long known that brain volume increases with latitude — that is, the closer one gets to the poles.

"That might be mistaken for implying that intelligence increases with latitude," said researcher Robin Dunbar, an evolutionary anthropologist at the University of Oxford. "Our data suggests that this isn't so." [10 Things You Didn't Know About the Brain]

The investigators noted that the amount of light that reaches Earth's surface decreases the higher one goes up in latitude. They reasoned that in order to compensate, both eyeballs and the brain regions linked with vision might increase in size. Nocturnal primates do have larger eyes than ones active during the daytime, presumably in order to help them see better in the dark, and the same holds true for birds that sing earlier in the dawn, when light is sparse.

Dunbar and his Oxford colleague Eiluned Pearce measured the size of eye sockets and brains in 55 people from 12 different areas of varying latitude across the globe, from Scandinavia to Kenya to Australia. They determined that eyeball size increased with latitude just as brain size did, findings that are detailed online in Wednesday's edition of the journal Biology Letters.

  1. Science news from NBCNews.com
    1. NOAA
      Cosmic rays may spark Earth's lightning

      All lightning on Earth may have its roots in space, new research suggests.

    2. How our brains can track a 100 mph pitch
    3. Moth found to have ultrasonic hearing
    4. Quantum network could secure Internet

The biggest brains belonged to populations who lived in Scandinavia, while the smallest brains were those of Micronesians, the researchers found.

Under daylight conditions considered typical for each latitude, people from higher latitudes were found to have the same level of visual keenness as those from lower latitudes, the researchers noted. However, at dawn or dusk, when light levels are lower, people from higher latitudes might have markedly sharper eyesight, though this idea hasn't been tested, the researchers said.

"In relatively recent evolutionary time, humans have adapted to the low light levels of high latitudes by adjusting how much light enters the visual system," Dunbar noted.

The researchers are now looking at a larger sample of brains and eyes and measuring their dimensions more accurately with modern imaging techniques.

© 2012 LiveScience.com. All rights reserved.

Interactive: Take a tour of the brain

Explainer: Weird Science: Ten mysteries of the mind

  • Much of what we don't understand about being human is simply in our heads. The brain is a befuddling organ, as are the very questions of life and death, consciousness, sleep, and much more. Here's a heads-up on what's known and what's not understood about your noggin.

  • Sweet dreams

    If you were to ask 10 people what dreams are made of, you'd probably get 10 different answers. That's because scientists are still unraveling this mystery. One possibility: Dreaming exercises the brain by stimulating the trafficking of synapses between brain cells. Another theory is that people dream about tasks and emotions that they didn't take care of during the day, and that the process can help solidify thoughts and memories. In general, scientists agree that dreaming happens during your deepest sleep, called Rapid Eye Movement (REM).

  • Slumber sleuth

    Fruit flies do it. Tigers do it. And humans can't seem to get enough of it. No, not that. We're talking about shut-eye, so crucial we spend more than a quarter of our lives at it. Yet the underlying reasons for sleep remain as puzzling as a rambling dream. One thing scientists do know: Sleep is crucial for survival in mammals. Extended sleeplessness can lead to mood swings, hallucination, and in extreme cases, death. There are two states of sleep — non-rapid eye movement (NREM), during which the brain exhibits low metabolic activity, and rapid eye movement (REM), during which the brain is very active. Some scientists think NREM sleep gives your body a break, and in turn conserves energy, similar to hibernation. REM sleep could help to organize memories. However, this idea isn't proven, and dreams during REM sleep don't always correlate with memories.

  • Phantom feelings

    It's estimated that about 80 percent of amputees experience sensations, including warmth, itching, pressure and pain, coming from the missing limb. People who experience this phenomenon, known as "phantom limb," feel sensations as if the missing limb were part of their bodies. One explanation says that the nerves in the area where the limb was severed create new connections to the spinal cord and continue to send signals to the brain as if the missing limb was still there. Another possibility is that the brain is "hard-wired" to operate as if the body were fully intact — meaning the brain holds a blueprint of the body with all parts attached.

  • Mission control

    Residing in the hypothalamus of the brain, the suprachiasmatic nucleus, or biological clock, programs the body to follow a 24-hour rhythm. The most evident effect of circadian rhythm is the sleep-wake cycle, but the biological clock also impacts digestion, body temperature, blood pressure, and hormone production. Researchers have found that light intensity can adjust the clock forward or backward by regulating the hormone melatonin. The latest debate is whether or not melatonin supplements could help prevent jet lag — the drowsy, achy feeling you get when "jetting" across time zones.

  • Memory lane

    Some experiences are hard to forget, like perhaps your first kiss. But how does a person hold onto these personal movies? Using brain-imaging techniques, scientists are unraveling the mechanism responsible for creating and storing memories. They are finding that the hippocampus, within the brain's gray matter, could act as a memory box. But this storage area isn't so discriminatory. It turns out that both true and false memories activate similar brain regions. To pull out the real memory, some researchers ask a subject to recall the memory in context, something that's much more difficult when the event didn't actually occur.

  • Brain teaser

    Laughter is one of the least understood of human behaviors. Scientists have found that during a good laugh three parts of the brain light up: a thinking part that helps you get the joke, a movement area that tells your muscles to move, and an emotional region that elicits the "giddy" feeling. But it remains unknown why one person laughs at your brother's foolish jokes while another chuckles while watching a horror movie. John Morreall, who is a pioneer of humor research at the College of William and Mary, has found that laughter is a playful response to incongruities — stories that disobey conventional expectations. Others in the humor field point to laughter as a way of signaling to another person that this action is meant "in fun." One thing is clear: Laughter makes us feel better.

  • Nature vs. nurture

    In the long-running battle of whether our thoughts and personalities are controlled by genes or environment, scientists are building a convincing body of evidence that it could be either or both! The ability to study individual genes points to many human traits that we have little control over, yet in many realms, peer pressure or upbringing has been shown to heavily influence who we are and what we do.

  • Mortal mystery

    Living forever is just for Hollywood. But why do humans age? You are born with a robust toolbox full of mechanisms to fight disease and injury, which you might think should arm you against stiff joints and other ailments. But as we age, the body's repair mechanisms get out of shape. In effect, your resilience to physical injury and stress declines. Theories for why people age can be divided into two categories: 1) Like other human characteristics, aging could just be a part of human genetics and is somehow beneficial. 2) In the less optimistic view, aging has no purpose and results from cellular damage that occurs over a person's lifetime. A handful of researchers, however, think science will ultimately delay aging at least long enough to double life spans.

  • Deep freeze

    Living forever may not be a reality. But a pioneering field called cryonics could give some people two lives. Cryonics centers like Alcor Life Extension Foundation, in Arizona, store posthumous bodies in vats filled with liquid nitrogen at bone-chilling temperatures of minus 320 degrees Fahrenheit (78 Kelvin). The idea is that a person who dies from a presently incurable disease could be thawed and revived in the future when a cure has been found. The body of the late baseball legend Ted Williams is stored in one of Alcor's freezers. Like the other human popsicles, Williams is positioned head down. That way, if there were ever a leak in the tank, the brain would stay submerged in the cold liquid. Not one of the cryopreserved bodies has been revived, because that technology doesn't exist. For one, if the body isn't thawed at exactly the right temperature, the person's cells could turn to ice and blast into pieces.

  • Consciousness

    When you wake up in the morning, you might perceive that the Sun is just rising, hear a few birds chirping, and maybe even feel a flash of happiness as the fresh morning air hits your face. In other words, you are conscious. This complex topic has plagued the scientific community since antiquity. Only recently have neuroscientists considered consciousness a realistic research topic. The greatest brainteaser in this field has been to explain how processes in the brain give rise to subjective experiences. So far, scientists have managed to develop a great list of questions.

Discuss:

Discussion comments

,

Most active discussions

  1. votes comments
  2. votes comments
  3. votes comments
  4. votes comments